Denison Achieves Key Milestone with Completion of Metallurgical Test Work to Define Phoenix Process Plant Components and Confirmation of Ability to Produce Yellowcake

 Denison Mines Corp. is pleased to announce the substantial completion of extensive metallurgical test work to define the mechanical components for the planned Phoenix processing plant (the “Phoenix Plant”), as part of the Feasibility Study (“FS”) underway for the Company’s 95% owned Wheeler River project (“Wheeler River” or the “Project”).  In addition, the metallurgical program has confirmed the ability to produce a yellowcake product that meets industry standard ASTM C967-13 specifications (see below for details).

Metallurgical test work intended to define the mechanical components for the Phoenix Plant was initiated in April 2021 at the Saskatchewan Research Council (“SRC”) laboratories in Saskatoon.  The test work consisted of bench-scale lab tests using uranium bearing solution (“UBS”) that was previously produced from lab-scale leaching of core samples from the Phoenix deposit.  These samples are intended to be representative of what is expected to be recovered from the In-Situ Recovery (“ISR”) wellfield planned for the Phoenix deposit (see news release dated August 4, 2021). 

Kevin Himbeault, Denison’s Vice President of Plant Operations & Regulatory Affairs, commented, “The comprehensive test work undertaken by the Denison team has demonstrated our ability to produce (i) a saleable uranium product utilizing a simplified chemical precipitation process and (ii) high–quality effluent for final discharge to the environment. This is a significant milestone from which we can continue to optimize the designs for the Phoenix Plant and further our de-risking of the overall Project as part of the FS.”

This press release constitutes a “designated news release” for the purposes of the Company’s prospectus supplement dated September 28, 2021 to its short form base shelf prospectus dated September 16, 2021.

The results of the metallurgical test work are highlighted by the following:

• The UBS from the high-grade Phoenix deposit was processed using simple chemical precipitation stages to remove certain elements prior to the yellowcake precipitation circuit.
• A yellowcake product that meets uranium industry standard ASTM C967-13 specifications (see below for details) has been precipitated in the lab.
• A high-quality effluent was obtained using typical industrial water treatment processes through pH control and precipitation.

Additionally, the metallurgical test program has provided several important inputs for the FS processes underway in relation to the planned Phoenix Plant and ISR operation, including confirmation of the following:

• The appropriateness of mechanical components for the Phoenix Plant similar to those outlined in the Pre-Feasibility Study (“PFS”).
• The suitability for the Phoenix Plant to process UBS head grades averaging 15 g/L uranium.
• Metallurgical recovery rates of over 95% from processing of UBS to yellowcake.
• The ability to achieve industry standards for yellowcake through drying at 110°C, indicating calcination is not required for the planned Phoenix Plant.
• The ability to produce a yellowcake product that meets industry standards without the use of ammonia and the specialized and additional processes typically associated therewith.
• The ability to meet final plant effluent quality discharge criteria for protection of the environment, which is expected to be outlined in the draft Environmental Impact Statement (“EIS”) planned to be submitted as part of the Environmental Assessment (“EA”) for the Project.

Additionally, extensive test work has been completed in defining any potential elements of concern, required process components, reagents, and general operating parameters necessary to mitigate processing risks and ensure the production of a yellowcake product that meets industry standards. This has allowed for the significant progression of the plant and process designs for the FS.

Additional targeted metallurgical test work continues in the following areas:

• Specialized test work to potentially further improve the effluent treatment process, optimize reagent usage and enhance overall environmental protection.
• Lab scale leaching of intact cores continues, with additional tests to further refine the production recovery curve for the Phoenix ISR operation, which will inform ISR simulation modelling for the FS and will provide additional results for future wellfield and ISR plant design optimization.
• Lab scale leaching and remediation tests of crushed core, representing different hydrogeological units within the Phoenix deposit, to determine achievable recovery, leaching rates, and remediation plans for the different units.

The laboratory work for the 2022 Metallurgical Program to support the feasibility study is being carried out at the SRC Mineral Processing and Geoanalytical Laboratories in Saskatoon, under the supervision of Wood Canada Limited (see news release dated September 22, 2021).

ASTM C967-13 is a set of quality specifications applied to uranium ore concentrate that are generally recognized in the uranium industry for meeting requirements for refining and conversion to uranium hexafluoride and, therefore, a saleable product. Parties may, however, agree to less or more stringent specifications of product quality on a case by case basis.

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