The Midwest Uranium Project is located in Canada. Image Representative. (Credit: jbdodane / Flickr)
McClean Lake Water Treatment Plant. (Credit: Orano Canada)
The project contains total Inferred Mineral Resources of 18.2Mlbs of triuranium octoxide . (Credit: Nuclear Regulatory Commission / Flickr)

The Midwest Uranium Project is an advanced exploration stage uranium mine located in the province of Saskatchewan, Canada.

The project is owned by a joint venture of Orano Canada (74.83%, operator) and Denison Mines (25.17%).

A technical report for the property along with an updated mineral resource estimate was published in March 2018.

In April 2023, Denison Mines announced the completion of an internal conceptual study to assess the potential application of the In-Situ Recovery (ISR) mining method in Midwest. The company will conduct additional ISR-related evaluation work for Midwest in 2023.

Midwest Project Location

The Midwest Uranium Project is located in eastern Athabasca Basin in Northern Saskatchewan, around 700km northeast of Saskatoon.

The project includes three contiguous mineral leases and contains Midwest Main (formerly Midwest) and Midwest A deposits.

The site is accessible throughout the year by provincial highway to Points North, a private service centre with accommodations and airstrip. The Points North Landing airstrip is within 1km from the property.

Ownership History

In 1968, Numac Oil & Gas became the initial operator when it acquired a large area of which Midwest was a part.

Numac was acting as the operator of the joint venture between Esso Resources Canada (50%), Numac (10%), Bow Valley Industries (20%), Mink Mining (10%), and Midwest Mining (10%).

It remained the operator of the project till 1977.

Esso Resources Canada Limited acquired the principal operatorship of the project in 1977 and in 1980, the company’s subsidiary Canada Wide Mines took over the responsibility of the work.

In 1982, Esso decided not to continue with the work and the project remained dormant until 1988.

The project got reactivated in 1988 when a new joint venture was established comprising Denison Mines Limited (45%), Bow Valley Industries (20%), Uranerz Exploration & Mining (20%), and PNC Exploration (Canada) (15%).

OURD acquired PNC’s stake in 1991 and Denison sold a part of its equity in the joint venture to Minatco (25.5%) in 1993 while retaining the rest under its subsidiary Tenwest (19.5%).

Thereafter, OURD sold a part of its interest to Minatco (10.5%) and Bow Valley sold its 20% equity to Minatco.

The new equities of the joint venture were Tenwest/Denison (19.5%), OURD (4.5%), Uranerz (20%), and Minatco (56%). Minatco became the operator of the project.

The uranium assets of TOTAL (Minatco in Canada) were acquired by COGEMA Resources (CRI) in 1994, becoming the operator of the Midwest project. Minatco was completely dissolved by 1996.

Redstone Resources acquired CRI and Tenwest/Denison’s equity portions and in 2004, it sold back the equities to Denison.

In 2006, CRI changed its name to AREVA Resources Canada. The joint venture partners became AREVA Resources Canada (69.16%), Denison Mines (25.17%), and OURD (5.67%).

In February 2018, AREVA changed its name to Orano Canada. It also acquired OURD’s stake in the project.

Geology and Mineralisation

The Midwest property lies within the Athabasca Basin of northern Saskatchewan.

The geology of the Athabasca bedrock comprises Archean orthogneiss and Paleoproterozoic Wollaston Group metasediments. These are part of the Wollaston-Mudjatik Transition Zone.

The Midwest Main and Midwest A deposits are hosted within the north-northeast trending ductile to brittle structural trend which follows a steeply-dipping graphitic pelitic gneiss metasedimentary unit.

The basement fault zones extensions that usually extend more than 100m into the overlying sandstone act as hosts for uranium.

Both, the Midwest A deposit and the Midwest Main deposits are egress-style unconformity-type deposits.

The Midwest Main deposit is nearly 920m long, 10m to 140m wide, and have a thickness of up to 33m. On the other hand, the 450m long Midwest A deposit is 10m to 60m wide with thickness ranging up to 70m.

Midwest Main and Midwest A have mineralisation consisting of mixtures of pitchblende/uraninite and nickel-cobalt arsenides.

Midwest Project Mineral Resource Estimate

There have been several mineral resource estimates since the discoveries of Midwest Main and Midwest A deposits in 1977 and 2005 respectively.

According to the updated mineral resource estimate announced in 2018, the project contains total Inferred Mineral Resources of 18.2 Mlbs of triuranium octoxide (U3O8) (846,000 tonnes at 1.0% U3O8) above a cut-off grade of 0.1% U3O8.

Total Indicated Mineral Resources stands at 50.78Mlbs U3O8 (1,019,000 tonnes at 2.3% U3O8) above a cut-off grade of 0.1% U3O8. This includes 39.9Mlbs of U3O8 in Midwest Main and 10.8Mlbs of U3O8 in Midwest A.

Mining and Processing

The mining method for the Midwest Main and Midwest A deposits are yet to be determined.

Previously, JEB, Sue A, B, C, and E, were mined using open pit methods. Surface Access Borehole Resource Extraction (SABRE) or Mine Equipment Development (MED) and Surface Access Borehole Mining (SABM) were used to mine at Pod 1 East of the McClean North deposit during 2009 and 2012.

In April 2023, Denison successfully completed the internal conceptual mining study to examine the in-Situ Recovery (ISR) mining method to be used as mining method at the property.

In a ISR operation, a mining solution (lixiviant) is injected into the ore zone through a series of drill holes and then extracted as a uranium bearing solution (UBS). Once recovered, the UBS is sent to a surface processing plant for the chemical separation of the uranium. After uranium removal, the lixiviant is reconditioned and sent back to the wellfield for further production.

The uranium mined from Midwest Main and Midwest A deposits is expected to be processed at the MLJV McClean Lake facilities.

The processing includes SAG and ball mill grinding; slurry leaching; Counter-Current Decantation (CCD);  clarification in pregnant solution; and solvent extraction.

The output, in the form of yellowcake, undergoes precipitation followed by the crystallisation of ammonium sulphate.

The tailings are neutralised and disposed safely while the remaining output is treated with water for recovery.

Contractors Involved

SRK Consulting (Canada) prepared the 2018 technical report of the Midwest Uranium Project.

Geostat carried out an independent mineral resource estimate review of the Midwest A uranium deposit. The results were published in January 2008.