Annual Report for Fiscal Year Ending 12-31, 2025 (Form 40-F)

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Exhibit 99.1

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Denison Mines Corp.

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2025 Annual Information Form

March 30, 2026

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About this Annual Information Form

This annual information form (“AIF”) is dated March 30, 2026. Information in this AIF is stated as at December 31, 2025 unless specified otherwise.

In this AIF, references to the “Company” or “Denison” refer to Denison Mines Corp., its subsidiaries and affiliates, or any one of them, as applicable.

This AIF has been prepared in accordance with Canadian securities laws and contains information regarding Denison’s history, business, mineral reserves and resources, the regulatory environment in which Denison does business, the risks that Denison faces and other important information for Denison’s shareholders.

Financial Information

Unless otherwise specified, all dollar amounts referred to in this AIF are stated in Canadian dollars (“CAD”). References to “US$” or “USD” mean United States dollars.

Financial information is generally derived from consolidated financial statements that have been prepared in accordance with International Financial Reporting Standards as issued by the International Accounting Standards Board.

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Caution about Forward-Looking Information

Certain information contained in this AIF and the documents incorporated by reference concerning the business, operations and financial performance and condition of Denison constitutes forward-looking statements and forward-looking information within the meaning of the United States Private Securities Litigation Reform Act of 1995 and similar Canadian legislation (collectively, “forward-looking information”).

Generally, the use of words and phrases like “plans”, “expects”, “is expected”, “budget”, “scheduled”, “estimates”, “forecasts”, “intends”, “anticipates”, or “believes”, or the negatives and/or variations of such words and phrases, or statements that certain actions, events or results “may”, “could”, “would”, “might” or “will” “be taken”, “occur”, “be achieved” or “has the potential to” and similar expressions are intended to identify forward-looking information.

Forward-looking information involves known and unknown risks, uncertainties, material assumptions and other factors that may cause actual results or events to differ materially from those expressed or implied by such forward-looking information. Denison believes that the expectations and assumptions reflected in this forward-looking information are reasonable, but no assurance can be given that these expectations will prove to be correct. Forward-looking information should not be unduly relied upon. This information speaks only as of the date of this AIF, and Denison will not necessarily update this information, unless required by securities laws.

Third Party Information

Certain of the forward-looking information and other information contained herein concerning the uranium industry and mining industry generally and the general expectations of the Company concerning the uranium industry and mining industry generally are based on estimates prepared by third-parties or by the Company using data from publicly available governmental sources, market research, industry analysis, and on assumptions based on data and knowledge of the uranium industry and mining industry generally, which the Company believes to be reasonable. However, such data is inherently imprecise, is subject to interpretation and cannot be verified with complete certainty. Denison has not independently verified any third-party information. While Denison is not aware of any misstatement regarding any industry or government data presented herein, the mining industry overall involves risks and uncertainties that are subject to change based on various factors.

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Examples of Forward-Looking Information

This AIF contains forward-looking information in a number of places, including but not limited to statements pertaining to Denison’s:

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Statements relating to “mineral resources” are deemed to be forward-looking information, as they involve the implied assessment, based on certain estimates and assumptions that the mineral resources described can be profitably produced in the future. Capitalized terms bear the meanings as defined elsewhere in this AIF.

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Material Risks

Denison’s actual results could differ materially from those anticipated or indicated by the forward-looking information contained in this AIF. Management has identified the following risk factors which could have a material impact on the Company or the trading price of its common shares (“Shares”):

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The risk factors listed above are discussed in more detail later in this AIF (see “Risk Factors”). The risk factors discussed in this AIF are not, and should not be construed as being, exhaustive or the only risks that affect the Company. Other risks and uncertainties that the Company does not presently consider to be material, or of which the Company is not presently aware, may become important factors that affect the Company’s future financial condition and results of operations.

Material Assumptions

The forward-looking information in this AIF and the documents incorporated by reference are based on material assumptions made by management of the Company, including the following, which may prove to be incorrect:

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Cautionary Notes to U.S. Investors Concerning Resource and Reserve Estimates

As a foreign private issuer reporting under the multijurisdictional disclosure system adopted by the United States, the Company has prepared this AIF in accordance with Canadian securities laws and standards for reporting of mineral resource estimates, which differ in some respects from United States standards. In particular, and without limiting the generality of the foregoing, the terms “measured mineral resources,” “indicated mineral resources,” “inferred mineral resources,” and “mineral resources” used or referenced in this AIF are Canadian mineral disclosure terms as defined in accordance with National Instrument 43-101 — Standards of Disclosure for Mineral Projects (“NI 43-101”) under the guidelines set out in the Canadian Institute of Mining, Metallurgy and Petroleum Standards for Mineral Resources and Mineral Reserves, Definitions and Guidelines, May 2014 (the “CIM Standards”). These standards differ significantly from the mineral property disclosure requirements of the U.S. Securities and Exchange Commission (the “SEC”) in Regulation S-K Subpart 1300 (the “SEC Modernization Rules”) under the U.S. Securities Exchange Act of 1934, as amended (the “U.S. Exchange Act”).

Accordingly, there is no assurance any mineral reserves or mineral resources that the Company may report as “proven mineral reserves”, “probable mineral reserves”, “measured mineral resources”, “indicated mineral resources” and “inferred mineral resources” under NI 43-101 would be the same had the Company prepared the mineral reserve or mineral resource estimates under the standards adopted under the SEC Modernization Rules. For the above reasons, information contained in the AIF and other documents incorporated by reference herein containing descriptions of mineral deposits may not be comparable to similar information made public by U.S. companies subject to the SEC Modernization Rules. Additionally, investors are cautioned that “inferred mineral resources” have a great amount of uncertainty as to their existence, and great uncertainty as to their economic feasibility. Under Canadian rules, estimates of inferred mineral resources may not form the basis of feasibility or other economic studies, except in limited circumstances. It cannot be assumed that all or any part of an inferred mineral resource will ever be upgraded to a higher category. The term “resource” does not equate to the term “reserves”. Investors should not assume that all or any part of measured or indicated mineral resources will ever be converted into mineral reserves. Investors are also cautioned not to assume that all or any part of an inferred mineral resource exists or is economically mineable.

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About Denison

Denison Mines Corp. is engaged in uranium exploration, development and mining. The registered and head office of Denison is located at 1100 – 40 University Avenue, Toronto, Ontario, M5J 1T1, Canada. Denison’s website address is www.denisonmines.com.

The Shares are listed on the Toronto Stock Exchange (“TSX”) under the symbol “DML” and on the NYSE American under the symbol “DNN.”

Computershare Investor Services Inc. acts as the registrar and transfer agent for the Shares. The address for Computershare Investor Services Inc. is 100 University Avenue, 8th Floor, Toronto, ON, M5J 2Y1, Canada, and the telephone number is 1-800-564-6253.

Denison is a reporting issuer in each of the Canadian provinces and territories. The Shares are also registered under the U.S. Exchange Act, and Denison files periodic reports with the SEC.

Acknowledgement

Denison respectfully acknowledges that its business operates in Canada on lands that are in the traditional territory of Indigenous peoples. Denison’s activities encompass the entire mining life cycle, from early-stage exploration to advanced project evaluation, construction, operation, closure and restoration – with the potential for activities to span many decades. As such, Denison is committed to collaborating with Indigenous peoples and communities to build long-term, respectful, trusting, and mutually beneficial relationships and aspires to avoid any adverse impacts of Denison’s activities and operations.

Denison has adopted an Indigenous Peoples Policy (“IPP”), which reflects the Company’s recognition of the important role of Canadian business in the process of reconciliation with Indigenous peoples in Canada and outlines the Company’s commitment to take action towards advancing reconciliation. See “Environmental, Health, Safety and Sustainability Matters – Indigenous Peoples Policy and Reconciliation Action Plan” in this AIF. A copy of the Indigenous Peoples Policy is available on Denison’s website, in Déne, Cree, English and French languages.

Denison’s head office is located in the traditional territory of many nations, including the Mississaugas of the Credit, the Anishnabeg, the Chippewa, the Haudenosaunee and the Wendat peoples, and is now home to many diverse First Nations, Inuit and Métis peoples. Denison also acknowledges that Toronto is covered by Treaty 13 with the Mississaugas of the Credit.

Denison’s mining and mineral exploration operations in Saskatchewan, including its office in Saskatoon and various project interests in northern Saskatchewan, are located in regions covered by Treaty 6, Treaty 8 and Treaty 10, which encompass the traditional lands of the Cree, Dakota, Déne, Lakota, Nakota, Saulteaux, within the homeland of the Métis and within Nuhenéné.

Denison’s flagship Wheeler River uranium project, in particular, is located in northern Saskatchewan within the boundaries of Treaty 10, in the traditional territory of English River First Nation, in the homeland of the Métis and within Nuhenéné.

Denison’s legacy mines operations in the Elliot Lake region of northern Ontario are located within the boundaries of the Robinson Huron Treaty of 1850, signatories to which include the Serpent River First Nation.

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Denison’s Team

At the end of 2025, Denison had a total of 95 active employees, all of whom were employed in Canada. None of the Company’s employees are unionized.

Denison’s Structure

Denison conducts its business through a number of subsidiaries and joint arrangements. The following is a diagram depicting the corporate structure of Denison, its active subsidiaries and corporate and partnership joint arrangements, including the name, jurisdiction of incorporation and proportion of ownership interest in each, as at December 31, 2025.

The Waterbury Lake Uranium Limited Partnership (“WLULP”) is held by Denison (70.55%) and Korea Waterbury Uranium Limited Partnership (“KWULP”) (29.43%) as limited partners and Waterbury Lake Uranium Corporation (“WLUC”) (0.02%), as general partner.

JCU (Canada) Exploration Company, Ltd. (“JCU”) is owned by Denison (50%) and UEX Corporation (“UEX”, 50%). UEX, a wholly-owned subsidiary of Uranium Energy Corp., is manager of JCU, and JCU’s operations are managed in accordance with a shareholders agreement between Denison, UEX and JCU.

The Formation of Denison Mines Corp.

The Denison name has a long history in the Canadian uranium mining industry. Based on company archives, Denison’s involvement in the uranium mining industry dates back to 1954, when a predecessor to modern Denison acquired uranium claims in the Elliot Lake region.

Modern Denison was established by articles of amalgamation as International Uranium Corporation (“IUC”) on May 9, 1997 pursuant to the Business Corporations Act (Ontario). On December 1, 2006, IUC completed a plan of arrangement (the “IUC Arrangement”) with Denison Mines Inc. (“DMI”). Pursuant to the IUC Arrangement, all of the issued and outstanding shares of DMI were acquired in exchange for IUC’s shares. Effective December 1, 2006, IUC’s articles were amended to change its name to “Denison Mines Corp.” Denison completed a plan of arrangement with Energy Fuels Inc. in 2012 and

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filed articles of amalgamation on January 1, 2014, July 1, 2014 and July 3, 2014 in connection with Denison’s acquisitions of JNR Resources Inc. and Fission Energy Corp.

Denison Overview

Uranium Mining, Development, and Exploration

Denison’s uranium property interests are held directly by the Company and/or indirectly through DMI, Denison Waterbury Corp. and Denison AB Holdings Corp.

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Toll Milling

Denison is a party to a toll-milling arrangement through its 22.50% interest in the MLJV, whereby ore is processed for the Cigar Lake Joint Venture (“CLJV”) at the McClean Lake processing facility (the “Cigar Toll Milling”). In February 2017, Denison completed a transaction (the “Ecora Transaction”) with Ecora Resources PLC (“Ecora”) and its wholly owned subsidiary Centaurus Royalties Ltd. to raise gross proceeds to Denison of $43,500,000. The Ecora Transaction monetized Denison’s future share of the Cigar Toll Milling, providing Denison with the financial flexibility to advance its interests in the Athabasca Basin, including the Wheeler River project. See “Denison’s Operations – Cigar Lake Toll Milling – Ecora Transaction”.

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Developments Over the Last Three Years

Developments in Q1 2026

In January, based on the substantial completion of project engineering and execution of significant procurement activities since the effective date of the 2023 feasibility study (the “Phoenix FS”) for the Phoenix In-Situ Recovery (“ISR”) uranium mine (“Phoenix” or the “Project”) at Wheeler, an updated initial capital cost estimate for the Project was released. Accounting for adjustments due to inflation, cost increases, and project refinements, Denison now estimates total initial capital for the Project to be $700 million at a Class 2 equivalent level of precision (the “2026 Capex Update”), including pre-final investment decision (“FID”) spend of approximately $100 million and post-FID spend of approximately $600 million.

Also in January, the Company announced that grid power from Saskatchewan Power Corporation (“SaskPower”) had become available at Phoenix following the installation of a new 138kV transmission line, representing a significant step in de-risking the execution of the Project.

In February, the Company announced the decision of the administrative tribunal (the “Commission”) of the Canadian Nuclear Safety Commission (“CNSC”) to approve the Environmental Assessment (“EA”) and issue the Licence to Prepare a Site & Construct (the “Construction Licence”) for Phoenix, which is the first uranium mine in Canada to receive federal approval for construction in over 20 years. With the EA having previously been approved by the Province of Saskatchewan, and other provincial approvals necessary to commence construction already received, federal approval of the EA and the issuance of the Construction Licence represented the final regulatory approvals required to commence construction of Phoenix.

And in February, Denison announced approval by its Board of Directors (the “Board”) to proceed with the construction of Phoenix. With construction anticipated to take approximately two years, Phoenix remains on track for first production by mid-2028, and Denison is positioned as one of the few uranium suppliers globally that is expected to be able to provide a sizeable new source of uranium production before the end of the decade.

Also in February, Denison announced that, following a competitive tender process, it awarded Wood Canada Limited (“Wood”), a global leader in consulting and engineering, with the construction management contract (the “CM Contract”) to oversee the building of the Phoenix mine. The CM Contract currently contemplates procurement and construction management scopes, whereby Wood is responsible for (i) construction management of the full processing plant scope, (ii) installation of certain site infrastructure, and (iii) integrated project controls, ongoing procurement support, on-site safety oversight, as well as maintaining reporting and performance management standards. Such services will be provided by Wood in close consultation with Denison, with members of Wood’s and Denison’s teams holding complementary roles in an integrated project management team (“IPT”).

In March, the IPT was formed and initial crews mobilized to Phoenix to commence site preparation and construction activities.

Wheeler River

2023…

In August, Denison filed the Wheeler Report (defined below), summarizing the results of (i) the Phoenix FS completed for ISR mining of Phoenix; and (ii) a cost update to the Pre-Feasibility Study (“PFS”) completed in 2018 for conventional underground mining of the basement-hosted Gryphon uranium deposit (“Gryphon PFS Update”). The results of the respective studies illustrated that both deposits have the potential to be competitive with the lowest cost uranium mining operations in the world. See “Wheeler River” for more details.

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In September, Denison announced the signing of a Shared Prosperity Agreement (“SPA”) with English River First Nation (“ERFN”) supporting the development and operation of the Wheeler River project. The SPA received support from a substantial majority of ERFN members who participated in a ratification vote on its key terms. The signing of the SPA follows years of active engagement, including a four-month-long ERFN-led community consultation process ahead of the ratification vote, and represents a significant milestone in the history of both Denison’s relationship with ERFN and the Wheeler River project.

In November, the Company announced the successful completion of the recovered solution management phase of the ISR Feasibility Field Test (“FFT”). The solution recovered during the FFT was stored on site and this final phase of the FFT involved the treatment of the recovered solution via an on-site purpose-built treatment plant. Following treatment, a uranium precipitate product and a treated effluent were produced. The mineralized precipitates were recovered from the process with over 99.99% efficiency. The treated effluent was tested to ensure compliance with permit conditions before being injected into a designated subsurface area.

2024…

In January, Denison awarded Wood a contract for approximately $16 million for the completion of detailed design engineering for Phoenix. The work commenced in the first quarter of 2024, with substantial completion achieved in 2025. Throughout 2024, the Company continued to focus its efforts on the advancement of Phoenix towards FID, in support of its objective to achieve first production by 2028, including the advancement of Phoenix detailed design engineering activities. Total engineering completion at end of 2024 was approximately 65%, supported by finalization of process design, piping and instrumentation diagrams, hazard and operability studies, as well as the selection of major process equipment and electrical distribution infrastructure.

In February, the Company announced its acquisition of fixed and mobile MaxPERF Tool Systems from Penetrators Canada Inc. (“Penetrators”). The MaxPERF Tool Systems have been successfully deployed several times as a method of permeability enhancement in ISR field studies conducted on the Company’s potential ISR mining projects, including at the Phoenix deposit. Penetrators has also agreed to work exclusively with Denison for a 10-year period with respect to the use of the MaxPERF Tool Systems for uranium mining applications, and related services, in Saskatchewan. In March, Denison signed a Sustainable Communities Investment Agreement (the “SCIA”) with the municipalities of the Northern Village of Beauval, the Northern Village of Île-à-la Crosse, the Northern Hamlet of Jans Bay, and the Northern Hamlet of Cole Bay (the “SCIA Communities”). The SCIA reflects a common goal of facilitating qualified businesses and workers in benefitting from opportunities associated with the development of the Wheeler River project. The SCIA establishes commitments for funding to support community development initiatives, focused on contributing to the current and future economic prosperity and sustainability of the Communities by promoting economic development and investments in capital projects, job creation and training, housing, education, and other initiatives. In consideration for such contributions to the Communities’ initiatives, the Communities have provided their consent and support for the Wheeler River project and have committed, amongst other things, to support all regulatory approvals issued for the Wheeler River project related to exploration, evaluation, development, operation, reclamation, and closure activities.

In July, Denison announced the signing of a Mutual Benefits Agreement (“MBA”) with Kineepik Métis Local #9 (“KML”) and a Community Benefit Agreement (“CBA”) with the northern Village of Pinehouse Lake (“Pinehouse”), in support of the development and operation of Wheeler River. The MBA acknowledges that Wheeler River is located within KML’s Land and Occupancy Area in northern Saskatchewan and provides KML’s consent and support to advance the project. Additionally, the MBA recognizes that the development and operation of Wheeler River can support KML in advancing its social and economic development aspirations, while mitigating the impacts on the local environment and KML members. The MBA provides KML and its Métis members an important role in environmental monitoring and commits to the sharing of benefits from the successful operation of Wheeler River – including benefits from community investment, business opportunities, employment and training opportunities, and financial compensation. The CBA acknowledges that Pinehouse is the closest residential community to Wheeler River by road, which relies on much of the same regional infrastructure that Denison will rely on as it advances the project. Pinehouse has provided its consent and support for Wheeler River, while Denison, on behalf of the Wheeler River Joint Venture (“WRJV”), is committed to help Pinehouse develop its own capacity to take advantage of economic and other development opportunities in connection with the advancement and operation of the project.

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Multiple key regulatory milestones were achieved in late 2024, including (i) filing of the final Environmental Impact Statement (“EIS”) with the Saskatchewan Ministry of Environment (“SKMOE”) in October; (ii) completion of a provincial public and Indigenous review period on the EIS in November and December 2024; (iii) completion of the technical review phase of the federal EA approval process and filing of the final EIS with CNSC in November, (iv) the CNSC’s determination of the sufficiency of Denison’s application for a Construction Licence in November, and (v) acceptance by the CNSC of the EIS in December. The next steps for approval of the EA and Phoenix permitting were: (1) ministerial approval of the EA from the Government of Saskatchewan and issuance of applicable provincial permits; and (2) following a two-part public hearing process, CNSC approval of the EA and issuance of the Construction Licence. Such steps were achieved in 2025 and early 2026. For further details, see “Wheeler River” and “Environmental, Health, Safety and Sustainability Matters” below.

In October, the WRJV Management Committee approved the findings and recommendations of the Phoenix FS, which became an Approved Development Program (“ADP”) under the WRJV Agreement, providing the WRJV’s approval for development and construction of the project in accordance with the Phoenix FS.

At the October meeting of the WRJV Management Committee, JCU abstained from voting on the ADP. In accordance with the terms of the WRJV Agreement, non-support of the ADP by a participant means that such participant is no longer liable for its cost share of WRJV expenditures. As a result of JCU’s non-support through abstention, Denison has funded, and expects to continue to fund, 100% of the project expenditures from October 2024. The WRJV Agreement further requires that a participant who does not support an ADP must sell or transfer their interest. UEX, as operator of JCU, has notified Denison that it does not agree that JCU’s abstention from the ADP vote should be taken as non-support for the ADP and the sale or transfer of JCU’s participating interest in the WRJV has not yet occurred. See “Legal and Regulatory Proceedings” for further information.

2025…

In July, Denison received SKMOE Ministerial approval of the EA under The Environmental Assessment Act of Saskatchewan to proceed with the development of Phoenix. With that, Denison submitted the Provincial application to Construct a Pollutant Control Facility. A Pollutant Control Facility Permit is required for the construction of the mining and processing components of the facility and is anticipated to be the primary provincial permit required for construction.

And in July, the Company announced the discovery of additional high-grade mineralization approximately 40 metres outside of the previously estimated mineralized domain associated with the D1 lens of the Gryphon deposit at Wheeler River. A total of ~12,500 metres of diamond drilling was completed in seventeen drill holes and multiple off cuts during the 2025 delineation program at Gryphon. Overall, the delineation program confirmed the current geological interpretation of the deposit and supported the grade-thickness assumptions in the resource block model. The delineation results demonstrate that Gryphon is an excellent high-grade basement-hosted uranium deposit that justifies further project development evaluation and de-risking. Gryphon is situated approximately 3 km northwest of the Phoenix ISR site

In August, the Company acknowledged an application for judicial review filed in the Court of King’s Bench for Saskatchewan by the Peter Ballantyne Cree Nation against the Government of Saskatchewan and the Company, asserting that the Province of Saskatchewan did not adequately exercise its duty to consult prior to its approval of the EA. See “Legal and Regulatory Proceedings” for further information.

In October and December, Denison participated in a two-part public hearing (“Hearing”) of the Commission, considering Denison’s application for the approval of the EA and the Construction Licence. Following the multi-year federal review of the EA and related processes, CNSC staff recommended in their submissions that the Commission grant the EA approval and the Construction Licence. The Hearing was the final step in the federal review process.

In December, the Company announced execution of an Impact Benefit Agreement (“IBA”) with the Métis Nation–Saskatchewan (“MN–S”), 13 individual MN–S Locals, MN-S Northern Region 1 (“MN–S NR-1”), and MN–S Northern Region 3 (“MN–S NR-3”) (collectively, the “Métis Parties”). The IBA confirms the Métis Parties’ consent to and support for the development and operation of Wheeler River. In addition, the parties have also entered into an Exploration Agreement covering Denison’s exploration and evaluation activities.

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And in December, the Company and the Ya’thi Néné Land and Resource Office (“YNLR”) announced the signing of the Nuhenéné Benefit Agreement, which is a regional mutual benefits agreement between Denison, YNLR, and each of the Hatchet Lake Denesułiné First Nation, Black Lake Denesułiné First Nation, Fond du Lac Denesułiné First Nation, the Northern Hamlet of Stony Rapids, the Northern Settlement of Uranium City, the Northern Settlement of Wollaston Lake, the Northern Settlement of Camsell Portage (collectively, the “Athabasca Communities”). The Agreement provides the Athabasca Communities’ consent to and support for the development and operation of Wheeler River, as well as Denison’s Waterbury Lake, Midwest, and McClean Lake projects.

Significant regulatory, engineering, and construction planning progress was made throughout 2025, positioning Phoenix in a construction-ready state and confirming an expected 2-year construction timeline. Approximately 87% of total engineering was completed at the end of 2025 and 92% of primary engineering deliverables were issued for construction.

Other Properties

2023…

In April, Denison announced the completion of an internal conceptual mining study examining the potential application of the ISR mining method at the Midwest project. The concept study was prepared by Denison in 2022 and formally issued to the MWJV in early 2023. Based on the positive results of the concept study, the MWJV approved the completion of additional ISR-related work for Midwest in 2023 and 2024.

In November, the Company announced the completion of an inaugural ISR field test program at THT on the Waterbury Lake property. The program included (i) the installation of an eight well ISR test pattern designed to collect an initial database of hydrogeological data, (ii) testing of a permeability enhancement technique, (iii) the completion of hydrogeologic test work, and (iv) the execution of an ion tracer test which established a 10 hour breakthrough time between the injection and extraction wells, while also demonstrating hydraulic control of the injected solution. Overall, the program successfully achieved each of its planned objectives.

2024…

In January, Denison and Orano Canada announced that the MLJV approved a restart of uranium mining operations using the joint venture’s patented Surface Access Borehole Resource Extraction (“SABRE”) mining method. Activities in 2024 focused on preparations necessary to ready the existing SABRE mining site and equipment for continuous commercial operations, as well as the installation of pilot holes for the first mining cavities planned for excavation. See “Denison Operations-SABRE Mining Program” for further details.

And in January, Denison entered into an agreement (the “KLP Agreement”) with Grounded Lithium Corp. (“Grounded Lithium”) with respect to the Kindersley Lithium Project (“KLP”) in Saskatchewan. The KLP Agreement includes a series of earn-in options, with each earn-in option comprised of a cash payment to Grounded Lithium as well as project expenditures to advance KLP. The investment in KLP was seen as an opportunity for Denison to leverage its technical expertise to potentially unlock greater value for the project. Should Denison complete all three earn-in options, it will have made cumulative cash payments to Grounded Lithium of $3.2 million and have funded $12 million in project expenditures to earn a 75% working interest in the KLP. Upon funding the total amounts of each earn-in option phase, Denison has the right to either exercise the earn-in option and acquire the working interest associated with that phase or move on to the ensuing option phase. The KLP Agreement terminates on the earliest of: (i) Denison electing to acquire its working interest and convert to a formal joint venture or to terminate, (ii) June 30, 2028, or (iii) a date as otherwise agreed between the parties.

In June, Denison and Orano Canada announced the completion of an ISR field test program at Midwest. The program involved drilling ten 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 concept study evaluating the potential use of ISR mining at Midwest.

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In September, Denison executed an option agreement with Foremost Clean Energy Ltd. (“Foremost”), which grants Foremost a multi-phase option to acquire up to 70% of Denison’s interest in 10 non-core uranium exploration properties (the “Foremost Transaction”). Pursuant to the Foremost Transaction, Foremost would acquire such total interests upon completion of a combination of direct payments to Denison and funding of exploration expenditures with an aggregate value of up to approximately $30 million. In October 2024, Foremost completed the conditions for the first tranche of the option, pursuant to which Denison received an upfront payment in Foremost common shares. If Foremost completes the remaining two phases of the Foremost Transaction, Denison will receive further cash and/or common share milestone payments of $4.5 million and Foremost will fund $20 million in project exploration expenditures.

2025…

In January, pursuant to an acquisition agreement with Cosa Resources Corp. (“Cosa”), Cosa acquired a 70% interest in three of Denison’s properties in the eastern portion of the Athabasca Basin region in northern Saskatchewan and formed three uranium exploration joint ventures, in exchange for approximately 14.2 million Cosa common shares, $2.25 million in deferred equity consideration, and a commitment to spend $6.5 million in exploration expenditures on the properties (the “Cosa Transaction”).

In July, the MLJV announced the successful start of SABRE uranium mining operations at the McClean North deposit. In 2025, on a 100% basis, 4,392 tonnes of high-grade ore was extracted (Denison’s share: 988 tonnes) with 648,558 pounds of U₃O₈ in finished product produced at the McClean Lake mill (Denison’s share: 145,926 pounds of U₃O₈) with an average operating cash cost of approximately $36 per pound U₃O₈ (approximately US$26 per pound U₃O₈).

And in July, Denison and Orano Canada announced that several significant new intercepts of shallow high-grade uranium mineralization were encountered at the McClean South zone during a 6,400-metre exploration drilling program completed during the first half of 2025.

In August, the Company reported the results of the Preliminary Economic Assessment (“PEA”) Denison completed for the MWJV assessing ISR mining of the Midwest Main deposit. The PEA highlights that ISR has the potential to be a technically sound and economically robust means to extract significant uranium production from the high-grade Midwest Main deposit with low initial capital costs, a high rate of return, and rapid payback.

In December, the Company completed a transaction with Skyharbour Resources Ltd. (“Skyharbour”) resulting in the formation of four joint ventures proximal to the Company’s Wheeler River property: Russell Lake (“Russell Lake – Skyharbour”), Getty East, Wheeler North, and Wheeler River Inliers. In addition, Denison and Skyharbour entered into option agreements, which will allow Denison to increase its ownership interest in each of the new Wheeler North and Getty East joint ventures to up to 70%.

Commercial Activities

2023…

In 2023, the Company sold 200,000 pounds U₃O₈ of its physical uranium holdings at a weighted average selling price of $99.50 per pound U₃O₈ (US$73.38 per pound U₃O₈), representing a realized gain on sale of $12.6 million (US$8.8 million), based on Denison’s average acquisition cost of $36.67 per pound U₃O₈ (US$29.66 per pound U₃O₈). As at December 31, 2023, the Company’s remaining uranium portfolio had increased in value by 228% since acquisition, to $120.35 per pound U₃O₈ (US$91.00 per pound U₃O₈), for an aggregate value of approximately $276.8 million (US$209.3 million).

2024…

In 2024, the Company sold 100,000 pounds U₃O₈ of its physical uranium holdings at a weighted average selling price of $135.98 (US$100.00) per pound, representing a realized gain on sale of $9.9 million (US$7.0 million), based on Denison’s average acquisition cost of $36.67 per pound U₃O₈ (US$29.66 per pound U₃O₈). As at December 31, 2024, the Company held 2,200,000 pounds U₃O₈.

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2025…

In 2025, Denison entered a uranium sales contract with a third party which included upfront cash prepayments. Under this arrangement, Denison received $8.2 million (US$6.0 million) in December 2025, with an additional US$4.0 million due by the end of 2026. As consideration for the prepayments, the counterparty will receive a discount from the then prevailing market price on the purchase of 4.5 million pounds of U₃O₈, with scheduled deliveries from 2028-2033.

And in 2025, the Company entered into sales commitments with market-related pricing terms for 550,000 pounds of U₃O₈ with deliveries in 2026 and 250,000 pounds of U₃O₈ with deliveries in 2027.

Finally in 2025, the Company sold 500,000 pounds U₃O₈ of its physical uranium holdings at a weighted average selling price of $108.50 (US$78.63) per pound, representing a realized gain on sale of $36.0 million (US$24.6 million), based on Denison’s average acquisition cost of $36.67 per pound U₃O₈ (US$29.66 per pound U₃O₈). As at December 31, 2025, the Company held 1.7 million pounds U₃O₈ of purchased physical uranium holdings, excluding Denison’s share of finished goods produced from McClean North.

Financing Activities

2023…

In October, Denison completed a bought deal equity financing resulting in the issuance of 37,000,000 shares at a price of $2.03 (US$1.49) per share for total gross proceeds of $75.1 million (US$55.1 million). The Company intends to use the net proceeds from the offering to fund (1) the advancement of the proposed Phoenix ISR uranium mining operation through the procurement of long lead items (including associated engineering, testing and design) identified during the ongoing Front End Engineering Design process and the Phoenix FS; (2) exploration and evaluation expenditures; and (3) general corporate and administrative expenses, including those in support of corporate development activities, and working capital requirements.

And in October, the Company completed a $15 million strategic investment in F3 Uranium Corp. (“F3”) with the acquisition of unsecured convertible debentures, which carry a 9% coupon payable quarterly, have a maturity dated of October 18, 2028, and are convertible at Denison’s option into common shares of F3 at a conversion price of $0.56 per share. F3 has the right to pay up to one third of the quarterly interest payable by issuing common shares. F3 will also have certain redemption rights on or after the third anniversary of issuance of the debentures and/or in the event of an F3 change of control.

In December, the Company amended and extended its credit facility with the Bank of Nova Scotia (the “Credit Facility”) to January 31, 2025.

During 2023, the Company issued 19,786,160 shares under its at-the-market equity offering program (“ATM”). The Shares were issued at an average price of $1.91 per share for aggregate gross proceeds of $37,877,000. The Company also recognized costs of $845,000 related to the maintenance of the ATM and Share issuances, which includes $757,000 of commissions, for net proceeds after commissions of $37,130,000.

2024…

In December, the Company completed a private placement of 3,000,000 Shares that qualify as “flow-through shares” for purposes of the Income Tax Act (Canada) at a price of $4.70 per share for gross proceeds of approximately $14,100,000, the proceeds of which are to be used on the Company’s exploration activities in 2025. The income tax benefits of this issue were renounced to subscribers with an effective date of December 31, 2024.

And in December, the Company extended the maturity date of its Credit Facility to January 31, 2026.

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2025…

In August, the Company completed its offering of ‘US-Style’ convertible senior unsecured notes due September 15, 2031 (the “Convertible Notes”) for an aggregate principal amount of US$345 million. The Convertible Notes bear a cash interest coupon rate of 4.25% per annum payable semi-annually in arrears on March 15th and September 15th of each year, beginning March 15, 2026. The initial conversion rate for the Convertible Notes is 342.9355 Shares of Denison per US$1,000 principal amount of Convertible Notes, equivalent to an initial conversion price of approximately US$2.92 per Share (approximately 35% premium to the closing price of the Shares at the time of pricing on August 12, 2025). The effective conversion price of the Convertible Notes is increased up to US$4.32 per Share (~100% premium to the closing price of the Shares at the time of pricing on August 12, 2025) after giving effect to the capped call overlay option strategy deployed by the Company, whereby Denison purchased cash-settled call options with a strike price equal to the initial conversion price of the Convertible Notes (US$2.92) and a cap price of US$4.32 (the “Capped Calls”). The purchase price for the Capped Calls was US$35.4 million.

In December, the Company completed a private placement of 2,702,703 Shares that qualify as “flow-through shares” for purposes of the Income Tax Act (Canada) at a price of $5.55 per share for gross proceeds of approximately $15,000,000, the proceeds of which are to be used on the Company’s exploration activities in 2026. The income tax benefits of this issue were renounced to subscribers with an effective date of December 31, 2025.

The Uranium Industry 2025

The uranium industry is relatively small, compared to other commodity or energy industries. Uranium demand is international in scope, but supply is characterized by a relatively small number of companies operating in only a few countries. Primary uranium production is concentrated amongst a limited number of producers and is also geographically concentrated. According to market research and analysis company, UxC, LLC (“UxC”) in its Q1’2026 Report, 79% of the world’s production in 2025 is projected to come from only four countries: Kazakhstan, Canada, Namibia, and Australia. Producers compete for market share and commercial terms necessary to support project economics. This is complicated by the influence of state-owned enterprises that operate within the uranium mining industry, often producing uranium supply as part of a vertical integration strategy that may be less sensitive to uranium pricing than those operating uranium mines as a primary business.

Uranium Price

In 2025, the long-term price of U₃O₈ steadily increased, finishing the year at US$86 per pound U₃O₈, which represents a 16-year high and an approximately 9% increase from the end of 2024. This comes after a significant year-over-year increase during 2024, when the long-term price increased by 16% from US$68 per pound U₃O₈ at the end of 2023 to US$79 per pound U₃O₈ at the end of 2024. The Company believes the strengthening long-term price is representative of strong underlying market fundamentals for uranium.

By comparison, the uranium spot price was somewhat volatile during 2025, reaching a low of US$63.45 per pound U₃O₈ in mid-March, but then increasing to a high of US$83.80 per pound U₃O₈ in September before settling at approximately US$82.00 per pound U₃O₈ – representing an annual increase of approximately 12%. The spot price reflects sporadic discretionary buying and selling activity and, as a result, continues to experience greater price volatility than the long-term price, which reflects base-escalated pricing terms that typically comes from producer-to-consumer contracting in the form of multi-year supply contracts. Generally, a significant majority of uranium sales occur via long-term supply agreements, with comparatively smaller annual volumes clearing through the spot market.

The Company believes the current uranium market environment demonstrates notable similarities to the last time prices reached these levels. In 1991, the USA and the Russian Federation signed an agreement under which 500 tonnes of high enriched uranium (“HEU”) were purchased by the USA to be down-blended to low enriched uranium (“LEU”) to be used in civilian nuclear reactors. As a result, in the early 2000s, HEU and other former Soviet Union supplies remained a market hangover from the Cold War with elevated inventory levels weighing on prices for years and limited new supply coming online. Ultimately, this period of low prices, then compounded with adverse supply shocks and significant expected demand growth driven by ambitious plans for nuclear power in China, created a favourable environment for uranium prices. Due to years of under investment, meaningful new sources of supply were scarce at a time of rapid demand growth, and weekly spot uranium prices reached a high of US$136.00/lb U₃O₈ in June of 2007, according to UxC.

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Following this period, the Japanese tsunami and associated Fukushima nuclear incident in 2011 disrupted the market and set in motion a similar period of low prices and excess inventories. Given the sudden shut-down of the entire Japanese nuclear fleet by 2012 and other reductions in demand, excess uranium inventories and excess enrichment capacity, which provided the ability to create additional uranium supply, catalyzed a downward shock to price. During this extended period, prices were below the cost of production for many producers, with weekly spot prices averaging ~US$30.00 per pound U₃O₈ and ranging from US$18.00 per pound U₃O₈ - US$44.00 per pound U₃O₈ between 2013 and 2019 according to UxC, leading to the shutdown of multiple mines and a sharp reduction in investment in new exploration and development activities across the sector. After years of supply discipline, and the accumulation of physical uranium positions amongst financial investors, the market reached an inflection point followed by six consecutive years of long-term price increases between 2020 and 2025, reflective of a market transition, where the cost of future production drives transactions rather than by the availability of surplus inventories. Looking ahead, the Company believes that increasing demand for nuclear energy, coupled with a prolonged period of limited investment in new supply creates supply-demand dynamics that are supportive of strong uranium prices for the foreseeable future.

Uranium Demand

In 2025, nuclear energy was the subject of growing investor interest due to its necessary role in the “clean energy transition” and its potential role in global energy security and energy growth initiatives. The Company believes these positive nuclear demand fundamentals support expectations for robust uranium markets. There is also increasing support from large technology companies that have announced partnerships with nuclear power utilities indicating a desire for reliable and emission-free electricity to meet expected growth in artificial intelligence and data centers’ electricity needs. This includes Meta’s 20-year power purchase agreement (“PPA”) announced in 2025 with Constellation to purchase nuclear energy from the Clinton Clean Energy Center in Illinois and Google’s 25-year PPA with NextEra Energy, announced in 2025 to support the potential restart of nuclear energy production at the Duane Arnold Energy Center in Iowa.

There is global focus on the importance of nuclear power in enabling the achievement of carbon emission goals and responding to growing energy demands. This recognition was further enshrined as over 20 nations pledged to triple nuclear energy generation capacity by 2050 at COP28 in Dubai in December 2023. This support continued to grow with over 30 nations pledging such support as of COP29 in Baku in November 2024, and now 38 nations have pledged such support as of March 2026 according to TradeTech LLC. The Company believes this wide-spread government support for nuclear energy represents a paradigm shift. In addition to the renewed commitment to nuclear from powerhouse nations like Japan, South Korea, France, and the United States in recent years, positive nuclear demand developments occurred in many nations in 2025.

Two notable nuclear reactor projects that had been in construction for nearly a decade reached commercial operations in 2025 including Rajasthan 7 in India, and Kursk 2-1 in Russia. Also in 2025, Zhangzhou 2 in China achieved first criticality and was connected to the grid for the first time. China continues to be a major source of growth for nuclear energy, with the International Atomic Energy Agency reporting that China currently has 33 reactors under construction. In Canada, Ontario Power Generation (“OPG”) continued refurbishment activities for the Darlington nuclear plant and Bruce Power continued its ongoing refurbishment efforts. OPG also signed contracts for reactor life extension projects at the Pickering B station and has begun planning a new nuclear plant in Port Hope, which could accommodate up to 10,000 megawatts of new generation capacity. Additionally, small modular reactors (“SMRs”) are being advanced in both Ontario and Saskatchewan, with OPG targeting completion of its first SMR project before 2030.

Looking forward, forecasts from UxC for global reactor units and nuclear capacity in 2035 is 549 units and 511 gigawatts electrical (“GWe”) installed capacity (estimated as of the fourth quarter of 2025) – representing a 28% increase in global nuclear power generation from 441 units producing nearly 400 GWe as of December 2025. UxC forecasts nuclear generation capacity growth to translate into similar increases in demand for uranium and forecasts 2035 base case uranium demand of 253 million pounds U₃O₈, an estimated 24% increase from expected 2025 demand of 204 million pounds U₃O₈.

Uranium Supply

On the supply side, uranium production for 2025 is estimated at 163 million pounds U₃O₈, which represents a 2% increase over 2024 production levels, largely due to the ramp-up of Budenovskoye 6 and 7, and Muyunkum in Kazakhstan. Taken together with the UxC estimate of total demand for 2025, there is a significant primary supply shortfall, estimated to be

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approximately 20% of total demand or 41 million pounds U₃O₈. In the fourth quarter of 2025, UxC estimated 2026 primary production to increase to 174 million pounds U₃O₈, with the production increase being supported by increasing production from Kazatomprom in Kazakhstan, increasing year over year production levels from McArthur River in Canada, and a ramp up of a series of mines in Africa. Additionally, UxC estimates secondary supplies for 2026 are projected at 25 million pounds of U₃O₈ equivalent (“U₃O₈e”), which is a significant reduction from 40 million pounds U₃O₈e of secondary supplies estimated in 2025, 32 million pounds U₃O₈e in 2024, and 60 million pounds U₃O₈e in 2023. Strong demand in past years has accelerated the process of drawing down these secondary sources of supply. With this rapid decline in secondary supplies, the market is expected to continue its shift from an inventory-driven market to a production-driven market in the coming years.

The market has been responding to an increased focus on energy security. The importance of security of supply was magnified in July 2023, after a military coup in Niger led to expropriation of Orano SA’s uranium mining operations in June 2024. In 2022, Niger ranked as the seventh largest uranium producing country.

The ongoing Russo-Ukrainian war, particularly since the Russian invasion of Ukraine in February 2022, continues to cause significant turmoil in the global nuclear fuel market. Russia is a significant supplier of enriched uranium to the rest of the world, with over 40% of the world’s uranium enrichment capacity prior to the Ukraine invasion. In 2021, Russian enrichment comprised 31% of European Union enrichment purchases and 28% of US utility enrichment purchases. While deliveries of material from Russia to Western utilities continue, increased demand for non-Russian supply has led to significantly increased prices for uranium processing services. From December 2021 to December 2025, the long-term price of conversion and enrichment services increased by 197% and 184%, respectively. In the short- to medium-term, in order to increase enriched uranium production in the supply-constrained Western enrichment market, Western enrichers are expected to input more UF₆ (overfeed) into their centrifuges in order to maximize production capacity. As a consequence, Western utilities in aggregate would require more natural uranium feedstock to produce the same quantity of enriched uranium (i.e., enrichment contracts contain higher tails assay levels). In 2023, US and European utilities demonstrated a path towards reduced reliance on Russian nuclear fuel supply and increasingly favouring Western supply chains. In December 2023, a US bill to curb imports of Russian uranium was approved by US Congress. In May 2024, the U.S. President signed law H.R. 1042, the Prohibiting Russia Uranium Imports Act, which prohibits the importation into the U.S. of low enriched uranium produced in the Russian Federations or by a Russian entity. This law includes a waiver provision to allow for imports if the U.S. Secretary of Energy determines no alternative source can be procured or if shipments are deemed in the national interest. This law reinforces the ongoing shift of Western uranium supply chains away from Russia, which increasingly favors North American uranium supply.

Russia is also a notable player in uranium logistics, with significant quantities of uranium from Central Asia typically transported through Russia to Russian ports for delivery to Western uranium conversion facilities. UxC estimates Kazakhstan and Uzbekistan combined for 47% of global primary uranium production in 2025. As a result, logistics of uranium shipped through Russia remains an item of concern to uranium end users. Some uranium has been successfully shipped from Kazakhstan to Canada via the Trans-Caspian International Transport Route, which does not include transit through Russia; however, reports indicate that this route is subject to operational limitations.

Overall, nuclear demand growth appears poised for acceleration led by a shifting global energy mix towards decarbonized energy at a time when limited investment in bringing new uranium mine supply online has occurred over the past decade. While some idled or curtailed production from existing uranium mining operations has returned to the market, it is expected that (i) production costs associated with further potential restart projects will be higher than previous levels due to inflation and other restart challenges, and (ii) much of the potential new or greenfield mine supply required to meet demand estimates remains several years away.

The accelerated decline in secondary sources of uranium supply in recent years, the depletion of existing mines, and growing future reactor demand, point to larger supply deficits that may prove difficult to balance without considerable and rapid investment in new large-scale uranium mining projects. Given that uncovered utility uranium requirements for the period from 2025 to 2045, not including typical inventory building or restriction on existing supply agreements with Russia, are estimated at 1.8 billion pounds U₃O₈, it is evident that the necessary new future sources of supply required by the market have not yet been secured by utilities, and that the response from incumbent suppliers to sign significant long-term supply contracts in recent years have not satisfied the needs of utility customers, meaning that there is good reason to expect sustained utility procurement directed at incentivizing new projects to meet long-term demand needs.

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Competition

Exploration for uranium is being carried out on various continents, but in recent years development activities by public companies have been generally concentrated in Canada, Africa, Australia, and the United States. In Canada, exploration has focused on the Athabasca Basin region in northern Saskatchewan. Explorers have been drawn to this area by the high-grade uranium deposits that have produced some of the most successful uranium mining operations in recent history. Within the Athabasca Basin region, exploration is generally divided between activity that is occurring in the eastern portion of the Basin and the western portion of the Basin. The eastern portion of the Basin is a district that is defined by rich infrastructure associated with existing uranium mines and uranium processing facilities. Infrastructure includes access to the provincial power grid and a network of all-weather provincial highways. By comparison, there are no uranium mines or processing facilities in the western portion of the Basin, and access to the provincial power grid is not currently available.

Several uranium discoveries have been made in the Athabasca Basin region in recent years, and competition for capital, high-quality properties, and professional staff can be intense.

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Mineral Reserves & Mineral Resources

NI 43-101 requires mining companies to disclose mineral reserve and resource estimates using the subcategories of proven mineral reserves, probable mineral reserves, measured mineral resources, indicated mineral resources and inferred mineral resources.

Chad Sorba, P.Geo., Denison’s Vice President Technical Services and Project Evaluation, is a “Qualified Person” in accordance with the requirements of NI 43-101, and has reviewed and approved all disclosure of scientific or technical information in this AIF.

Denison Mineral Reserves and Mineral Resources

The following tables show the Company’s current estimates of mineral reserves and mineral resources as at December 31, 2025. For more information about the Company’s properties, see “Wheeler River” and “Other Exploration & Evaluation Projects”.

Proven Mineral Reserve Estimates ^(1,14)

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Probable Mineral Reserve Estimates ^(1,2,3,4,14)

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Measured Mineral Resource Estimates ^(1,5,7,14)

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Indicated Mineral Resource Estimates ^(1,5,7,14)

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Inferred Mineral Resource Estimates ^(1,6,14)

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Historical Estimates

A qualified person has not done sufficient work to verify and classify these historical estimates as current mineral resources for the Company or confirm their reporting of resources is in accordance with NI 43-101 categories, though the Company has no reason to believe the information is not relevant or reliable. The Company is not treating this information as current mineral resources. As these do not represent material properties for the Company at this time, the Company does not currently have any plans to conduct work to verify the historical estimates.

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JCU Estimates

Historical Indicated Mineral Resource Estimates ⁽¹⁴⁾

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Historical Inferred Mineral Resource Estimates ⁽¹⁴⁾

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McClean South

McClean South Historical Estimates ⁽¹⁵⁾

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Notes to Mineral Resource and Mineral Reserve & Historical Estimates Tables:

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Mineral Properties – Athabasca Basin

Denison’s mineral property interests are primarily located in the Athabasca Basin region of northern Saskatchewan, the majority of which are located in the eastern portion of the Athabasca Basin, which is host to considerable existing infrastructure including uranium mines and mills, and provincial powerlines and highways (see location map, below). As at December 31, 2025, Denison has direct interests in 39 mineral properties in the Athabasca Basin, comprised of 256 claims covering approximately 457,000 hectares. Denison holds additional indirect interests in various uranium project joint ventures in Canada through its 50% ownership interest in JCU. Denison also holds an earn-in option to acquire an interest in the KLP from Grounded Lithium.

Location Map of Denison’s Athabasca Basin Mineral Properties

Athabasca Basin Overview

The Athabasca Basin covers an area of approximately 100,000 square kilometres in northern Saskatchewan and northeastern Alberta. The Athabasca Basin is one of the principal uranium-producing districts in the world and is host to the world’s highest-grade and some of the world’s largest uranium mines and deposits, including the McArthur River mine and Cigar Lake mine located in the eastern Athabasca Basin.

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The uranium deposits are classified as unconformity-associated (also unconformity-related and –type) deposits owing to their spatial association with a major unconformable contact between a relatively undeformed Proterozoic sedimentary basin (the Athabasca Basin) and underlying metamorphosed and deformed Archean to Palaeoproerozoic basement rocks. A broad variety of unconformity-associated deposit shapes, sizes, and compositions have been discovered. Two distinct varieties have been classified; 1) ‘egress-style’ polymetallic lenses at and above the unconformity, with variable and often highly elevated base metal and rare earth elements (“REE”) contents, and 2) ‘ingress-style’ vein sets within basement rocks, with typically lower base metal and REE contents.

Egress-style deposits can occur in the sandstone, directly above the unconformity (e.g., Cigar Lake, Sue A and B), straddling the unconformity (e.g., Phoenix, Collins Bay B Zone, Midwest Main, Midwest A, McClean North, Key Lake) or perched high above the unconformity (certain zones at McClean Lake, Midwest, Cigar Lake). Ingress-style deposits are located in the basement rocks (e.g., Gryphon, Huskie, Eagle Point, Sue C, Sue E, Millennium, Arrow, Triple R); however, the Millennium deposit and, to an extent, the Gryphon deposit also contain subordinate mineralization at and above the unconformity. The Shea Creek deposits contain mineralization in the basement, deep in the basement, at the unconformity, and perched in the sandstone. In some deposits, there is a plunge to the mineralized pods from sandstone-hosted to basement-hosted within deposit–scale strike lengths (e.g., the Rabbit Lake-Collins Bay-Eagle Point trend, Sue trend deposits, McClean North).

The Athabasca unconformity-associated deposits are typically related to graphite-bearing structural zones within the metamorphosed and deformed Archean to Palaeoproerozoic basement rocks, which are often termed ‘corridors’ or ‘trends’. Alteration ‘halos’ or ‘envelopes’ tend to surround the mineralization, most notably in the overlying sandstone, and provide an enlarged exploration target through the detection of diagnostic alteration clays and geochemical pathfinder elements. Empirical exploration for the deposits typically involves mapping of structural corridors/trends by geophysical methods (dominantly electromagnetics, resistivity, or magnetics), followed by drill testing, given the buried or blind nature of the deposits below glacial cover or Athabasca sandstone, respectively. Drill core is subject to a variety of sampling and analytical methods to determine possible vectors toward mineralization, and downhole surveying is commonplace to test for elevated radioactivity or reconcile geophysical responses. The significant number of Athabasca uranium discoveries to date has also led to the development of numerous exploration models which are commonly used to facilitate interpretations and prioritize target areas.

Historical uranium production in the Athabasca Basin region used conventional open pit mining methods, such as the operations at Rabbit Lake, Cluff Lake, Key Lake and McClean Lake. Later in the mine life of Cluff Lake and Rabbit Lake, there was a transition to underground mining of other deposits on those properties.

The discovery of high-grade deposits such as Midwest, McArthur River and Cigar Lake in the 1980s did not immediately lead to production. The combination of challenging ground conditions (most notably the friable and water-saturated Athabasca sandstone conditions above the mineralization), depth, and the high-grade nature of the deposits required extensive research and development to design safe extraction methods before production was possible. Production from McArthur was achieved in the early 2000s, and Cigar Lake initiated production in 2014. Production from these mines was only made possible by their unique combination of high grades (average grades > 10% U₃O₈) and large scale (>300 million lbs U₃O₈), as well as the development of innovative mining techniques, including ground freezing combined with either raise-bore mining or the use of the jet-boring mining system (“JBS”). The Midwest deposits are smaller in size than McArthur River and Cigar Lake and remain undeveloped ; however, mining options (including SABRE and ISR) have been considered and/or remain under evaluation by the MWJV.

In terms of mineral processing, each historical mining operation included a dedicated processing plant: Cluff Lake, Key Lake, Rabbit Lake and McClean Lake operations included on-site processing plants. Due to the rising cost of construction for such facilities and the availability of highways and other infrastructure in Saskatchewan’s North, processing of ores has transitioned to toll milling at existing facilities. McArthur River ore production is toll milled at the Key Lake mill, while Cigar Lake production is toll milled at the McClean Lake mill.

In 2025, the MLJV restarted uranium mining operations at the McClean North deposit using the joint venture’s patented SABRE mining method. See “Denison’s Operations-SABRE Mining Program” for further details. The SABRE ore produced from McClean Lake North is being processed at the McClean Lake mill.

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Wheeler River

Wheeler River, Denison’s material project, is the largest undeveloped uranium project in the infrastructure-rich eastern portion of the Athabasca Basin region, in northern Saskatchewan. The project is host to the high-grade Phoenix and Gryphon uranium deposits, discovered by Denison in 2008 and 2014, respectively. The Wheeler River Joint Venture participants are Denison (90%) and JCU (10%). Denison is the operator/manager of the project.

Wheeler Report

In June 2023, Denison announced the results of (i) the Phoenix FS completed for ISR mining of the high-grade Phoenix deposit and (ii) the Gryphon PFS Update for conventional underground mining of the basement-hosted Gryphon deposit.

The results of the Phoenix FS and Gryphon PFS Update were summarized in the technical report entitled “NI 43-101 Technical Report on the Wheeler River Project, Athabasca Basin, Saskatchewan, Canada”, filed on August 9, 2023, with an effective date of June 23, 2023 (the “Wheeler Report”), authored by David Myers P.Eng., Lorne Schwartz P.Eng., and Paul O’Hara P.Eng. of Wood; Gordon Graham P.Eng. of Engcomp Engineering and Computing Professionals Inc. (“Engcomp”), Mark Hatton P.Eng. of Stantec Consulting Ltd., Dan Johnson P.E., RM SME, then of WSP USA Environment and Infrastructure Inc., Gregory Newman P.Eng. of Newmans Geotechnique Inc., Jeffrey Martin P.Eng. of Ecometrix Incorporated (now Egis Canada Ltd.), Mark Mathisen C.P.G. of SLR International Corporation (“SLR”), William McCombe P.Eng. of Hatch Ltd., Cliff Revering P.Eng. of SRK Consulting (Canada) Inc. (“SRK”), and Geoffrey Wilkie P.Eng. of CanCost Consulting Inc. The Wheeler Report is available under the Company’s profile on the SEDAR+ website at www.sedarplus.ca and on EDGAR at www.sec.gov/edgar.

The conclusions, projections and estimates summarized herein are subject to the qualifications, assumptions and exclusions set out in the Wheeler Report and in the “Risk Factors” below; in particular, the development and construction of Phoenix is subject to license and permit conditions, agreements, or resources, including capital funding.

The Phoenix FS reflects several design changes and the results of a rigorous technical de-risking program completed by Denison following the publication of the 2018 PFS and confirms robust economics and the technical viability of an ISR uranium mining operation with low initial capital costs and a high rate of return. Highlights of the Phoenix FS include:

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Phoenix Initial Capital Cost Update

Based on the substantial completion of project engineering and execution of significant procurement activities since the effective date of the Phoenix FS, an updated initial capital cost estimate for the Project was released by the Company in January 2026. Accounting for increases in inflation, cost increases, and project refinements, the Company now estimates the total post-FID initial capital estimate for the Project to be approximately $600 million, with improved accuracy equivalent to an AACE Class 2 cost estimate level of precision. This updates the Class 3 cost estimate (based on 2022 costing) reported in the Phoenix FS.

Updated initial capital costs have increased by 20% relative to the 2023 Phoenix FS once adjusted for inflation (see table below). The updated capital cost estimate includes $65 million in contingency funds and owners’ reserves, which represents approximately 12.5% of direct and indirect Project costs.

A notable refinement to the 2023 Phoenix FS is the planned installation of large diameter wells throughout the Phase 1 mining area to enable each well to act as an injection or recovery well. The Phoenix FS was based on approximately half of the wells in Phase 1 being large diameter and the other half being smaller diameter wells for injection only. While this modification increases initial capital costs, it is expected to improve the operational flexibility of the wellfield, optimize rates of recoveries, and support achievement of the Phoenix FS production targets.

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Notes

The 2026 Capex Update excludes approximately $100 million in pre-FID expenditures, which compares to $67.4 million in pre-FID expenditures estimated in the Phoenix FS.

When compared to the Phoenix FS, using the same basis to determine the base-case uranium sales price for the Project (UxC’s “Composite Midpoint” spot price scenario, using constant dollars), the projected base-case adjusted after-tax NPV for the Project remains effectively the same, as the increase in initial post-FID capital costs is offset by a modest improvement in the uranium price assumptions since mid-2023. After incorporating the 2026 Capex Update, Phoenix continues to be projected to produce robust economic results across all economic measures (see table below), including a base-case adjusted after-tax NPV to Initial Capital Cost factor of 2.6 to 1, and a high IRR.

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Notes:

Based on the Updated Capex, the Project’s sensitivity to the uranium price has been updated. Since the Phoenix FS, expected uranium spot prices have increased slightly, whereas long-term uranium prices, which are intended to represent the pricing for base-escalated long-term contracts in today’s dollars, have increased over 50% to US$86.00 per pound U₃O₈ compared to US$56.00 per pound U₃O₈ at the time of announcing the Phoenix FS.

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All amounts are stated in Canadian dollars unless otherwise noted and computed using the same foreign exchange rate assumptions as used in the Phoenix FS (i.e. a US dollar to Canadian dollar exchange rate of 1.35).

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Notes:

This Wheeler River project description (including the technical details underlying the 2026 Capex Update) is supported by the Wheeler Report. There are no material changes to the technical information used for the Phoenix FS as described in the Wheeler Report, and Denison continues to expect the estimated construction timeline, annual rates of uranium production, operating costs, sustaining capital costs and reclamation costs to be largely consistent with the Phoenix FS. Accordingly, Denison is not, at this time, providing any updates to the Phoenix operating cost or other estimates in the Wheeler Report; however, it may do so in the future.

The Wheeler Report is recommended to be read in its entirety for a more fulsome understanding of the technical aspects of the Wheeler River project.

Gryphon PFS Update Summary

The Gryphon PFS Update was targeted at the review and update of capital and operating costs. Mining and processing plans remain largely unchanged from the 2018 PFS, aside from minor scheduling and construction sequencing optimizations. The key points include:

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Wheeler River Property Description, Location and Access

Project Area and Location

Wheeler River is located in the eastern Athabasca Basin, approximately 600 km north of Saskatoon, 260 km north of La Ronge, and 110 km southwest of Points North Landing, in northern Saskatchewan. Wheeler River is comprised of a total of 19 contiguous mineral claims covering 11,720 ha and hosts the Phoenix deposit and Gryphon deposit. The Gryphon deposit is located approximately 3 km northwest of the Phoenix deposit. The centre of the Wheeler River property is located approximately 35 km northeast of the Key Lake mill and 35 km southwest of the McArthur River mine along Provincial Highway 914.

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The Wheeler River property is located within the boundaries of Treaty 10 (entered into between the Government of Canada and the First Nations People of Saskatchewan and Alberta). It is also located within the traditional territory of the English River First Nation, within the homeland of the Métis and within Nuhenéné.

Location Map, Showing Regional and Proposed Infrastructure.

Permits, Environmental Liabilities, Royalties and other Encumbrances

Denison has obtained all permits known to be required for the work conducted on the Wheeler River property to date. The advancement of Wheeler River will be subject to comprehensive permitting, approvals and licensing processes. Environmental and permitting considerations for future work are discussed in detail in Section 20 of the Wheeler Report. See “Risk Factors” for more information on this and other potential risks that may affect access, title or the right or ability to perform work on the property.

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Wheeler River is subject to royalties on mineral sales and profits levied by the Province of Saskatchewan in accordance with Part III of The Crown Mineral Royalty Regulations. See “Government Regulation - Saskatchewan Royalties” for further details. There is also a 10% Net Profits Interest associated with the property held by the WRJV in proportion to the ownership interests of each WRJV participant, of which Denison is also a beneficiary. There are no other back-in rights or third-party royalties applicable to this property.

Denison has recognized certain environmental liabilities associated with the Wheeler River project in connection with historical and current operations, including without limitation, exploration activities, camp facilities and the feasibility field test conducted at Phoenix in 2022 and 2023.

Access

Access to Wheeler River is by road, helicopter, or fixed-wing aircraft. Vehicle access to Wheeler River is by Highway 914, which terminates at the Key Lake mill. The Wheeler River Project is well located with respect to all-weather roads. The haul road between the Key Lake and McArthur River operations lies within the eastern part of the Wheeler River property.

The Fox Lake Road between Key Lake and McArthur River provides access to most of the northwestern side of the Wheeler River property. Gravel and sand roads and drill trails provide access by either four-wheel-drive or all-terrain vehicles to the rest of the property.

Climate / Operating Season

The climate is typical of the continental sub-arctic region of northern Saskatchewan, with temperatures ranging from +32°C in summer to -50°C in winter. Winters are long and cold, with mean monthly temperatures below freezing for seven months of the year. Winter snowpack averages 70 to 90 cm. Field operations are possible year-round, except for limitations imposed by lakes and swamps and the periods of break-up and freeze-up. Freezing of surrounding lakes, in most years, begins in November, and break-up occurs around the middle of May. The average frost-free period is approximately 90 days.

The average annual precipitation for the region is approximately 450 mm, of which 70% falls as rain, with more than half occurring from June to September. Snow may occur in all months but rarely falls in July or August. The prevailing annual wind direction is from the west, with a mean speed of 12 km/h.

It is expected that any future mining operations will operate year-round. Field operations currently operate year-round and are conducted from Denison’s Wheeler River camp, 4 km south of the Gryphon deposit and 3 km southwest of the Phoenix deposit.

Sufficiency of Surface Rights, Power, Water, Personnel

There are sufficient surface rights for the planned future mining operations, including sufficient land to construct various facilities, including potential waste disposal areas and the process plant.

The site currently generates its own power. The Wheeler River property is also well located with respect to the provincial power grid and Phoenix has been designed to be powered by electricity from the SaskPower grid.

Subsequent to the effective date of the Phoenix FS, SaskPower completed the installation and electrification of a new 6 km transmission line connecting an existing 138kV transmission line to the Phoenix site. Electrification of the Phoenix site will now only require the installation of on-site electrical distribution infrastructure, including the main site transformer, substation high-voltage equipment, switchgear, and substation e-house – all of which are currently scheduled to be installed during the first year of construction.

Fuel and miscellaneous supplies are stored in the existing warehouse and tank facilities at the Wheeler River camp. Abundant water is available from the numerous lakes and rivers in the area.

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To support the local economy, Denison has made a commitment to utilize local businesses whenever possible. Many of these local businesses are also Indigenous-owned. However, given the nature of Denison’s remote operations, mining supplies and labour will also need to be sourced from major centres such as Saskatoon, Regina, and possibly others.

Topography, Elevation, Vegetation

The Wheeler River Project is characterized by a relatively flat till plain with elevations ranging from 477 to 490 metres above sea level (“masl”). Throughout the area, there is a distinctive north-easterly trend to landforms resulting from the passage of Pleistocene glacial ice from the northeast to the southwest. The topography and vegetation at the Wheeler River Project are typical of the taiga forest common to the Athabasca Basin area of northern Saskatchewan.

The area is covered with overburden from 0 to 119 m in thickness. The terrain is gently rolling and characterized by forested sand and dunes. Vegetation is dominated by black spruce and jack pine, with occasional small stands of white birch occurring in more productive and well-drained areas. Lowlands are generally well drained but can contain some muskeg and poorly drained bog areas with vegetation varying from wet, open, non-treed vistas to variable density stand of primarily black spruce and tamarack, depending on moisture and soil conditions. Lichen growth is common in this boreal landscape, mostly associated with mature coniferous stands and bogs.

Significant Risks

Reference should be made to the “Risk Factors” and the factors and risks described in the Wheeler Report for more information.

History

The Wheeler River Project was staked on July 6, 1977 and was vended into the WRJV pursuant to the Wheeler River joint venture agreement dated December 28, 1978 (the “Wheeler JV Agreement”), among AGIP Canada Ltd. (“AGIP”), E&B Explorations Ltd. (“E&B”), and Saskatchewan Mining Development Corporation (“SMDC”), with each holding a one-third interest.

On July 31, 1984, all parties divested a 13.3% interest in the WRJV and allowed Denison Mines Limited, a predecessor company to Denison, to earn a 40% interest. On December 1, 1986, E&B allowed PNC Exploration (Canada) Co. Ltd. (“PNC”) to earn a 10% interest from its 20% interest. In the early 1990s, AGIP sold its 20% interest to Cameco (successor to SMDC), resulting in Cameco holding 40%. In 1996, Imperial Metals Corporation (successor to E&B), sold its remaining 8% interest to Cameco and 2% interest to PNC. Participating interests became Cameco 48%, PNC 12%, and Denison 40%.

In late 2004, Denison earned a further 20% interest from the other parties to the WRJV, after which the participating interests were Denison 60%, Cameco 30%, and JCU (a successor to PNC) 10%. Since November 2004, Denison has been the operator of the WRJV.

In January 2017, Denison executed an agreement with the partners of the WRJV to fund 50% of Cameco’s ordinary share of joint venture expenses in 2017 and 2018 in exchange for a transfer of a portion of Cameco’s interest. Based on spending during 2017, Denison increased its interest in the WRJV to 63.3%. In October 2018, Denison acquired all of Cameco’s remaining interest, and the WRJV became Denison (90%) and JCU (10%).

In August 2021, Denison acquired an additional 5% indirect interest in the Wheeler River Project through the acquisition of a 50% ownership interest in JCU. Denison currently has an effective 95% ownership interest in the WRJV.

Geological Setting, Mineralization and Deposit Types

Regional, Local and Property Geology

Wheeler River is located near the southeastern margin of the Athabasca Basin in the southwest part of the Churchill Structural Province of the Canadian Shield. The Athabasca Basin is a broad, closed, and elliptically shaped cratonic basin with an area of 425 km east-west by 225 km north-south. The bedrock geology of the Athabasca basin area consists of

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Archean and Paleoproterozoic gneisses unconformably overlain by up to 1,500 m of flat-lying unmetamorphosed sandstones and conglomerates of the mid-Proterozoic Athabasca Group.

Wheeler River is located near the transition zone between two prominent litho-structural domains within the Precambrian basement, namely the Mudjatik Domain to the west and the Wollaston Domain to the east. The Mudjatik Domain is characterized by elliptical domes of Archean granitoid orthogenesis separated by keels of metavolcanic and metasedimentary rocks. The Wollaston Domain is characterized by tight to isoclinal, northeasterly trending, doubly plunging folds developed in Paleoproterozoic metasedimentary rocks of the Wollaston Supergroup, which overlie Archean granitoid orthogenesis identical to those of the Mudjatik Domain. The area is cut by a major northeast-striking fault system of Hudsonian Age. The faults occur predominantly in the basement rocks but often extend up into the Athabasca Group due to several periods of post-depositional movement. Local geology is very much consistent with the regional geology.

Phoenix

Phoenix was discovered in 2008 and can be classified as an unconformity-associated deposit of the unconformity-hosted variety. The deposit straddles the sub-Athabasca unconformity approximately 400 m below surface and comprises three zones (A, B, C and D) which cover a strike length of about 1.1 km. The Phoenix deposit’s zones A and B comprise an exceptionally high-grade core, averaging 46.0% and 22.3% U₃O₈, respectively. A lower-grade shell surrounds the high-grade core. The basement mineralization at Zone A occurs within local dilation zones near both ends of the deposit associated with the interpreted cross faults. No mineral resources have been estimated for either Zone C or Zone D.

Phoenix is interpreted to be structurally controlled by the WS Shear, a prominent basement thrust fault which occurs footwall to a graphitic-pelite and hanging wall to a garnetiferous pelite and quartzite unit. A minor amount of basement, fracture-hosted mineralization occurs within local dilation zones near both ends of the deposit associated with the interpreted cross faults.

The mineralization within the Phoenix deposit is dominated by massive to semi-massive uraninite associated with an alteration assemblage comprising hematite, dravitic tourmaline, illite and chlorite. Secondary uranium minerals, including uranophane and sulphides, are trace in quantity. Average nickel, cobalt, and arsenic concentrations are at the low end of the range found in other uranium deposits in the Athabasca basin.

Phoenix Zones A and B exhibit elevated concentrations of certain rare earth elements. While there is a strong correlation between the REEs and uranium mineralization, the correlation between heavy rare earth elements and the high-grade uranium domains is comparatively stronger than the correlation between high-grade uranium mineralization and light rare earth elements.

Gryphon

Gryphon was discovered in 2014 and can be classified as an unconformity-related deposit of the basement-hosted variety. The deposit occurs within southeasterly dipping crystalline basement rocks of the Wollaston Supergroup below the regional sub-Athabasca Basin unconformity. The deposit is located from 520 to 850 m below surface, has an overall strike length of 610 m and dip length of 390 m, and varies in thickness between 2 and 70 m, depending on the number of mineralized lenses present.

A series of 24 stacked lenses referred to as the A, B, C, D and E-series, are controlled by reverse fault structures, which are mainly conformable to the basement stratigraphy and dominant foliation. The A, B and C series of lenses comprise stacked, parallel lenses that plunge to the northeast along the G-Fault, which occurs between hangingwall graphite-rich pelitic gneisses and a more competent pegmatite-dominated footwall. A ubiquitous zone of silicification (Quartz-Pegmatite Assemblage) straddles the G-Fault, and the A, B and C series of lenses occur in the hangingwall of, within, and in the footwall of the Quartz-Pegmatite Assemblage, respectively. The D series lenses occur within the pegmatite-dominated footwall along a secondary fault zone (Basal Fault) or within extensional relay faults which link to the G Fault. The E series lenses occur along the G-Fault, up-dip and along strike to the northeast of the A and B series lenses, within the upper basement or at the sub-Athabasca unconformity. The E series of lenses differ from the remaining sets of lenses as they do not follow the local scale plunge of the deposit. Instead, the mineralization is located planar to foliation and tight to the unconformity. The E series lenses are the only lenses to host unconformity mineralization at Gryphon.

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Mineralization within the Gryphon deposit lenses is dominated by massive, semi-massive or fracture-hosted uraninite associated with an alteration assemblage comprising hematite, dravitic tourmaline, illite, chlorite and kaolinite. Secondary uranium minerals, including uranophane and carnotite, and sulphides are trace in quantity.

Gangue mineralogy is dominated by alteration clays (illite, kaolinite, chlorite), dravite and hematite with minor relict quartz, biotite, graphite, zircon, and ilmenite. Only trace concentrations of sulphides, comprising galena, chalcopyrite, and pyrite, are noted. Notable concentrations of molybdenum and lithium have also been identified within and around the mineralization, represented visually as lepidolite and molybdenite.

Mineral Deposit Type

The Phoenix and Gryphon deposits are classified as an Athabasca Basin unconformity-associated (also unconformity-related and -type) uranium deposit. Phoenix straddles the unconformity contact between the Athabasca sandstone and the underlying basement, signifying the unconformity as a major fluid pathway for uranium mineralization. Gryphon is primarily hosted in the basement rocks, with minor portions of the deposit situated at the unconformity.

Unconformity-associated uranium deposits are pods, veins, and semi-massive replacements consisting of mainly uraninite, close to basal unconformities, in particular those between Proterozoic conglomeratic sandstone basins and metamorphosed basement rocks. The uranium deposits in the Athabasca Basin occur below, across, and immediately above the unconformity, which can lie within a few metres of surface at the rim of the Basin to over 1,000 m deep near its centre. The deposits are formed by extensive hydrothermal systems occurring at the unconformity’s structural boundary between the older and younger rock units.

Two end-members of the deposit model have been defined: (1) a sandstone-hosted egress-type model (i.e., Midwest A deposit) involved the mixing of oxidized sandstone brine with relatively reduced fluids issuing from the basement into the sandstone, and (2) a basement-hosted, ingress-type deposits (i.e., Rabbit Lake deposit) formed by fluid-rock reactions between oxidizing sandstone brine entering basement fault zones and the local wall rock.

Unconformity-type uranium deposits are surrounded by extensive alteration envelopes. In the basement, these envelopes are generally relatively narrow but become broader where they extend upwards into the Athabasca Group for tens of metres to even 100 m or more above the unconformity. Hydrothermal alteration is variously marked by chloritization, tourmalinization (high boron, dravite), hematization (several episodes), illitization, silicification/desilicification, and dolomitization. Modern exploration for these types of deposits relies heavily on deep-penetrating geophysics and whole-rock geochemical results from core samples.

Recently, basement-hosted deposits have become more recognized as a viable exploration target through the development of Eagle Point mine and the discovery of deposits such as Millennium, Triple R, and Arrow. Exploration typically requires the recognition of significant fault zones within basement metasediments (often associated with graphite) with associated clay and geochemical alteration haloes.

Exploration

Excluding the years 1990 to 1994, exploration activities comprising airborne and ground geophysical surveys, geochemical surveys, prospecting, and diamond drilling have continuously been carried out on the Wheeler River property from 1978 to present.

After the discovery of the Key Lake deposits in 1975 and 1976, the Key Lake exploration model has emphasized the spatial association between uranium deposition at, immediately above, or immediately below the unconformity with graphitic pelitic gneiss units in the basement subcrop under the basal Athabasca sandstone. The graphitic pelitic gneiss units are commonly intensely sheared and are highly conductive in contrast to the physically more competent adjoining rock types that include semipelitic gneiss, psammite, meta-arkose, or granitoid gneiss. From the late 1970s to the present, the Key Lake model has helped discover blind uranium deposits throughout the Athabasca Basin, although it is worth noting that the vast majority of EM conductors are unmineralized.

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Following the Key Lake exploration model, EM techniques were the early geophysical methods of choice for the Wheeler River Project area from 1978 to 2004. More than 152 line-km of electromagnetic (“EM”) conductors have been delineated on the Wheeler River Project to depths of 1,000 m through the quartz-rich Athabasca Group sandstones that are effectively transparent from an EM perspective. These conductors or conductor systems were assigned a unique designation, and follow-up exploration drilling successfully identified several zones of uranium mineralization.

Since 2004, Denison has completed ground geophysical surveys over the Wheeler River property, including the DC resistivity surveys that identified the drilling target that led to the discovery of the Phoenix deposit in 2008. In 2004, a GEOTEM airborne EM and magnetic survey collected data covering the entire Wheeler River Project, while a FALCON airborne gravity gradiometer survey in 2005 targeted the unconformity uranium mineralization. A helicopter-borne versatile time-domain electromagnetic (“VTEM”) magnetic-radiometric survey was conducted over the Wheeler River Project in 2013 in an attempt to remove noise in the interpretation of a previous survey.

Drilling

Diamond drilling has been the principal method of exploration and delineation of uranium mineralization after initial geophysical surveys. Drilling can generally be conducted year-round. Since 1979, over 1,000 diamond drill holes and 84 reverse circulation (“RC”) drill holes totalling in excess of 490,000 m have been completed on the Wheeler River property.

Phoenix

Since 2008, 318 drill holes totalling 145,982 m have delineated the Phoenix deposit. The Phoenix deposit area has been systematically drill tested over approximately 1 km of strike length at a nominal spacing of 25 to 50 m northeast-southwest by 10 m northwest-southeast (perpendicular to strike). Delineation diamond drilling at Phoenix was primarily done with NQ sized core (47.6 mm diameter) in holes WR-249 through WR-275 and HQ sized core (63.5 mm diameter) reducing to NQ at 350 m in holes thereafter, with most holes successfully penetrating into the basement. Some additional infill holes were drilled primarily to test the spatial continuity of the mineralization. The bulk of the flat-lying high-grade mineralization is positioned at and sub-parallel to the unconformity.

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Phoenix Drilling Completed by Denison

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Gryphon

The first exploration drilling in the Gryphon area began in 1988 and continued intermittently through 2013. In 2014, Denison completed a drilling campaign of 23 holes for 16,666 m, which included the Gryphon discovery hole WR-556. Following the discovery of Gryphon, definition drilling has been carried out on all lenses (A through E series). Denison and predecessor companies have completed extensive drilling in the immediate Gryphon deposit area, of which 216 holes, totalling 119,720 m, drilled between 1985 and 2017 delineated the Gryphon deposit. Diamond drilling at Gryphon was primarily done with NQ-sized core (47.6 mm diameter) with most holes angled between 60° and 79° to the northwest.

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Gryphon Drilling Completed by Denison

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Sampling, Analysis and Data Verification

See “Athabasca Exploration: Sampling, Analysis and Data Verification” for details.

Mineral Processing and Metallurgical Testing

Phoenix

Test programs, including various forms of leaching tests, process plant circuit tests, and effluent and solid waste streams treatment steps, have been conducted on the Phoenix deposit before and during the Phoenix FS. The results of the tests indicate the ability to leach uranium using in-situ techniques, allow a representative recovery curve to be assembled, and indicate geochemistry requirements for subsurface remediation.

Leaching testwork for Phoenix has included:

The main objective of the FFT was to demonstrate injection of lixiviant and recovery of uranium bearing solution from the commercial scale well test pattern. The FFT was a full-scale proof of concept of the ISR method in a thick and high-grade area of the deposit likely to be targeted for initial production.

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The following process plant testwork has been conducted on the Phoenix deposit. The results informed the criteria and design of the process plant described in the Phoenix FS, with specific attention paid to environmental requirements for waste streams and to end-product quality.

In 2024 and 2025, metallurgical testing continued with programs performed by SRC, including a hybrid core leach test, expected to provide information on leach progression during mining operations at the Phoenix deposit, and process circuit testing, to optimize performance.

Gryphon

In 2017, Denison undertook a metallurgical testwork program at SRC Geoanalytical Laboratories, directly managed by Denison. Denison also completed a parallel test program at the Orano Service d’Études de Procédés et Analyses (“SEPA”) laboratories at Bessines-sur-Gartempe, France. SRC and SEPA are ISO 17025 certified. The objectives of the testwork programs were to further develop the optimum processing conditions and collect additional data to support engineering design, including confirming the adequacy of the McClean Lake mill for processing Gryphon ore. Tests conducted included: grinding test; leaching tests on three composite samples to validate leaching characteristics; settling and filtration tests; solvent extraction tests; yellowcake precipitation tests; and a tailings neutralization test.

In 2025, further grinding and leaching testwork was completed and validated the processing of various types of mineralization across the deposit lenses.

Mineral Resource and Mineral Reserve Estimates

Mineral resources are reported in accordance with CIM Definition Standards (CIM, 2014) and prepared in accordance with the CIM Estimation of Mineral Resources and Mineral Reserves Best Practice Guidelines (CIM, 2019).

The estimates for Phoenix are presented assuming ISR extraction. The estimates for Gryphon are presented assuming underground mining methods.

Denison is not aware of any environmental, permitting, legal, title, taxation, socio-economic, marketing, political, or other relevant factors that could materially affect the mineral resource estimate, other than what is described in this AIF and the Wheeler Report. See “Risk Factors”.

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Phoenix Mineral Resource Statement, Effective Date June 23, 2023

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Due to the high-grade nature of the Phoenix deposit, additional infill drilling related to installation of an ISR well field will provide further definition of the high-grade uranium mineralization within the deposit footprint, leading to possible changes in the estimated uranium content. However, it is estimated that, given the current drill density within the deposit, any possible changes to the estimated uranium content would not be material based on the current geological understanding of the deposit.

Phoenix Mineral Reserve Statement, Effective Date June 23, 2023

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The aggregate mine feed to the plant has been estimated to contain 56.7 million pounds U₃O₈. This represents 80.6% recovery of the measured and indicated mineral resource available for in-situ recovery and is the mineral reserve estimate determined from this study.

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The FS analyzed the varying recovery rates amongst hydrogeological units (“HGUs”) and was a significant step in the definition of ISR efficacy for this deposit. Recovery varies based on the permeability and geochemistry of the HGUs and their interaction with adjoining units. To characterize the behaviour of ISR, a hydraulic tomography model was developed to estimate permeabilities in three dimensions throughout the deposit. These values were used in a hydrogeologic simulation to calculate in-situ flows between injection and recovery wells through the HGUs. The resulting flow field was input to a geochemical model to simulate recovery per well, per HGU. This recovery result was used to revise the well layout and individual flows in the hydrogeologic model. Several iterations of this modelling system were run to realize the optimized result. The recovery curve used as a basis for the geochemical model was obtained empirically from metallurgical testing.

In determining the conversion of mineral resources to mineral reserves for the application of the ISR mining method to a heterogeneous unconformity-style deposit, several modifying factors were considered. These include, but were not restricted to, mining, processing, metallurgical, infrastructure, economic, marketing, legal, environmental, social, and government factors. While a significant portion of the Phoenix mineral resource is classified as measured, demonstrating the highest degree of confidence in relation to geologic parameters, the cumulative assessment of all modifying factors supports the classification of probable mineral reserves for a large portion of the deposit, with a requirement of higher confidence in the modifying factors achieved through operating experience.

Estimated proven mineral reserves are based on the 2022 FFT, which provided additional confidence in the ISR method and ability to recover U₃O₈ within the tested region of the deposit. A stockpile of 14,400 lb U₃O₈ in uranium bearing solution was recovered to surface during the FFT, representing the initial ramp-up of a leach recovery curve. To calculate the proven mineral reserves, the recovery determined through computer modelling for Phase 1 was applied to the estimated in situ mass contacted during the FFT.

Gryphon Mineral Resource Statement, Effective Date August 7, 2018

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Gryphon Mineral Reserve Statement, Effective Date September 1, 2018

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The mineral reserve for Gryphon is estimated at 49.7 Mlb U₃O₈ (1.2 Mt grading at 1.8% U₃O₈) as summarized in the above table.

The mine design and mineral reserve estimate have been completed to a level appropriate for a PFS. The Gryphon block model did not include any measured mineral resource material. All mineral reserves were converted from indicated mineral resources and are classified as probable mineral reserves. The inferred mineral resources contained within the mine design are considered as waste.

Mining Operations

Phoenix

The uranium ISR process, as proposed for Phoenix, involves the preparation of an acidic mining solution in the process plant that is transferred to the injection solution handling system at the wellfield to cause the dissolution of uranium compounds from the targeted mineralized zone. The acidic solution will dissolve and mobilize the uranium, allowing the dissolved uranium to be pumped to the surface as uranium bearing solution (“UBS”). UBS is recovered from the wellfield and transferred to the nearby process plant for uranium precipitation, drying, and packaging.

Containment of the solution is a requirement in ISR operations to ensure recovery of the uranium and to minimize regional groundwater infiltration into the mineralized zone and associated dilution of the mining solution. For Phoenix, it is proposed that artificial ground freezing will be implemented around the perimeter of the mineralized zone creating a vertical hydraulic barrier between the ISR zone and the external natural hydrogeology. The freeze wall will be established by drilling a series of vertical cased holes from surface and keying them into the basement rock. Circulation of a low temperature brine solution in the holes will remove heat from the ground, freezing the natural groundwater, and establishing an impermeable frozen wall around the deposit.

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Benefits of ISR operations relative to traditional mining methods generally include:

As detailed in the Wheeler Report, the Company’s evaluation of the ISR mining method at Phoenix has identified several significant environmental and permitting advantages, particularly when compared to the impacts associated with conventional uranium mining in Canada. The proposed ISR mining operation for Phoenix is expected to produce a low tonnage of solid waste relative to conventional uranium mill tailings, generate very small volumes of waste rock, and has the potential for low volumes of treated water discharge to surface water bodies, as well as the potential to use the existing power grid to operate on a near zero carbon emissions basis.

The planned use of ground freezing to isolate the ISR operation has the potential to streamline the mining process, minimize interaction with the environment, and facilitate controlled reclamation of the site at decommissioning.

Taken together, ISR mining at Phoenix has the potential to achieve a superior standard of environmental sustainability when compared to conventional mining and milling operations.

Gryphon

The planned mining method for Gryphon is conventional longhole stoping with backfill. Longhole stoping is a widely used conventional mining method applied in both the Canadian uranium industry as well as in the broader mining industry for the extraction of base metals, gold, and other commodities.

According to the planned approach, access to the Gryphon deposit will be established through two shafts. The primary shaft will provide for movement of personnel and supplies, ore/waste hoisting, and fresh air to the underground operations. The second shaft will be solely for exhaust air and secondary egress. Heated fresh air will be delivered via the production shaft, with return air exhausted up the ventilation shaft. Both shafts will be excavated through blind boring methods. Blind bored shafts have been selected for vertical access in favour of typical full-face shaft sinking with cover grouting or freeze curtain protection. Blind bored shafts offer more competitive costs and construction schedules, and a reduced risk profile while sinking through saturated ground conditions. A composite steel/concrete liner will be installed over the full length of the shaft and grouted into basement rock. The main mine dewatering system will consist of a clean water pumping system that will pump decanted water to surface via piping in the ventilation shaft.

Access from the production shaft to the mine workings will be via a single ramp located on the hangingwall. Stope overcut and undercut drifts will include 100% shotcrete coverage and 150 mm of ballast on the floor to reduce the potential for radiation exposure.

The mine has been divided into five mining blocks, E Zone, Lower D, Upper and Lower Main, and Upper SW. Each mining block will be mined from the bottom up. Ore will be truck hauled to a rockbreaker/grizzly station and hoisted to surface. The mine is expected to produce approximately 605 t/d of ore and an average of 330 t/d of waste rock during the steady state operating period.

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The Gryphon PFS Update assumes that the ore will be hoisted to surface and transported to the McClean Lake mill for processing. A two-year ramp-up to full production is planned, with the full production rate set at 9 million pounds U₃O₈ per year. Processing at the McClean Lake mill will require the negotiation and execution of a toll milling agreement, which is not currently established, and will also require regulatory approvals, which have not been obtained.

Processing and Recovery

Phoenix

The uranium bearing solution from the Phoenix wellfield will be directed to a self-contained processing facility located adjacent to the wellfield. The process design was developed from the process plant testing campaigns, using UBS column leach test solution as feed.

In the process plant, the first step is removal of impurities such as iron and radium from the UBS as solids in the stage 1 (Fe/Ra) precipitation circuit. The stage 1 solids are temporarily stored. Next, the purified leach solution (“PLS”) feeds the stage 2 (YC) precipitation circuit, producing uranyl peroxide YC product solid, which is then dried and packaged for shipment.

The barren leach solution (“BLS”) from stage 2 (YC) precipitation feeds the effluent treatment (ET) circuit, comprised of three stages. The first ET stage (ET stage 1) is low pH neutralization, which precipitates most of the remaining radionuclides. The resulting solids are temporarily stored along with the process plant stage 1 (Fe/Ra) precipitation circuit cake product for subsequent shipment offsite. The second stage (ET stage 2) is high pH neutralization, which removes most of the remaining dissolved solids, forming a waste solids stream composed mainly of gypsum. This is pumped as slurry to a disposal pond for consolidation. The third ET stage neutralization (ET stage 3) targets selenium removal and adjusts final pH to near neutral. A small selenium-bearing waste solids stream is blended with the gypsum waste for disposal.

The different types of chemical reagents will be stored, used, and managed to ensure worker and environmental safety in accordance with standards developed by regulatory agencies and vendors.

Uranium recovery was estimated by evaluating the losses of the individual circuits and combining into an overall steady state recovery. The final mass balance recovery is estimated to be 96.5%, as shown in the following table:

Phoenix Process Plant Steady State Recovery

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It is estimated that during the ramp-up period for production recovery will be lower, resulting in a Year 1 recovery of 93.4% and a life of mine (“LOM”) process plant recovery of 96.3%.

The majority of the Fe/Ra and ET losses end up in the process precipitate solids (“PPS”). Preliminary estimates for the recovery from the PPS, based on the assumptions in the Wheeler Report, potentially increases the overall Phoenix recovery by 2.7%. The potential LOM recovery is summarized in the following table:

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Potential Phoenix Life of Mine Recovery

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Gryphon

The Gryphon PFS Update assumes that Gryphon ore will be transported to the McClean Lake mill for processing. The mill is currently processing material from the Cigar Lake mine; however, it has additional licensed processing capacity to a total annual production of up to 24 million pounds U₃O₈.

The mine plan for Gryphon aligns well with expected available capacity at the McClean Lake mill. Proposed Gryphon deposit production scenarios do not exceed McClean Lake’s production capacity given certain assumptions regarding future production from the Cigar Lake mine. Gryphon ore is expected to be milled in parallel to Cigar Lake Phase 2 production, assumed in the Wheeler Report to be up to 15 million pounds U₃O₈ per year, allowing for Gryphon ore processing at a peak of 9 million pounds U₃O₈ per year.

Processing the Gryphon deposit will require certain modifications to the McClean Lake mill. These modifications include expansion of the leaching circuit, the addition of a filtration system to complement the counter current decantation circuit capacity, the installation of an additional tailings thickener, and expansion of the acid plant. Various other upgrades will also be required throughout the mill to permit production at the full licensed capacity.

Infrastructure, Permitting and Compliance Activities

Phoenix Infrastructure

The Phoenix site layout is reasonably compact around the deposit, and working within the natural terrain where practical, to limit environmental disturbance. Modular or temporary facilities are planned where practical to reduce impact and simplify site closure. The camp is designed for 100 occupants and for expansion to 150 if and as needed.

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Phoenix Indicative Site Plan

The site plan is organized into radiological areas for control purposes. The wellfield, plant and nearest ponds are designated site locations where radioactive materials may be used or stored. Unauthorized persons are prohibited from entering radiation areas. The camp and operations facilities south of the production area are deemed non-radiation areas. Non-radiation areas are areas where no radioactive materials are used or stored. The main site road will form a tertiary barrier between the radiation and non-radiation areas.

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The planned infrastructure includes a gravel road from Highway 914 to site and the electrical power line from existing SaskPower distribution. A new airstrip and domestic and construction waste management areas are also included in site infrastructure plans.

Water is drawn from Whitefish Lake to the east. Well water is also available, which will be used to prepare potable water in the treatment plant near the camp. Domestic wastewater is sent to a mechanical treatment plant which produces water usable in the wellfield, and solids that are disposed in the industrial landfill.

Phoenix Permitting and Compliance Activities

At the date of the Phoenix FS, environmental studies of the Phoenix ISR operation were significantly advanced: baseline environmental data collection, technical assessments, plus extensive engagement and consultation with Indigenous and non-Indigenous interested parties had been completed with sufficient rigor to support development and submission of the draft EIS, and associated technical documents, to the provincial and federal regulators in 2022.

The EIS outlines the Company’s EA, being the assessment of the potential effects, including applicable mitigation measures, of the proposed ISR uranium mine and processing plant planned for Wheeler River.

Based on the information and related evaluation and assessment of effects, the EA shows that the ISR operation can be constructed, operated, and decommissioned in a manner that is not likely to cause significant residual adverse effects to the biophysical or human environments, on its own or cumulatively with existing and reasonably foreseeable developments. Importantly, the Phoenix FS designs and plans incorporate learnings and mitigation measures identified through the EA process.

See “Government Regulation – Environmental Assessments” for more information.

In addition to the EA process, Denison is required to obtain construction and operations permits from the Saskatchewan Ministry of Environment and licences from the CNSC.

See “Government Regulation – Licensing and Permitting” for more information.

Denison understands the importance of protecting the area in which it is working, including the land, the water, the animals, the air and culture. Denison further recognizes the importance of early and ongoing engagement and has been developing relationships with key interested parties since 2016. Amongst Denison’s guiding principles is the utmost respect for Indigenous communities, Indigenous Rights, and traditional knowledge. Denison wishes to work in partnership to return meaningful benefits from the Wheeler River project to potentially impacted Rights holders, communities, and/or groups.

Since 2016, Denison has engaged with interested parties to develop meaningful relationships and facilitate a collaborative approach to engagement and the advancement of Wheeler River.

See “Environmental, Health, Safety & Sustainability Matters” for further details.

Gryphon

A conceptual layout of the plan view of the Gryphon site surface facilities shows the relative scale and nominal footprint size of major infrastructure items, including shafts, ore stockpile, waste rock storage, backfill plant, water treatment plant, water treatment and management ponds, fuel and propane storage, explosive storage and operations centre. It is assumed the Phoenix camp will be used during Gryphon mine development and production.

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Gryphon Indicative Site Plan

Gryphon is approximately 3 km northwest of the Phoenix deposit. Access to the Gryphon site will be via a 2 km road extension from the Phoenix site development. It will also be accessible by the airstrip northeast of the Phoenix deposit. Production from the Gryphon site will be trucked to the existing McClean Lake mill to the northeast via existing Provincial Highway 914, including approximately 50 km of new road between the McArthur River mine and the Cigar Lake mine.

Gryphon Permitting and Compliance Activities

Although the current EIS and licensing efforts are not focused on the Gryphon project, significant baseline information has been gathered through the EA programs completed on the Wheeler River property. It is likely that additional and confirmatory baseline data collection will be required to complete the environmental approval process for the Gryphon project. As a result of a change in Federal legislation in 2019, the Gryphon project will undergo an EA to meet the requirements of the Saskatchewan Environmental Assessment Act; however, no Federal EA will be required.

Based on the existing understanding of the proposed Gryphon project, there is no reason to assume the Gryphon project could not successfully complete an environmental assessment which could be acceptable to the federal and provincial regulatory regimes and the Gryphon project’s stakeholders.

Additional regulatory approvals will be similar to those of the Phoenix ISR operation, whereby a Provincial permit and a CNSC licence will be prerequisites ahead of Gryphon project construction and operation. When Gryphon moves forward, while consultation for Phoenix is relevant, consultation specific to Gryphon will be undertaken.

The decommissioning and reclamation plan for Gryphon will need to be reviewed and developed in more detail as the Gryphon project is advanced.

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Phoenix Capital and Operating Costs and Economic Analysis

Capital Costs

The Phoenix FS provided an estimated initial capital cost of the Phoenix project of $419.4 million, expressed in first-quarter 2023 Canadian dollars. This estimate falls under the AACE International Recommended Practice No. 47R-11 Class 3 Classification Guideline, with an expected accuracy to be within -15%/+25% of the Phoenix project’s final cost, including contingency. The costs include construction of the initial ground freezing plant and wells, the first phase of production wells, and the ISR process plant and infrastructure required for first production.

See “Wheeler River – Phoenix Initial Capital Cost Update” for more information.

Sustaining capital is estimated to be $234.1 million and considers expansion of the wellfield and ground freezing system, and development of the injection solution system as the wellfield advances, expansion of the gypsum storage pad and modification to the process plant to accommodate well remediation.

Operating Costs

The operating costs over the Phoenix LOM are estimated at $478.1 million. Average operating costs are estimated at $8.51/lb U₃O₈ (US$6.28/lb U₃O₈) produced. Operating costs during the first five years of production are expected to be $6.64 (US$4.90) per pound U₃O₈, benefitting from increased scale of operations and higher concentrations of uranium contained in recovered UBS. During the remaining years of production, operating costs are expected to be $13.69 (US$10.10) per pound U₃O₈.

Phoenix Operating Costs

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