Cameco : Cigar Lake 2023 Technical Report

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

• 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
	20.4	Environmental aspects	135
	20.5	Decommissioning and reclamation	137

iii

	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

3D three-dimensional

• percent

• degrees

°C	degrees Celsius
CCD	counter current decantation
CLJV	Cigar Lake Joint Venture
eU3O8	equivalent uranium oxide

• grams

• hour(s)

ha	hectares (10,000 square metres)
hp	horsepower
Hwy	highway
IRR	internal rate of return
JBS	jet boring system
km	kilometres
km2	square kilometres
kV	kilovolts
kW	kilowatts

• litre

lbs pounds

• million

• metres

m3	cubic metres
m3/h	cubic metres per hour

m3/s	cubic metres per second
MASL	metres above sea level (elevation)
MLJV	McClean Lake Joint Venture

1. millimetres MW megawatts

NPV	net present value
SX	solvent extraction

• tonnes (metric)

• uranium

• U percent uranium (% U x 1.179 = % U3O8) U3O8 uranium oxide (yellowcake)
• U3O8 percent uranium oxide (% U3O8 x 0.848 =
• U)

$Cdn	Canadian dollars
$US	US dollars
$/t	Canadian dollars per tonne
US$/lb	US dollars per pound

• greater than
  < less than

viii

• 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