Denison Mines Moves Phoenix Uranium Project Into Full-Scale Construction Phase

• Site preparation at Phoenix is substantially complete, marking the transition to full-scale construction, roughly four months after early works began in March 2026
• Installation of the perimeter freeze wall for Phase 1 has started, following near completion of civil subgrade work at the process plant and wellfield areas
• Concrete pours for the process plant and substation foundations are scheduled to begin in August 2026
• Temporary construction camp facilities are now operational, raising site accommodation capacity to nearly 400 people
• A second shift is being added this summer to support around the clock construction, targeting first-year milestones including the freeze wall program and airstrip earthworks

Denison Mines Corp. (TSX: DML) (NYSE American: DNN) is a Canada-based uranium exploration and development company focused on the Athabasca Basin region of northern Saskatchewan. Its principal asset is the Wheeler River project, host to the Phoenix and Gryphon uranium deposits. Denison also holds ownership interests in several other Athabasca Basin properties and joint ventures, including a stake in the McClean Lake uranium mill. The company has operated in the uranium sector since 1954, when it acquired its first mining claims in northern Ontario.

Transition From Site Preparation to Full-Scale Construction at Phoenix ISR Uranium Mine

Denison's update confirms that Phoenix has moved from site preparation into full-scale construction. Site preparation work, which began in March 2026, included site clearing, early civil works, and the establishment of construction management infrastructure. With these activities substantially complete, the project has moved into the physical construction phase.

Phoenix uses in-situ recovery, a mining method that extracts uranium by injecting fluid underground to dissolve the mineral, rather than through conventional shaft or open-pit mining. This method is applied to the high-grade Phoenix deposit at Wheeler River, discovered by Denison in 2008.

Full-scale construction at Phoenix formally commenced in July 2026, following the project's final investment decision and the completion of regulatory approvals, including the construction licence granted by the Canadian Nuclear Safety Commission in February 2026.

Perimeter Freeze Wall Installation Initiated for Phase 1 With Concrete Pours for Process Plant Foundations Commencing August 2026

Installation of the perimeter freeze wall for Phase 1 of the mine has begun. A freeze wall is a barrier created by freezing the ground around the ore zone, helping to contain the fluids used in the in-situ recovery process. Its installation follows near completion of civil subgrade work, which involves levelling and stabilising the ground, at the process plant and wellfield areas.

Concrete-related work for the substation and the main process plant foundations is scheduled to begin in August 2026. Aggregate production continues at a nearby quarry to support these activities, and the concrete batch plant has been mobilised to site.

These steps place the freeze wall and foundation work on a defined schedule heading into the second half of 2026, both of which are identified in the release as key first-year construction milestones for the project.

Construction Workforce Ramp-Up to Near 400 People With Second Shift Supporting 24-Hour Seasonal Construction Activities

Temporary construction camp facilities have been installed and commissioned at the Wheeler River site, increasing accommodation capacity to nearly 400 people. This expanded capacity supports a larger on-site workforce as the project moves into full-scale construction.

Denison plans to add a second shift during the summer months, allowing seasonally sensitive civil and construction work to continue close to 24 hours a day. The company has linked this schedule to a set of first-year construction targets, including the process plant and main power transformer foundation pours, the freeze wall installation, and earthworks for the site airstrip and power distribution systems.

David Cates, President and CEO of Denison, said: 

"Completing the site-preparation activities needed to ramp up our on-site workforce and achieve a full-scale rate of construction is an important initial milestone for the Phoenix project. Site civil work has progressed well during the early works program, with +20% of overall site civil work estimated to be completed to date. Importantly, we have achieved near 100% completion of civil subgrade work for the process plant and wellfield areas, which is needed to facilitate the planned concrete pour for the plant and the initiation of the freeze wall installation program. Construction activity is expected to accelerate through the remainder of the summer months with the commencement of a second shift, which means seasonally sensitive civil and other construction work can continue virtually 24 hours a day in support of the completion of our key first-year construction milestones."

Milestones and Next Steps

Denison has identified several construction milestones for the remainder of 2026, including concrete pours for the process plant and main power transformer foundations, continued freeze wall installation, and earthworks for the airstrip and on-site power distribution. The addition of a second shift is intended to support this schedule through the summer construction season.

‍