Tag Archives: Athabasca Basin

Wood to investigate ISR potential of Phoenix uranium deposit in Wheeler River JV FS

Denison Mines Corp says it has selected engineering firm Wood PLC to lead and author a feasibility study for the in-situ recovery (ISR) mining operation proposed for the Phoenix uranium deposit in the Athabasca Basin of Canada, part of the Wheeler River Joint Venture (WRJV) project.

The completion of the study is, Denison says, a critical step in the progression of the project and is intended to advance de-risking efforts to the point where the company and the WRJV will be able to make a definitive development decision.

Denison has an effective 95% ownership interest in Wheeler River (90% directly, and 5% indirectly through a 50% ownership in JCU), which has combined indicated mineral resources of 132.1 MIb of U3O8 (1.8 Mt at an average grade of 3.3% U3O8), plus combined inferred mineral resources of 3 MIb of U3O8 (82,000 t at an average grade of 1.7% U3O8).

Key objectives of the study are expected to include:

  • Environmental stewardship: extensive planning and technical work undertaken as part of the ongoing Environmental Assessment (EA), including applicable feedback from consultation efforts with various interested parties, is expected to be incorporated into the feasibility study project designs to support Denison’s aspiration of achieving a superior standard of environmental stewardship that meets and exceeds the anticipated environmental expectations of regulators and aligns with the interests of local Indigenous communities;
  • Updated estimate of mineral resources: mineral resources for Phoenix were last estimated in 2018. Since then, additional drilling has been completed in and around the Phoenix deposit as part of various ISR field tests, including drill hole GWR-045 (22% eU3O8 over 8.6 m), and exploration drilling. The updated mineral resource estimate will form the basis for mine planning in the study;
  • Mine design optimisation: feasibility study mine design is expected to reflect the decision to adopt a freeze wall configuration for containment of the ISR well field, as well as the results from multiple field test programs and extensive hydrogeological modelling exercises, which have provided various opportunities to optimise other elements of the project – including well pattern designs, permeability enhancement strategies, and both construction and production schedules;
  • Processing plant optimization: feasibility study process plant design is expected to reflect the decision to increase the ISR mining uranium head-grade to 15 g/L, as well as the results from extensive metallurgical laboratory studies designed to optimize the mineral processing aspects of the project; and
  • Class 3 capital cost estimate: the feasibility study is also intended to provide the level of engineering design necessary to support a Class 3 capital cost estimate (AACE international standard with an accuracy of -15% /+25%), which is expected to provide a basis to confirm the economic potential of the project highlighted in the prefeasibility study completed in 2018.

The 2018 prefeasibility study considered the potential economic merit of developing the Phoenix deposit as an ISR operation and the Gryphon deposit as a conventional underground mining operation. Taken together, the project was estimated to have mine production of 109.4 Mib of U3O8 over a 14-year mine life.

David Cates, Denison’s President & CEO, said: “The ISR de-risking activities we’ve completed since the publication of the prefeasibility study for Wheeler River in 2018 have been designed to support the completion of a future feasibility study, and the results to date have further confirmed the technical viability of the project – leading to the decision to advance the project and initiate the formal feasibility study process.

“During this de-risking phase, we have been able to verify orebody permeability and the leachability of high-grade uranium in conditions representative of an ISR mining setting. We’ve also engineered an improved containment design using a more conventional ground freezing approach. Based on the results of field programs and metallurgical lab testing completed over the last three years, we are confident that the project is ready to advance into a full feasibility study. Taken together with the selection of globally recognised engineering firm Wood, the decision to launch the formal feasibility study process for Phoenix represents another important step towards achieving our objective of bringing low-cost ISR mining to the high-grade uranium deposits of the Athabasca Basin.”

NexGen marries ESG and financials in Arrow uranium project feasibility study

NexGen Energy CEO, Leigh Curyer, says the company’s Rook I uranium project has earnt its place as one of the “leading global resource projects with an elite ESG profile” after the publication of feasibility study results on the project’s Arrow deposit in the Athabasca Basin of Saskatchewan, Canada.

The study was completed jointly by consultants including Stantec, Wood and Roscoe Postle Associates (now part of SLR Consulting), with other technical inputs completed by sub-consultants.

Financial highlights from this study included an initial capital bill of C$1.3 billion ($1.03 billion) repaid with a post-tax net present value (8% discount) of C$3.47 billion based on a $50/Ib uranium price. From years 1-5 average annual production was due to come in at 28.8Mlb of uranium oxide, with average production over the life of mine of 10.7 years of 21.7 MIb/y.
The company laid out plans for a 1,300 t/d mill processing an average feed grade of 2.37% U3O8.

Listed within the “top five feasibility study outcomes” was enhanced environmental performance, with NexGen saying an optimised facilities layout had reduced the project footprint by around 20% and lowered on-site personnel transportation and ore haulage.

Optimised shaft sizing, water usage through advanced water recycling, and plant engineering reflected elite environmental standards, it added.

“With respect to the proposed shaft, mine workings and underground tailings management facility (UGTMF) locations, geotechnical and hydrogeological testing validated highly competent rock with no significant alteration, no major structures, and low hydraulic conductivity,” the company said.

The mine plan at Arrow was based on conventional long-hole stoping using the 239.6 MIb of declared reserves, the company said.

“Geotechnical studies during the feasibility study re-emphasised the conventional long-hole stoping mining method, including the use of longitudinal and transverse stopes, 30 m level spacing, and the nominal stope strike length of 12 m to 24 m,” it said. “This represents an excellent stope stability range for underground mining in the highly competent conditions.”

Given the competency and conditions of the underground environment, all waste streams from the process plant are planned to be stored underground in the UGTMF, while process water streams will be treated on surface in the optimised effluent treatment plant, NexGen said.

The underground workings will be accessed by two shafts, with the production shaft supporting personnel movements, materials, ore, waste and fresh air. The production shaft was increased to 8 m in diameter (from 6.5 m in diameter in the prefeasibility study (PFS)) to optimise radiation and ventilation management, ensuring the mine is elite from a safety perspective, the company said.

“Additionally, the production shaft will have divided compartments, ensuring that fresh air and personnel entering the mine, remain isolated from ore being skipped to surface,” it added.

The exhaust shaft was ultimately decreased to 5.5 m in diameter (from 6.5 m in diameter in the PFS) and will be used for exhaust air and emergency secondary egress, NexGen said.

Like some other projects in the region, shaft freezing will be required to a point to secure the underground project, NexGen confirmed.

In terms of processing, NexGen said extensive test work and engineering had determined that proven technology in a conventional uranium processing flowsheet is most effective to produce uranium oxide from the Arrow deposit.

The main components of the processing plant are ore sorting; grinding; leaching; liquid-solid separation via counter current decantation and clarification; solvent extraction; gypsum precipitation and washing; yellowcake precipitation and washing; yellowcake drying; calcining and packaging; and tailings preparation and paste tailings plant.

Metallurgical testing resulted in supporting and refining process design parameters, with the process recovery of 97.6% confirming the predictable nature of the processing flow sheet, it said.

“The feasibility study also confirmed that all processed waste streams can be stored in the UGTMF and no surface tailings facility is required,” NexGen said. “The UGTMF is a reflection of NexGen’s industry-leading environmental design approach, contributing to the significant reduction of the project’s surface footprint, and representing an opportunity to implement best practice of progressive closure of tailings facilities during the operational phase of the mine.”

A feasibility study drill program validated the geotechnical conditions and favourable conditions for the UGTMF, with the study also optimising the geotechnical design, size and sequencing of the UGTMF included in the mine plan.

The study test work demonstrated paste fill strength met or exceeded all requirements set in the feasibility study design for a potential paste-backfill to be used for underground stope stability.

In terms of the timeline to production, NexGen said it planned to submit its Environmental Impact Statement in the second half of this year, along with relevant licences.

Denison Mines aims to bring ISR mining to Athabasca Basin uranium sector

The prefeasibility study on Denison Mines’ Wheeler River uranium project, in the Athabasca Basin of Canada, has brought with it a significant change in the mining process for the high-grade Phoenix deposit.

Denison is now considering the use of in-situ recovery (ISR) mining at Phoenix, a lower cost method than the previously considered jet bore system, which requires freeze wall protection and is used at Cameco’s Cigar Lake mine.

The PFS envisages co-developing both the Phoenix and Grypon deposits using two different mining methods. The former would use ISR, with the latter using conventional long-hole underground mining.

Taken together, the project is estimated to produce 7.8 MIb/y of U3O8 over a 14-year mine life, with a base case pre-tax net present value (8% discount rate) of C$1.31 billion ($1.01 billion), and initial pre-production capital expenditures of C$322.5 million.

This is based on a probable reserve of 109.4 MIb averaging 3.5% U3O8. Of this amount, 59.7 MIb comes from Phoenix, which has an average grade of 19.1% U3O8.

David Cates, President and CEO of Denison, said: “The selection of ISR mining for the high-grade Phoenix deposit is a defining moment for our company and a potentially transformational development for the future of uranium mining in the Athabasca Basin – bringing the world’s lowest cost uranium mining method to the jurisdiction hosting the world’s highest-grade uranium deposits.”

Denison said the selection of ISR mining at Phoenix came after considering 32 alternate mining methods to replace the high-cost jet bore mining system assumed for the Phoenix deposit in the 2016 preliminary economic assessment.

“The suitability of ISR mining for Phoenix has been confirmed by significant work completed in the field and laboratory – including drill hole injection, permeability, metallurgical leach, agitation, and column tests,” the company said.

Results demonstrated high rates of recovery in both extraction (+90%) and processing (98.5%) following a simplified flowsheet that precipitates uranium directly from the uranium bearing solution, without the added costs associated with ion exchange or solvent extraction circuits, Denison added.

“Given the unique geological setting of the Phoenix deposit, straddling the sub-Athabasca unconformity in permeable ground, the project development team has combined the use of existing and proven technologies from ISR mining, ground freezing, and horizontal directional drilling to create an innovative model for in-situ uranium extraction in the Athabasca Basin.

“While each of the technologies are well established, the combination of technologies results in a novel mining approach applicable only to deposits occurring in a similar geological setting to Phoenix – which now represents the first deposit identified for ISR mining in the Athabasca Basin.”

Wheeler River is a joint venture between Denison (63.3% and operator), Cameco (26.7%), and JCU (Canada) Exploration Company (10%).

The PFS assumes initial construction activities will commence in 2021 and that first production will be achieved from the Phoenix operation by mid-2024. Initial construction is expected to commence at Gryphon by 2026 and first production from Gryphon is expected to be achieved in 2030.