Denison Provides Initial Progress Update ON Installation of Isr Test Pattern at Wheeler River
Denison Mines Corp.
1100 – 40 University Ave
Toronto, ON M5J 1T1
www.denisonmines.com
PRESS RELEASE
DENISON PROVIDES INITIAL PROGRESS UPDATE ON
INSTALLATION OF ISR TEST PATTERN AT WHEELER RIVER
Toronto, ON – April 21, 2021. Denison Mines Corp. (“Denison” or the “Company”) (DML: TSX, DNN:
NYSE American) is pleased to announce the initiation and ramp-up of In -Situ Recovery (“ISR”) field test
activities, including the installation of a five-spot ISR test pattern (“Test Pattern”), at the Company’s 90%
owned Wheeler River Uranium Project (“Wheeler River” or the “Project”). Mobilization of drilling equipment
necessary to complete the large diameter drill holes, for each Commercial Scale Well (“CSW”) planned for
the Test Pattern, was completed in early April 2021 and, to date, four of the five planned CSWs have been
successfully drilled to target depths, cased, and cemented into position. The fifth CSW is in progress and
is expected to be completed within the next week. The installation of the Test Pattern is the first step in an
ambitious 2021 ISR field program, which is designed to support the further de-risking of the application of
the ISR mining method at the high-grade Phoenix uranium deposit (“Phoenix”).
David Bronkhorst, Denison’s VP Operations, commented, “We are excited to have our 2021 ISR field
program underway at Wheeler River. Our Saskatoon based technical team has assembled an
industry-leading group of experts to design, install and operate the Test Pattern as part of our 2021
ISR field program. We are very pleased with the pr oductivity achieved to date, for the installation
of the large diameter CSWs, and are looking forw ard to further validating the effectiveness of
various permeability enhancement tools and collecting additional hydrogeologic data to support
the permitting and set-up of a lixiv iant test in 2022. The lixiviant test is expe cted to be a key de-
risking milestone for the Project – as it is intende d to confirm technical feasibility by verifying the
permeability, leachability, and containment parameters needed for the successful application of the
ISR mining method at Phoenix.”
The 2021 ISR field program is expected to involve the following key components:
Installation of a Five-spot Test Pattern: The Test Pattern is located in the Phase 1 area of the
Phoenix deposit and is planned to consist of five new CSWs (see Figure 1 and Figure 2). The
Test Pattern has been designed to facilitate the further evaluation of the ISR mining conditions
at Phoenix – for incorporation into detailed mine planning that is expected to be completed as
part of a future Feasibility Study (“FS”) for the Project;
Installation of 11 Additional Monitoring Wells (“MWs”): In addition to the existing small-
diameter MWs, eleven further MWs are planned to be installed in the Phase 1 area (see Figure
1 and Figure 2) and are designed to surround the Test Pattern on all sides and above the ore
zone horizon, in order to facilitate detailed m onitoring of pressure changes and observations of
fluid flow patterns during active hydrogeological tests. Certain MWs will also allow for water
quality sampling over the duration of test work;
Extensive Hydrogeologic Testing: Approximately twenty-five hydrogeologic tests are planned
to be completed during the ISR field program. Tests are expected to (1) evaluate baseline
conditions, (2) evaluate the effectiveness of permeability enhancement tools deployed on an
individual well basis, and (3) assess the Test Pattern’s total permeability on a full-scale basis.
Additionally, ion tracer tests using inorganic salt s are expected to be conducted on the full Test
Pattern to establish breakthrough times for each CSW and confirm sub-surface pathways – thus
allowing for a more complete understanding of the hydrogeologic characteristics expected
throughout Phase 1, which is expected to suppor t the permitting and design of a lixiviant test,
planned for 2022, utilizing the existing Test Pattern.
Please refer to the Company’s news release dated Febr uary 8, 2021 for additional details related to the
Company’s 2021 evaluation program plans for Wheeler River, which also includes information about the
resumption of the Environmental Assessment process.
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Phoenix Phase 1
As outlined in the Company’s freeze wall trade-off study (see news release dated Dec. 1, 2020), Denison
has decided to adapt its plans for the Project to use a freeze wall in future Project design and environmental
assessment efforts. The trade-off study highlighted a key opportunity for the Project – whereby the freeze
wall could be installed in stages to facilitate a phased mining approach at Phoenix. In a phased mining
approach, only a limited portion of the freeze wall is required to support first production, with the subsequent
expansion of the freeze wall perimeter allowing for additional mining phases to be brought into production
over the duration of the mine life.
The phased mining approach is expected to allow for the targeted extraction of the least capital-intensive
reserves first, based on the grade and distribution of ore in various areas of the deposit. The trade-off study
provides for mining to occur over 5 phases.
Phase 1 of the deposit is estimated to c ontain approximately 22.2 million pounds U 3O8 (37,242 tonnes at
27.1% U3O8, above a cut-off grade of 0.8% U3O8) in Probable mineral reserves. Based on current designs,
the Company estimates approximately 6.6 million pounds U3O8 (7,717 tonnes at 39.2% U3O8, above a cut-
off grade of 0.8% U3O8) in Probable mineral reserves are contained within the expected operating perimeter
of the Test Pattern (see Figure 1). These estimates are derived as a direct subset of those reported in the
Technical Report titled "Pre-feasibility Study for the Wheeler River Uranium Project, Saskatchewan,
Canada" dated October 30, 2018 with an effective dat e of September 24, 2018. The key assumptions,
parameters and methods used to estimate the mineral reserves herein remain unchanged.
COVID-19
The Company is committed to ensuring that the Wheeler River site is a safe operating environment for its
staff and contractors and that the Company's field activities do not compromise the health and safety of the
residents of northern Saskatchewan. In 2020, the Company's Occupational Health and Safety Committee
in Saskatoon developed a comprehensive guide for the safe resumption of work at Wheeler River. The
protocols consider the unique health and safety risks associated with operating a remote work camp amidst
the ongoing COVID-19 pandemic. Public health guidelines and best practices (including testing) have been
incorporated into the Company's protocols.
Despite the Company's current intentions, it is possible that the 2021 ISR field program may be disrupted
by the continuously evolving social and/or economic disruptions associated with the COVID-19 pandemic,
which are outside of the control of the Company – for example, the ability of Company or contractor staff to
attend to the site, Provincial or local travel restrictions, and changing public health guidelines.
About Wheeler River
Wheeler River is the largest undeveloped uranium projec t in the infrastructure rich eastern portion of the
Athabasca Basin region, in northern Saskatchewan – including combined Indicated Mineral Resources of
132.1 million pounds U3O8 (1,809,000 tonnes at an average grade of 3.3% U 3O8), plus combined Inferred
Mineral Resources of 3.0 million pounds U 3O8 (82,000 tonnes at an average grade of 1.7% U 3O8). The
project is host to the high-grade Phoenix and Gryphon uranium deposits, discovered by Denison in 2008
and 2014, respectively, and is a joint venture between Denison (90% and operator) and JCU (Canada)
Exploration Company Limited (10%).
A PFS was completed for Wheeler River in late 2018, considering the potential economic merit of
developing the Phoenix deposit as an ISR operati on and the Gryphon deposit as a conventional
underground mining operation. Taken together, the project is estimated to have mine production of 109.4
million pounds U3O8 over a 14-year mine life, with a base ca se pre-tax NPV of $1.31 billion (8% discount
rate), Internal Rate of Return ("IRR") of 38.7%, and initial pre-production capital expenditures of $322.5
million. The Phoenix ISR operation is estimated to have a stand-alone base case pre-tax NPV of $930.4
million (8% discount rate), IRR of 43.3%, initial pr e-production capital expenditures of $322.5 million, and
industry leading average operating costs of US$3.33/lb U 3O8. The PFS is prepared on a project (100%
ownership) and pre-tax basis, as each of the partner s to the Wheeler River Joint Venture are subject to
different tax and other obligations.
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Further details regarding the PFS, including additional scientific and technical information, as well as after-
tax results attributable to Denison's ownership intere st, are described in greater detail in the NI 43-101
Technical Report titled "Pre-feasibility Study for the Wheeler River Uranium Project, Saskatchewan,
Canada" dated October 30, 2018 with an effective date of September 24, 2018. A copy of this report is
available on Denison's website and under its prof ile on SEDAR at www.sedar.com and on EDGAR at
www.sec.gov/edgar.shtml.
Denison suspended certain activities at Wheeler River during 2020, including the EA process, which is on
the critical path to achieving the project development schedule outlined in the PFS. While the EA process
has resumed, the Company is not currently able to estimate the impact to the project development schedule
outlined in the PFS, and users are cautioned against re lying on the estimates provided therein regarding
the start of pre-production activities in 2021 and first production in 2024.
About Denison
Denison is a uranium exploration and development company with interests focused in the Athabasca Basin
region of northern Saskatchewan, Canada. In addition to the Wheeler River project, Denison's interests in
the Athabasca Basin include a 22.5% ownership interest in the McClean Lake joint venture ("MLJV"), which
includes several uranium deposits and the McClean Lake uranium mill that is contracted to process the ore
from the Cigar Lake mine under a toll milling agreement, plus a 25.17% interest in the Midwest and Midwest
A deposits, and a 66.90% interest in the Tthe Heldeth Túé ("THT," formerly J Zone) and Huskie deposits
on the Waterbury Lake property. The Midwest, Midwest A, THT and Huskie deposits are located within 20
kilometres of the McClean Lake mill. In addition, Denison has an extensive portfolio of exploration projects
covering approximately 280,000 hectares in the Athabasca Basin region.
Denison is engaged in mine decommissioning and environmental services through its Closed Mines group
(formerly Denison Environmental Services), which manages Denison's Elliot Lake reclamation projects and
provides post-closure mine care and maintenance services to a variety of industry and government clients.
Denison is also the manager of Uranium Participat ion Corp., a publicly traded company which invests in
uranium oxide and uranium hexafluoride.
For more information, please contact
David Cates (416) 979-1991 ext 362
President and Chief Executive Officer
Sophia Shane (604) 689-7842
Investor Relations
Follow Denison on Twitter @DenisonMinesCo
Qualified Persons
The technical information contained in this re lease has been reviewed and approved by Mr. David
Bronkhorst, P.Eng, Denison's Vice President, Operations, who is a Qualified Person 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 c an be identified by the use of forward-look ing terminology such as ‘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’, ‘be achieved’ or ‘has
the potential to’.
In particular, this news release contains forward-looking in formation pertaining to the following: the planned scope, elements, and
objectives of the 2021 ISR field programs, including the drilli ng of CSWs and MWs and development of the Test Pattern; other
evaluation activities, including a planned future lixiviant test and those connected with the EA process; the results of the PF S and
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expectations with respect thereto; expectations with respect to freeze wall containment and phased development, and the estimates
of reserves in each such phase; other development and expansion plans and objectives, including plans for a feasibility study; and
expectations regarding its joint venture ownership interests and the continuity of its agreements with its partners.
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 which the work plans are based may not be maintained after further
testing or be representative of actual conditions within the Phoenix deposit. In addition, Denison may decide or otherwise be required
to discontinue its field test ac tivities or other testing, ev aluation and development work at W heeler River if it is unable to maintain or
otherwise secure the necessary resources (such as testing fac ilities, capital funding, regulatory approvals, etc.) or operation s are
otherwise affected by COVID-19 and its potent ially far-reaching impacts. Denison believe s that the expectations reflected in t his
forward-looking information are reasonable but no assurance can be given that these expectations will prove to be accurate and
results may differ materially from those anticipated in this fo rward-looking information. For a discussion in respect of risks and other
factors that could influence forward-looking events, please refer to the factors discussed in Denison’s Annual Information Form dated
March 29, 2021 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.
Cautionary Note to United States Investors Concerning Estimates of Measured, Indicated and Inferred Mineral Resources
and Probable Mineral Reserves: This press release may use the terms 'measured', 'indicated' and 'inferred' mineral resources.
United States investors are advised that while such terms have been prepared in accordance with the definition standards on mineral
reserves of the Canadian Institute of Mining, Metallurgy and Pe troleum referred to in Canadian National Instrument 43-101 Miner al
Disclosure Standards ('NI 43-101' ) and are recognized and required by Canadian regul ations, these terms are not defined under
Industry Guide 7 under the United States Securities Act and, unt il recently, have not been permitted to be used in reports and
registration statements filed with the United States Securities and Exchange Commission ('SEC'). 'Inferred mineral resources' have a
great amount of uncertainty as to their existence, and as to their economic and legal feasibility. It cannot be assumed that al l or any
part of an inferred mineral resource will ever be upgraded to a higher category. Under Canadian rules, estimates of inferred mi neral
resources may not form the basis of feasibility or other economic studies. United States investors are cautioned not to assume that
all or any part of measured or indicated mineral resources will ever be converted into mineral reserves. United States investor s are
also cautioned not to assume that all or any part of an inferr ed mineral resource exists, or is economically or legally mineabl e. In
addition, the terms "mineral reserve", "pro ven mineral reserve" and "probable mineral reserve" for the purposes of NI 43-101 di ffer
from the definitions and allowable usage in Industry Guide 7. Effective February 2019, the SEC adopted amendments to its disclosure
rules to modernize the mineral property di sclosure requirements for issuers whose secu rities are registered with the SEC under the
Exchange Act and as a result, the SEC now re cognizes estimates of "measured mineral re sources", "indicated mineral resources"
and "inferred mineral resources". In addition, the SEC has amended its definitions of "proven mineral reserves" and "probable mineral
reserves" to be "substantially similar" to the corresponding definitions under the CI M Standards, as required under NI 43-101.
However, information regarding mineral res ources or mineral reserves in Denison's disclosure may not be comparable to similar
information made public by United States companies.
Figure 1: Plan Map Showing Location of Phoenix Deposit (Phase 1) – ISR Test Pattern
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Figure 2: 3D Isometric Views of the Phoenix Deposit (Phase 1) – ISR Test Pattern
Showing Locations of Monitoring Well Horizons