Exhibit 99.1

 

TSX: CCO				website: cameco.com
NYSE: CCJ				currency: Cdn (unless noted)

2121 – 11th Street West, Saskatoon, Saskatchewan, S7M 1J3 Canada

Tel: 306-956-6200 Fax: 306-956-6201

Cameco Reports Document Filings

Saskatoon, Saskatchewan, Canada, March 22, 2024 . . . . . . . . . . . . . 

Cameco (TSX: CCO; NYSE: CCJ) reported today that it filed its annual report on Form 40-F with the US Securities and Exchange Commission. The document includes Cameco’s audited annual financial statements for the year ended December 31, 2023, its management’s discussion and analysis (MD&A), and its Canadian annual information form (AIF).

In addition, Cameco filed with Canadian securities regulatory authorities its AIF. Its audited annual financial statements for the year ended December 31, 2023, and its MD&A were filed with Canadian securities regulatory authorities in February 2024.

Cameco also filed a technical report for the Cigar Lake operation under Canadian Securities Administrators’ National Instrument 43-101.

All of these documents are posted on our website. Shareholders may obtain hard copies of these documents, including the financial statements, free of charge by contacting:

Cameco Investor Relations

2121 11th Street West

Saskatoon, SK S7M 1J3

Phone: 306-956-6294

On April 5, 2024, Cameco plans to post on its website the management proxy circular that is being distributed to shareholders of record as of March 11, 2024, for its annual meeting of shareholders on

May 9, 2024. Cameco, on behalf of itself and certain subsidiaries (collectively, “Cameco”), will also post its Modern Slavey Report in accordance with the Fighting Against Forced Labour and Child Labour in Supply Chains Act (Canada) (the “Act”). This is Cameco’s first Modern Slavery Report pursuant to the Act.

Profile

Cameco is one of the largest global providers of the uranium fuel needed to energize a clean-air world. Our competitive position is based on our controlling ownership of the world’s largest high-grade reserves and low-cost operations, as well as significant investments across the nuclear fuel cycle, including ownership interests in Westinghouse Electric Company and Global Laser Enrichment. Utilities around the world rely on Cameco to provide global nuclear fuel solutions for the generation of safe, reliable, carbon-free nuclear power. Our shares trade on the Toronto and New York stock exchanges. Our head office is in Saskatoon, Saskatchewan, Canada.

- End –

 

Exhibit 99.2

 

Cigar Lake Operation

Northern Saskatchewan, Canada

National Instrument 43-101

Technical Report

Effective Date: December 31, 2023

Date of Technical Report: March 22, 2024

PREPARED FOR CAMECO CORPORATION BY:

BIMAN BHARADWAJ, P. ENG.

C. SCOTT BISHOP, P. ENG.

ALAIN D. RENAUD, P. GEO.

LLOYD ROWSON, P. ENG.

Table of Contents

 

1    SUMMARY			1
1.1   Preamble			1
1.2   Introduction			1
1.3   Property tenure			2
1.4   Location and site description			2
1.5   Geology and mineralization			3
1.6   Exploration of Cigar Lake deposit			4
1.7   Mineral resources and mineral reserves			4
1.8   Mining			7
1.9   Processing			9
1.10  Environmental assessment and licensing			10
1.11  Cigar Lake water inflow incidents and remediation			11
1.12  Current status of development			11
1.13  Production plan			12
1.14  Economic analysis and costs			13
1.15  Mining and milling risks			14
1.16  Conclusions and recommendations			14
2    INTRODUCTION			17
2.1   Introduction and purpose			17
2.2   Report basis			18
3    RELIANCE ON OTHER EXPERTS			19
4    PROPERTY DESCRIPTION AND LOCATION			20
4.1   Location			20
4.2   Mineral tenure			21
4.3   Surface tenure			25
4.4   Royalties			28
4.5   Known environmental liabilities			28
4.6   Permitting			28
5    ACCESSIBILITY, CLIMATE, LOCAL RESOURCES, INFRASTRUCTURE AND PHYSIOGRAPHY			29
5.1   Access			29
5.2   Climate			31
5.3   Physiography			31
5.4   Local resources			31

 

i

5.5   Mine and infrastructure			32
6    HISTORY			35
6.1   Ownership			35
6.2   Exploration and development history			36
6.3   Historical mineral resource and mineral reserve estimates			38
6.4   Historical production			38
7    GEOLOGICAL SETTING AND MINERALIZATION			39
7.1   Regional geology			39
7.2   Local geology			39
7.3   Property geology			42
7.4   Mineralization			46
8    DEPOSIT TYPES			48
9    EXPLORATION			49
9.1   ORANO 1980 – present			49
9.2   Cameco 2007 – present			54
10   DRILLING			55
10.1  Surface drilling			55
10.2  Underground drilling			60
10.3  Factors that could materially affect the accuracy of the results			62
11   SAMPLE PREPARATION, ANALYSES AND SECURITY			63
11.1  Sample density and sampling methods			63
11.2  Core recovery			63
11.3  Sample quality and representativeness			64
11.4  Sample preparation by Cameco employees			64
11.5  Sample preparation			64
11.6  Assaying			65
11.7  Radiometric surveying			65
11.8  Density sampling			67
11.9  Quality assurance/quality control			67
11.10  Adequacy of sample preparation, assaying, QA/QC and security			70
12   DATA VERIFICATION			72
13   MINERAL PROCESSING AND METALLURGICAL TESTING			73
13.1  Cigar Lake processing metallurgical test work			73
13.2  McClean Lake processing metallurgical test work			73
14   MINERAL RESOURCE ESTIMATES			76

 

ii

14.1  Definitions			76
14.2  Key assumptions, parameters and methods			76
14.3  Geological modelling			79
14.4  Compositing			81
14.5  Block modelling			85
14.6  Validation			86
14.7  Mineral resource classification			87
14.8  Factors that could materially affect the mineral resource estimate			89
15   MINERAL RESERVE ESTIMATES			91
15.1  Definitions			91
15.2  Key assumptions, parameters and methods			91
15.3  Mineral reserves estimation and classification			95
15.4  Factors that could materially affect the mineral reserves estimate			96
16   MINING METHODS			98
16.1  Design parameters			98
16.2  Mine design			105
16.3  Mine production			117
17   RECOVERY METHODS			123
17.1  Overview			123
17.2  Cigar Lake flowsheet			123
17.3  Processing at McClean Lake			124
17.4  McClean Lake mill flowsheet			124
18   PROJECT INFRASTRUCTURE			126
18.1  Cigar Lake infrastructure			126
18.2  McClean Lake infrastructure			126
19   MARKET STUDIES AND CONTRACTS			128
19.1  Markets			128
19.2  Material contracts for property development			129
19.3  Uranium price assumptions used for economic analysis			130
20   ENVIRONMENTAL STUDIES, PERMITTING AND SOCIAL OR COMMUNITY IMPACT			133
20.1  Regulatory framework			133
20.2  Licences and permits			133
20.3  Environmental assessment			134

 

iii

20.4  Environmental aspects			135
20.5  Decommissioning and reclamation			137
20.6  Known environmental liabilities			138
20.7  Social and community factors			139
21   CAPITAL AND OPERATING COSTS			141
21.1  Capital and other costs			141
21.2  Operating cost estimates			143
22   ECONOMIC ANALYSIS			145
22.1  Economic analysis			145
22.2  Sensitivities			147
22.3  Payback			147
22.4  Mine life			147
22.5  Taxes			148
22.6  Royalties			148
23   ADJACENT PROPERTIES			149
24   OTHER RELEVANT DATA AND INFORMATION			150
24.1  Cigar Lake water inflow incidents			150
24.2  Mining and milling risks			150
24.3  Caution about forward-looking information			153
25   INTERPRETATION AND CONCLUSIONS			155
26   RECOMMENDATIONS			157
27   REFERENCES			158
28   DATE AND SIGNATURE PAGE			161

 

iv

Tables

 

TABLE 1-1: CIGAR LAKE MINERAL RESOURCES – DECEMBER 31, 2023			5
TABLE 1-2: CIGAR LAKE MINERAL RESERVES – DECEMBER 31, 2023			6
TABLE 3-1: RELIANCE ON OTHER EXPERTS			19
TABLE 4-1: CIGAR LAKE OPERATION - MINERAL CLAIMS STATUS			24
TABLE 6-1: CIGAR LAKE HISTORICAL PRODUCTION (100% BASIS)			38
TABLE 9-1: SUMMARY OF EXPLORATION OUTSIDE OF ML 5521			52
TABLE 13-1: McCLEAN LAKE OVERALL MILL RECOVERY (2014 TO 2023)			75
TABLE 14-1: GENERAL SUMMARY OF CL MAIN SEARCH PARAMETERS FOR ORDINARY KRIGING MODEL (U3O8 and DENSITY)			85
TABLE 14-2: GENERAL SUMMARY OF CLEXT SEARCH PARAMETERS			86
TABLE 14-3: RECONCILIATION OF PRODUCTION AND MODEL			87
TABLE 14-4: CIGAR LAKE MINERAL RESOURCES – DECEMBER 31, 2023			89
TABLE 15-1: CIGAR LAKE MINERAL RESERVES – DECEMBER 31, 2023			95
TABLE 16-1: UNDERGROUND MINING EQUIPMENT			115
TABLE 16-2: CAVITY DILUTION FACTORS			119
TABLE 16-3: CIGAR LAKE 2024 – 2036 PLANNED PRODUCTION SCHEDULE SUMMARY			121
TABLE 19-1: EXPECTED AVERAGE REALIZED URANIUM PRICES BY YEAR			132
TABLE 21-1: CLJV CAPITAL AND OTHER COSTS FORECAST BY YEAR			142
TABLE 21-2: CLJV OPERATING COST FORECAST BY YEAR			144
TABLE 22-1: CLJV ECONOMIC ANALYSIS – CAMECO’S SHARE			146

 

v

Figures

 

FIGURE 1-1: MINE PRODUCTION			13
FIGURE 1-2: MILL PRODUCTION			13
FIGURE 4-1: CIGAR LAKE MINERAL PROPERTY LOCATION			21
FIGURE 4-2: MINERAL LEASE AND MINERAL CLAIMS			23
FIGURE 4-3: SURFACE LEASE, MINERAL LEASE AND MINERAL CLAIMS			25
FIGURE 4-4: MAP OF MINE FACILITIES AND SURFACE LEASE BOUNDARY			27
FIGURE 5-1: CIGAR LAKE SITE - REGIONAL LOCATION AND ROADS			30
FIGURE 5-2: SITE PLAN OF EXISTING AND PLANNED SURFACE FACILITIES			34
FIGURE 7-1: GEOLOGICAL MAP OF NORTHERN SASKATCHEWAN			40
FIGURE 7-2: CIGAR LAKE - REGIONAL BASEMENT GEOLOGY			42
FIGURE 7-3: BASEMENT GEOLOGY OF THE CL MAIN AREA RELATIVE TO MINERALIZATION			44
FIGURE 7-4: BASEMENT GEOLOGY OF THE CLEXT AREA RELATIVE TO MINERALIZATION			45
FIGURE 7-5: CL MAIN DEPOSIT - SCHEMATIC CROSS SECTION LOOKING WEST			46
FIGURE 9-1: EXPLORATION WORK AREAS OUTSIDE OF ML 5521			51
FIGURE 10-1: CIGAR LAKE DEPOSIT - SURFACE EXPLORATION AND DELINEATION DRILLHOLE LOCATIONS			57
FIGURE 10-2: CIGAR LAKE DEPOSIT - SURFACE FREEZE HOLE LOCATIONS (CL MAIN)			58
FIGURE 10-3: CL MAIN GEOLOGICAL CROSS SECTION AT 10781E – LOOKING WEST (±3 m)			59
FIGURE 10-4: UNDERGROUND GEOTECHNICAL DIAMOND DRILLHOLE LOCATION MAP - CL MAIN			61
FIGURE 11-1: GT COMPARISON OF eU3O8 CORRELATION AGAINST CHEMICAL ASSAY			66
FIGURE 11-2: CIGAR LAKE STANDARDS (CL MAIN AND CLEXT): BL4A, BL2A, CL-1, BL5, CL-2, CL-3, CL-4, AND CL-5			68
FIGURE 11-3: CIGAR LAKE (CL MAIN AND CLEXT) PULP DUPLICATE AR-ICP RESULTS			70
FIGURE 14-1: MINERAL RESOURCE AND RESERVE ESTIMATES - DECEMBER 31, 2023			78
FIGURE 14-2: ISOMETRIC VIEW OF CL MAIN MINERALIZED PODS AND LENSES			79
FIGURE 14-3: CL MAIN INTERNAL HIGH-GRADE DOMAINS			80
FIGURE 14-4: SECTION 10749E (±1 m) SHOWING HIGH-GRADE DOMAIN (MAGENTA) WITHIN EAST POD (GREEN) RELATIVE TO DRILL COMPOSITE GRADES – LOOKING WEST			80
FIGURE 14-5: ISOMETRIC VIEW OF CLEXT MINERALIZED LENSES			81
FIGURE 14-6: SECTION 9170E (±8 m) SHOWING LENSES AND DRILL COMPOSITES - LOOKING WEST			81
FIGURE 14-7: HISTOGRAM AND SUMMARY STATISTICS OF ALL CL MAIN %U3O8 AND DENSITY COMPOSITES			83

 

vi

FIGURE 14-8: HISTOGRAM AND SUMMARY STATISTICS OF ALL CLEXT %U3O8 AND DENSITY COMPOSITES			84
FIGURE 14-9: CL MAIN MINERAL RESOURCE CLASSIFICATION INCLUDING MINERALIZED POTENTIAL			88
FIGURE 14-10: CLEXT MINERAL RESOURCE CLASSIFICATION INCLUDING MINERALIZED POTENTIAL			88
FIGURE 15-1: CL MAIN MINERAL RESERVES - ESTIMATED JBS CAVITY GRADE DISTRIBUTION – PLAN VIEW			93
FIGURE 15-2: CLEXT MINERAL RESERVES - ESTIMATED JBS CAVITY GRADE DISTRIBUTION – PLAN VIEW			94
FIGURE 16-1: GEOTECHNICAL DOMAINS OF THE 480L OF CL MAIN WITH INTERPRETED FAULT ZONES			100
FIGURE 16-2: GEOTECHNICAL DOMAINS OF THE 480L OF CLEXT WITH INTERPRETED FAULT ZONES			101
FIGURE 16-3: CL MAIN GEOTECHNICAL SCHEMATIC CROSS SECTION AT 10783E – LOOKING WEST			102
FIGURE 16-4: CLEXT GEOTECHNICAL SCHEMATIC CROSS SECTION AT 9580E – LOOKING WEST			103
FIGURE 16-5: THREE-DIMENSIONAL GENERAL MINE LAYOUT OF CL MAIN AND CLEXT – LOOKING NORTHWEST			106
FIGURE 16-6: CL MAIN FREEZE HOLE LAYOUT			112
FIGURE 16-7: CLEXT FREEZE HOLE LAYOUT			113
FIGURE 16-8: SCHEMATIC VERTICAL SECTION OF THE JBS MINING METHOD			118
FIGURE 16-9: MINE PRODUCTION			122
FIGURE 16-10: MILL PRODUCTION			122
FIGURE 17-1: CIGAR LAKE ORE PROCESSING ACTIVITIES – BLOCK DIAGRAM			124
FIGURE 22-1: CIGAR LAKE OPERATION SENSITIVITY ANALYSIS			147

 

vii

Units of measure and abbreviations

 

 

viii

1

Summary

 

1.1

Preamble

This technical report replaces the previous Cigar Lake Operation technical report, filed in March of 2016 (2016 Technical Report). This report is based on new technical and scientific information, and reflects experience gained since 2016.

The Cigar Lake deposit has historically been divided into two parts. The eastern portion, previously referred to as Phase 1, is now referred to as the Cigar Lake Main (CL Main) portion of the deposit, whereas the western portion, previously referred to as Phase 2, is now referred to as the Cigar Lake Extension (CLEXT).

Key highlights of this report include:

 

•

extension of the mine life to 2036 subject to receipt of all regulatory approvals

 

•

an increase in Cameco’s ownership interest in the Cigar Lake Joint Venture (CLJV) to 54.547% with the 2023 acquisition of a 4.522% interest from Idemitsu Canada Resources Ltd.

 

•

estimated pre-tax net present value (NPV) at an 8% discount rate to Cameco of $2.5 billion for its share of current mineral reserves

 

•

estimated pre-tax internal rate of return (IRR) of 8.3%, using Cameco’s share of the total capital invested to date, along with the operating and capital cost estimates for the remainder of the mineral reserves

 

•

on an undiscounted pre-tax basis, payback for Cameco, including total capital invested to date, is expected to be achieved in 2024

 

•

increase in estimated average cash operating costs per pound—from $18.75 to $20.58

 

•

total estimated Cigar Lake mine capital and McClean Lake mill capital to bring the remaining mineral reserves (CL Main and CLEXT) into production is approximately $1.2 billion (Cameco’s share – $680 million)

 

•

mine development and capital expenditures for CLEXT are expected to be approximately $895 million (Cameco’s share – $487 million), including approximately $520 million (Cameco’s share – $284 million) required in advance of first ore from CLEXT in 2030

 

•

conversion of 73.4 million pounds of CLEXT mineral resources into mineral reserves based on information from 235 holes totaling approximately 99,000 metres of diamond drilling

 

•

expected total packaged production of 205.9 million pounds U3O8, based on remaining mineral reserves and an overall milling recovery of 98.7%

 

•

a plan to develop and mine CLEXT utilizing the same methods and approach as used for CL Main, including utilizing existing infrastructure for mine access, ventilation, dewatering, processing and jet bore mining support activities

 

•

completion of modifications to the McClean Lake mill to increase capacity in the front-end circuits (leaching, CCD) from a nominal 45 kt ore/year to 59 kt ore/year plus regulatory approval for the continued expansion of the tailings management facility (TMF) at Orano’s McClean Lake mill to allow processing of all Cigar Lake’s current mineral reserves

 

1.2	Introduction

PROFILE

Located in northern Saskatchewan’s Athabasca Basin, Cigar Lake is the world’s highest grade uranium mine.

 

 

2024 CIGAR LAKE TECHNICAL REPORT 1

Cigar Lake is owned by the CLJV participants:

 

•

Cameco Corporation (Cameco) (54.547%)

 

•

Orano Canada Inc. (40.453%)

 

•

TEPCO Resources Inc. (TEPCO) (5.000%)

Cameco has been the operator of Cigar Lake since January 2002.

BACKGROUND

In December 2004, the CLJV decided to proceed with development of the Cigar Lake mine and received a construction licence from the Canadian Nuclear Safety Commission (CNSC) that same month. Construction began in January 2005, but development was delayed due to water inflows in April and October 2006, and an additional water inflow in August 2008.

In October 2009, Cameco successfully sealed the August 2008 inflow, and the underground workings were dewatered in February 2010. Safe access to the 480-metre (480L) and 500-metre (500L) levels was restored and the restoration of underground mine systems and infrastructure was completed in 2011.

With the mine re-entry and remediation milestone attained, construction of the permanent underground infrastructure began and was substantially complete in 2013. Staged commissioning of the JBS machine and supporting underground circuits began shortly thereafter, with the first commissioning cavity mined in barren rock in October 2013, and first ore cavity mined in December 2013.

The first shipment of ore slurry to McClean Lake occurred in March 2014, and the first yellowcake was packaged in October 2014. With the completion of commissioning of all circuits attained and sustainable, and acceptable performance demonstrated, commercial production was declared in May 2015. Since that time, mine operation has achieved full nameplate capacity.

 

1.3	Property tenure

The mineral property consists of one mineral lease (ML 5521) and 38 mineral claims totaling 95,601 hectares. The mineral lease and mineral claims are contiguous.

The Cigar Lake deposit is located in the area subject to the mineral lease, totaling 308 hectares. The right to mine this uranium deposit was acquired under this mineral lease. The current mineral lease expires November 30, 2031, with the right to renew for successive 10-year terms, absent a default by the CLJV.

A mineral claim grants the holder the right to explore for minerals within the claim lands and to apply for a mineral lease.

The surface facilities and mine shafts for the Cigar Lake operation are located on lands owned by the Province of Saskatchewan. The CLJV acquired the right to use and occupy the lands under a surface lease agreement with the Province. The term of the surface lease expires May 31, 2044. The Cigar Lake surface lease covers a total area of 715 hectares of Crown land.

See Section 4.2 and 4.3 for further detail.

 

1.4	Location and site description

The Cigar Lake mine site is located near Waterbury Lake, approximately 660 kilometres north of Saskatoon. The McClean Lake mill is located 69 kilometres northeast of the mine site by road.

The property is accessible by an all-weather road and by air. Site activities occur year-round, including supply deliveries.

 

 

2024 CIGAR LAKE TECHNICAL REPORT 2

The topography and the environment are typical of the taiga forested lands common to the Athabasca Basin area of northern Saskatchewan. The area is covered with 30 to 50 metres of overburden. The surface facilities are at an elevation of approximately 490 metres above sea level.

The site is connected to the provincial electricity grid with a 138-kilovolt overhead power line. There are standby generators in case of grid power interruption.

Personnel are recruited on a preferential basis from northern Saskatchewan. Development and construction work is tendered to a number of contractors.

More information is available in Section 4.

 

1.5	Geology and mineralization

The Cigar Lake deposit is located approximately 40 kilometres west of the eastern margin of the Athabasca Basin. It is an unconformity related uranium deposit occurring at the unconformity contact between rock of the Athabasca Group and underlying lower Proterozoic Wollaston Group metasedimentary gneiss and plutonic rocks. In this way, it is similar to the Key Lake, McClean Lake, Collins Bay and McArthur River deposits. As a result, Cigar Lake shares many geological similarities with these deposits, including general structural setting, mineralogy, geochemistry, host rock association and the age of the mineralization. However, the Cigar Lake deposit is distinguished from other similar deposits by its size, high grade, the intensity of its alteration process, and the high degree of associated hydrothermal clay alteration.

The Cigar Lake deposit is similar to the McArthur River deposit in that sandstone overlies the basement rock and contains large volumes of water at significant pressure, but unlike McArthur River, this deposit is flat-lying.

The Cigar Lake deposit is approximately 1,950 metres long, 20 to 100 metres wide, and ranges up to 13.5 metres thick, with an average thickness of about 5.4 metres. It occurs at depths ranging between 410 and 450 metres below surface.

Two distinct styles of mineralization occur within the Cigar Lake deposit:

 

•

high-grade mineralization at or proximal to the unconformity (“unconformity” mineralization), which includes almost all of the mineral resources and mineral reserves

 

•

low-grade, fracture controlled, vein-like mineralization which is located either higher up in the sandstone (“perched” mineralization) or in the basement rock mass

The high-grade mineralization located in proximity to the unconformity contains the bulk of the total uranium metal in the deposit and currently represents the only economically viable style of mineralization, in the context of the selected mining method and ground conditions. It is characterized by the occurrence of massive clays and very high-grade uranium concentrations.

The unconformity mineralization consists primarily of three dominant rock and mineral facies occurring in varying proportions: quartz, clay (primarily chlorite with lesser illite) and metallic minerals (oxides, arsenides, sulphides). In the relatively higher grade eastern CL Main zone, the ore consists of approximately 50% clay matrix, 20% quartz and 30% metallic minerals, visually estimated by volume. In this area, the unconformity mineralization is overlain by a weakly mineralized contiguous clay cap 1 to 10 metres thick. In the western CLEXT zone, the proportions change to approximately 20% clay, 60% quartz and 20% metallic minerals.

See Section 7 for further detail.

 

2024 CIGAR LAKE TECHNICAL REPORT 3

1.6	Exploration of Cigar Lake deposit

The Cigar Lake uranium deposit was discovered in 1981 on lands now covered by ML 5521. The discovery was a result of initial airborne and ground geophysical surveys followed by a regional program of diamond drill testing.

The deposit was subsequently delineated by surface diamond drilling during the period 1982 to 1986 and was followed by several small campaigns of geotechnical and infill drilling to the end of 2007. Additional drilling campaigns were conducted by Cameco after 2007 which targeted a broad range of technical objectives, including geotechnical, geophysical, delineation and ground freezing.

Since 2012, diamond drilling managed by Cameco has mainly focused on underground geotechnical and surface ground freezing programs on CL Main along with continued delineation drilling on CLEXT.

The CL Main zone was discovered in 1983. Drilling was initially done at a nominal drillhole grid spacing of 50 metres east-west by 20 metres north-south. A surface drill program was conducted from 2010 to 2012 to tighten up the spacing in areas with gaps in coverage. Similarly, a small program of six holes was completed on mineralized zones situated between East Pod and West Pod in 2023. Apart from this area, CL Main has been fully delineated by surface freeze holes on a nominal 7 x 7 metre pattern.

The CLEXT zone had been outlined through several exploration drilling campaigns conducted between 1981 and 2012. Since 2016, Cameco has completed additional surface delineation drilling to confirm and upgrade the mineral resources contained in CLEXT and to collect metallurgical, hydrogeological and geotechnical information used to support the prefeasibility study for CLEXT. Drillholes are variably spaced 12 to 25 metres apart in the western portion and 20 to 50 metres in its eastern portion.

Diamond core drilling from underground locations has been done primarily to ascertain rock mass characteristics in advance of development and mining. Underground geotechnical drilling has occurred since 1989.

More information on exploration and drilling can be found in Sections 9 and 10.

 

1.7	Mineral resources and mineral reserves

The known mineralization at Cigar Lake is divided into two zones, the western CLEXT zone and the eastern CL Main zone. The CL Main mineral resource and mineral reserve estimates are based on 1,284 mineralized surface drillholes while the CLEXT mineral resource estimate is based on 135 mineralized surface drillholes. The vast majority of drillholes were drilled perpendicular to the mineralization and their intercepts approximate the true thickness of the mineralization.

The Cigar Lake mineral resources, exclusive of mineral reserves, with an effective date of December 31, 2023, are presented in Table 1-1. Al Renaud, P. Geo. with Cameco, is the qualified person within the meaning of National Instrument 43-101 Standards of Disclosure for Mineral Projects (NI 43-101) for the purpose of the mineral resource estimates.

The Cigar Lake mineral reserves estimates, with an effective date of December 31, 2023, are shown in Table 1-2. B. Bharadwaj, P. Eng., C. Scott Bishop, P. Eng., Al Renaud, P. Geo., and Lloyd Rowson, P. Eng., each with Cameco, are the qualified persons within the meaning of NI 43-101 for the purpose of the mineral reserve estimates.

 

2024 CIGAR LAKE TECHNICAL REPORT 4

TABLE 1-1: CIGAR LAKE MINERAL RESOURCES – DECEMBER 31, 2023

 

Category		Area		Total tonnes (x 1,000)				Grade % U3O8				Total M lbs  U3O8				Cameco’s share M lbs  U3O8
Measured and Indicated
Measured		CL Main			86.3				5.32				10.1				5.5
Indicated		CL Main			30.6				6.61				4.5				2.4
Indicated		CLEXT			113.0				4.98				12.4				6.8
Total Measured and Indicated					229.9				5.32				27.0				14.7
Inferred
Inferred		CL Main			6.2				4.41				0.6				0.3
Inferred		CLEXT			157.1				5.60				19.4				10.6
Total Inferred					163.4				5.55				20.0				10.9

 

Notes:

(1)

Cameco reports mineral reserves and mineral resources separately. Reported mineral resources do not include amounts identified as mineral reserves. Totals may not add up due to rounding.

 

(2)

Mineral resources that are not mineral reserves do not have demonstrated economic viability.

 

(3)

Cameco’s share is 54.547% of total mineral resources.

 

(4)

Inferred mineral resources are estimated using limited geological evidence and sampling information. We do not have enough confidence to evaluate their economic viability in a meaningful way. You should not assume that all or any part of an inferred mineral resource will be upgraded to an indicated or measured mineral resource, but it is reasonably expected that the majority of inferred mineral resources could be upgraded to indicated mineral resources with continued exploration.

 

(5)

Reasonable expectation for eventual economic extraction of the mineral resources is based on a constant dollar average uranium price of $62.00 (US) per pound U3O8 with a $1.00 US = $1.26 Cdn fixed exchange rate, mining and process recoveries, production costs, royalties and mineralized area tonnage, grade, and spatial continuity considerations.

 

(6)

Mineral resources have been estimated with a minimum mineralization thickness of one metre and a cut-off grade of 1.0% U3O8 for CL Main and 0.8% U3O8 for CLEXT based on the use of the JBS method combined with bulk freezing of the orebody.

 

(7)

The mineralized lenses have been interpreted from drillhole information on vertical cross-sections or with 3D implicit modelling and validated on plan views and in 3D.

 

(8)

Mineral resources have been estimated with no allowance for mining dilution and mining recovery.

 

(9)

Mineral resources were estimated using 3D block models.

 

(10)

There are no known environmental, permitting, legal, title, taxation, socio-economic, political, marketing or other relevant factors that could materially affect the above estimate of mineral resources.

 

2024 CIGAR LAKE TECHNICAL REPORT 5

TABLE 1-2: CIGAR LAKE MINERAL RESERVES – DECEMBER 31, 2023

 

Category		Area		Total tonnes (x 1,000)				Grade % U3O8				Total M lbs  U3O8				Cameco’s share M lbs  U3O8
Proven		Broken CL Main			1.1 337.0				27.55 18.07				0.7 134.3				0.4 73.3
Total proven					338.1				18.11				135.0				73.6
Probable		CL Main CLEXT			1.7 215.8				7.17 15.42				0.3 73.4				0.1 40.0
Total probable					217.5				15.36				73.7				40.2
Total mineral reserves					555.6				17.03				208.6				113.8

 

Notes:

(1)

Cameco reports mineral reserves and mineral resources separately. Totals may not add up due to rounding.

 

(2)

Total pounds U3O8 are those contained in mineral reserves and are not adjusted for the estimated mill recovery of 98.8% for CL Main and 98.5% for CLEXT.

 

(3)

Cameco’s share is 54.547% of total mineral reserves.

 

(4)

Mineral reserves have been estimated on the basis of designed JBS cavities having greater revenue than the cost to mine and process.

 

(5)

Mineral reserves have been estimated with an average allowance of 34% dilution at 0% U3O8, inclusive of dilution material above and below the planned cavity and include dilution from the JBS pilot hole and from adjacent backfill.

 

(6)

Mineral reserves have been estimated based on 86% mining recovery.

 

(7)

Mineral reserves were estimated based on the use of the JBS mining method combined with bulk freezing of the orebody. Mining rate assumed to vary between 115 and 160 tonnes per day, and a full mill production rate of approximately 18 million pounds U3O8 per year. The reference point at which mineral reserves are defined is when the ore is delivered to the McClean Lake mill.

 

(8)

An average uranium price of $54.00 (US) per pound U3O8 with a $1.00 US = $1.26 Cdn fixed exchange rate was used to estimate the mineral reserves.

 

(9)

Broken ore is defined as ore that has been mined with the JBS but not yet processed at McClean Lake. This includes all in-circuit inventory at Cigar Lake plus the ore slurry stored in the ore storage pachucas at McClean Lake.

 

(10)

Other than the challenges related to water inflows, jet boring and geotechnical issues described in Section 15.4, there are no known mining, metallurgical, infrastructure, permitting, or other relevant factors that could materially affect the above estimate of mineral reserves.

CHANGES TO MINERAL RESOURCE AND RESERVE ESTIMATES

The updated mineral resource and mineral reserve estimates (December 31, 2023) reflect changes from the 2022 year-end estimates that are mainly due to:

 

•

addition of 98 surface freeze holes in portions of CL Main

 

•

addition of six delineation holes in the Central lenses

 

•

addition of 12 surface delineation holes in CLEXT

 

•

reinterpretation of the mineralized envelope of CL Main and CLEXT

 

2024 CIGAR LAKE TECHNICAL REPORT 6

•

an adjustment to the correlation to convert corrected probe count rates into equivalent %U3O8 applied to address a slight eU3O8 overestimation bias

 

•

reclassification of the mineral resources and mineral reserves based on drillhole spacing, geological and grade continuity, estimation confidence and reconciliation of mined production to the end of 2023

 

•

updated operating cost estimates, metal price and exchange rate assumptions

 

•

conversion of 73.4 million pounds (100% basis) of CLEXT mineral resources into mineral reserves based on information from 235 holes totaling approximately 99,000 metres of diamond drilling, with a corresponding decrease in mineral resources

 

•

removal of the reserve estimates for the mined cavities contributing to the mill feed to December 31, 2023

More information on mineral reserves and mineral resources is available in Sections 14 and 15.

 

1.8

Mining

JET BORING MINING SYSTEM

The jet boring mining system, a non-entry mining method, has been selected to mine the Cigar Lake deposit because of the challenges associated with mining the deposit, including control of groundwater, weak rock formations, radiation protection, and relatively thin, flat-lying mineralization. This method was selected after many years of exploration and test mining activities following the discovery of the deposit in 1981.

The JBS mining method consists of cutting cavities out of frozen ore using a high-pressure water jet. Access to the orebody is achieved by drilling boreholes upwards from the production crosscuts below and then inserting specialized jetting tools to the ore horizon. Jetting begins at the top of a cavity and retreats vertically downward in thin slices, resulting in a cylindrical void with a height corresponding to the thickness of the orebody (up to 13.5 metres) and a diameter of 4.5 to 6 metres. The resulting void is tightly backfilled with concrete, and the cycle is repeated to recover adjacent ore.

This non-entry method was developed and adapted specifically for the Cigar Lake deposit, and does not directly expose personnel to the ore. The mining process is controlled from headings located in barren basement rock below the orebody, where the levels of radiation exposure to workers are very low. Radiation protection is further enhanced through the containment of the ore cuttings within cuttings collection and hydraulic conveyance systems, and via the application of ground freezing which limits the mobility of potentially radon-bearing water. These unique properties of the mining method have proven very effective at minimizing workers’ exposure to radiation.

The mine production fleet is currently comprised of three JBS units and supporting infrastructure and ancillary equipment. This fleet size is sufficient for the remainder of the mine life, including CLEXT.

MINE DEVELOPMENT

Mine development for construction and operation uses two basic approaches: for good quality, competent rock mass, drill and blast with conventional ground support is applied; for poor quality, weak rock mass, the New Austrian Tunnelling Method (NATM) is applied. Most permanent areas of the mine, which contain the majority of the installed equipment and infrastructure, are hosted in competent rock mass and are excavated and supported conventionally. The production tunnels immediately below the orebody are primarily in poor, weak rock mass and are excavated and supported following NATM principles.

 

2024 CIGAR LAKE TECHNICAL REPORT 7

NATM, as applied at Cigar Lake, involves a multi-stage sequential mechanical excavation, extensive external ground support and a specialized shotcrete liner. The liner system incorporates yielding elements which permit controlled deformation required to accommodate additive pressure from mining and ground freezing activities. The production tunnels have an inside diameter of five metres and are circular in profile.

Cameco plans its mine development to take place away from known groundwater sources whenever possible. In addition, Cameco assesses all planned mine development for relative risk and applies extensive additional technical and operating controls for all higher risk development.

MINE ACCESS

The main access to the mine is via Shaft No. 1, a circular concrete-lined shaft, 4.9 metres in diameter which extends to a depth of 500 metres below the surface and provides direct access to the working level on the 480L. Shaft No. 1 is used as the main access and services shaft, and as a route for delivery of fresh ventilation underground.

Shaft No. 2 is a circular lined shaft, 6.1 metres in diameter, also sunk to a depth of 500 metres. This shaft is located 90 metres south of Shaft No. 1 and provides access to 480L. It is divided into two compartments by a central airtight partition: one compartment serves as the main path for exhaust air from the mine; the second compartment is used to downcast additional fresh ventilation air, as well as provide secondary egress and a number of additional services. The primary ventilation system has been designed to supply a volume of up to 240 m3/s of fresh air to the mine.

MINE LEVELS – 480L AND 500L

There are two main levels in the mine: the 480L and the 500L. Both levels are located in the basement rocks below the unconformity. Mining is conducted from the 480L, which is located about 40 metres below the ore zone. The main underground processing and infrastructure facilities are also located on this level. The 500L is accessed via a ramp from the 480L. The main ventilation exhaust drift for the mine, the mine dewatering sump and additional processing facilities are located on 500L.

ARTIFICIAL GROUND FREEZING

Cameco bulk freezes the ore zone and surrounding ground prior to mining an area. This system freezes the deposit and underlying basement rock in two to four years, depending on water content and geological conditions.

Freezing is key to the success of mining the deposit, and results in several enhancements to mining conditions, including: (1) increasing the stability of the area being mined; (2) minimizing the risk of water inflows into the mine from the water-bearing rock above the unconformity; and (3) reducing the radiation resulting from radon dissolved in the water.

In 2015, the CLJV decided to pursue a strategy of freezing exclusively from surface. This strategy has resulted in the following benefits:

 

•

reducing risk to mine development

 

•

allowing ground freezing to start before development of underground production tunnels

 

•

simplifying mining operations, since ground freezing infrastructure and activities are located on surface

Artificial ground freezing for mining of CLEXT mineral reserves will follow a similar strategy of freezing exclusively from surface.

Artificial ground freezing is accomplished by drilling a systematic grid of boreholes through the orebody from surface. A network of supply and return pipes on surface convey a calcium chloride

 

2024 CIGAR LAKE TECHNICAL REPORT 8

brine to and from each hole. The warmed brine returning from each hole is chilled to a temperature of approximately -30ºC at the surface freeze plant and recirculated.

The Cigar Lake production schedule relies upon the ground being sufficiently frozen prior to the start of JBS mining.

WATER MANAGEMENT

A mine water handling strategy was developed which includes increasing the mine’s water-handling capabilities for routine and potential non-routine inflows above the existing capability previously assessed by Cameco in its 2004 environmental assessment. In addition to treating all routine water inflows (both seepage and process water) prior to releasing to the environment, water from any non-routine inflow will also be treated prior to releasing to the environment until such time as the inflow can be mitigated at the source.

As of early 2012, the installed mine dewatering capacity has been increased to 2,500 m3/h. Mine water treatment capacity has been increased to 2,550 m3/h, of which a minimum operational capacity of 1,740 m3/h is maintained at all times. Regulatory approval to discharge routine and non-routine treated water to Seru Bay is in place. See Sections 1.10, 16.2 and 20.4 for more details.

Cameco believes it has sufficient pumping, water treatment and surface storage capacity to handle the estimated maximum inflow.

The Cigar Lake orebody contains elements of concern with respect to water quality and the receiving environment. The distribution of elements such as arsenic, molybdenum, selenium and others is non-uniform throughout the orebody, and this could result in complications in attaining the effluent concentrations included in the licensing basis. Cameco continues to optimize the water treatment process to attain effluent quality consistent with the licensing basis.

Further information on mining at Cigar Lake is available in Section 16.

 

1.9	Processing

Cigar Lake ore is processed at two locations. Comminution is conducted underground at Cigar Lake, while leaching, purification and final yellowcake production and packaging occurs at the McClean Lake mill. The ore is trucked as a finely ground slurry from Cigar Lake to the McClean Lake mill in purpose-built containers identical to those used to transport McArthur River ore slurry to the Key Lake mill.

The McClean Lake mill is owned by the McClean Lake Joint Venture (MLJV) and operated by Orano Canada Inc. (Orano). The MLJV owners are:

 

•

Orano (77.5%)

 

•

Denison Mines Inc. (22.5%)

The milling arrangements are subject to the terms and conditions of a toll milling agreement made effective January 1, 2002 between the CLJV and the MLJV, and amended and restated effective November 30, 2011 (JEB Toll Milling Agreement).

In accordance with the JEB Toll Milling Agreement, the McClean Lake mill was expanded to process and package all of Cigar Lake’s mineral reserves. Originally, the mill had a production capacity of 12 million pounds U3O8 per year. In order to process all of Cigar Lake’s mineral reserves and other ores at McClean Lake, projects were identified to increase the total production capacity at the mill to 24 million pounds U3O8 per year. Construction of the expanded facility began in 2012 and was completed in 2016. Further changes were completed in 2021 to increase the capacity in the front-end circuits (leaching, CCD) from a nominal 45 kt ore/year to 59 kt ore/year.

 

2024 CIGAR LAKE TECHNICAL REPORT 9

No additional changes are required to the McClean Lake circuit to process the CLEXT mineral reserves.

During processing at McClean Lake mill, tailings are generated. The residue is treated in the upgraded McClean Lake mill tailings neutralisation circuit. Neutralised tailings are pumped to the existing TMF.

In 2022, Orano received regulatory approval for the continued expansion of the JEB TMF to allow the disposal of tailings up to a consolidated tailings elevation of 462 MASL, which is the approximate high point of the natural ground elevation. The expansion will be achieved by the continued construction of an engineered embankment and placement of the bentonite amended liner to an elevation of 468 MASL.

With these extensions, the JEB TMF will have the capacity to receive tailings from processing all of Cigar Lake’s current mineral reserves.

See Section 20.4 for a discussion of the TMF and the related licensing, and Section 19.2 for a discussion of the JEB Toll Milling Agreement. See Section 17 for information on processing at the McClean Lake mill.

 

1.10	Environmental assessment and licensing

The Cigar Lake operation has regulatory obligations to both the federal and provincial governments. Classified as a nuclear facility, primary regulatory authority resides with the federal government and its agency, the CNSC. The main regulatory agencies that issue permits / approvals and inspect the Cigar Lake operation are: the CNSC (federal), Fisheries and Oceans Canada (federal), Environment and Climate Change Canada (federal), Transport Canada (federal), Saskatchewan Ministry of Labour Relations and Workplace Safety (provincial), and Saskatchewan Ministry of Environment (provincial) (SMOE). Environment and Climate Change Canada, specifically, is responsible for administering the federal Metal and Diamond Mining Effluent Regulations (MDMER) and approves environmental effects monitoring programs required under the MDMER.

There are three key permits that are required to operate the mine. Federally, Cigar Lake holds a “Uranium Mine Licence” from the CNSC with a corresponding Licence Conditions Handbook (LCH). Provincially, Cigar Lake holds an “Approval to Operate Pollutant Control Facilities” from the SMOE and a “Water Rights Licence to Use Surface Water and Approval to Operate Works” from the Saskatchewan Water Security Agency (SWA). These documents are current.

The CNSC licence was issued for a ten-year term in June 2021, authorizing Cameco to mine, process and ship uranium ore to McClean Lake. Valid until June 30, 2031, this licence and associated LCH, authorizes an average annual production rate of 18 million pounds U3O8.

The SMOE Approval to Operate Pollutant Control Facilities was renewed in 2024 and expires on October 31, 2030. The SWA water rights licence was amended in 2023 and expires November 30, 2028. The SWA Approval to Operate Works was issued in January 2020 and is valid for an indefinite period of time.

The CNSC licence and LCH for the McClean Lake operation, issued by the CNSC in 2017, authorizes the production of up to 24 million pounds U3O8 annually. The licence and LCH were amended in 2022 to authorize the expansion of the JEB TMF. See Section 20.4 for a discussion of the TMF and related licensing.

Previous environmental assessments (EAs) completed for Cigar Lake form the basis for the current CNSC licence, LCH, and SMOE approval to operate. Approvals, issued by SMOE pursuant to the Saskatchewan Environmental Assessment Act, for Cigar Lake are based on estimated annual

 

2024 CIGAR LAKE TECHNICAL REPORT 10

production rates of 18 million pounds U3O8 for CL Main and 6 million pounds U3O8 for CLEXT. As such, it is anticipated that the planned annual production rate of 18 million pounds U3O8 for CLEXT represents a change to the approved development that will require Ministerial Approval. Cameco plans to submit the information required to obtain this approval in 2025.

A detailed history of Cigar Lake EAs is provided in Section 20.3.

 

1.11	Cigar Lake water inflow incidents and remediation

Over the period 2006 through 2008, Cigar Lake suffered setbacks as a result of three water inflows.

The first occurred in April of 2006, resulting in the flooding of the then partially completed Shaft No. 2. The two subsequent incidents involved inflows in the mine workings connected to Shaft No. 1 and resulted in flooding of the mine workings completed to that point in time.

Cameco developed and successfully executed recovery and remediation plans for all three inflows.

Through 2010 and 2011, Cameco developed a comprehensive plan and successfully proceeded with remediation to restore the underground workings at Cigar Lake.

Successful re-entry into the main mine workings was achieved in early 2010 and work to secure the mine was completed in 2011.

The mine is fully remediated, and entered commercial production in 2015. Lessons learned from the inflows have been applied to the subsequent mine plan and development in order to reduce the risk of future inflows and improve Cameco’s ability to manage water inflows. These improvements are detailed in sections throughout the report.

 

1.12	Current status of development

Construction of all major permanent underground development and process facilities required for the duration of the mine life is complete. A number of underground access drifts and production crosscuts remain to be driven as part of ongoing mine development to sustain production, most notably in the western CLEXT areas.

On surface, construction of all permanent infrastructure required to achieve nameplate capacity has been completed. As CLEXT progresses, new or expanded surface infrastructure will be required including:

 

•

access road and adjacent pipe bench construction

 

•

construction of surface freeze pads to the west and east of Cigar Lake, including runoff ponds for each pad

 

•

freeze hole drilling, outfitting, activation and ongoing operation to facilitate ongoing bulk freezing of the orebody from surface

 

•

construction of a new brine booster station and routing of additional brine supply/return and distribution piping for the freeze systems on the freeze pads

 

•

routing of other required services to support surface freeze hole drilling and ongoing freeze system operation (e.g., drill fresh water supply, runoff pond water return, electrical and instrumentation)

 

•

expansion of the waste rock crushing pad

 

•

a minor expansion of the freeze plant capacity

McClean Lake has all major permanent infrastructure in place to process the remaining Cigar Lake mineral reserves.

 

2024 CIGAR LAKE TECHNICAL REPORT 11

1.13	Production plan

The remaining mine life based on current mineral reserves will be approximately 13 years, with estimated full annual production of 18 million pounds U3O8 recovered from the mill for 11 years followed by a two-year ramp down until depletion.

The following is a general summary of the Cigar Lake production schedule, based on current remaining mineral reserves:

 

•

total mill production of 205.9 million pounds U3O8, based on an overall milling recovery of 98.7%

 

•

total remaining mine production of 554,500 tonnes of ore (excluding mineral reserves already mined)

 

•

average mill feed grade of 17.0% U3O8

 

•

remaining mine operating life of approximately 13 years

 

•

variable mining rate to achieve a constant production level of U3O8 (the average mine production varies annually from 115 to 160 tonnes per day, depending on the grade of ore being mined)

The mine and mill production schedules for Cigar Lake are shown in Figures 1-1 and 1-2, respectively.

See Section 16 for more information on the production plan.

 

2024 CIGAR LAKE TECHNICAL REPORT 12

FIGURE 1-1: MINE PRODUCTION

 

FIGURE 1-2: MILL PRODUCTION

 

 

1.14	Economic analysis and costs

The economic analysis results in an estimated pre-tax NPV (at a discount rate of 8%) to Cameco, for net cash flows from January 1, 2024 forward, of $2.5 billion for its share of the Cigar Lake mineral reserves. Using the total capital invested to date, along with the operating and capital cost estimates for the remaining mineral reserves, the pre-tax IRR has been estimated to be 8.3%.

Sensitivity analysis shows changes in uranium price and production can have a significant impact on the size of the positive NPV. On an undiscounted pre-tax basis, payback for Cameco, including

 

2024 CIGAR LAKE TECHNICAL REPORT 13

total capital invested to date, is expected to be achieved in 2024. All future capital expenditures are forecasted to be covered by operating cash flow.

The CLJV’s estimated capital cost to bring the remaining mineral reserves into production is approximately $1.2 billion and includes sustaining capital for the Cigar Lake mine and McClean Lake mill, as well as underground development at Cigar Lake.

The total capital cost estimate as of December 31, 2023 for the CLJV is discussed further in Section 21 and summarized in Table 21-1.

Operating costs for the Cigar Lake operation are estimated to be $20.58 per pound U3O8 over the remaining life of the current mineral reserves. The current operating cost projections are based on operational experience to date and assumes the throughput described in Section 1.13 and in more detail in Section 16.3.

The total operating cost estimate as of December 31, 2023 for the CLJV is discussed further in Section 21 and summarized in Table 21-2.

 

1.15	Mining and milling risks

Cigar Lake is a challenging deposit to develop and mine. These challenges include, but are not limited to, variable or unanticipated ground conditions, ground movement and cave-ins, water inflows, performance of the water treatment system, variable dilution, recovery values, mining productivity, equipment reliability and other mining-related challenges. Additionally, the realization of risks associated with processing the ore at Orano’s McClean Lake mill would adversely affect production at Cigar Lake.

Specific mining and milling risks are described in more detail in Section 24.2.

 

1.16	Conclusions and recommendations

Conclusions

The Cigar Lake operation outlined in this report represents a significant economic source of feed material for the McClean Lake mill. With an estimated remaining operating mine life of approximately 13 years, Cigar Lake is expected to produce approximately 205.9 million pounds U3O8. At the forecast average realized uranium price over this 13-year period, it is estimated that Cameco will receive substantial positive net cash flows from its share of Cigar Lake production.

Since the previous technical report was issued, the following has been achieved:

 

•

commissioned all circuits, demonstrating acceptable performance at both the mine and the mill

 

•

achieved mine production rampup to full nameplate capacity of 18 million pounds U3O8 per year and produced 138.4 million pounds U3O8 to December 31, 2023

 

•

completed JBS production from seven crosscuts excavated using the NATM technique

 

•

completed the surface drilling program for bulk ground freezing of CL Main

 

•

received 10-year Cigar Lake licence renewal from CNSC in 2021

 

•

regulatory approval for the continued expansion of Orano’s JEB TMF to allow the disposal of tailings up to a consolidated tailings elevation of 462 MASL

 

•

finalized a prefeasibility study for the CLEXT portion of the deposit, leading to a production decision and declaration of mineral reserves

 

•

increased Cameco’s ownership interest in the CLJV to 54.547% with the 2023 acquisition of a 4.522% interest from Idemitsu Canada Resources Ltd.

 

•

constructed a waste rock crushing pad to enable processing of waste rock into backfill aggregate

 

2024 CIGAR LAKE TECHNICAL REPORT 14

ECONOMIC ANALYSIS AND COSTS (100% BASIS)

Cameco’s estimated pre-tax NPV (at a discount rate of 8%) of $2.5 billion for its share of the Cigar Lake mineral reserves supports the decision to extend the mine life to 2036. Economic sensitivity to factors such as average realized price, production rates and annual costs show that the reserves present a robust economic outlook in several scenarios.

MINE PLAN

Mine design changes and refinements since 2012 achieved their objective. Application of the NATM tunnel excavation technique has proven to be effective and reliable in reducing tunnel rehabilitation requirements. Lateral mine development is largely complete at CL Main.

The ground freezing system has seen a number of improvements, including optimizing of freezing capacity, drilling patterns and freeze hole installations.

The CLEXT mine plan is largely based on the design criteria, processes and experience gained during mining of the CL Main portion of the deposit. Application of the same mining methods and techniques are expected to continue to increase the reliability of development, production and cost forecasts.

JBS MINING METHOD

Since 2012, comprehensive JBS testing and commissioning was completed to advance three JBS units to full production. This mining method has been successfully demonstrated through the mining of 572 cavities and extraction of 358,000 tonnes of ore.

MINE WATER TREATMENT

Adjustments to our circuits have been successful in reducing the amount of water requiring treatment and release and increasing the amount of water that can be recycled.

MCCLEAN LAKE MILL

The McClean Lake mill was successfully restarted in 2014, and ongoing process improvement projects have been implemented in the mill to achieve required production rates.

With Orano’s receipt of regulatory approval for the continued expansion of the JEB TMF, Cigar Lake has access to sufficient tailings capacity to allow mining of the current Cigar Lake mineral reserves.

MINERAL RESOURCES AND MINERAL RESERVES

The CL Main zone is now fully delineated and CL Main mineral reserves are largely in the proven category. Additional surface delineation drilling programs at CLEXT since 2016 were conducted in order to better define the mineral resource, gather metallurgical, hydrogeological and geotechnical information and used to support a prefeasibility study for CLEXT.

Mineral reserves in CLEXT are entirely in the probable category due to the sparser drilling density and are located in its western portion. The eastern portion of CLEXT is mostly in the inferred mineral resource category.

As of December 31st, 2023, total proven and probable mineral reserves at Cigar Lake amount to 555,600 tonnes at a grade of 17.03% U3O8 and 208.6 million pounds. Mineral resources total 132,900 tonnes at a grade of 2.65% U3O8 and 7.8 million pounds in the measured and indicated category. Inferred mineral resources total 80,500 tonnes at a grade of 2.25% U3O8 for 4.0 million pounds.

Other than the challenges related to water inflows, jet boring and geotechnical issues described in Section 15.4, there are no known issues with respect to mining, metallurgical, infrastructure,

 

2024 CIGAR LAKE TECHNICAL REPORT 15

permitting, or other relevant factors that could materially affect the mineral resource or reserve estimates.

Recommendations

The Cigar Lake operation outlined in this report represents a significant economic source of feed material for the McClean Lake mill. To realize the economic benefits from this operation and to mitigate risk, the authors of this technical report make the following recommendations:

OPERATIONAL EXCELLENCE/RELIABILITY

 

•

continue process and equipment optimization initiatives related to tooling, leveraging instrumentation and operational technology for improved cavity excavation control to increase recovery and reduce dilution

 

•

continue to advance industry best practices related to asset management to improve equipment reliability for the life of mine

 

•

investigate options for sustainable life of mine aggregate sources

 

•

continue investigation of opportunities to optimize the leach circuit at McClean Lake to manage a wider range of arsenic to uranium slurry feed ratios to reduce potential throughput limitations in leaching while also providing positive effects in downstream unit operations

 

•

continue monitoring the reliability of the arsenic block model to improve short-term forecasting

ENVIRONMENTAL PERFORMANCE

 

•

continue to monitor and review the process water balance related to effluent generation and effluent concentrations that form part of the licensing basis

 

•

investigate opportunities to reduce environmental liabilities during operations and decrease decommissioning costs associated with waste rock management

FREEZE INFRASTRUCTURE OPTIMISATION

 

•

complete trade-off studies to determine optimal capital spending on freeze projects to sustain production for the life of the mine

GEOTECHNICAL DRILLING

 

•

undertake geotechnical drilling ahead of the two main access drifts for CLEXT to allow for the collection of information to support excavation and ground support plans

MINERAL RESOURCES AND RESERVES

 

•

focus exploration efforts mainly on the relatively sparsely drilled, eastern portion of CLEXT, given the current proven and probable mineral reserve inventory, the forecast rate of production and the 13-year mine life

 

•

continue to invest in further exploration on the Waterbury Lake lands, subject to annual reviews of ongoing exploration results, to allow for the extended timelines associated with exploring, designing, permitting and developing new uranium deposits

 

2024 CIGAR LAKE TECHNICAL REPORT 16

2	Introduction

 

2.1	Introduction and purpose

The Cigar Lake Operation is a material property for Cameco under Canadian securities laws.

This technical report has been prepared for Cameco by, or under supervision of, internal qualified persons in support of disclosure of new scientific and technical information about the Cigar Lake operation as contained in Cameco’s annual Management’s Discussion and Analysis for the year ended December 31, 2023, Cameco’s Annual Information Form and 40-F for the year ended December 31, 2023, and Cameco’s press release dated February 8, 2024. This new information is the result of progress at Cigar Lake, combined with experience gained since the 2016 Technical Report.

This report has an effective date of December 31, 2023, and has been prepared in accordance with NI 43-101 by the following individuals:

 

•

Biman Bharadwaj, P. Eng., Principal Metallurgist, Technical Services, Cameco Corporation

 

•

C. Scott Bishop, P. Eng., Director, Technical Services, Cameco Corporation

 

•

Alain D. Renaud, P. Geo., Principal Resource Geologist, Technical Services, Cameco Corporation

 

•

Lloyd Rowson, P. Eng., General Manager, Cigar Lake Operation, Cameco Corporation

These individuals are the qualified persons responsible for the content of this report. All four qualified persons have visited the Cigar Lake site.

Mr. Bharadwaj has been a process engineer/metallurgist and operations manager in the mining/milling industry for over thirty years and has in-depth knowledge of the process unit operations associated with the Cigar Lake Operation and the McClean Lake Mill. Over the years Mr. Bharadwaj has been directly involved in several studies and projects related to the processing of the Cigar Lake ore and water treatment systems. Recently Mr. Bharadwaj was directly involved in the modelling of the CL Main and CLEXT outputs from a processing perspective. Mr. Bharadwaj’s last visit to both the Cigar Lake Operation and the ore slurry receiving mill were in 2016, which included an end-to-end tour of both operations.

Mr. Bishop, from October 2004 to September 2010, was the Chief Mine Engineer of the Cigar Lake project and was present at the site at least several times a month for periods extending up to seven days. Since 2010, Mr. Bishop has been directly and indirectly involved in a number of studies, projects and technical reviews of specific Cigar Lake mine design and operational practices, including the prefeasibility study of the CLEXT. Mr. Bishop’s last personal inspection of the Cigar Lake operation occurred from May 9-10, 2023, and included inspections of both the surface and underground facilities.

Mr. Renaud has been involved with the Cigar Lake Operation since 2016 and has visited the site on several occasions. Mr. Renaud’s last personal inspection of the Cigar Lake Operation occurred from March 13-15, 2023, and included a review of drilling, core handling, radiometric probing, logging, sampling facilities, sampling and data verification procedures in place. Mr. Renaud was involved with the 2023 CL Main and CLEXT mineral resource updates as well as the year-end mineral reserves and resources compilation and review.

Mr. Rowson has been continuously involved in the Cigar Lake Operation since 2012 and is regularly present on site currently overseeing all aspects of the operation as General Manager. During this time, Mr. Rowson has held various site-based leadership roles initially focused on mine development and jet boring system commissioning and operations, followed by a focus on

 

2024 CIGAR LAKE TECHNICAL REPORT 17

Technical Services including Mine Engineering, Geology and Metallurgical Engineering functions. Mr. Rowson also visits the McClean Lake Mill one to two times per year, with the most recent personal inspection occurring February 14, 2024.

 

2.2	Report basis

This report has been prepared with available internal Cameco data and information, and data and information prepared for the CLJV. Technical and certain financial information for processing Cigar Lake ore at the McClean Lake mill was provided to Cameco by Orano.

The principal technical documents and files relating to the Cigar Lake operation and the McClean Lake mill that were used in preparation of this report are listed in Section 27.

All monetary references in this technical report are expressed in Canadian dollars, unless otherwise indicated. Illustrations (Figures) in this report are from Cameco, and are dated December 31, 2023, unless otherwise specified.

Within this technical report, three different coordinate systems are used: latitudes/longitudes, Universal Transverse Mercator (UTM) coordinates and mine grid. The UTM coordinates are calculated using the latest World Geodetic System (WGS) standard WGS 84. The conversion from mine grid to UTM coordinates is as follows:

 

 

2024 CIGAR LAKE TECHNICAL REPORT 18

3	Reliance on other experts

The authors have relied, and believe they have a reasonable basis to rely, upon the following individuals who have contributed the environmental, legal and taxation information stated in this report, as noted below in Table 3-1.

TABLE 3-1: RELIANCE ON OTHER EXPERTS

 

 

2024 CIGAR LAKE TECHNICAL REPORT 19

4	Property description and location

 

4.1

Location

The Cigar Lake mine site is located near Waterbury Lake, approximately 660 kilometres north of Saskatoon, at latitude 580 04’ 14” north and longitude 1040 32’ 18” west, and about 40 kilometres inside the eastern margin of the Athabasca Basin region in northern Saskatchewan.

See Figure 4-1.

The mine site is in close proximity to two uranium milling operations: McClean Lake is 69 kilometres northeast by road and Rabbit Lake is 87 kilometres east by road. The McArthur River mine is 46 kilometres southwest by air from the mine site.

 

2024 CIGAR LAKE TECHNICAL REPORT 20

FIGURE 4-1: CIGAR LAKE MINERAL PROPERTY LOCATION

 

 

4.2	Mineral tenure

 

•

One mineral lease: ML 5521

 

•

38 mineral claims. See Table 4-1

 

•

Total contiguous area: 95,601 hectares

 

2024 CIGAR LAKE TECHNICAL REPORT 21

The Cigar Lake deposit is located in the area subject to the mineral lease, totaling 308 hectares. The right to mine this deposit was granted by the Province of Saskatchewan under the Crown Minerals Act (Saskatchewan) through the mineral lease, effective December 1, 2001. The term of the current mineral lease is for 10 years and expires on November 30, 2031, but is subject to a right to renew for successive ten-year terms, absent a default by the CLJV. The Province of Saskatchewan may only terminate the lease if the CLJV breaches a provision of the lease or fails to satisfy any of its obligations under The Crown Minerals Act (Saskatchewan) or associated regulations, or in the event that any prescribed environmental concerns arise.

Adjoining the mineral lease, there are 38 mineral claims which were also granted by the Province of Saskatchewan under The Crown Minerals Act (Saskatchewan), totaling 95,293 hectares. These mineral claims grant the CLJV the right to explore for minerals within the claim lands, and to convert a mineral claim into a mineral lease if the CLJV remains in good standing. Surface exploration work of a mineral claim requires additional government approval.

There is an annual requirement of $2.4 million, either in work or cash, to retain title to the 38 mineral claims. Based on previous work submitted and approved by the Province of Saskatchewan, title is secured until 2037 or later. The mineral lease has a yearly rental payment of $3,080.00.

Under the Cigar Lake Joint Venture Agreement and related agreements, made effective January 1, 2002 and as amended on November 30, 2011 (CLJV Agreement), the mineral lease and the 38 mineral claims noted above were divided into the Cigar Lake lands, consisting of ML 5521 and claim S-106558, and the Waterbury Lake lands, consisting of the remaining 38 claims. Orano is the operator of the Waterbury Lake lands and is also contract exploration operator of the Cigar Lake lands other than the area on ML 5521 from which the mineral reserves are being mined. Cameco has been the mine operator for the Cigar Lake lands with respect to ML 5521 since 2002.

Figure 4-2 shows the Cigar Lake mineral lease and mineral claims as currently registered with the Province of Saskatchewan.

 

2024 CIGAR LAKE TECHNICAL REPORT 22

FIGURE 4-2: MINERAL LEASE AND MINERAL CLAIMS

 

 

2024 CIGAR LAKE TECHNICAL REPORT 23

TABLE 4-1: CIGAR LAKE OPERATION - MINERAL CLAIMS STATUS

 

Lease/Claim		Record Date				Area				Annual				Next Payment
ML 5521 (Lease)			1981-Dec-01				308				Yearly Rent				2024-Dec-01
MC00012765			2019-Mar-27				2,533			$	38,007				2042-Mar-28
S-106541			1975-Dec-16				4,270			$	106,750				2043-Dec-16
S-106542			1975-Dec-16				3,039			$	75,975				2037-Dec-16
S-106543			1975-Dec-16				4,316			$	107,900				2041-Dec-16
S-106545			1975-Dec-16				4,410			$	110,250				2041-Dec-16
S-106546			1975-Dec-16				4,334			$	108,350				2042-Dec-16
S-106547			1975-Dec-16				2,550			$	63,750				2043-Dec-16
S-106556			1975-Dec-16				635			$	15,875				2042-Dec-16
S-106557			1975-Dec-16				935			$	23,375				2042-Dec-16
S-106558			1975-Dec-16				1,872			$	46,800				2042-Dec-16
S-106559			1975-Dec-16				2,210			$	55,250				2042-Dec-16
S-106560			1975-Dec-16				4,742			$	118,550				2042-Dec-16
S-106561			1975-Dec-16				3,150			$	78,750				2042-Dec-16
S-106562			1975-Dec-16				4,175			$	104,375				2041-Dec-16
S-106563			1975-Dec-16				4,149			$	103,725				2042-Dec-16
S-106564			1975-Dec-16				3,945			$	98,625				2041-Dec-16
S-113756			1975-Dec-16				1,900			$	47,510				2043-Dec-16
S-113757			1975-Dec-16				2,223			$	55,568				2042-Dec-16
S-113758			1975-Dec-16				1,484			$	37,108				2042-Dec-16
S-113759			1975-Dec-16				823			$	20,565				2041-Dec-16
S-113760			1975-Dec-16				2,076			$	51,910				2042-Dec-16
S-113761			1975-Dec-16				1,523			$	38,081				2042-Dec-16
S-113762			1975-Dec-16				1,510			$	37,740				2042-Dec-16
S-113763			1975-Dec-16				1,489			$	37,213				2042-Dec-16
S-113764			1975-Dec-16				2,273			$	56,826				2042-Dec-16
S-113765			1975-Dec-16				2,268			$	56,710				2042-Dec-16
S-113766			1975-Dec-16				2,290			$	57,262				2042-Dec-16
S-113767			1975-Dec-16				2,192			$	54,792				2042-Dec-16
S-113768			1975-Dec-16				1,244			$	31,095				2043-Dec-16
S-113769			1975-Dec-16				3,232			$	80,799				2042-Dec-16
S-113770			1975-Dec-16				2,111			$	52,764				2043-Dec-16
S-113771			1975-Dec-16				2,021			$	50,532				2042-Dec-16
S-113772			1975-Dec-16				1,028			$	25,696				2043-Dec-16
S-113773			1975-Dec-16				3,405			$	85,131				2042-Dec-16
S-113774			1975-Dec-16				1,047			$	26,175				2043-Dec-16
S-113775			1975-Dec-16				3,647			$	91,178				2042-Dec-16
S-113776			1975-Dec-16				918			$	22,946				2043-Dec-16
S-113777			1975-Dec-16				3,323			$	83,075				2040-Dec-16

 

2024 CIGAR LAKE TECHNICAL REPORT 24

4.3	Surface tenure

 

•

Total area: 715 hectares of Crown land

 

•

Covers a portion of ML 5521, along with portions of claims S-106556 to 106560, inclusive

Figure 4-3 shows the outline of the surface lease in relation to the mineral lease and mineral claims

FIGURE 4-3: SURFACE LEASE, MINERAL LEASE AND MINERAL CLAIMS

 

 

2024 CIGAR LAKE TECHNICAL REPORT 25

The surface facilities and mine shafts for the Cigar Lake mine are located on lands owned by the Province of Saskatchewan. The CLJV owners acquired the right to use and occupy these lands for the purpose of developing and mining the Cigar Lake deposit under a surface lease agreement with the Province of Saskatchewan. The surface lease was amended April 1, 2023 and expires May 31, 2044.

The Province of Saskatchewan uses surface leases as a mechanism to achieve certain environmental protection and socio-economic objectives. As a result, the Cigar Lake surface lease contains certain undertakings from the CLJV in that regard, including annual reporting on the status of the environment, land development and progress on northern Saskatchewan employment and business development.

Figure 4-4 shows the general site arrangement with the outline of the surface lease.

In 2023, annual rent was approximately $390,000 for the surface lease, together with taxes of approximately $4,635,000 in respect thereof.

 

2024 CIGAR LAKE TECHNICAL REPORT 26

FIGURE 4-4: MAP OF MINE FACILITIES AND SURFACE LEASE BOUNDARY

 

 

2024 CIGAR LAKE TECHNICAL REPORT 27

4.4

Royalties

For a discussion of royalties, see Section 22.6.

 

4.5	Known environmental liabilities

For a discussion of known environmental liabilities, see Section 20.6.

 

4.6	Permitting

For a discussion of permitting, see Section 20.2.

 

2024 CIGAR LAKE TECHNICAL REPORT 28

5	Accessibility, climate, local resources, infrastructure and physiography

 

5.1

Access

The property is accessible by an all-weather road and by air. Supplies are transported by truck and can be shipped from anywhere in North America through Cameco’s transit warehouse in Saskatoon. Trucks travel north from Saskatoon on a paved provincial road through Prince Albert and La Ronge and further north along the gravel surfaced Provincial Road 905, and finally to the mine site via a 52-kilometre long two-lane gravel road. The latter section is accessible to the public from the intersection with Provincial Road 905 to the access gate near the Cigar Lake airstrip, situated approximately six kilometres from the mine site. Ore is shipped from Cigar Lake to McClean Lake by truck year-round. Yellowcake is shipped from the McClean Lake mill by truck to Saskatoon. Figure 5-1 shows the regional location of the Cigar Lake site and local roads.

An unpaved airstrip is located east of the mine site, allowing flights to and from the Cigar Lake property.

 

2024 CIGAR LAKE TECHNICAL REPORT 29

FIGURE 5-1: CIGAR LAKE SITE - REGIONAL LOCATION AND ROADS

 

 

2024 CIGAR LAKE TECHNICAL REPORT 30

5.2

Climate

The climate is typical of the continental sub-arctic region of northern Saskatchewan. Summers are short and rather cool, even though daily temperatures can reach above 30°C on occasion. Mean daily maximum temperatures of the warmest months are around 20°C and only three months on average have mean daily temperature of 10°C or more. The winters are cold and dry with mean daily temperature for the coldest month below -20°C. Winter daily temperatures can reach below -40°C on occasion.

Freezing of surrounding lakes, in most years, begins in November and breakup occurs around the middle of May. The average frost-free period is approximately 90 days.

Average annual total precipitation for the region is approximately 450 millimetres, of which 70% falls as rain, more than half occurring from June to September. Snow may occur in all months but rarely falls in July or August. The prevailing annual wind direction is from the west with a mean speed of 12 kilometres per hour.

Site operations are carried out year-round, despite cold winter conditions. The fresh air necessary to ventilate the underground working areas is heated during winter months using propane-fired burners.

 

5.3	Physiography

The topography and vegetation at the Cigar Lake property are typical of the taiga forested lands common to the Athabasca Basin area of northern Saskatchewan. The area is covered with between 30 and 50 metres of overburden. The terrain is gently rolling and characterized by forested sand and dunes. Vegetation is dominated by black spruce and jack pine. Occasional small stands of white birches may occur in more productive and well-drained areas. Lowlands are generally well drained but can also contain some muskeg and poorly drained bog areas, with vegetation varying from wet, open non-treed vistas to variable density stands of primarily black spruce and tamarack, depending on moisture and soil conditions. Productive lichen growth is common to this boreal landscape, mostly associated with mature coniferous stands and treed bogs.

The mine site elevation is approximately 490 metres above sea level and Waterbury Lake is approximately 455 metres above sea level. The body of water known as Cigar Lake which, in part, overlays the deposit, is approximately 464 metres above sea level.

 

5.4	Local resources

The closest inhabited site is Points North Landing, 56 kilometres northeast by road from the Cigar Lake mine site, close to where the site access road connects to Provincial Road 905. The community of Wollaston Lake is approximately 80 kilometres by air east of the Cigar Lake site.

The Cigar Lake site is in close proximity to two other uranium milling operations: Orano’s McClean Lake operation is approximately 69 kilometres northeast by road, and Cameco’s Rabbit Lake operation is approximately 87 kilometres east by road.

Athabasca Basin community resident employees and contractors fly from various pick-up points to the mine site. Southern resident employees and contractors fly to site from Saskatoon with stop-over pick-up points in Prince Albert and La Ronge. Most employees and contractors are on a two-week-in and two-week-off schedule. Personnel are recruited on a preferential basis from northern Saskatchewan.

Site activities, such as mine development and construction work, are tendered to several northern owned or joint venture contractors, and major contractors that can hire qualified personnel from the major mining regions across Saskatchewan and Canada.

 

2024 CIGAR LAKE TECHNICAL REPORT 31

The Cigar Lake site is linked by road and by air to the rest of the province of Saskatchewan, facilitating easy access to any population centre for purchasing of goods at competitive prices. Saskatoon is a major population centre some 660 kilometres south of the Cigar Lake operation, with highway, rail and air links to the rest of North America.

 

5.5	Mine and infrastructure

Cigar Lake is a developed producing property with sufficient surface rights to meet its current mining operation needs. The Cigar Lake mine site contains all the necessary services and facilities to operate a remote underground mine, including personnel accommodation, access to water, airport, site roads and other necessary buildings and infrastructure.

SITE FACILITIES

 

•

an underground mine with two shafts

 

•

access road joining the provincial highway and McClean Lake

 

•

site roads and site grading

 

•

airstrip and terminal

 

•

employee residence and construction camp

 

•

Shaft No. 1 and No. 2 surface facilities

 

•

freeze plants and brine distribution equipment

 

•

surface freeze pads

 

•

water supply, storage and distribution for industrial water, potable water and fire suppression

 

•

propane, diesel and gasoline storage and distribution

 

•

electrical power substation and distribution

 

•

emergency power generating facilities

 

•

compressed air supply and distribution

 

•

mine water storage ponds and water treatment

 

•

sewage collection and treatment

 

•

surface and underground pumping system installation

 

•

surface runoff containment infrastructure

 

•

waste rock stockpiles and aggregate processing infrastructure

 

•

garbage disposal landfill

 

•

administration, maintenance and warehousing facilities

 

•

ore load out facility

 

•

concrete batch plant

 

•

Seru Bay treated water effluent pipeline

Water and electricity

The Cigar Lake mine site has access to sufficient water from nearby Waterbury Lake for all planned industrial and residential activities. The site is connected to the provincial electricity grid with a 138-kilovolt overhead power line, and there are standby generators in case of power outages.

Tailings and waste

No tailings are stored at the Cigar Lake site since all ore mined is transported to Orano’s McClean Lake mill for processing. The processing facility at the McClean Lake site is discussed in Section 17, and the TMF is discussed in Sections 20.2 and 20.4.

 

2024 CIGAR LAKE TECHNICAL REPORT 32

Waste rock piles from the excavation of the two shafts and all underground development are confined to a small footprint within the surface lease. The waste piles have been segregated into three types depending on the nature of the waste rock: The first is clean waste, which will remain at the mine site. The second is mineralized waste (>0.03% U3O8) contained on a lined pad, which is planned to be disposed of underground at the Cigar Lake mine. The third is potentially acid generating (PAG) waste rock, which will be temporarily stored at site on lined pads and will be transported to the Sue C pit at the McClean Lake facility for permanent disposal. Waste rock management is further discussed in Section 20.4.

A site plan of the existing and planned surface facilities is shown in Figure 5-2. A description of planned infrastructure for Cigar Lake can be found in Section 18.1.

 

2024 CIGAR LAKE TECHNICAL REPORT 33

FIGURE 5-2: SITE PLAN OF EXISTING AND PLANNED SURFACE FACILITIES

 

 

2024 CIGAR LAKE TECHNICAL REPORT 34

6

History

 

6.1

Ownership

There have been numerous changes in ownership of participating interests in the joint venture that governs Cigar Lake, the most recent of which occurred in 2022. The current owners and their participating interests in the CLJV are as follows:

 

•

Cameco (54.547%)

 

•

Orano (40.453%)

 

•

TEPCO (5.000%)

1976

 

•

Original joint venture established between Canadian Kelvin Resources Ltd. and Asamera Oil Corporation Ltd (Asamera) to explore the Keefe Lake area

 

•

Operator: Asamera

1977

 

•

Saskatchewan Mining Development Corporation (SMDC) acquires 50% interest

1979

 

•

Keefe Lake Joint Venture divides the Keefe Lake area into three separate project areas of Dawn Lake, McArthur River and Waterbury Lake (which includes a portion of the lands now known as Cigar Lake)

1980

 

•

Joint venture agreement entered to govern exploration of the Waterbury Lake area

 

•

Operator: SERU (predecessor to Cogema Canada Ltd. (Cogema))

1985

 

•

Waterbury Lake Joint Venture Agreement terminated and replaced by a new joint venture agreement, which divided the Waterbury Lake area into the Waterbury Lake lands and the Cigar Lake lands

 

•

Participating interests: SMDC (50.75%), Cogema (32.625%), Idemitsu (12.875%), Corona Grande Exploration Corporation (3.75%)

 

•

Operator (Waterbury Lake lands): Cogema

 

•

Operator (Cigar Lake lands): Cigar Lake Mining Corporation (CLMC)

1988

 

•

Eldorado Resources Limited and SMDC merge to form Cameco

2002

 

•

Cigar Lake reorganization takes place, and three agreements are entered into:

 

•

CLJV established to govern further exploration, development and production from the Waterbury Lake lands and the Cigar Lake lands

 

•

Joint venture owners: Cameco (50.025%), AREVA (37.1%), Idemitsu (7.875%), TEPCO (5%)

 

•

Operator (Waterbury Lake lands, includes claims No. S-106540 to 106557 and 106559 to 106564): AREVA

 

2024 CIGAR LAKE TECHNICAL REPORT 35

•

Mine Operating Agreement established as part of reorganization, which engages Cameco as mine operator for the Cigar Lake mine property (which includes ML 5521, the Cigar Lake surface lease and the mine)

 

•

Contract Exploration Agreement established, which engages AREVA (now Orano) as contract exploration operator to operate the Cigar Lake exploration property (Claim No. 106558 as well as the area of ML 5521 from which mineral reserves are not mined)

2022

 

•

In May, Cameco and Orano reach agreement with Idemitsu to acquire its 7.875% participating interest in the CLJV, increasing Cameco’s ownership stake to 54.547%

 

6.2	Exploration and development history

1970s

 

•

Asamera (operator of the Keefe Lake Joint venture) conducts exploration work:

 

•

Lake sediment and water geochemistry, airborne magnetic and Input (Questor) surveys, airborne radiometric and VLF (Geoterrex) surveys, gravimetric (Kenting) and seismic surveys

 

•

After the division of the Keefe Lake area into three separate projects, Cogema, (operator of the Waterbury joint venture) revisits all field survey results and conducts complementary exploration work:

 

•

Lake-bottom sediment geochemistry and airborne high resolution magnetic (Geoterrex) surveys, regional geology photointerpretation as well as outcrop and overburden mapping and sampling activities conducted across the mineral property

 

•

Ground geophysical surveys allowed depth and conductivity evaluation of geological formations using electromagnetic frequency (Geoprobe EMR-16) and time (Crone DEEPEM) methods

1980s

 

•

Definition drilling programs conducted throughout the 1980s

 

•

1980 – 81: during the winter months, detailed DEEPEM work activity intensifies, targeting several Waterbury Lake zones with conductor structures previously identified, which are systematically drilled

 

•

May 9, 1981: high-grade mineralized core is recovered from hole WQS2-015, which was the last hole planned to be drilled for the winter program

 

•

October 21, 1987: test mine proposal to assess conditions and to field test new mining methods approved

 

•

1987 – 1992: test mining, including the sinking of Shaft No. 1 to a depth of 500 metres and lateral development on three levels takes place

1990s

 

•

September 1992: Government Environmental Review Panel guidelines are issued for the Cigar Lake project by the Joint Federal-Provincial Panel (the Panel) on Uranium Mining Developments in Northern Saskatchewan. Later the same year, consulting firms are hired to perform engineering studies and, at the same time, metallurgical and environmental testing programs are launched

 

•

1993: mine site activities are placed on a care and maintenance basis and initial engineering studies for development and operation of the property based on the jet boring mining method

 

2024 CIGAR LAKE TECHNICAL REPORT 36

are started. These and other engineering studies are completed between 1993 and 1996. Several additions and improvements to site infrastructure are also performed

 

•

1997: detailed engineering studies are undertaken for the purpose of developing a feasibility study of the mining project. In addition, testing of a specially designed tunnel boring machine with capability to install a high-strength concrete liner (or mine development system) is conducted. In conjunction with this work, significant mine development is also carried out

 

•

1998: after an environmental review, carried out from 1996 to 1997, the Panel issues recommendations to the federal and provincial governments and the CLJV that the project proceed to the next stage of licensing. In April 1998, both governments respond favourably to the recommendations

 

•

1999: the specially designed jetting tools for the jet boring machine are successfully tested within a three-metre diameter culvert lined raise, filled with simulated ore

2000s

 

•

2000: activities at the mine site are focused on the testing of several tools and systems forming the basis of the future mining method, and the jet boring system is successfully tested in waste and frozen ore

 

•

December of 2000: the mine site is again placed on a care and maintenance basis

 

•

May 2001: feasibility study is completed, targeting peak annual production of 18 million pounds U3O8 for CL Main

 

•

2002: Cameco becomes mine operator

 

•

December 2004: the CLJV approves development of Cigar Lake and construction of the project begins in January 2005

 

•

2006: Two water inflow incidents delay development. Work to remediate the underground development areas begins but is interrupted by another inflow in 2008

2010s

 

•

2010: Complete dewatering of underground development areas and backfilling of the 465-metre level. Underground development in the south end of the mine resumes

 

•

2011: Regulatory approval of mine plan is received

 

•

2013: Jet boring in ore begins and first Cigar Lake ore is shipped to McClean Lake mill for processing into uranium concentrate

 

•

2015: Commercial production is declared

 

•

Definition drilling programs conducted at CLEXT

2020s

 

•

2020: Temporary production suspensions implemented in March as a precautionary measure due to the COVID-19 pandemic. Production resumes in September. Production is again temporarily suspended in December

 

•

2021: Announced plans to restart production in April 2021

 

•

2022: Announced plans to reduce production to 13.5 million pounds per year (100% basis) starting in 2024. Acquired additional 4.522 percentage points in Cigar Lake, increasing Cameco’s interest to 54.547%. Completion of prefeasibility study for CLEXT

 

•

2023: Surface freeze drilling at CL Main completed. Production plan updated to maintain 18 million pounds per year (100% basis) in 2024

 

2024 CIGAR LAKE TECHNICAL REPORT 37

6.3	Historical mineral resource and mineral reserve estimates

There are no historical estimates within the meaning of NI 43-101 to report.

 

6.4	Historical production

Historical mine production from the Cigar Lake deposit was initially from test mining in ore conducted during three separate test mining programs:

 

•

boxhole boring of two cavities in 1991

 

•

jet boring tests No. 1, 2 and 3 in 1992

 

•

jet boring industrial tests in 2000: four cavities in waste and four cavities in ore

The mineralized material from the historical production tests, amounting to 767 tonnes at 17.4% U3O8, was sent to the McClean Lake mill and processed.

Cigar Lake mine production by the jet boring method and McClean Lake mill production from Cigar Lake to year-end 2023 is shown in Table 6-1 below.

TABLE 6-1: CIGAR LAKE HISTORICAL PRODUCTION (100% BASIS)

 

		Mine Production												McClean Lake Packaged Production
Year		Total tonnes (x 1,000)				Grade % U3O8				M lbs U3O8				M lbs U3O8
2013-2014			3.3				7.16				0.5				0.3
2015			30.3				20.03				13.4				11.3
2016			37.3				21.56				17.7				17.3
2017			36.5				22.24				17.9				18.0
2018			43.1				19.00				18.0				18.0
2019			46.1				17.86				18.1				18.0
2020			24.6				17.34				9.4				10.1
2021			34.3				16.60				12.5				12.2
2022			53.7				15.76				18.7				18.0
2023			48.8				14.09				15.2				15.1

 

2024 CIGAR LAKE TECHNICAL REPORT 38

7	Geological setting and mineralization

 

7.1	Regional geology

The Cigar Lake uranium deposit is located approximately 40 kilometres west of the eastern margin of the Athabasca Basin of northern Saskatchewan (Figure 7-1). Like other major uranium deposits of the basin, it is located at the unconformity contact separating late Paleoproterozoic to Mesoproterozoic sandstone of the Athabasca Group from middle Paleoproterozoic metasedimentary gneiss and plutonic rocks of the Wollaston Group.

The Athabasca Group appears largely undeformed and its maximum preserved thickness is about 1,500 metres. The Manitou Falls (MF) Formation, within the Athabasca Group, was deposited in an intra-continental sedimentary basin that was filled by fluviatile terrestrial quartz sandstone and conglomerate. On the eastern side of the basin, the sandstone units of the MF Formation, and the Wollaston Group metasedimentary gneiss that unconformably lie immediately beneath them, host most of the uranium mineralization. This sandstone which overlies the basement rock contains large volumes of water at significant pressure.

The Lower Pelitic unit of the Wollaston Group, which lies directly on the Archean granitoid basement, is considered to be the most favourable unit for uranium mineralization. During the Hudsonian orogeny (1800 – 1900 million years), the group underwent polyphase deformation and upper amphibolite facies metamorphism, with local greenschist facies retrograde metamorphism. The Hudsonian orogeny was followed by a long period of erosion and weathering along with the development of a paleoweathering profile that is locally preserved at, and beneath, the unconformity.

 

7.2	Local geology

In the Cigar Lake area, the MF Formation is 420 to 445 metres thick and corresponds to members MFd, MFc, and MFb. The MFb member hosts the Cigar Lake deposit, which is positioned atop an east-west trending 20-metre basement high. Overburden in the project area ranges up to a thickness of 50 metres.

Two major lithostructural domains are present in the metamorphic basement of the larger Waterbury/Cigar Lake property. These are as follows (Figure 7-1):

 

•

Wollaston Domain: a southern area composed mainly of metasedimentary gneiss overlying Archean granitoids, with an overall northeast-trending structural orientation

 

•

Mudjatik Domain: a northern area with large Archean granitoid domes and lesser inliers of metasedimentary gneiss with a dome and basin structural morphology

 

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FIGURE 7-1: GEOLOGICAL MAP OF NORTHERN SASKATCHEWAN

 

The Cigar Lake east-trending psammopelitic to pelitic unit, which underlies the deposit, is located in the transitional zone between the two basement domains. The metamorphic basement rocks in this unit consist mainly of biotite, graphite and lesser amounts of calc-silicate paragneisses, which are inferred to be part of the Wollaston Group’s Lower Pelitic sequence. Graphite and pyrite-rich

 

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“augen gneiss”, an unusual facies within the graphitic pelite gneiss, occurs primarily below the Cigar Lake deposit (Figure 7-2).

The mineralogy and geochemistry of the graphitic gneiss suggest that they were originally carbonaceous shales. The abundance of magnesium in the intercalated carbonate layers indicates an evaporitic origin.

The structural framework in the Cigar Lake mine area is dominated by large northeast-trending lineaments and wide east-trending mylonitic corridors. The unconformable contact between these mylonites, which contain the augen gneiss, and the overlying Athabasca sandstone, are considered to be the most favourable features for the concentration of uranium mineralization, specifically where graphitic basement fault zones were locally reactivated as brittle faults after sandstone deposition.

 

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FIGURE 7-2: CIGAR LAKE - REGIONAL BASEMENT GEOLOGY

 

 

7.3	Property geology

The Cigar Lake uranium deposit, which has no direct surface expression, is located at the unconformity between the middle Paleoproterozoic Wollaston Group metasediments and the late Paleoproterozoic to Mesoproterozoic Athabasca Group, between 410 and 450 metres below surface. It has the shape of a flat, elongated lens, approximately 1,950 metres in total length, 25 to 100 metres in width, and ranges up to 15.7 metres thick, with an average thickness of about

 

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5.4 metres. It shows longitudinal and lateral geological continuity. It has a crescent-shaped cross-sectional outline that closely reflects the topography of the unconformity. The deposit is subdivided into the eastern CL Main and the western CLEXT zones. CL Main is further divided into the East and West Pods.

The deposit and host rocks consist of three principal geological and geotechnical elements:

 

•

the deposit itself

 

•

the overlying sandstone

 

•

the underlying metamorphic basement rocks

The MF Formation is 420 to 445 metres thick. The basement lithological domains consist of:

 

•

a variably graphitic pelite unit located directly below the deposit

 

•

a biotite pelite unit located to the south of the deposit area within which most of the mine access infrastructure is located

 

•

a minor calc-silicate rich unit located near the boundary between the graphitic and biotite pelites

The graphitic pelite unit has been further divided into two sub-domains, including a graphite and sulphide-rich portion located directly below the uranium mineralization that has undergone variable and locally significant shear deformation, and a lesser graphite-rich portion that contains significantly less sulphides and shows less shear deformation. Figures 7-3 and 7-4 depict the basement lithological domains in the immediate vicinity of the CL Main and CLEXT mineralization.

The structural framework in the Cigar Lake area is dominated by an east-west trending protomylonitic zone containing numerous steeply dipping, east-striking fault zones. Directly below the ore zone, these east-striking faults consist of graphitic breccia zones that are up to several metres wide and largely coincide with the 20-metre basement high, along which the uranium mineralization is located. This area of east-striking faults generally controls the most extensive clay alteration observed within the Cigar Lake area, both at the mineralized horizon and down to the 500L.

The deposit is surrounded by a strong alteration halo affecting both sandstone and basement rocks, characterized by extensive development of Mg-Al rich clay minerals (illite-chlorite). This alteration halo in the sandstone is centred on the deposit and reaches up to 200 metres in width and 250 metres in height, tapering with elevation. In the basement rocks, this zone extends in the range of 200 metres in width and as much as 100 metres in depth below the deposit. The mineralization is hosted principally by the Athabasca Group and consists mainly of uraninite and pitchblende along with nickel and cobalt arsenides (Bruneton, 1983).

Figure 7-5 shows a schematic geological cross-section of the CL Main deposit that illustrates the shape of the deposit, fault structures, the main fracture zone and the clay alteration halo in the sandstone and the basement rocks.

 

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FIGURE 7-3: BASEMENT GEOLOGY OF THE CL MAIN AREA RELATIVE TO MINERALIZATION

 

 

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FIGURE 7-4: BASEMENT GEOLOGY OF THE CLEXT AREA RELATIVE TO MINERALIZATION

 

 

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FIGURE 7-5: CL MAIN DEPOSIT - SCHEMATIC CROSS SECTION LOOKING WEST

 

 

7.4	Mineralization

Two distinct styles of mineralization occur within the Cigar Lake deposit (Figure 7-5):

 

•

high-grade mineralization at or proximal to the unconformity (“unconformity” mineralization), which includes all of the mineral resources and mineral reserves

 

•

low-grade, fracture controlled, vein-like mineralization which is located either higher up in the sandstone (“perched” mineralization) or in the basement rock mass

The high-grade mineralization located in proximity to the unconformity contains the bulk of the total uranium metal in the deposit and currently represents the only economically viable style of mineralization, in the context of the selected mining method and ground conditions. It is characterized by the occurrence of massive clays and very high-grade uranium concentrations.

The unconformity mineralization consists primarily of three dominant rock and mineral facies occurring in varying proportions. These are quartz, clay (primarily chlorite with lesser illite) and metallic minerals (oxides, arsenides, sulphides). In the relatively higher grade eastern CL Main zone, the ore consists of approximately 50% clay matrix, 20% quartz and 30% metallic minerals, visually estimated by volume. In this area, the unconformity mineralization is overlain by a weakly

 

2024 CIGAR LAKE TECHNICAL REPORT 46

mineralized contiguous clay cap 1 to 10 metres thick. In the western CLEXT zone, the proportion changes to approximately 20% clay, 60% quartz and 20% metallic minerals.

While pre- and post-mineralization faulting played major roles in creating preferential pathways for uranium-bearing fluids and, to some extent, in remobilizing uranium, the internal distribution of uranium within the unconformity mineralization has likely been largely controlled by geochemical processes. This is reflected in the continuity and homogeneity of the mineralization and its geometry, particularly in the eastern part of the deposit. A very sharp demarcation exists between well mineralized and weakly mineralized rocks, both at the upper and particularly at the lower surface of the deposit.

Uranium oxide in the form of uraninite and pitchblende occurs in both a sooty form and as botryoidal, metallic masses. It occurs as disseminated grains in aggregates ranging in size from millimetres to decimetres, and as massive metallic lenses up to a few metres thick in a matrix of sandstone and clay. Coffinite (uranium silicate) is estimated to form less than 3% of the total uranium mineralization. The mineralized rock is variably black, red and/or green in colour.

Uranium grades of the unconformity mineralization range up to 86% U3O8 for a 0.5 metre interval from a drillhole intersection within the mining area. Geochemically, the deposit contains quantities of the elements nickel, copper, cobalt, lead, zinc, molybdenum, arsenic and rare earth elements, but in non-economic concentrations. Higher concentrations of these elements are associated with massive pitchblende or massive sections of arseno-sulphides. Primary age of the unconformity mineralization has been estimated at 1.3 billion years.

The deposit has been subjected to faulting after its formation, which has contributed to the formation of vein-type mineralization that has been termed “perched” within the sandstone and vein-type mineralization within the basement. These mineralized bodies form, volumetrically, a very small part of the total mineralized rock and are currently of no economic significance.

 

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8	Deposit types

Cigar Lake is an unconformity-related uranium deposit. Deposits of this type are believed to have formed through an oxidation-reduction reaction at a contact where oxygenated fluids meet with reducing fluids. That contact broadly coincides with the unconformity surface. The Cigar Lake deposit occurs at the unconformity contact between rock of the Athabasca Group and underlying Wollaston Group, an analogous setting to the Key Lake, McClean Lake, Collins Bay and McArthur River deposits. It shares many similarities with these deposits, including general structural setting, mineralogy, geochemistry, host rock association and the age of the mineralization; however, it is distinguished by its flat-lying geometry, size, the intensity of its alteration process, the high degree of associated hydrothermal clay alteration and the presence of massive, extremely rich, high-grade uranium mineralization.

The Cigar Lake deposit is similar to the McArthur River deposit in that the sandstone that overlies the basement rock contains large volumes of water at significant pressure. Unlike McArthur River, however, this deposit is flat-lying with the ore zone being overlain by variably developed clay alteration as opposed to silica enrichment.

 

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9	Exploration

The Cigar Lake deposit is located within ML 5521, which is surrounded by 38 mineral claims. Orano is responsible for all exploration activity on these claims, as per the CLJV agreements. Section 9.1 is a synopsis of exploration activities on the 38 mineral claims. For the purpose of the discussion in that section, the 38 mineral claims are called the Waterbury Lake lands. Section 9.2 is a summary discussion of geophysical programs that have been conducted by Cameco on behalf of the CLJV within ML 5521 since the October 2006 water inflow.

Drilling activity is described in Section 10.

 

9.1	ORANO 1980 – present

From 1980 to 1986, SERU (which became Cogema in 1984, AREVA in 2006 and subsequently Orano in 2018) completed various airborne and ground geophysical programs, lake sediment and water sampling programs and substantial diamond drilling. The Cigar Lake uranium deposit was discovered in 1981, on lands now covered by ML 5521, by a regional program of diamond drill testing of geophysical anomalies (electromagnetic conductors) located by airborne and ground geophysical surveys.

All exploration activities ceased after the 1986 field season for a period of 12 years until work on the Waterbury Lake lands recommenced in 1999. After initially focusing upon data compilation and a review of all work conducted to date, new exploration has focused upon developing further understanding of the Cigar trend, and developing knowledge of the large, unexplored parts of the project. Concurrent with this new work, a program of reboxing, relogging and sampling of historical exploration drillholes was undertaken to develop a further understanding of the Cigar Lake mineralization, alteration processes and structural setting to aid with near-mine and greenfields exploration on the project.

Electromagnetic (EM) and resistivity surveys have been used as the primary exploration geophysical tools with a variety of surveys conducted. EM surveys starting with an airborne GEOTEM survey in 1999 have consisted of Moving Loop UTEM, Fixed Loop TEM, moving loop transient electromagnetic induction coil (ML-TEM), and Moving Loop SQUID transient EM. ML-SQUID TEM has been the dominant EM survey type since 2011. Dipole-Pole-Dipole DC resistivity is heavily used on the Power Line grid, as EM is not possible with the presence of the high voltage transmission line. Pseudo 3D resistivity surveys were completed along a portion of the Cigar trend and the Kelly Bay grid, with limited success.

Ground geophysics has been completed on a number of grids and has produced drill-ready targets. These areas include Cigar East, Cigar West, Cigar Southwest, Contact Conductor, Powerline East, Powerline Central, Powerline West, Tucker East, Waterbury Central, Waterbury North and Waterfound grid areas. The 2019 VTEM survey helped to identify areas for future ground geophysical work, to infill existing coverage, modernize existing data sets, or in some cases, as a first pass ground survey. Areas identified for future ground geophysical work include Tucker East, Andrew Lake, Kelly Bay, Johnston East, Waterbury Central, Waterbury North and the Johnston North grid areas.

Numerous spectral clay and geochemistry sampling, core reviews and core box replacement programs have been completed throughout the history of the project. These have included both reconnaissance exploration drill holes and numerous drill fences through the Cigar Lake orebody.

A property-wide boulder lithogeochemistry survey was completed in 2000.

Diamond drilling programs have focused mainly on the Cigar Lake corridor, with specific attention on Cigar East, Cigar North, Tibia, and Tibia East zones. Grids outside of the Cigar Lake corridor,

 

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Power Line trend, Jigger and Jigger North, Andrew Lake, Kelly Bay, and Waterbury North, were drilled with varying intensity through the history of the project.

In 2006, drill hole WC-244 discovered the Cigar East zone that is located outside ML 5521, approximately 650 metres east of CL Main mineralization. Further exploration has been conducted in this area since 2006 and has delineated a zone of unconformity style uranium mineralization approximately 210 metres in length and 30 metres in width. No mineral resource has been reported for the Cigar East zone.

A figure displaying the location of all current exploration work areas outside of ML 5521 is included as Figure 9-1. A list of all work completed outside of ML 5521 between 1980 and 2023 is included as Table 9-1.

 

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FIGURE 9-1: EXPLORATION WORK AREAS OUTSIDE OF ML 5521

 

 

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TABLE 9-1: SUMMARY OF EXPLORATION OUTSIDE OF ML 5521

 

		Diamond drillholes				Airborne geophysics				Ground geophysics				Other exploration
Year		# holes		Metres drilled		Type		Line km		Type		Line km		Type
1980						Magnetic VLF and radiometric survey		Project-wide		EM soundings DEEPEM		60
1981		13		5,208						DEEPEM		134		Lake sediment sampling
1982		4		1,845						DEEPEM		588		Lake sediment sampling
										EM-37		28
										Gravity		59
1983		4		2,616		INPUT		2,685 km		DEEPEM		545		Lake sediment sampling
1984		4		1,657
1985		14		7,132						DEEPEM		120		Lake sediment sampling
1986		17		8,113
		38		2,138						DEEPEM		135		Shallow geochemistry
1987-1998		No exploration activities
1999														Data compilation, structural study, re- logging and resampling of historical drill core
2000						GEOTEM		3,587 km						Boulder lithogeochemistry on most of the property
2001										Moving Loop EM		26
										Fixed Loop EM		57
										Pole-pole DC 2D Resistivity		5
2002		2		1,150						Pole-pole 2D Resistivity		16
										EScan Pole-pole DC3D Resistivity		51
2003		4		1,790						UTEM Moving Loop EM		11		Historical drill core logging and resampling
2004										Moving Loop EM		29		Historical drill core logging and resampling
										Pole- pole DC 2D Resistivity		18
2005		3		1,680
2006		7		4,075						Pole- pole DC 2D Resistivity		84		Historical drill core logging and resampling
2007		12		6,044		FALCON gravity magnetic and radiometric surveys		Project-wide		Moving Loop EM		11		Historical drill core logging and resampling
2008		12		5,492		High resolution magnetic gradiometer survey		Project-wide		Pole- pole DC 2D Resistivity		86		Historical drill core logging and resampling
										Fixed Loop EM		51

 

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		Diamond drillholes				Airborne geophysics				Ground geophysics				Other exploration
Year		# holes		Metres drilled		Type		Line km		Type		Line km		Type
2009		14		7,733						Fixed Loop EM		51		Historical drill core logging and resampling
										Small Moving Loop EM		44
										Pole- pole DC 2D Resistivity		51
2010		15		8,040										Relogging and resampling of historical drill core
2011		11		5,366						Moving loop EM		37
2012		10		4,108						Moving loop EM Dipole-pole-dipole DC Resistivity		44 89		Re-sampling and re-boxing of historical drill core
2013		16		8,040						Moving loop EM Dipole-pole-dipole DC Resistivity		32 80		Re-sampling and re-boxing of historical drill core
2014		19		9,044						Moving loop EM Dipole-pole-dipole DC Resistivity		37 68
2015		24		12,456						Moving loop EM Stepwise moving loop EM		63 4
2016		25		13,302						ML-SQUID TEM Swath Resistivity		108 67.7		Petrography samples and Hyperspectral scanning of drill core
2017		30		16,937						ML-SQUID TEM DC Resistivity		8.95 135.2		Relogging program of Cigar North drill holes.
2018		27		14,634		VTEM		3990.0		ML-SQUID TEM		35.9
2019		28		14,904						ML-SQUID TEM		54.3
2020		13		6,180						ML-SQUID TEM DC Resistivity		11.9 17.5		Water hammer drill test holes (included in reported meterage)
2023		14		5,068										Borehole EM (WC-592)
Total		380		174,753								3,153

Source: Orano

 

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9.2	Cameco 2007 – present

After the 2006 water inflow events, it was recognized that more detailed geophysical information in the immediate deposit area was required. The initial focus was to gain an understanding of the structure associated with the Shaft No. 2 inflow. Ground surveys, including gravity, TITAN (DC/IP resistivity and magnetotelluric survey), and VLF electromagnetic surveys were conducted in the summer of 2007 over a portion of the CL Main area of the deposit.

In the fall of 2007, a supplementary geophysical program was conducted over a portion of the CL Main area of the deposit to identify major structures within the sandstone column. The survey was conducted in six boreholes to produce three vertical seismic profiles and six single-hole side-scan seismic surveys around the mine site to meet these objectives. Both survey designs are best for optimally imaging vertical to sub-vertical structures at various scales based on their input frequencies.

In 2015, Cameco conducted a geotechnical drill program consisting of nine surface diamond holes (drilled to a vertical depth of 525 metres) over the western portion of the CL Main deposit. Downhole cross-well seismic was done within these boreholes to image major fault structures and geotechnical characteristics of this portion of the deposit.

The knowledge gained of structures and fault zones, identified through the correlation of all the geophysical datasets, particularly seismic, with geological mapping and engineering parameters has allowed for better mine planning and mitigation of potential risk.

 

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10

Drilling

 

10.1	Surface drilling

Surface drilling on the Waterbury Lake lands conducted by Orano and its predecessor companies since 1981 is presented in Table 9-1. Initial exploration activities by SERU were conducted in the southern region of the Waterbury Lake lands near Jigger Lake. Thirteen exploration drillholes (totaling 5,208 metres) were completed prior to the discovery hole during the first drilling campaign in 1981, eight of which were drilled on the Q17 grid (Jigger Lake). The last drillhole (WQS2-015), completed to a depth of 563 metres in 1981, was located on the QS-2 grid south of Cigar Lake and was the discovery hole for the Cigar Lake uranium deposit.

The deposit was subsequently delineated by surface diamond drilling during the period 1982 to 1986 and was followed by several small campaigns of drilling to gather geotechnical and infill data between 1986 and 2007. Additional drilling campaigns were conducted by Cameco after 2007 which targeted a broad range of technical objectives, including geotechnical, geophysical, delineation and ground freezing. Since 2012, diamond drilling managed by Cameco has mainly focused on underground geotechnical and surface ground freezing programs on CL Main along with continued delineation drilling on CLEXT.

Drillhole location maps are provided in Figures 10-1 and 10-2, which depict the locations for surface delineation and surface freeze holes, respectively. Drill depths for surface delineation holes range from approximately 460 to 550 metres.

The CL Main zone was discovered in 1983. Drilling was initially done at a nominal drillhole grid spacing of 25 to 50 metres east-west by 20 to 25 metres north-south. A surface drill program was conducted from 2010 to 2012 to tighten up the spacing in areas with gaps in coverage (Figure 10-1). Similarly, a small program of six holes was completed on mineralized zones situated between East and West Pods in 2023. Apart from this area, CL Main has been fully delineated by surface freeze holes on a nominal 7 x 7 metre pattern (Figure 10-2). A total of 1,328 surface freeze holes have been completed totaling over 613,000 metres of drilling. Figure 10-3 provides a geological cross-section along mine grid easting 10781, depicting the predominant lithological domains, location of the orebody and uranium grade distribution.

The CLEXT zone had been outlined through several exploration drilling campaigns conducted between 1981 and 2012. Since 2016, Cameco has completed additional surface delineation drilling to confirm and upgrade mineral resources contained in CLEXT. Several holes were additionally used to collect metallurgical, hydrogeological and geotechnical information including: five holes used for detailed ore zone metallurgical investigations, four holes with deep packer testing and two holes with deep piezometer installations. Information from 235 holes totaling approximately 99,000 metres of diamond drilling has been used to support the prefeasibility study for CLEXT. Figure 10-1 illustrates the CLEXT drillhole coverage, with drillhole fences and clusters variably spaced 12 to 25 metres apart in the western portion and 20 to 50 metres in its eastern portion.

The orientation and shape of the deposit was recognized at an early stage of the exploration drilling. It was soon learned that the bulk of the mineralization was high grade and positioned at and sub-parallel to the unconformity, although rare vein-like bodies of mineralized rock were also present. Subsequently, almost all drilling was completed using vertical drillholes rather than inclined drillholes because it was recognized that vertical intersections were essentially normal to the dominant orientation of the deposit. These intersections, therefore, represent the true thickness of the flat-lying deposit (Figure 10-3).

Well established drilling industry techniques were used in the drilling programs, including wireline core drilling. Core recovery was generally very good; in some areas where ground conditions

 

2024 CIGAR LAKE TECHNICAL REPORT 55

dictated, triple tube drilling to maximize core recovery was done. Wedging techniques were used in some areas to obtain step-out intersections without the expense of collaring additional holes.

All pre-2007 holes were surveyed for direction using single shot or multi-shot surveying tools. Holes drilled since January 2007 have been surveyed either with a gyroscope or a Reflex tool. The collar locations of drillholes within the area of the surface infrastructure footprint have been surveyed by Cameco and their locations confirmed.

The more recent surface delineation drillholes (since 1988) have been grouted in their entirety. Holes drilled prior to 1988 were plugged in the range of 250 to 350 metres by mechanical plugs and/or cement plugs up to 10 metres thick.

In almost all cases, gamma surveys have been conducted through the mineralization in these holes. For further discussion see Section 11.7.

Drilling results have been used to delineate and interpret the 3D geometry of the mineralized areas, the lithostructural settings, the geotechnical conditions, and to estimate the distribution and content of uranium and other elements within the CL Main and CLEXT mineral resources and mineral reserves.

 

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FIGURE 10-1: CIGAR LAKE DEPOSIT - SURFACE EXPLORATION AND DELINEATION DRILLHOLE LOCATIONS

 

 

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FIGURE 10-2: CIGAR LAKE DEPOSIT - SURFACE FREEZE HOLE LOCATIONS (CL MAIN)

 

 

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FIGURE 10-3: CL MAIN GEOLOGICAL CROSS SECTION AT 10781E – LOOKING WEST (±3 m)

 

 

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10.2	Underground drilling

Diamond core drilling from underground locations is primarily to ascertain rock mass characteristics in advance of development and mining. CLMC and Cameco have conducted underground geotechnical drilling at Cigar Lake since 1989. A total of 519 underground geotechnical holes have been completed on CL Main. In addition, 24 holes have been completed with respect to the CLEXT ramp access south-southwest of the West Pod. Holes drilled prior to 2001 were surveyed for downhole deviation using a single shot or multi-shot survey tool. Since 2001, holes have been surveyed for downhole deviation using a Reflex survey tool and, locally, a gyroscope.

Underground freeze holes were drilled into the deposit for the purposes of freezing the ground prior to mining during the test mining phase. A total of 83 holes at a spacing of 1 to 1.5 metres were drilled in two periods of drilling in 1991 and again in 1999. Generally, these upward holes were rotary drilled holes from which no core was recovered; however, in a limited number of cases, core was recovered and sampled, and in almost all cases, gamma surveys of the holes were done through the deposit.

Underground freeze hole drilling started up again in late 2004 with the start of the construction phase of development. During this phase, a total of 347 freeze and temperature monitoring holes were drilled, of which 182 were gamma surveyed. The latter freeze holes were all drilled by percussion methods, so no core was available for assays. The gamma surveys show the mineralization to generally conform with the projected ore outline. A gyro tool was used for directional surveying in the 2004 to 2006 phase of freeze hole drilling. No underground freeze holes have been drilled since 2006.

The locations of the underground geotechnical holes in CL Main are shown in Figure 10-4. Additional underground geotechnical drilling is planned to assist in the design of the remaining underground tunnels in both CL Main and CLEXT. Underground freeze holes are not shown in this figure.

 

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FIGURE 10-4: UNDERGROUND GEOTECHNICAL DIAMOND DRILLHOLE LOCATION MAP - CL MAIN

 

 

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10.3	Factors that could materially affect the accuracy of the results

Except for the underground freeze holes, there are no known drilling, sampling or core recovery factors that could materially affect the accuracy and reliability of the results. Underground freeze holes were not used in the 2023 mineral resource estimate due to data quality concerns and their redundancy given the presence of overlapping surface freeze hole data. For a further discussion of sampling and core recovery factors, see Section 11.

 

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11	Sample preparation, analyses and security

 

11.1	Sample density and sampling methods

Delineation drilling in the CL Main zone, 670 metres long by 100 metres wide, was originally completed at a nominal drillhole fence spacing of 25 to 50 metres (east-west), with holes at 20 to 25 metres (north-south) spacing on the fences. Since then, the entire portion of the CL Main deposit has had surface freeze holes installed at a nominal 7 x 7 metre pattern.

The CLEXT zone, approximately 1,280 metres long by 75 metres wide, was historically drilled at a nominal drillhole fence spacing of 200 metres, with holes at 20 metres spacing on the fences. Subsequent drill programs occurring between 2011 and 2023 have since reduced the drillhole spacing down to 15 x 15 metres in local areas of the deposit. Geological, geotechnical and hydrological information was collected and assessed.

Across the deposit, all surface holes were core drilled and gamma probed when possible. In-hole gamma surveys and hand-held scintillometer surveys were used to guide sampling of core for assay purposes. After recognition of the significance of the deposit and its geometry in 1982, sampling of core was thereafter primarily concerned with ensuring that all core within the mineralized zone containing at least 0.10% U3O8 was sampled and assayed. An Automess GmbH gamma detector was used to determine the outer limits of sampling and to validate the core depths.

In the early stages of exploration drilling, sampling of mineralized intervals was done on a geological basis, whereby sample limits were determined based on geological differences in the character of the mineralization. Samples were of various lengths, up to 0.5 metre. Since 1983, sampling intervals for core from the deposit have been fixed at a standard guideline of 0.5 metre. Sample results are generally composited to the standard interval of 0.5 metre for mineral resource estimation purposes. In the case of CL Main, approximately 25% of surface freeze holes were sampled for uranium analysis while the remaining holes rely solely on equivalent grade determinations from downhole radiometric probing.

On each of the upper and lower contacts of the mineralized zone, at least one additional 0.5 metre sample was taken to ensure that the zone was fully sampled at the 0.10% U3O8 cut-off.

Since 2012, all core logging and sampling of uranium mineralized drill core has been conducted in a separate core logging facility. Sampling is done only after all other geological logging, including photography of the core, is completed. Sampling is done in a separate room attached to the core shack to maintain cleanliness in the sampling area and reduce radiation levels in the core logging area.

The typical sample collection process includes the following procedures:

 

•

marking the sample intervals on the core boxes at the nominal 0.5 metre sample lengths

 

•

collection of the samples in plastic bags, taking the entire core

 

•

documentation of the sample location, assigning a sample number and description of the sample, including radiometric values from a hand-held device

 

•

bagging and sealing, with sample tags inside bags and sample numbers on the bags

 

•

placement of samples in steel drums for shipping

 

11.2	Core recovery

Reliance for uranium grade determinations in surface delineation drillholes has been placed primarily on chemical assays of drill core. Core recovery through the ore zone has generally been very good. Where necessary, uranium grade determinations have been supplemented by downhole radiometric probing.

 

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For mineral resource and reserve estimation purposes, assayed values where core recovery is above 75% are deemed representative of the whole interval. If the core recovery was below 75%, the sample was replaced by probing values. These replacement values account for approximately 5% of the overall sample database.

From about 1983 onward, all drilling and sampling procedures have been standardized and documented resulting in increased confidence in the accuracy and reliability of results of all phases of the work.

 

11.3	Sample quality and representativeness

Most of the exploration and delineation drilling completed by Cameco on the surface of the mineral lease consists of wireline diamond drilling recovering NQ size (47.6 millimetres) drill core. All surface freeze hole core is of PQ size (85.0 millimetres). Except for some of the earliest sampling in 1981 and 1982, the entire core from each sample interval was taken for assay. This was done to reduce the potential for sampling bias, given the high-grade nature and variability of the grades of the mineralization, and to minimize human exposure to gamma radiation and radon gas during the sampling process. Some of the core remains available for viewing at the site in a gated compound.

 

11.4	Sample preparation by Cameco employees

None of the samples sent to testing laboratories prior to January 1, 2002 were prepared by an employee, officer or director of Cameco; however, limited assaying was carried out at Cameco’s Rabbit Lake mill laboratory, as discussed in Section 11.6. All samples for Cigar Lake prior to this date were prepared by employees of Orano or its predecessor companies or CLMC. This would include a very minor number of samples used in the mineral resource and mineral reserve estimates.

Beginning in 2009, numerous surface delineation and surface freeze holes were drilled through the CL Main and CLEXT deposits. Drill cores selected for assaying were sampled by Cigar Lake personnel.

Since 2016, the qualified person for this section has been involved with providing support and guidance for sampling of mineralization.

 

11.5	Sample preparation

The majority of historical samples used for the mineral resource estimate were prepared and analysed by Loring Laboratories Ltd. (Loring), which is located in Calgary, Alberta, and is independent of the CLJV owners.

Sample preparation at Loring consisted of drying the sample, if necessary, followed by primary (jaw) and secondary (cone) crush, homogenization, and cutting the sample using a Jones-type riffle splitter down to 25- to 300-gram portions for pulp preparation. The material was then pulverized in a TM Vibratory Pulverizer to maintain a 95% passing 150 mesh sieve. Samples were then rolled 100 times on a rolling mat to ensure total homogeneity and placed in a numbered sample bag ready for analysis. Any particulates created from sample preparation were carefully swept up from all areas and placed in a separate container for return to the property site, along with all pulps and reject material after the sample had been analyzed.

Since 2002, sample preparation has been done at Saskatchewan Research Council Geoanalytical Laboratories (SRC), which is located in Saskatoon, Saskatchewan, and is independent of the CLJV owners. It involves jaw crushing to 80% passing at less than two millimetres and splitting out a 100- to 200-gram sub-sample using a riffle splitter. The sub-sample is pulverized to 90% passing at less than 106 microns using a puck and ring grinding mill. The pulp is then transferred to a bar coded plastic snap top vial.

 

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11.6

Assaying

Assaying of drill core for uranium and other elements has been performed at different commercial laboratories and Cameco’s Rabbit Lake laboratory since 1981.

As referenced in Section 11.5, Loring did all the assaying for uranium between 1983 and 1994. They were not certified by any standards association at that time.

Cameco’s Rabbit Lake mill laboratory has carried out limited assaying since 1994, and SRC was used after 2001. The Rabbit Lake laboratory was not formally certified at that time; however, between July 1994 and July 1997, there were inter-laboratory tests on uranium determination involving Rabbit Lake, Key Lake, Cluff Lake, Rio Algom and SRC laboratories. Different analytical methods were used in the comparison studies and showed that results from the Rabbit Lake laboratory were within acceptable limits.

Records indicate that SERU deemed the assay results from two commercial laboratories, from drilling done in 1982, were not calibrated properly. As a result, the assay results from this period were adjusted in 1983 based upon a systematic comparison of laboratory results and cross checks. These adjusted grades applied to only three holes (38, 39, 39A) out of 641 holes used for the CL Main uranium block model. Nineteen of the 23 holes affected were from the CLEXT portion of the mineralization. These 23 holes have not been reassayed and the adjusted results are included in the mineral resource and mineral reserve estimates.

Assaying by Loring was done by both the fluorimetric method and the volumetric method (volumetric ferrous iron reduction in phosphoric acid). All samples assaying greater than 5% U3O8 as determined by fluorimetry were reassayed using the volumetric method. Chemical standards were systematically assayed on a regular basis to ensure the accuracy of the assaying procedure. Senior staff of the operator at the time (CLMC) visited Loring on a regular basis to view and discuss laboratory procedures with Loring.

Assaying at the Rabbit Lake mill was done by the fluorimetric method for low-grade samples, and by a combination of titration and x-ray fluorescence for high-grade samples, collected for metallurgical purposes in 1998.

Sample analysis since 2002 has been conducted by SRC. SRC is licenced by the CNSC for possession, transfer, import, export, use and storage of designated nuclear substances under CNSC Licence Number: 01784-1-09.3. SRC is an accredited testing laboratory assessed by the Standards Council of Canada under the requirements of ISO/IEC 17025:2017, General Requirements for the Competence of Mineral Testing and Calibration Laboratories. Assaying by SRC involved digesting an aliquot of pulp in concentrated 3:1 HCI:HNO3 on a hot plate for approximately one hour, then making up to volume in a 100 millilitre volumetric flask with deionized water prior to analysis by ICP-OES. Instruments used in the analysis are calibrated using certified commercial solutions.

Chemical assay results were systematically checked against radiometric results to ensure their accuracy. Sample pulps and reject materials are retained and systematically catalogued. Check assays were done on an as-required basis.

 

11.7	Radiometric surveying

For drillholes completed prior to 2011, the reliance on downhole radiometric probing for determination of uranium grades for mineral resource estimation is minimal. Boreholes completed prior to 2011 were consistently sampled to obtain U3O8 chemical assays when uranium mineralization was encountered. In areas of poor core recovery or missing sample intervals, equivalent %U3O8 grades from downhole radiometric data were used to supplement the assay

 

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data. However, this accounts for a very small proportion of the grade data for holes completed prior to 2011.

Since 2011, downhole radiometric data has provided most of the grade data used for mineral resource estimation in areas where freeze holes have been installed. To the end of 2023, 1,328 surface freeze holes have been completed at Cigar Lake, and approximately 75% of these rely on equivalent grade data obtained from downhole probing.

Cigar Lake uses a high-flux (HF) gamma probe designed and constructed by alphaNUCLEAR, a member of the Cameco group of companies. This HF gamma probe utilizes two Geiger Müller tubes to detect the amount of gamma radiation emanating from the surroundings. Servicing and recalibration is performed annually or when probes undergo repairs and the accuracy of the probes is verified in a designated calibration hole prior to use. If accuracy issues are identified at any time, the probe in question is sent for repair and recalibration and its past radiometric measurements are reviewed.

The count rate obtained from the high-flux probe is compared against chemical assay results to establish a correlation to convert corrected probe count rates into equivalent %U3O8 grades. The consistency between probe data and chemical assays demonstrates that secular equilibrium exists within the deposit.

The correlation to convert corrected probe count rates into equivalent %U3O8 is periodically reviewed and updated as required based on comparisons between probing results and chemical assays which are performed on a quarterly basis. A comparison of radiometric probing grade x thickness (GT) against chemical assay GT intervals using the correlation at year-end of 2022 is shown in Figure 11-1. Following review in 2023, an adjustment to the correlation was applied to address a slight eU3O8 overestimation bias.

FIGURE 11-1: GT COMPARISON OF eU3O8 CORRELATION AGAINST CHEMICAL ASSAY

 

 

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11.8	Density sampling

Density sampling and analysis has occurred at Cigar Lake since the initial exploration campaign in the early 1980s. Historical density analysis was performed using two methodologies:

 

•

competent drill core samples were oven dried, weighed in air, then submersed in water and weighed again

 

•

less competent and/or altered core samples were oven dried, and the volume of the sample was determined by measuring the length and diameter of the sample

Since 2010, density sampling and analysis has been conducted at SRC using a dry bulk method. For this method, samples are weighed dry, then coated with an impermeable layer of wax and re-weighed. Samples are then submersed in water and weighed. Weights are recorded into a database and rock densities are calculated for the samples.

Comparison of recent and historical density estimates has demonstrated there is good correlation between the two datasets. Therefore, historical measurements are deemed reliable for use in further studies.

 

11.9	Quality assurance/quality control

From 1983 to 1994, assaying was done by Loring. For uranium assays up to 5% U3O8, 12 standards and two blanks were run with every sample batch (certified standards were used). For uranium assays over 5% U3O8, a minimum of four standards were analyzed with each run. These historical assays represent a very small portion of assay results in the current mineral resource estimate and their results have been reviewed against more recent drilling results from the infill surface freeze hole program.

Quality control for the more recent assaying at SRC includes the preparation and analysis of standards, duplicates and blanks. Prior to June 2013, standards used included BL2a, BL3, BL4a and BL5, all from CANMET, and in-house samples, UHU-1 and USTD5. In June 2013, five new standards were developed at the SRC from Cigar Lake ore (CL-1, CL-2, CL-3, CL-4 and CL-5) to provide more robust quality control and assurance due to the high-grade nature of the Cigar Lake deposit.

At least two standards are analyzed for each 40-sample batch as well as one replicate pulp analysis using an aqua regia (AR) digestion followed by ICP. We also include one split sample repeat with every group. See Figures 11-2 and 11-3 for relevant results of standards and pulp duplicates from CL Main and CLEXT sample batches. Except for two results on standards CL-2 and CL-3 in 2014 and 2015, all quality control results are within specified limits. Samples that fail quality controls are re-analyzed.

Quality control for equivalent grade determination is described in Section 11.7.

 

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FIGURE 11-2: CIGAR LAKE STANDARDS (CL MAIN AND CLEXT): BL4A, BL2A, CL-1, BL5, CL-2, CL-3, CL-4, AND CL-5

 

 

 

 

 

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FIGURE 11-3: CIGAR LAKE (CL MAIN AND CLEXT) PULP DUPLICATE AR-ICP RESULTS

 

The QA/QC program results have not identified issues with the analytical procedures. The qualified person for this section has reviewed the data and is of the opinion that it is of adequate quality to be used for mineral resource and mineral reserve estimation purposes. Supporting this opinion is the fact that since 2014, the model performance is within 6% on tonnage and 1% on uranium content of the reported mine production, as presented in Section 14.6.

 

11.10

Adequacy of sample preparation, assaying, QA/QC and security

Current sampling protocols dictate that all samples are collected and prepared under the close supervision of a qualified geoscientist in a restricted core processing facility. The core samples are collected and transferred from the core boxes to high-strength plastic sample bags, then sealed. The sealed bags are then placed in steel drums and shipped under the Transportation of Dangerous Goods Regulations with tamper-resistant security seals through the Cameco warehouse facilities directly to the laboratory. Chain of custody documentation is present from inserting samples into steel drums to final delivery of results by SRC. All samples collected are

 

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prepared and analyzed under close supervision of qualified personnel at SRC, which is a restricted access laboratory licensed by the CNSC.

The qualified person for this section is satisfied with all aspects of sample preparation and assaying. The sampling records are documented and samples were whole core assayed to reduce bias. The assaying was done to a high standard and the QA/QC procedures employed by the laboratories were adequate. Regarding the 23 holes, predominantly in CLEXT, that had their grades adjusted in 1983 by SERU, the qualified person for this section is satisfied that the mineral resources classification for the general area they cover and their subsequent conversion to mineral reserves reflects the degree of uncertainty attached to the grade.

The qualified person for this section is not aware of the historic security measures in place at the time of the deposit delineation, from 1981 to 1986. Sample security is largely defined by regulation, and since 1987 all samples have been stored and shipped in compliance with regulations. The qualified person believes that the sample security was and is maintained throughout the process. There has been no indication of significant inconsistencies in the data used for the latest update of the mineral reserve and resource estimates.

 

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12	Data verification

The original database, which forms part of the database used for the current mineral resource and mineral reserve estimates, was compiled by previous operators. Many of the original signed assay certificates are available and have been reviewed by Cameco geoscientists.

In 2013, Cigar Lake implemented an SQL server based centralized geological data management system to manage all drillhole and sample related data. All core logging, sample collection, downhole probing and sample dispatching activities are carried out and managed within this system. All assay and geochemical analytical results obtained from the external laboratory are uploaded directly into the centralized database, thereby mitigating potential for manual data transfer errors.

Additional data verification measures taken on the data collected at Cigar Lake are as follows:

 

•

surveyed drillhole collar coordinates and downhole deviations are entered into the database and visually validated and compared to the planned location of the holes

 

•

all CLEXT holes drilled in 2011 and 2012 were resurveyed between the summer of 2012 and summer of 2015

 

•

comparison of the information in the database against the original data, including paper logs, assay certificates and original probing data files as required

 

•

validation of core logging information in plan and section views, and review of logs against photographs of the core

 

•

using the Maptek Vulcan software package, a validation query was developed that checks for data entry errors such as overlapping intervals and out of range values

 

•

downhole radiometric probing results are compared with radioactivity measurements made on the core and drilling depth measurements

 

•

downhole radiometric probes are subjected to control probing to ensure precision and accuracy

 

•

equivalent %U3O8 grades based on radiometric probing are validated with chemical assay results

A discussion of quality assurance and quality control measures relating to assay and radiometric results is included in Sections 11.6, 11.7, 11.8 and 11.10. The geotechnical information collected from drilling was validated visually in excavated areas underground. Validity of the metallurgical samples is discussed in Section 13.2.

The qualified person for this section supervised professional geoscientists who verified the data at the site and at the corporate office. The qualified person was involved in reviewing a portion of the assay and probing results, as well as the correlations between radioactivity and uranium grade, and between density and multi-elements. The qualified person attended all internal peer reviews involving the data informing interpretation and estimation, communicating regularly with internal personnel including the Mine Chief Geologist. In consideration of the above, the qualified person for this section is satisfied with the quality of the data and considers it valid for use in the estimation of the mineral resources and mineral reserves. Comparison of life-of-mine production with the mineral reserve model supports this opinion.

 

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13	Mineral processing and metallurgical testing

 

13.1	Cigar Lake processing metallurgical test work

The design for processing ore at Cigar Lake was largely based on the experience gained at McArthur River, including modifications and improvements incorporated since that operation was commissioned in early 2000. The primary difference between the two sites is that mining at McArthur River is carried out using dry methods, while high-pressure water is used to mine the deposit at Cigar Lake. As a result, coarse low percent solids/density slurry is pumped at Cigar Lake from the discharge of the JBS mining machines to the underground ore storage facilities.

Several pump and pipeline testing programs were conducted between 1996 and 1999 to establish design criteria for the system, utilizing simulated Cigar Lake ore at SRC’s Pipeline Research Centre. Slurries in the one to four percent solids by weight range were produced using solids consisting of clay, selected size fractions of rock, and various sizes and shapes of steel pieces. The key findings from these test programs included the determination of minimum slurry velocities and practical pump box designs. In 2011, further pumping tests were done at the centre to ensure that large, heavy particles could be transported by pipeline. In the tests, different sizes, shapes and densities of particles were pumped in pipes that were sloped between 0 and 90 degrees. A report of these tests was prepared by SRC.

In addition, wet crushing test work on simulated Cigar Lake ore was carried out in 1998 by Cron Metallurgical Engineering Ltd. using a prototype of a reduced size version of a Nordberg water flush cone crusher. Capacities exceeding 40 tonnes per hour were achieved on a maximum 75- millimetre feed to produce a product suitable for grinding in a ball mill.

The operational experience thus far has been consistent with metallurgical test work expectations. Due to the geological and geotechnical similarities between the CL Main and CLEXT orebodies, no significant changes are expected in the comminution of the ore.

The CLEXT ore will be mined in the same manner as the CL Main ore. A low percent solids discharge slurry from the JBS will be pumped from the CLEXT zone to the run of mine (ROM) ore storage sumps and processed in the existing CL Main underground crushing and grinding circuits before being pumped to surface for thickening and eventually shipped to the Orano McClean Lake mill.

Due to the additional distance of the CLEXT ore workings and cavities from the CL Main processing area, booster stations will be installed to move the JBS produced low percent solids slurry. The design of the boosting and ore handling system is based on the slurry test work completed between 1996 and 1999 at the SRC Pipeline Research Centre and the experience and operational information gained during the historical and ongoing CL Main ore processing.

The existing process design criteria was updated for CLEXT; however, no further test work was deemed necessary due to the relative similarities of the CLEXT and CL Main ore. The inherent high variability within the CL Main ore itself and subsequent successful processing of the slurry provides another validation of the processing circuit’s robustness and ability to process a wide range of ore characteristics.

 

13.2	McClean Lake processing metallurgical test work

Extensive metallurgical test work was performed on core samples of Cigar Lake ore from 1992 to 1999. Samples used for the metallurgical test work during this period may not have been representative of the deposit as a whole. Additional test work completed by Orano in 2012 with drill core samples verified that a high uranium recovery rate could be achieved regardless of the variability of the ore. Test work also concluded that more hydrogen gas evolution took place than

 

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previously anticipated, which resulted in safety related modifications being implemented in the leaching circuit. Leaching modifications began in 2013 and were completed in 2014, with mill start-up in September 2014.

The 1992 to 1999 work was performed in France at Orano’s CIME test centre. The results of this test work program provided the process design criteria for the additions and modifications required at the McClean Lake mill for processing Cigar Lake ore. Since 2014, the McClean Lake mill has processed on a daily basis a range of ore grades, at times in excess of 28% U.

CLEXT METALLURGICAL TEST WORK

Testing was completed in 2018 and 2019 by Orano on both discrete core and composite samples to account for ore variability within the CLEXT deposit. The laboratory testing on CLEXT ore focused on the following primary areas of interest:

 

•

hydrogen evolution rates

 

•

leaching efficiencies and retention time

 

•

CCD settling

 

•

tailings preparation, settling and aging tests

Hydrogen generation was observed to varying degrees, but it was concluded that the existing leach circuit is capable of handling the observed H2 gas generation.

Leaching uranium extraction in the 2018 test work was noted as typically >99% in a wide range of uranium and arsenic values within the range of ore samples. A 7-hour minimum retention time was deemed acceptable for both uranium and arsenic leaching with arsenic leaching efficiency being more variable than uranium. Based on that test work and the expected performance of the downstream circuits, the overall mill recovery for the CLEXT ore is projected to average 98.5%.

The test work confirmed that no modifications would be required to the leaching circuit to process CLEXT ore but that the CCD circuit would need to be looked at more closely. Ongoing optimization in the CCD circuit since that time has significantly reduced the production related risk.

The tailings neutralization and aging tests completed in 2019 verified that the current operating practices at the McClean Lake Mill will produce tailings that are stable over the long-term and meet the requirements of the decommissioning plans related to the control of contaminants to the environment.

MILL RECOVERY

Based on the test results and mill performance processing Cigar Lake ore since 2014, overall uranium recoveries of 98.8% for CL Main and 98.5% for CLEXT are expected for the remainder of the mine life. Anticipated losses are distributed as follows:

 

•

leach residue loss: 0.5% – 0.8%

 

•

CCD soluble loss: 0.3 – 0.5%

 

•

solvent extraction loss: 0.2 – 0.4%

The actual overall mill recovery is shown below in Table 13-1 on a yearly basis and overall weighted average since the McClean Lake mill began processing Cigar Lake ore.

The expected mill recovery is similar to that achieved at Cameco’s other Saskatchewan operations. For reference, historically, the Key Lake mill treating McArthur River mine ore achieves an overall recovery of approximately 99.0%, and the Rabbit Lake mill treating Eagle Point mine ore achieved a recovery of approximately 97.0%. The lower recovery at the Rabbit Lake mill is due to the lower feed grade from the mine to the mill as compared to the McArthur River ore feeding the Key Lake mill.

 

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TABLE 13-1: McCLEAN LAKE OVERALL MILL RECOVERY (2014 TO 2023)

 

Year		Average Overall Mill Recovery2
20141			97.6
2015			99.0
2016			99.1
2017			99.0
2018			98.9
2019			98.9
2020			98.8
2021			98.7
2022			98.9
2023			98.9
Average3			98.9

 

1	September to December, inclusive

2	weighted monthly average for year (production is reconciled on a monthly basis)

3	weighted average for the period 2014 to 2023, inclusive

DELETERIOUS ELEMENTS IN CIGAR LAKE ORE

The average arsenic content in CLEXT ore is higher than CL Main based on the existing geological drill core data. Ore higher in arsenic requires more reagents for processing, increasing the overall operating costs. The primary reagents used in the control of arsenic include:

 

•

Ferric sulphate - used to neutralise and stabilize arsenic in the tailings preparation circuit. Lime is used to neutralise the ferric sulphate

 

•

Hydrogen peroxide - utilized in the leaching process in order to ensure efficient leaching of the highly reduced arsenic mineralization present in Cigar Lake ores

The McClean Lake mill produces ferric sulphate on site. During periods of peak ferric sulphate demand, commercial ferric sulphate may be required to supplement the ferric sulphate produced on site based on the ore blend arsenic content. With the additional ferric sulphate addition, the tailings tonnage and associated volume requirement increases. The arsenic concentration is factored into tailings projections, which are re-visited annually.

Molybdenum is an uneconomic constituent of the Cigar Lake ore. However, molybdenum content in the final concentrate above certain thresholds results in refinery penalties, which are refinery dependent. The McClean Lake mill uses activated carbon columns to remove molybdenum prior to the precipitation of yellowcake. These carbon columns have an efficiency of approximately 60%. Refinery penalties attributable to molybdenum content have been negligible to date.

For a further discussion of ore processing at Cigar Lake, see Section 17. A high-level operation flow sheet of the ore processing activities is shown in Figure 17-1.

 

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