enCore Energy's February 2025 technical report on the Gas Hills uranium project in Fremont and Natrona counties, Wyoming, effective December 31, 2024, bases its plant on the Dewey-Burdock design but recovers uranium with sulfuric acid.
The Technical Report on the Gas Hills Uranium Project, Fremont and Natrona Counties, Wyoming, USA, was prepared by WWC Engineering for enCore Energy Corp. with an effective date of December 31, 2024 and signed on February 4, 2025. The project is an in-situ recovery (ISR) operation. Production fluid carrying dissolved uranyl sulfate is pumped from the well fields to a central processing plant (CPP), which recovers the uranium by ion exchange, elution, precipitation, drying and packaging. Most cost and design assumptions are taken from enCore's more advanced Dewey-Burdock project. The main difference is that Gas Hills uses low-pH recovery with sulfuric acid rather than oxygen and sodium bicarbonate.
Critical Data
| Parameter | Value | Unit | Notes |
|---|---|---|---|
| Report effective date | December 31, 2024 | Not applicable | WWC Engineering for enCore Energy Corp.; signed February 4, 2025 |
| CPP available flow | 4,400 | gpm | Not applicable |
| Planned average production flow | About 2,400 | gpm | Not applicable |
| Lixiviant | Sulfuric acid (low pH) | Not applicable | Up to $2.66/lb U3O8 more in chemical cost |
| Barren lixiviant target | Below 2 | ppm U | After ion exchange |
| Well field bleed | 0.5 to 1.0 | % of total flow | About 22 gpm to deep disposal |
| Precipitate | Uranyl peroxide (UO4) | Not applicable | Vacuum dried, packed in 208.4 L drums |
| Product shipping | About 1,500 miles by truck | Not applicable | To the conversion facility in Metropolis, Illinois |
| Staffing at full production | Up to 43 | employees | Based on Dewey-Burdock staffing |
| Contaminated (11e.(2)) waste | About 90 | yd³/a | Non-contaminated about 700 yd³/a |
Overview
The CPP runs four main solution circuits: ion exchange (IX) to extract uranium from the mining solution, elution to strip it from the resin, precipitation to make yellowcake, and dewatering, drying and packaging. The report expects the low-pH method to give higher head grades and lower water flows than the alkaline method assumed at Dewey-Burdock, but it makes no operating-cost reduction for this.
Key Process Stages
Ion exchange. Pregnant lixiviant enters pressurized down-flow IX columns, which keep radon and its progeny in solution. The ion-specific resin captures anionic uranium complexes in exchange for common anions such as chloride and bicarbonate. Barren lixiviant, ideally below 2 ppm uranium, is reconstituted, pH corrected and reinjected. The IX circuit shares a metal building with the resin transfer equipment and the restoration circuit.
Bleed and restoration. A small permanent bleed keeps an inward hydraulic gradient in the well fields and is disposed of in a Class I deep disposal well (DDW). During groundwater restoration, the bleed is treated by reverse osmosis: clean permeate, of better quality than the native groundwater, is reused, and the brine goes to the DDW.
Elution. A sodium chloride and sodium carbonate brine strips uranium from the loaded resin and restores its exchange capacity.
Precipitation. In agitated tanks in series, sulfuric acid breaks down the uranium complexes in the rich eluate, caustic soda raises the pH, and hydrogen peroxide precipitates insoluble uranyl peroxide.
Filtering, drying and packaging. The yellowcake slurry is washed and filtered in a filter press to remove chlorides and other soluble contaminants, reslurried and dried in an enclosed vacuum dryer. It is then packed through a rotary airlock and ventilated drum hood into 208.4 L drums.
Additional Interesting Data and Summary
At the planned 2,400 gpm, liquid waste for deep disposal is about 22 gpm, and a single DDW is assumed to serve both production and restoration. Non-contaminated solid waste, about 700 yd³ a year, goes to an approved industrial landfill. About 90 yd³ a year of 11e.(2) byproduct material, such as filters, spent resin and protective equipment, is trucked to a licensed disposal site. Labor of up to 43 people includes 15 to run the CPP. CPP construction is expected to start in Year −2, once the last permit is received.
In summary, Gas Hills is designed as a conventional Wyoming ISR operation built on the Dewey-Burdock template. It differs in using sulfuric acid lixiviant, which adds up to $2.66 per pound to chemical costs, and its IX, elution and peroxide precipitation train is sized for 4,400 gpm.
Key Processes
- In-situ recovery with low-pH sulfuric acid lixiviant
- Pressurized down-flow ion exchange
- Brine elution of loaded resin
- Hydrogen peroxide precipitation of uranyl peroxide
- Filter press washing and vacuum drying
- Drum packaging of yellowcake
- Well field bleed and RO restoration with deep well disposal
Source: Technical Report on the Gas Hills Uranium Project, Fremont and Natrona Counties, Wyoming, USA, prepared by WWC Engineering for enCore Energy Corp., effective date December 31, 2024.
Earlier report summaries
Earlier versions of this profile, based on older technical reports, are retained below for source traceability. Dates and figures reflect each report’s own effective date and are superseded by the current information above.
Gas Hills Uranium Project PEA — 2021 Technical Report
This technical report describes a preliminary economic assessment for a satellite uranium ion-exchange facility feeding a central processing plant.
Report context
The Gas Hills Uranium Project PEA was prepared for Azarga Uranium Corporation in August 2021. The project is designed as an in-situ recovery (ISR) satellite facility that will operate in conjunction with the company’s Dewey-Burdock Project. The satellite plant will house only the ion-exchange (IX) circuit, with loaded resin transported to the Dewey-Burdock Project for elution, precipitation, drying, and packaging.
Processing route
Overall ISR circuit structure
ISR operations consist of four major solution circuits: ion exchange to extract uranium from the mining solution, an elution circuit to remove uranium from the IX resin, a yellowcake precipitation circuit, and a dewatering, drying, and packaging circuit. Because the project will be a satellite facility to the Dewey-Burdock Project, only the first circuit (IX) will be located at the project site.
Satellite operations (proposed design)
Production fluid containing dissolved uranyl sulfate from the wellfields is pumped to the satellite IX plant for beneficiation. The satellite plant considered in this PEA will have an available flow rate of 4,400 gpm. The planned average production flow rate for the project is approximately 2,400 gpm.
The IX circuit will be housed in a metal building that will also house the resin transfer equipment and the restoration circuit. Uranium is extracted from the pregnant solution in the IX circuit. The barren lixiviant is then reconstituted as needed and pH is corrected prior to being pumped back to the wellfield for reinjection.
A low-volume bleed is permanently removed from the lixiviant flow to maintain an inward gradient within the wellfields. The wellfield bleed is disposed of by injection into an Underground Injection Control (UIC) Class I Deep Disposal Well (DDW). During groundwater restoration activities, the bleed is treated by reverse osmosis (RO) to remove metals and salts (calcium, sodium, sulfate) and the clean permeate is reused in the process. The RO brine is then disposed of by injection into the DDW.
Associated with the satellite operation will be office, construction, maintenance, warehouse, and drilling support buildings. Satellite construction is expected to commence in Year -1 upon receipt of the last required permit.
Transportation (proposed design)
Once the IX resin is loaded to a point where it is no longer economically capturing uranium, the IX resin column is taken offline and the loaded resin is moved to a trailer. The resin will be shipped in 1,000 cu. ft. loads with the majority of water drained off prior to shipping. Bulk pneumatic trailers will transport loaded resin to and unloaded resin from the Dewey-Burdock processing plant, located on the Wyoming-South Dakota border between Dewey and Burdock, South Dakota. A contract carrier licensed to haul radioactive materials in Wyoming and South Dakota will be used.
Two possible routes are identified. The preferred route is approximately 250 miles, going north on Gas Hills Road, east on U.S. Highway 20/26, east on Interstate 25, northeast on U.S. Highway 18/85, then east on gravel roads to the Dewey-Burdock Project. The alternate route is approximately 290 miles, going north on Gas Hills Road, east on Wyoming Highway 20/26, north on Interstate 25, east on Wyoming Highways 259, 387, and 450, south on U.S. Highway 85, then east on gravel roads. Once a loaded trailer is delivered, an empty trailer will be immediately returned to the project.
Energy, water and process materials (basis of estimate)
The Gas Hills satellite plant will generally be identical in flow rates and operation to the planned satellite plant at the Dewey-Burdock facility, for which the design is much further advanced. Energy and reagent use will be identical to Dewey-Burdock, adjusted for a change to sulfuric acid and for inflation. The low pH recovery methods are expected to result in higher headgrades and lower water flow rates than the alkaline recovery methods considered for Dewey-Burdock. No reductions in operational costs were made to adjust for this change.
Liquid disposal (proposed design and historical basis)
Typical ISR mining operations generate limited quantities of wastewater that cannot be returned to the production aquifers. Wastewater will come from two sources: wellfield production bleed and satellite processes. The production bleed is a net withdrawal generating an area of low hydrostatic pressure within the mining zone. The wellfield production bleed rate is estimated at 0.5 to 1.0 percent of the total mine flow rate. The wastewater flow rate from satellite processes will be minimal, on the order of 1 gpm, because the facilities will house only the IX circuit. At the planned average production flow rate of 2,400 gpm, liquid wastes for deep disposal will be approximately 22 gpm. One DDW is planned, with a surge pond holding 30 days of wellfield bleed as backup. The CAPEX and OPEX estimates assume this well will support production and restoration operations. Restoration wastewater treatment will entail passing portions of the fluid through a RO system, with permeate returning to the wellfield and brine injected into the DDW.
Solid waste disposal (estimates from similar facilities)
Non-contaminated solid waste is waste not contaminated with radioactive material or waste that can be decontaminated and reclassified. Current estimates from similar uranium ISR facilities are approximately 700 cubic yards per year. This waste will be collected and disposed of in an approved industrial solid waste landfill.
Contaminated solid waste is waste contaminated with radioactive material that cannot be decontaminated, classified as 11e.(2) byproduct material under NRC regulations. This includes filters, personal protective equipment, spent resin, piping, and similar items. It will be shipped by truck to a licensed disposal site. Based on waste generation rates of similar uranium ISR facilities, the project is estimated to produce approximately 90 cubic yards of 11e.(2) byproduct material per year.
Key reported parameters
| Parameter | Value | Unit | Basis |
|---|---|---|---|
| Satellite plant available flow rate | 4,400 | gpm | Proposed design (PEA) |
| Planned average production flow rate | 2,400 | gpm | Proposed design (PEA) |
| Resin shipment size | 1,000 | cu. ft. | Proposed design (PEA) |
| Preferred transport route distance | 250 | miles | Proposed design (PEA) |
| Alternate transport route distance | 290 | miles | Proposed design (PEA) |
| Wellfield production bleed rate | 0.5 to 1.0 | percent of total mine flow | Proposed design (PEA) |
| Wastewater flow rate for deep disposal (at 2,400 gpm average) | 22 | gpm | Proposed design (PEA) |
| Surge pond capacity | 30 | days of wellfield bleed | Proposed design (PEA) |
| Non-contaminated solid waste generation | 700 | cubic yards/year | Estimate from similar ISR facilities |
| Contaminated solid waste (11e.(2)) generation | 90 | cubic yards/year | Estimate from similar ISR facilities |
| Satellite process wastewater flow | 1 | gpm | Proposed design (PEA) |
Technical qualifications
The PEA assumes the Gas Hills satellite plant will be identical in flow rates and operation to the planned satellite plant at the Dewey-Burdock facility, for which design is much further advanced. Energy and reagent use estimates are based on Dewey-Burdock costs adjusted for increased sulfuric acid costs and inflation. No reductions in operational costs were made to adjust for the change to low pH recovery methods. Solid waste generation estimates are based on similar uranium ISR facilities, not site-specific data. The wellfield production bleed rate is estimated at 0.5 to 1.0 percent of total mine flow. The CAPEX and OPEX estimates assume the DDW will support both production and restoration operations.
Source: Gas Hills Uranium Project PEA , 2021 Technical Report, August 2021, Azarga Uranium Corporation, Section 17.0 Recovery Methods through Section 17.5 Solid Waste Disposal.
