Click Down to Dig In

McArthur River & Key Lake

North America map showing location of McArthur River and Key Lake properties

McArthur River is the world’s largest, high-grade uranium mine, and Key Lake is the largest uranium mill in the world.

Ore grades at the McArthur River mine are 100 times the world average, which means it can produce more than 18 million pounds per year by mining only 150 to 200 tonnes of ore per day. We are the operator.

McArthur River is one of our three material uranium properties.

Location Saskatchewan, Canada
Ownership 69.805% – McArthur River
83.33% – Key Lake
End product Uranium concentrates
ISO certification ISO 14001 certified
Mine type Underground
Estimated reserves (our share) 251.6 million pounds (proven and probable), average grade U3O8: 15.76%
Estimated resources (our share) 9.5 million pounds (measured and indicated), average grade U3O8: 4.81%
39.9 million pounds (inferred), average grade U3O8: 7.38%
Mining methods Primary: raiseboring
Secondary: blasthole stoping, boxhole boring
Licensed capacity Mine and mill: 18.7 million pounds per year
(can be exceeded – see Flexibility provisions)
Total production:
(100% basis)
2000 to 2013 250.6 million pounds (McArthur River/Key Lake)
  1983 to 2002 209.8 million pounds (Key Lake)
2013 production (our share) 14.1 million pounds (20.1 million pounds on 100% basis)
2014 forecast production (our share) 13.1 million pounds (18.7 million pounds on 100% basis)
Estimated decommissioning cost
(100% basis)
$48 million – McArthur River
$218 million – Key Lake (estimate currently under review)


Mining methods and techniques

We use a number of innovative methods to mine the McArthur River deposit:

Ground freezing

The sandstone that overlays the deposit and basement rocks is water-bearing, with large volumes of water under significant pressure. We use ground freezing to form an impermeable wall around the area being mined. This prevents water from entering the mine, and helps stabilize weak rock formations. To date, we have installed five freezewalls and are currently preparing a sixth.

Raisebore mining

Raisebore mining is an innovative non-entry approach that we adapted to meet the unique challenges at McArthur River. It involves:

  • drilling a series of overlapping holes through the ore zone from a raisebore chamber in waste rock above the mineralization
  • collecting the broken ore at the bottom of the raises using line-of-sight remote-controlled scoop trams, and transporting it to a grinding circuit
  • once mining is complete, filling each raisebore hole with concrete´┐╝´┐╝´┐╝
  • when all the rows of raises in a chamber are complete, removing the equipment and filling the entire chamber with concrete
  • starting the process again with the next raisebore chamber

We have used the raisebore mining method to successfully extract about 250 million pounds (100% basis) since we began mining in 1999. Raisebore mining is scheduled to remain the primary extraction method over the life of mine.

Diagram of McArthur River underground mine

McArthur River currently has six areas with delineated mineral reserves (zones 1 to 4, zone 4 south and zone B) and eight areas with delineated mineral resources. We are currently mining zone 2 and the lower area of zone 4.

Zone 2 has been actively mined since production began. It is divided into four panels (panels 1, 2, 3 and 5) based on the configuration of the freezewall around the ore. As the freezewall is expanded, the inner connecting freezewalls are decommissioned in order to recover the uranium that was inaccessible around the active freeze pipes. Panel 5 represents the upper portion of zone 2, overlying part of the other panels. Mining is nearing completion in panels 1, 2 and 3, and the majority of the remaining zone 2 proven mineral reserves are in panel 5.

Zone 4 is divided into three mining areas: central, north and south. We are actively mining the central area. A new mining area is also under development – zone 4 north – and is forecast to be in production in 2014.

In 2013, the CNSC granted approval for the use of two secondary extraction methods: blasthole stoping and boxhole boring. We expect that these extraction methods will only be used in limited situations to complement our primary extraction method of raiseboring.

Boxhole boring

Boxhole boring is similar to the raisebore method, but the drilling machine is located below the mineralization, so development is not required above the mineralization. This method is currently being used at a few mines around the world, but had not been used for uranium mining prior to testing at McArthur River.

We expect boxhole boring will only be used as a secondary method, in areas where we determine raiseboring is not feasible or practical. Test mining to date has identified this as a viable mining option; however, only a minor amount of ore is scheduled to be extracted using this method.

Blasthole stoping

Blasthole stoping involves establishing drill access above the mineralization and extraction access below the mineralization. The area between the upper and lower access levels (the stope) is then drilled off and blasted. The broken rock is collected on the lower level and removed by line-of-sight remote-controlled scoop trams, then transported to a grinding circuit. Once a stope is mined out, it is backfilled with concrete to maintain ground stability and allow the next stope in sequence to be mined. This mining method has been used extensively in the mining industry, including uranium mining.

Blasthole stoping is planned in areas where blast holes can be accurately drilled and small stable stopes excavated without jeopardizing the freezewall integrity. We expect this method to complement the raiseboring method and to allow for more economic recovery of ore on the periphery of the orebody, as well as smaller, lower grade areas.

Initial processing

We carry out initial processing of the extracted ore at McArthur River:

  • the underground circuit grinds the ore and mixes it with water to form a slurry
  • the slurry is pumped 680 metres to the surface and stored in one of four ore slurry holding tanks
  • it is blended and thickened, removing excess water
  • the final slurry, at an average grade of 15% U3O8, is pumped into transport truck containers and shipped to Key Lake mill on an 80 kilometre all-weather road

Water from this process, including water from underground operations, is treated on the surface. Any excess treated water is released into the environment.

2013 update


Total production from McArthur River/Key Lake was 20.1 million pounds, which is the highest annual output from a uranium facility anywhere in the world. Our share of production in 2013 was 14.1 million pounds U3O8, 4% higher than our forecast for the year, and 4% higher than annual production in 2012.

At McArthur River and Key Lake, we realized benefits under the production flexibility provision in our operating licences (see Flexibility provisions). Ongoing efforts to improve the efficiency and reliability of the Key Lake mill resulted in record mill performance.

Licensing and production capacity

On October 29, 2013, the CNSC granted a renewal of our McArthur River and Key Lake operating licences. The licence term is from November 1, 2013 to October 31, 2023.

Flexibility provisions

As long as average annual production does not exceed 18.7 million pounds per year, production flexibility provisions in the licence conditions handbooks allow:

  • the Key Lake mill to produce up to 20.4 million pounds (100% basis) per year
  • the McArthur River mine to produce up to 21 million pounds (100% basis) per year

Our average annual production at McArthur River/Key Lake over the past five years is 19.7 million pounds. Consequently, we have limited flex capacity remaining under our licence provisions.

McArthur River production expansion

A limiting factor for production at the McArthur River mine is the licence limit of 18.7 million pounds (100% basis) per year, and in order to maintain the flexibility to produce more, we plan to request a production limit increase to 21 million pounds (100% basis) in 2014. This would match the currently approved maximum production level. We expect a decision on this increase in 2014.

In addition, we will continue the work to further increase our annual production rate to 22 million pounds (100% basis) by 2018, subject to regulatory approval, as contemplated in the revision to our mine plan in 2012.

We were notified by the CNSC that the environmental assessment for the planned increase in production to 22 million pounds would be transitioned to the CNSC licensing and compliance processes, rather than the federal environmental assessment process.

In order to implement the planned production increases, we must continue to successfully transition into new mine areas through mine development and investment in support infrastructure. In addition, we plan to:

  • obtain all the necessary regulatory approvals, including at Key Lake, to ensure the mill can process all of the ore mined annually at McArthur River
  • expand the freeze plant and electrical distribution systems
  • increase ventilation by sinking a fourth shaft at the northern end of the mine
  • improve our dewatering system and expand our water treatment capacity

New mining areas

We completed installation of the freezewall and brine lines in the upper mining area of zone 4 north. We began freezing the ground in the third quarter of 2013, with plans to start mining the zone in late 2014.

In addition to the underground work, we continued to upgrade our electrical infrastructure on surface to address the future need for increased ventilation and freeze capacity associated with mining new zones and increasing mine production.

Key Lake extension project and mill revitalization

The Key Lake mill began operating in 1983 and is currently licensed to produce 18.7 million pounds (100% basis) per year. Mill production at Key Lake is expected to closely follow McArthur River production, subject to receipt of regulatory approval. As part of our Key Lake extension environmental assessment (EA), we are seeking approval to increase Key Lake’s nominal annual production rate to 25 million pounds and to increase our tailings capacity; in 2014, we expect the federal and provincial EA to conclude and expect a decision to be made on these increases.

The mill revitalization plan includes upgrading circuits with new technology to simplify operations and improve environmental performance. Major components of a new calciner circuit were installed in 2013 and commissioning is expected to be completed in 2014. As part of the revitalization plan, we also replaced the existing electrical substation in order to meet future electrical demands.

Tailings capacity

This year we:

  • submitted the final environmental impact statement for review by the regulators, and plan to pursue the required regulatory approvals in 2014
  • completed flattening of the Deilmann tailings management facility pitwalls


In 2013, our surface exploration programs continued to test zones of mineralization north of the current mining areas.

Planning for the future


We plan to produce 18.7 million pounds per year (13.1 million pounds our share) until we receive the required regulatory approvals and complete the work necessary to increase production at both McArthur River and Key Lake.

New mining zones

Zone 4 north is the next area to be mined. Freezing has begun and we forecast initial production to start in 2014.

We expect to use raisebore mining in this area, applying the ground freezing experience we gained in zone 2, panel 5. This should significantly improve production efficiencies compared to boxhole boring.

Mill revitalization

In 2014, we expect to:

  • complete installation and commissioning of the new calciner
  • upgrade the electrical services necessary to add standby electrical generating capacity for the new electrically heated calciner

Key Lake extension project

In 2014, we expect to complete the regulatory process required to increase production to 25 million pounds per year at Key Lake. We will also seek approval to deposit tailings in the Deilmann tailings management facility to a higher level, providing enough tailings capacity to potentially mill all the known McArthur River mineral reserves and resources, should they be converted to reserves, with additional capacity to toll mill ore from other regional deposits.

See Key Lake tailings capacity risk below for additional information.


In 2014, we plan to continue advancing the underground exploration drifts to the southwest and northeast directions. Additional drilling is planned underground to delineate zone A, and from surface to identify additional mineral resources in the deposit.

Managing our risks

Production at McArthur River/Key Lake poses many challenges: control of groundwater, weak rock formations, radiation protection, water inflow, mine area transitioning, regulatory approvals and tailings capacity. Operational experience gained since the start of production has resulted in a significant reduction in risk.

Labour relations

The current collective agreement with unionized employees at the McArthur River and Key Lake operations expired on December 31, 2013 and bargaining for a new agreement is currently underway. There is risk to production in 2014 if we are unable to reach an agreement and employees go on strike.

Transition to new mining areas

In order to successfully achieve the planned production schedule, we must continue to successfully transition into new mining areas, which includes mine development and investment in critical support infrastructure.

The zone 4 north transition planned in late 2014 carries a slightly higher transition risk than other mining area transitions due to the site’s limited flexibility to offset a shortfall in production due to schedule delays.

Key Lake tailings capacity risk

Tailings from processing McArthur River ore are deposited in the Deilmann tailings management facility. At current production rates, the facility will reach licensed capacity by 2018. A significant delay in obtaining or a failure to receive, the necessary regulatory approval for the expansion of the facility could interrupt or prevent the operation of McArthur River/ Key Lake as planned.

In the past, sloughing of material from the pitwalls has resulted in loss of capacity. Technical studies show that stabilizing and reducing water levels in the pit enhances the stability of the pitwalls and reduces the risk of sloughing. In 2009, regulators approved our plan for the long-term stabilization of the Deilmann tailings management facility pitwalls. We implemented the plan and completed the project in 2013. We are proceeding with the environmental assessment to support an application for regulatory approval to deposit tailings to a higher level. This would provide enough tailings capacity to mill all the known McArthur River mineral reserves and resources, should they be converted to reserves, with additional capacity to toll mill ore from other regional deposits.

Water inflow risk

The greatest risk is production interruption from water inflows. A 2003 water inflow resulted in a three-month suspension of production. We also had a small water inflow in 2008 that did not impact production.

The consequences of another water inflow at McArthur River would depend on its magnitude, location and timing, but could include a significant interruption or reduction in production, a material increase in costs or a loss of mineral reserves.

We take the following steps to reduce the risk of inflows, but there is no guarantee that these will be successful:

  • Ground freezing: Before mining, we drill freezeholes and freeze the ground to form an impermeable freezewall around the area being mined. Ground freezing reduces but does not eliminate the risk of water inflows.
  • Mine development: We plan for our mine development to take place away from known groundwater sources whenever possible. In addition, we assess all planned mine development for relative risk and apply extensive additional technical and operating controls for all higher risk development.
  • Pumping capacity and treatment limits: Our standard for this project is to secure pumping capacity of at least one and a half times the estimated maximum sustained inflow. We review our dewatering system and requirements at least once a year and before beginning work on any new zone.

We believe we have sufficient pumping, water treatment and surface storage capacity to handle the estimated maximum sustained inflow.

We also manage the risks listed here.