Focused. Experienced. Growing.
DML.CA   $0.71 -0.02    DNN   $0.56 -0.01

Exploration &

McClean Lake and the McClean Lake Mill

McClean Lake is comprised of several uranium deposits and a state of the art mill located on the eastern edge of the Athabasca Basin in northern Saskatchewan, approximately 750 kilometres north of Saskatoon. McClean Lake is owned by Denison (22.5%) and its joint venture partners, ARC (70.0%) and OURD Canada Co., Ltd. ("OURD") (7.5%). ARC is the operator/manager of the facility. Denison, ARC and OURD also jointly own the nearby Midwest project, although ownership percentages are slightly different. It is planned that the Midwest ore will be milled at the McClean Lake mill.

Development of the McClean Lake project began in March 1995. Construction and commissioning were completed in 1997. The JEB deposit was mined out and the ore stockpiled. The JEB pit was then converted in 1999 into the JEB Tailings Management Facility ("TMF"). The McClean Lake mill began production of uranium concentrates in 1999, processing ore from the JEB deposit. The first ore was fed to the mill on June 22, 1999 and commercial production was achieved on November 1, 1999. The mill operated until the end of June 2010 producing approximately 49.9 million pounds U3O8 when it was placed on stand-by due to a lack of ore.

In 2014, the McClean Lake mill re-commenced operations with the delivery of ore shipments from the Cigar Lake Mine, owned by the CLJV and operated by Cameco. Operations have continued since, as described further below.

McClean Lake Mill

The McClean Lake mill is specially designed and constructed to process high grade uranium ores in a safe and environmentally responsible manner. The mill uses sulphuric acid and hydrogen peroxide leaching and a solvent extraction recovery process to extract and recover the uranium product from the ore. In addition to the mill facility, other infrastructure on the site includes a sulphuric acid plant, a ferric sulphate plant, an oxygen plant, an electricity transmission line tied into the provincial power grid, a 14 megawatt back-up diesel power plant, warehouses, shops, offices and living accommodations for site personnel. In 2016, mill expansion construction and licensing was completed and the licensed production capacity of the mill was increased to 24 million pounds U3O8 per year. This increased licensed capacity allows for the processing of 100% of ore production from the Cigar Lake mine, forecasted to be 18 million pounds U3O8 per year, and the flexibility to mill ore from other sources.

In 2014, the McClean Lake mill re-commenced operations and processed over 456,800 pounds of U3O8 with a 97.5% recovery rate. Re-start of the mill proceeded smoothly with no significant production problems. Mill feed consisted of a blend of Cigar Lake ores and stockpiled Sue B and McClean Lake North ores (mined via SABRE). In 2015, production ramped up and the mill produced approximately 11.3 million pounds of U3O8 with a 98.9% recovery including several months with production over 1.5 million pounds. In 2016, the mill produced 17.3 million pounds of U308 with a 99% recovery, and mill feed was all Cigar Lake ore. While mill personnel continue to refine operational practices and procedures to further improve performance, overall mill performance included no major upsets in the areas of safety, the environment or production.


McClean Lake consists of nine known ore deposits, five of which have been mined out with some of the ore still stockpiled on the surface.

The first ore body, JEB, was mined from 1997 to 1999 and the ore was stockpiled. Mining of the Sue C ore body was completed in February 2002, and all of the ore was stockpiled on the surface. Mining was then suspended until the third quarter of 2005 when mining began on the Sue A, Sue E and Sue B deposits. Mining was completed at Sue A in the first quarter of 2006, at Sue E in the first quarter of 2008 and at Sue B at the end of 2008. Exploration activities intended to expand the known deposits and identify new deposits are ongoing.

Low-grade special waste from the mining of the JEB, Sue C, Sue A, Sue E and Sue B deposits has been disposed of in the mined-out Sue C pit. In the future, Cigar Lake special waste will also be disposed of in the Sue C pit. By agreement between the CLJV and the MLJV, costs to upgrade the Sue Water Treatment Plant and costs to dewater the Sue C pit for Cigar Lake special waste will be shared 50/50 between the CLJV and the MLJV.


Approximately 87,500 tonnes of Sue B ore at a grade of 0.35% U3O8 and 534 tonnes of McClean Lake North ore (mined via SABRE) at an average grade of 4.78% U3O8, remain on the stockpile as at the end of 2016.

Cigar Lake Toll Milling

In 2002, Denison and its partners entered into an agreement with the CLJV to process Cigar Lake ore at the McClean Lake mill. Pursuant to that agreement, all Cigar Lake ore was to be leached at the McClean Lake mill with the pregnant aqueous solution being divided between the McClean Lake and Rabbit Lake facilities for processing into uranium concentrates. In order to process this Cigar Lake ore, an expansion of the McClean Lake mill was required. The expansion and modifications of the McClean Lake mill to raise its capacity to 13.0 million pounds U3O8 were completed in 2008 and all costs were paid for by the CLJV.

As a result of delays in the startup of the Cigar Lake mine and the exhaustion of permitted ore deposits at McClean Lake, the McClean Lake mill was placed on stand-by at the end of June of 2010. Under the Cigar Lake toll milling agreement, the CLJV funded a considerable portion of the McClean Lake stand-by costs, with the relative proportion of the stand-by costs paid by each party calculated on the basis of the percentage of mineral reserves between the McClean Lake and Cigar Lake joint ventures.

In 2011, the CLJV and the MLJV agreed to amend the toll milling agreement. Under the new milling arrangement, the McClean Lake operation is expected to process and package 100% of the uranium produced from the Cigar Lake mine. To accommodate the annual production of 18.0 million pounds U3O8 from the CLJV, the mill has been further expanded to an annual licensed capacity of 24.0 million pounds U3O8. All costs for the expansion of the McClean Lake mill and a portion of the TMF Optimization and TMF Expansion (See "Denison's Operations - McClean Lake - Tailings Disposal") are paid for by the CLJV.

Cigar Lake Toll Milling - APG Financing

Pursuant to the APG Financing in February 2017, certain of Denison's interests in the Cigar Lake toll milling proceeds have been sold to APG and Centaurus for aggregate gross proceeds to Denison of CAD$43,500,000. The APG Financing is comprised of the following elements: (1) a 13 year limited recourse lending arrangement involving a loan from APG to 9373721 Canada Inc. ("SPV") (the "APG Loan") and a further loan from SPV to DMI (the "SPV Loan") each for CAD$40,800,000 (collectively, the "Lending Arrangement"); and (2) CAD$2,700,000 in proceeds from the sale, to Centaurus, of a stream equal to Denison's 22.5% share of proceeds from the toll milling of Cigar Lake ore by the McClean Lake mill for specified Cigar Lake toll milling throughput in excess of 215 million pounds U3O8 after July 1, 2016 (the "Stream Arrangement").

Additional details of the APG Financing are as follows:
  • No Warranty of the Future Rate of Production - No warranty is provided by Denison (including DMI and SPV) to APG (including Centaurus), under the terms of the Lending Arrangement or the Stream Arrangement, regarding: the future rate of production at the Cigar Lake mine and / or the McClean Lake mill; or the amount or collectability of proceeds to be received by the MLJV in respect of toll milling of Cigar Lake ore.
  • APG Loan Details - The APG Loan will accrue interest at a rate of 10% per annum and does not have a predetermined principal repayment schedule. The APG Loan is secured by a first priority interest in the assets of SPV which will essentially consist of the SPV Loan to DMI.
  • SPV Loan Details - The SPV Loan will accrue interest at a rate of approximately 10% per annum and does not have a predetermined principal repayment schedule. The SPV Loan is limited in its recourse against DMI such that it is generally repayable only to the extent of Denison's share of the toll milling revenues earned by the MLJV from the processing of the first 215 million pounds of U308 from Cigar Lake ore on or after July 1, 2016. Denison will guarantee the limited recourse loan repayments and will grant a second ranking pledge of its share of DMI to secure performance by DMI of its obligations to pay the SPV Loan. The share pledge is second ranking to Denison's existing pledge of its shares of DMI to the Bank of Nova Scotia ("BNS") under the terms of its Letters of Credit Facility.
Please see Annual Information Form for further information on the McClean Lake and McClean Lake Mill Project.
Show printable version of 'McClean Lake and the McClean Lake Mill' in a New Window