Denison Announces Completion of Inaugural ISR Field Test Program at Midwest
Denison Mines Corp.
1100 – 40 University Ave
Toronto, ON M5J 1T1
www.denisonmines.com
PRESS RELEASE
Denison Announces Completion of
Inaugural ISR Field Test Program at Midwest
Toronto, ON – June 3, 2 024. Denison Mines Corp. (“Denison”) (TSX: DML; NYSE American: DNN) is
pleased to announce it has completed the inaugural In -Situ Recovery (“ISR”) field test program (the
“Program”) at Denison’s 25.17% owned Midwest Ur anium Project (“Midwest”). The Program involved
drilling 10 small diameter boreholes within the Midwest Main deposit primarily undertaken to evaluate site-
specific conditions for ISR mining. A series of tests were successfully performed on each borehole, creating
an extensive database of geological, hydrogeological , geotechnical, and metallurgical data and validating
certain key assumptions in the previously completed internal conceptual mining study (the “Concept Study”)
evaluating the potential use of ISR mining at Midwest (see Press Release dated April 12, 2023).
Denison carried out the Program in collaboration wi th Orano Canada Inc. (“Orano Canada”), as operator
and owner of 74.83% of the Midwest Joint Venture (“MWJV”). Midwest is located approximately 25
kilometres, by existing roads, from the Denison-Orano Canada owned McClean Lake Operation (see
Figure 1), which is currently processing ore for the Cigar Lake mine under a toll milling agreement and has
excess licensed processing capacity. Orano Canada is part of the Orano Group, which is recognized as a
leading international operator in t he field of nuclear materials, with activities including uranium mining,
conversion, enrichment, and other fuel services.
David Cates, Denison’s President and Chief Executive Officer, commented “Denison would like to thank
Orano Canada for its support and encouragement of our joint efforts to evaluate the Midwest Main
deposit for potential future extraction via ISR mining. Orano has significant global expertise in ISR
mining and Denison brings industry leadership in the advancement of ISR mining in the Athabasca
Basin region – allowing the joint venture to assemble a very strong team to carry out and oversee
this inaugural test program.
The Program achieved its planned objectives, and the results provide preliminary validation that
the Midwest Main deposit possesses the characteristics necessary for an ISR operation.
Accordingly, further evaluation is warranted and, building on the Concept Study and incorporating
the data acquired in the test program, we are proceeding with a Preliminary Economic Assessment
(“PEA”) for ISR mining. Midwest represents Deni son’s third project evaluated for potential ISR
mining in the Athabasca Basin.”
Highlights from the Program include the following:
Confirmed Hydraulic Conductivity: Pump and injection tests validated hydraulic connectivity in
the test wells within the mineralized zone and ac hieved hydraulic conductivity values (a measure
of permeability) consistent with the Concept Study. Sufficient per meability within the mineralized
zone is a key criterion for the successful deployment of the ISR mining method.
Demonstrated the Effectivenes s of Permeability Enhancement: One method of permeability
enhancement was succ essfully deployed within two wells, demonstrating the suitability of the
method to the Midwest Main deposit. Effici ency of permeability enhancement was verified by
comparison of pre- and post-permeability enhancement hydraulic testing.
Metallurgical Samples Defined and Co llected for Leaching Characteristics: Core samples
representative of the Midwest deposit were co llected during the Program for use in future
metallurgical tests to determine the leaching characteristics.
2024 ISR Field Test Program
The 2024 ISR field test program was designed to vali date various deposit-specific characteristics of the
Midwest Main deposit, and to collect a database of geotechnical, hydrogeological, and metallurgical data
to further evaluate the ISR mining conditions present at the deposit.
Ten small-diameter test wells were installed within the Midwest Main deposit during the Program – including
a 4-well test pattern (the “Test Pattern”) and 6 individual wells to test specific areas of the deposit for various
characteristics. The Test Pattern included one inject ion well, one extraction well, a recharge well, and a
monitoring well outfitted with a multi-channel vibrating wire piezometer. The six additional wells were drilled
to their target depths and, as applicable, outfitted with well screens and/or pressure monitoring devices to
facilitate hydrogeological testing. All wells were decommi ssioned at conclusion of the Program consistent
with regulatory commitments. See Figures 2 and 3 for an illustration of the well locations within the northeast
portion of the Midwest Main deposit.
Core collected from the test wells within the mineral ized zone is also expected to be used to verify and
update the current mineral resource estimate for the deposit and support future wellfield design and mineral
processing assessments.
Successful Completion of Hydrogeologic Test Work
The Program included the completion of various pump, injection, and packer tests designed to assess the
permeability of the Midwest Main deposit.
The test program measured pressure changes within the mineralized zone, which provides evidence of the
deposit’s hydraulic conditions and is indicative of the potential for the movement of mining solution in an
ISR mining operation. Sufficient permeability within the mineralized zone is a key criterion for the successful
deployment of the ISR mining method.
The results from the hydrogeological testing at Midwes t Main produced hydraulic conductivity values that
are consistent with those assumed in the Concept Study.
Additional supportive test work completed during th e Program included permeability and porosity tests
conducted either downhole or on mineralized drill core recovered during the test program.
Demonstration of the Effectiveness of Permeability Enhancement Method
One method of permeability enhancement was successf ully evaluated on two test wells within the
mineralized zone, with efficacy ve rified by the comparison of pr e- and post-permeability enhancement
hydraulic conductivity tests. Permeability enhancement has been demonstrated to increase and normalize
hydraulic conductivity in the area proximal to the wellbore, allowing for increased contact of injected fluids
within the mineralized zone in order to maximize uranium recoveries in an ISR mining environment.
Collection of Other Supporting Datasets
In addition to the tests described above, data and samples were collected from the drill core recovered from
the test wells to facilitate: (1) t he assessment of matrix permeability, to inform an initial model of the
hydrogeological variations of the deposit; (2) geot echnical evaluations; (3) sediment analysis using
Standard Penetration Test (“SPT”) for measuring mud depths and the overburden below lake bottom; and
(4) testing of compressive and tensile strength for incorporation into future geotechnical assessments.
About Midwest
Midwest is situated in the eastern portion of the Athabasca Basin region in northern Saskatchewan. The
property is approximately one kilometre from the Po ints North Landing airstrip and about 25 kilometres
west, by existing roads, from the McClean Lake Mill, which is jointly owned by Denison (22.5%) and Orano
Canada (77.5%). Access to Midwest is by both road and air. Goods are transported to the site by truck
over an all-weather road connecting with the provincial highway system . Air transportation is provided
through the Points North airstrip (See Figure 1).
Initial exploration work at Midwest began in 1966, and Denison first became an owner of the project in 1987.
In 2007, Orano Canada completed an internal study ev aluating the feasibility of mining the Midwest Main
deposit via open pit mining methods with processing of the resulting ore at the McClean Lake Mill. The
MWJV subsequently advanced the project through the environmental assessment process as an open pit
mine and the final version of the Midwest Pr oject Environmental Impact Statement was
approved in September 2012.
The MWJV is currently evaluating the viability of a number of potential options for the future development
of the Midwest Main deposit, including ISR. Even if a mining method is selected, any future development
by the MWJV will be subject to various review and approval processes, including MWJV approval
processes, provincial and federal regulatory review, and engagement.
About Denison
Denison is a uranium mining, exploration and development company with interests focused in the
Athabasca Basin region of northern Sa skatchewan, Canada. Denison has an effective 95% interest in its
flagship Wheeler River Uranium Project, which is the largest undeveloped uranium project in the
infrastructure rich eastern portion of the Athabasca Basin region of northern Saskatchewan. In mid-2023,
the Phoenix Feasibility Study was completed for the P hoenix deposit as an ISR mining operation, and an
update to the previously prepared 2018 Pre-Feasibility Study was completed for Wheeler River's Gryphon
deposit as a conventional underground mining operation. Based on the respective studies, both deposits
have the potential to be competitive with the lowest cost uranium mining operations in the world. Permitting
efforts for the planned Phoenix ISR operation commenced in 2019 and have advanced significantly, with
licensing in progress and a draft Environmental Impact Study submitted for regulatory and public review in
October 2022.
Denison's interests in Saskatchewan also include a 22.5% ownership interest in the McClean Lake Joint
Venture (“MLJV”), which includes unmined uranium deposits (planned for extraction via the MLJV's SABRE
mining method starting in 2025) and the McClean Lake uranium mill (currently utilizing a portion of its
licensed capacity to process the ore from the Cigar Lake mine under a toll milling agreement), plus a 25.17%
interest in the MWJV’s Midwest Main and Midwest A deposits, and a 69.35% interest in the Tthe Heldeth
Túé (”THT”) and Huskie deposits on the Waterbury Lake Property. The Midwest Main, Midwest A, THT and
Huskie deposits are located within 20 kilometres of the McClean Lake mill. Tak en together, Denison has
direct ownership interests in properties covering ~384,000 hectares in the Athabasca Basin region.
Additionally, through its 50% ownership of JCU (Canada) Exploration Company, Limited (“JCU”), Denison
holds additional interests in various uranium project joint ventures in Canada, including the Millennium
project (JCU, 30.099%), the Kiggavik project (JCU, 33.8118%), and Christie Lake (JCU, 34.4508%).
In 2024, Denison is celebrating its 70th year in uranium mining, exploration, and development, which began
in 1954 with Denison’s first acquisition of mining claims in the Elliot Lake region of northern Ontario.
For more information, please contact
David Cates (416) 979-1991 ext 362
President and Chief Executive Officer
Geoff Smith (416) 979-1991 ext 358
Vice President Corporate Development & Commercial
Follow Denison on X (formerly Twitter) @DenisonMinesCo
Qualified Persons
The disclosure of scientific or technical informat ion contained in this release has been reviewed and
approved, as applicable, by Mr. Chad Sorba, P.Geo., Denison's Vice President, Technical Services &
Project Evaluation or Mr. Andrew Yackulic, P. Geo. , Denison's Vice President, Exploration, who are
Qualified Persons in accordance with the requirements of NI 43-101.
Cautionary Statement Regarding Forward-Looking Statements
Certain information contained in this news release constitutes ‘forward-looking information’, within the meaning of the applicable United
States and Canadian legislation, concerning the business, operations and financial performance and condition of Denison. Generally,
these forward-looking statements can be identif ied by the use of forward-looking termi nology such as ‘potential’, ‘plans’, ‘expects’,
‘budget’, ‘scheduled’, ‘estimates’, ‘forecasts’, ‘intends’, ‘anticipates’, or ‘believes’, or the negatives and/or variations of such words and
phrases, or state that certain actions, events or results ‘may’, ‘could’, ‘would’, ‘might’ or ‘will’ ‘be taken’, ‘occur’ or ‘be achieved’.
In particular, this news release contains forward-looking information pertaining to the following: scope, objectives and interp reted
results of the ISR test program; future plans and objective s for Midwest, including further studies, analysis and a potential f uture
resource estimate update and PEA; and expecta tions regarding its joint venture ownersh ip interests and the continuity of its
agreements with its partners and third parties.
Forward looking statements are based on the opinions and estimates of management as of the date such statements are made, and
they are subject to known and unknown risks, uncertainties and other factors that may c ause the actual results, level of activi ty,
performance or achievements of Denison to be materially different from those expre ssed or implied by such forward-looking
statements. For example, the modelling and assumptions upon whic h the plans for Midwest are based may not be maintained after
further work is completed. In addition, Denison may decide or otherwise be required to discontinue testing, evaluation and other work
if it is unable to maintain or otherwise secure the necessary resources (such as testing facilities, capital funding, joint ven ture
approvals, regulatory approvals, etc.). Deni son believes that the expectations reflect ed in this forward-looking information a re
reasonable but no assurance can be given that these expectations will prove to be accu rate and results may differ materially fr om
those anticipated in this forward-looking information. For a discussion in respect of risks and other factors that could influence forward-
looking events, please refer to the factor s discussed in Denison’s Annual Informati on Form dated March 28, 2024 or subsequent
quarterly financial reports under the heading ‘Risk Factors’. These factors are not, and should not be construed as being, exhaustive.
Accordingly, readers should not place undue re liance on forward-looking statements. The forward-looking information contained i n
this news release is expressly qualified by this cautionary statement. Any forward-looking information and the assumptions made with
respect thereto speaks only as of the date of this news release. Denison does not undertake any obligation to publicly update or revise
any forward-looking information after the date of this news rel ease to conform such information to actual results or to changes in
Denison's expectations except as otherwise required by applicable legislation.
Figure 1: Midwest Site Location Map
Figure 2: Midwest Main Test Pattern and Well Locations - Plan View
Figure 3: Midwest Main Test Pattern and Well Locations – Long Section View