Start-up marks Alta Mesa acceleration

Thursday, 13 March 2025

In-situ recovery - also known as in-situ leach - uranium operations use ion exchange (IX) circuits to collect uranium from process water pumped from recovery wells in the wellfield. The second IX circuit at Alta Mesa doubles the total flow capacity from 2500 to 5000 gallons per minute (in litres that's about 9400 to 19,000 litres per minute), allowing more uranium to be collected.

In conjunction with the expansion of processing capacity, enCore has installed additional injection and extraction wells in the currently permitted and operational Wellfield 7. The combination of the second IX circuit and wellfield expansion utilises approximately 75% of the current processing capacity, the company says, and further wells will be brought online systematically in order to reach the plant's capacity.

"At any given concentration of dissolved uranium in water, the more solution you pump, the more uranium that can be captured," enCore Executive Chairman William Sheriff said. "At the Alta Mesa CPP, we have learned that our extraction process is faster than anticipated, which is expected to be positive for revenue and return on investment."

Earlier this month the company said it was implementing an accelerated action plan to expand its uranium operations at Alta Mesa, which resumed production in 2024 after being curtailed between 2005 and 2013 due to low prices. The central processing plant is ramping up to its nameplate capacity of 1.5 million pounds U3O8 (577 tU) per year.

The wellfield decline curve - a way of analysing production rates from wells as they decrease with time - at Alta Mesa is described by the company as "quite steep", with around 80% uranium capture achieved in just over 4 months: the wellfield decline curve at other projects tends to be much flatter, taking 12 to 15 months for 80% recovery due to differences in physical and chemical properties of the host rock and the process water. This capture rate means a very quick recovery of uranium, but also necessitates an aggressive drilling and well completion schedule, the company said.

The company is planning to recommission a third IX circuit at Alta Mesa in 2026, which will bring the Alta Mesa plant to 100% of its IX capacity.

Alta Mesa is operated and 70%-owned by enCore, with Boss Energy owning a 30% stake.