Overview
Stage | Production |
Mine Type | Underground |
Commodities |
|
Mining Method |
- Raiseboring
- Blast Hole Stoping
- Cemented (undefined) backfill
|
Shaft Depth |
680 m |
Processing |
- Calcining
- Sulfuric acid (reagent)
- Solvent Extraction
- Crush & Screen plant
- Reverse osmosis
- Agitated tank (VAT) leaching
- Counter current decantation (CCD)
- Acid tank leaching
- Dewatering
|
On-Site Camp |
473 rooms Source: |
Production Start | 2000 |
Mine Life | 2044 |
McArthur River is the world’s largest, high-grade uranium mine, and Key Lake is the world’s largest uranium mill. Ore grades at the McArthur River mine are 100 times the world average.
The McArthur River and Key Lake operation was in a state of safe care and maintenance from 2018 through 2021 due to weak market conditions. In November 2022, was announced the restart of McArthur River/Key Lake. Throughout 2023, the operations continued to ramp up production. |
Source:
p. 73
McArthur River is owned by a joint venture (MRJV) between two companies:
- Cameco – 69.805%;
- Orano’s (previously AREVA) – 30.195%.
Key Lake is owned by two companies:
- Cameco – 83.3%;
- Orano’s (previously AREVA) – 16.7%.
Contractors
Contractor | Contract | Description | Ref. Date | Expiry | Source |
Saskatchewan Power Corp.
|
Power supply
|
The mine site is serviced by a 138 kilovolt (kV) branch line fed from the SaskPower I2P utility line, which runs from the Island Falls generating station to Points North in northern Saskatchewan.
|
Feb 28, 2023
|
|
|
Source:
Summary:
Geological setting
The deposit is in the southeastern portion of the Athabasca Basin in northern Saskatchewan, within the southwest part of the Churchill structural province of the Canadian Shield. The deposit is located at or near the unconformity contact between the Athabasca Group sandstones and underlying metasedimentary rocks of the Wollaston Domain.
The deposit is similar to other Athabasca Basin deposits but is distinguished by its very high grade and overall size. Unlike Cigar Lake, there is no development of extensive hydrothermal clay alteration in the sandstone above the uranium mineralization and the deposit is geochemically simple with negligible amounts of other metals.
McArthur River’s geological setting is similar to the Cigar Lake deposit in that the sandstone that overlies the deposit and basement rocks contains large volumes of water at significant pressure.
Mineralization
McArthur River’s mineralization is structurally controlled by a northeast-southwest trending reverse fault (the P2 fault), which dips 40-65 degrees to the southeast and has thrust a wedge of basement rock into the overlying sandstone with a vertical displacement ranging between 60 and 80 metres.
The deposit consists of nine mineralized zones with delineated mineral resources and/or reserves: Zones 1, 2, 3, 4, 4 South, A, B, McA North 1 and McA North 2. These and three under-explored mineralized showings, known as McA North 3, McA North 4 and McA South 1, as well as other mineralized occurrences have also been identified over a strike length of 2,700 metres.
The main part of the mineralization, generally at the upper part of the basement wedge, averages 12.7 metres in width and has a vertical extent ranging between 50 metres and 120 metres.
The deposit has two distinct styles of mineralization:
• high-grade mineralization at the unconformity near the P2 reverse fault and within both sandstone and basement rocks;
• fracture controlled and vein like mineralization that occurs in the sandstone away from the unconformity and within the basement quartzite.
The high-grade mineralization along the unconformity constitutes the majority of the mineralization within the McArthur River deposit. Mineralization occurs across a zone of strongly altered basement rocks and sandstone across both the unconformity and the P2 structure. Mineralization is generally within 15 metres of the basement/sandstone contact with the exception of Zone 2.
Uranium oxide in the form of uraninite and pitchblende (+/- coffinite) occurs as disseminated grains in aggregates ranging in size from millimetres to decimetres, and as massive mineralization up to several metres thick.
Geochemically, the deposit does not contain any significant quantities of the elements nickel, copper, cobalt, lead, zinc, molybdenum, and arsenic that are present in other unconformity related Athabasca uranium deposits although locally elevated quantities of these elements have been observed in Zone B.
Deposit type
McArthur River is an unconformity-associated 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. The geological model was confirmed by surface drilling, underground drilling, development and production activities.
Mining Methods
- Raiseboring
- Blast Hole Stoping
- Cemented (undefined) backfill
Source:
Summary:
The mineral reserves at McArthur River are contained within seven zones: zones 1, 2, 3, 4, 4 South, A and B. There are currently two active mining zones (zone 2 and 4), one with development significantly advanced (zone 1), and one in the early stages of development (zone 4 South).
The McArthur River deposit presents unique challenges that are not typical of traditional hard or soft rock mines. These challenges are the result of mining in or near high pressure ground water in challenging ground conditions with significant radiation concerns due to the high-grade uranium ore. As such, mine designs and mining methods are selected based on their ability to mitigate hydrological, radiological and geotechnical risks.
Zone 2 has been actively mined since production began in 1999. The ore zone was initially divided into three freeze panels. As the freeze wall was expanded, the inner connecting freeze walls were decommissioned to recover the inaccessible uranium around the active freeze pipes. Mining of zone 2 is almost complete. About 3.5 million pounds of mineral reserves remain, and we expect to recover them using a combination of raisebore and blasthole stope mining.
Zone 4 has been actively mined since 2010. The zone was divided into four freeze panels, and like in zone 2, as the freeze wall was expanded, the inner connecting freeze walls were decommissioned. Zone 4 has 103.9 million pounds of mineral reserves secured behind freeze walls, and it will be the main source of production for the next several years. Raisebore and blasthole stope mining will be used to recover the mineral reserves.
Zone 1 is the next planned mine area to be brought into production. Freeze hole drilling was completed in 2023 and brine distribution construction work has resumed. A small section of the planned freeze wall is currently actively freezing. Once brine distribution construction is complete and an active freeze wall has been established, drill and extraction chamber development will need to be completed prior to the start of production. Once complete, an additional 48.0 million pounds of mineral reserves will be secured behind freeze walls. Blasthole stope mining is currently planned as the main extraction method in zone 1.
Zone 4 South is in the early development stages. Access development for the freeze drifts has resumed on the lower levels and freeze drilling began at the end of 2023 on the upper freeze drifts which were established prior to the 2018 shutdown.
There are three approved mining methods at McArthur River: raisebore mining, blasthole stope mining and boxhole mining. However, only raisebore and blasthole stope mining remain in use. Before we begin mining an area, we freeze the ground around it by circulating chilled brine through freeze holes to form an impermeable frozen barrier.
Blasthole stope mining
Blasthole stope mining began in 2011 and is the main extraction method planned for future production. It is planned in areas where blastholes can be accurately drilled and small stable stopes excavated without jeopardizing the freeze wall integrity. The use of this method has allowed the site to improve operating costs by increasing overall extraction efficiency by reducing underground development, concrete consumption, mineralized waste generation and improving extraction cycle time.
Raisebore mining
Raisebore mining is an innovative non-entry approach that we adapted to meet the unique challenges at McArthur River, and it has been used since mining began in 1999. This method is favourable for mining the weaker rock mass areas of the deposit and is suitable for massive high-grade zones where there is access both above and below the ore zone.
Ground freezing
All the mineralized areas discovered to date at McArthur River are in, or partially in, water-bearing ground with significant pressure at mining depths. This high pressure water source is isolated from active development and production areas in order to reduce the inherent risk of an inflow. To date, McArthur River has relied on pressure grouting and ground freezing to successfully mitigate the risks of the high pressure ground water.
Chilled brine is circulated through freeze holes to form an impermeable freeze barrier around the area being mined. This prevents water from entering the mine, and helps stabilize weak rock formations. Ground freezing significantly reduces, but does not fully eliminate, the risk of water inflows.
When a raise has been extracted of ore, it is filled with a concrete backfill that is produced at McArthur River. Components of the backfill include cement, sand, potentially acid generating (PAG) fines, aggregates and chemical admixtures.
Source:
- subscription is required.
Processing
- Calcining
- Sulfuric acid (reagent)
- Solvent Extraction
- Crush & Screen plant
- Reverse osmosis
- Agitated tank (VAT) leaching
- Counter current decantation (CCD)
- Acid tank leaching
- Dewatering
Flow Sheet:
Source:
p.104-107
Summary:
McArthur River produces two product streams, high-grade slurry and low-grade mineralization, which both report to the Key Lake mill to produce calcined uranium ore concentrate.
High-grade ore is slurried, ground, and thickened underground at McArthur River. The resulting slurry is pumped to surface and, after blending and further thickening, is transported to Key Lake in slurry trucks.
Low-grade mineralization is hoisted to surface and stored on the low-grade mineralization pads. This material is then hauled to the Key Lake low-grade mineralization blend pads.
McArthur River low-grade mineralization, including legacy low-grade mineralized waste stored at Key Lake, is slurried, ground and thickened at Key Lake and then blended with the McArthur River high-grade slurry to a nominal 5% U3O8 mill feed grade. All remaining uranium processing (leaching through to calcined uranium ore concentrate packaging) and tailings disposal also occur at Key Lake.
Key Lake activities
High-grade ore slurry arriving at the Key Lake ore slurry receiving plant is unloaded from the truck-mounted containers by a vacuum aspiration system and pumped to one of four large air-agitated slurry storage pachucas.
High-grade ore slurry is withdrawn from the ore storage pachucas and pumped to the blending tank where it is mixed with the neutral thickener underflow. The resulting slurry is pumped to one of three storage pachucas located in the leaching plant. Blending is necessary as the original Key Lake processing facilities were not designed from a radiation protection perspective to accommodate the high ore grades found at McArthur River. In addition to reducing the radiation exposure in the mill, the dilution of the high-grade ore serves two other purposes: recovery of uranium from the low-grade mineralized material; and final disposal of the low-grade mineralized waste.
The uranium is leached from the ore in the atmospheric leach pachuca and three continuous stirred tank reactors, while uranium-bearing solution is separated from waste solids in the counter current decantation (CCD) wash circuit. The high pressure autoclave secondary leaching circuit is on stand-by as the current ore is amenable to leaching at atmospheric pressure. Sulphuric acid, steam and oxygen are injected into the leach vessels to promote uranium extraction.
The CCD circuit consists of eight thickeners in series. The slurry flow is counter current to the wash water. The slurry moves from thickener one to thickener eight, while the wash water moves from thickener eight to one. The uranium-rich CCD overflow is pumped to the clarifier whilst the CCD underflow, with minimal residual uranium, is sent to the Deilmann tailings management facility.
In the solvent extraction plant, the clarified overflow pregnant solution is concentrated and purified by mixing with an organic solvent. The uranium transfers from the aqueous solution to the organic phase leaving behind most of the dissolved impurities. The organic solvent, loaded with uranium, is contacted with ammonium sulphate solution causing the uranium to transfer back to a highly concentrated aqueous phase known as loaded strip solution. A molybdenum removal circuit treats the loaded strip solution to remove molybdenum, an undesirable impurity in the final product.
Using ammonia, uranium is precipitated from the loaded strip solution in the precipitation tank as ammonium diuranate. The precipitate is dewatered in the yellowcake thickener followed by a centrifuge then calcined to U3O8 in a multi-hearth furnace. The final calcined uranium ore concentrate is packed in 200 litre drums for shipment to refineries around the world.
Excess ammonium sulphate is recovered from the yellowcake thickener overflow by evaporating the water and drying the resulting product, which is sold locally for use as a high purity fertilizer.
Contaminated water from the dewatering system associated with the depleted Gaertner and Deilmann open pits at Key Lake is treated in a reverse osmosis plant with the permeate used as industrial water.
Reject water from the reverse osmosis plant along with waste solvent extraction solution (raffinate) is sent to the bulk neutralization plant where the streams are neutralised with lime and other reagents are added to precipitate dissolved impurities. The resulting solids are combined with the CCD underflow and pumped to the Deilmann tailings management facility for final disposal. The treated water is sampled and released to one of four monitoring ponds. If all federal and provincial regulations are met, the treated water is released to the environment. If not, the pond is recycled through the bulk neutralization plant until the treated effluent becomes suitable for release.
The powerhouse/utilities/acid plant/oxygen plant complex provides acid, steam and oxygen for leaching and backup power as required.
Recoveries & Grades:
Commodity | Parameter | 2023 | 2022 | 2018 | 2017 |
Uranium
|
Recovery Rate, %
| 99 | 99 | 99 | 99 |
Uranium
|
Head Grade, %
| | 8.3 | 6.42 | |
Source:
- subscription is required.
Production:
McArthur River mine restart production in November 2022.
All production numbers are expressed as U3O8.
^ Guidance / Forecast.
Operational Metrics:
Metrics | 2022 | 2018 |
Ore tonnes mined
| 3.53 kt | 2.79 kt |
Reserves at December 31, 2023:
Category | Tonnage | Commodity | Grade | Contained Metal |
Proven
|
2,047 kt
|
U3O8
|
7.02 %
|
316.8 M lbs
|
Probable
|
520.7 kt
|
U3O8
|
5.55 %
|
63.8 M lbs
|
Proven & Probable
|
2,568 kt
|
U3O8
|
6.72 %
|
380.5 M lbs
|
Measured
|
78.7 kt
|
U3O8
|
2.27 %
|
3.9 M lbs
|
Indicated
|
60.6 kt
|
U3O8
|
2.3 %
|
3.1 M lbs
|
Measured & Indicated
|
139.3 kt
|
U3O8
|
2.28 %
|
7 M lbs
|
Inferred
|
37.2 kt
|
U3O8
|
2.9 %
|
2.4 M lbs
|
Financials:
| Units | 2019 | 2018 |
Sustaining costs
|
M CAD
|
2
|
9
|
Heavy Mobile Equipment as of December 31, 2018:
Source:
p.98
HME Type | Model | Size | Quantity |
Bolter
|
|
|
2
|
Concrete sprayer
|
|
|
2
|
Concrete sprayer
|
|
|
2
|
Continuous Miner
|
Sandvik AM75
|
|
1
|
Dozer
|
|
|
2
|
Drill
|
Cubex
|
|
4
|
Drill (long hole)
|
Cubex
|
|
2
|
Drill jumbo (two boom)
|
|
|
2
|
Grader
|
|
|
2
|
Loader
|
|
|
3
|
Raise boring rig
|
|
3 m
|
8
|
Scoop Tram
|
|
8 cu. yd
|
4
|
Scoop Tram
|
|
6 cu. yd
|
3
|
Scoop Tram
|
|
4 cu. yd
|
2
|
Trans Mixer
|
|
|
2
|
Truck (fuel / lube)
|
|
|
4
|
Truck (haul)
|
|
|
2
|
Mine Management:
Job Title | Name | Profile | Ref. Date |
General Manager - Processing
|
Daley McIntyre
|
|
Feb 29, 2024
|
Mill Manager
|
Keith Perry
|
|
Feb 29, 2024
|
Operations Superintendent
|
Drew Williams
|
|
Feb 29, 2024
|
Process Superintendent
|
Nathan Rolston
|
|
Feb 29, 2024
|
Senior Maintenance Planner
|
Kris Halland
|
|
Feb 29, 2024
|
Sr. Mine Engineer
|
Austin Roberts
|
|
Feb 29, 2024
|
Staff:
Employees | Total Workforce | Year |
|
1,088
|
2023
|
|
833
|
2022
|
|
670
|
2021
|
185
|
|
2020
|
175
|
|
2019
|
Corporate Filings & Presentations: