Thursday 19th September 2019

Resource Clips


Lower cost, higher grade

Denison Mines considers the Athabasca Basin’s first ISR uranium operation

by Greg Klein

Less than 80 kilometres from the technological marvel of Cigar Lake, another uranium project could introduce an extraction method that’s less innovative but a regional novelty just the same. Denison Mines TSX:DML now has testing underway for in-situ recovery at the Wheeler River project’s Phoenix deposit. Should the studies succeed and the mine become a reality, this would be ISR’s first application in Canadian uranium mining.

Denison Mines considers the Athabasca Basin’s first ISR uranium operation

Denison Mines hopes to apply low-cost extraction
to high-grade resources. (Photo: Denison Mines)

ISR finds common use in Kazakhstan, Uzbekistan, the U.S., Australia and enough other countries to account for 48% of global uranium production in 2016, according to the World Nuclear Association. The lower-cost method has often been associated with lower-grade deposits that have geological conditions making the process viable. With a Phoenix probable reserve averaging 19.1%, Denison was able to consider other options. In fact the company originally planned to use Cigar Lake’s jet-boring technique.

But the experience of Cameco Corp TSX:CCO proved to be a cautionary tale. “Among 
the most technically challenging mining projects in the world” according to the company, Cigar Lake took nine years to build, with setbacks that included two serious floods. Finally opened in 2014, its jet-boring extraction makes the very high-grade operation “one of the technically most sophisticated mines in the world.”

Two years later, when Wheeler River reached PEA, Denison was still considering jet-boring for Phoenix. But capex, opex, length of construction and technical risks similar to Cigar Lake’s “catastrophic events” persuaded the company to pursue other options.

That Denison did, examining some 32 extraction techniques over two years before selecting ISR for Phoenix in the pre-feasibility study released last October. Wheeler’s Gryphon deposit, about three kilometres northwest, has more conventional underground mining proposed.

Both deposits are classified as Athabasca Basin unconformity-related. But Gryphon features basement-hosted mineralization while Phoenix mineralization is unconformity-hosted and also shows ISR potential.

Denison Mines considers the Athabasca Basin’s first ISR uranium operation

With its current drill program, Denison hopes to find
potential satellite ISR deposits. (Photo: Denison Mines)

Put simply, the process involves drilling wells into the deposit, injecting a liquid solution that leaches uranium from ore, then pumping the uranium-bearing liquid to a surface processing facility. No tailings or waste rock come to surface. The solution then gets recharged with fresh reagents for re-use in a closed system.

ISR, also known as ISL or in-situ leaching, can be used for copper and other minerals as well.

However Phoenix differs from many ISR projects by the permeability of the deposit’s sandstone walls, which will require freezing to contain the solution. Ground freezing involves pumping very cold brine into holes outside the deposit’s circumference to extract heat from the surrounding rock. Cigar Lake also uses underground freezing to contain the jet-boring process. One advantage of Phoenix over other ISR projects, however, is the relatively compact size of the high-grade deposit, about one kilometre by 50 metres.

Should geology, engineering, permitting and financing come together, Phoenix would take only about two and a half years to build, according to the PEA. With an estimated 11-year lifespan, production would average six million pounds U3O8 annually for nine of those years.

Hinting at satanic numerology, Gryphon would spend six years in construction and another six in operation, producing six million pounds a year. Processing would take place at the McClean Lake mill, now chewing through Cigar Lake ore. Denison holds 22.5% of the mill, along with Orano Canada (70%) and OURD Canada (7.5%).

As for Wheeler River ownership, Denison maintains a 90% stake, with JCU Canada holding the rest.

Denison Mines considers the Athabasca Basin’s first ISR uranium operation

With a deposit lying below Patterson Lake South,
Fission Uranium now has second thoughts
about open pit mining. (Photo: Fission Uranium)

Denison has further ISR tests now underway, part of the project’s feasibility studies. With work conducted by Petrotek Engineering Corp, the program has so far sunk two pump/injection wells and four observation wells along a 34-metre portion of the deposit’s strike. This week president/CEO David Cates described early results as encouraging, “with initial pump and injection tests confirming hydraulic connectivity between all of the test wells within the ore zone.”

The tests also suggest the basement rock beneath the unconformity would contain the solution, unlike the sandstone walls which would require freezing.

Three more test areas will be evaluated up to summer 2020 to compile a hydro-geological model to simulate ground water flow and other factors. The current campaign also includes environmental baseline studies and a 10-hole, 5,000-metre drill program searching for potential satellite ISR operations along the project’s K West trend.

While Wheeler River holds the largest undeveloped deposits in the eastern Basin, the Patterson corridor extending beyond the Basin’s southwestern rim claims fame for two even larger projects.

A pre-feas released by Fission Uranium TSX:FCU in May for Patterson Lake South’s Triple R deposit examined a hybrid open pit and underground mine, but the company was quick to reconsider. An alternative pre-feas began in July to evaluate an underground-only operation. The May pre-feas foresaw four years of construction, six years of open pit operation and two years of underground operation to produce 87.5 million pounds U3O8 over the eight-year span.

The company hopes its new pre-feas, expected in September, will find “further-improved economics, even lower capex and a reduced construction time.” Permitting might also have been a concern, however, for open pit mining on a uranium deposit currently underneath a lake. With the new report using the same resource estimate, Fission plans to compare both scenarios before moving on to feasibility.

Another basement-hosted deposit, NexGen Energy’s (TSX:NXE) Arrow deposit on the Rook 1 project reached pre-feas in December. The proposed underground mine would begin production during the second year of development, ultimately producing 228.4 million pounds U3O8 over a nine-year life, enough to give the company an estimated 21% of global output, just behind first-place Kazatomprom’s 22%, NexGen says.

The company plans full feasibility for Arrow in H1 next year.


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