Effectively Resolving the Issue of Legacy Uranium Waste Piles: Turning a Liability into an Asset
In the 1940s, the uranium mining industry operated under the leadership and direction of the U.S. Atomic Energy Commission (now the Department of Energy) to support production of weapons and later fuel for emerging nuclear reactor technologies. Currently, the Department of Energy (DOE) estimates there are 15,000 abandoned uranium mines (AUMs) throughout the western US, with most of these sites located in Colorado, Utah, New Mexico, Arizona, and Wyoming. Approximately 75% of these AUMs are on federal and tribal lands. We estimate over 683 million tons of low-grade uranium waste rock is located solely across the Navajo Nation and Defense Related Uranium Mines (DRUMs). Grades of this uranium waste rock vary between 100 and 1000 mg/kg, amounting to up to 683,100 tons of U3O8.
Waste minimization is a key strategy of the U.S. Environmental Protection Agency under the Resource Conservation and Recovery Act and the U.S. Department of Interior under 43 CFR 3809 – Surface Management enacted to prevent unnecessary and undue degradation of public lands. Waste minimization at uranium mine sites comes in the form of reducing the volume of ore-containing rock transported offsite for processing. Reducing the amount of transported ore-containing rock, consequently, reduces the amount of waste a conventional uranium mill must manage after processing the ore/rock.
Disa’s High-Pressure Slurry Ablation (HPSA) Technology: HPSA technology uses a mechanical process—no chemicals—to separate radioactive material from waste rock and produce higher concentration uranium ore to later be used for uranium milling, consequently, minimizing resulting mill waste tailings. HPSA enables uranium to be separated from mining waste materials, significantly reducing the radioactivity in the material volume left onsite. HPSA further reduces the tailings waste volume that is generated by recycling this material at a uranium milling facility. HPSA technology can be highly valuable for remediating abandoned and inactive mine sites, reducing waste volume generated from operating mines, and substantially increasing the efficiency of uranium processing at operating mills. HPSA technology has demonstrated its exceptional ability to fulfill the specific need for selective liberation of uranium and other valuable minerals in an energy efficient manner, particularly when mineral-rich layers can easily be separated from the host rock. Evidence of HPSA’s efficiency is best represented by HPSA’s processing of uranium mine waste rock from uranium hosted sandstone formations, where the soft mineral patina coatings of uranium can be easily separated (disassociated) from the harder sand grain. This disassociation concentrates uranium into the finer particle fraction of the material mass, making it more economically viable for physical and chemical separation (milling) downstream.
Summary of Benefits: HPSA technology provides environmental and societal benefits while also demonstrating economic advantages.
Environmental and Societal Benefits: HPSA is revolutionary to the uranium reclamation market as its application allows for 85% of the original material to remain onsite as a remediated and stable coarse fraction (residual) while the concentrated uranium mineral-rich fines (representing 15% of the original material and 90% of the overall uranium) can be recycled to a conventional uranium mill and converted to yellowcake (U3O8).
Any remaining uranium in the remediated and stable coarse fraction of the original feed is below source material limits and interlocked in the quartz gains inhibiting its mobility. Thus, this portion of the mass does not pose any hazard to the surrounding communities or watersheds.
The liberated, concentrated, and separated uranium-bearing fine fraction of the post-processed material possesses sufficiently high uranium concentrations that it can be subsequently recycled at a traditional uranium mill where it can continue in its journey to ultimately be used as nuclear fuel, providing carbon-free electricity.
This mechanical technique, where HPSA uses water instead of chemicals, reduces radioactive waste at mine sites, which renders HPSA technology an environmentally friendly remediation option.
Finally, this technology provides economic value. By increasing uranium concentrations in a smaller volume of material, uranium recovery facilities can more easily recover and further concentrate the uranium while generating less waste to be stored onsite.
Domestic Nuclear Fuel Supply Chain Benefits: The domestic nuclear fuel supply chain can be dramatically reinvigorated by using HPSA to convert uranium waste piles from a liability into an asset, while, at the same time, protecting the environment.
Given the quantity of low-grade uranium waste rock in the U.S., even if a fraction of these waste rocks were processed by HPSA technology and recycled at a conventional uranium mill, domestic uranium production could easily meet the imported 21,300 tons of U3O8 in 2019.
This technology also reduces the overall radioactivity levels in the waste at mine sites, simplifying site remediation efforts and decreasing remediation costs. In addition, Congress appropriated funds for a domestic uranium fund which could be partially supplied by these environmentally responsible activities.
While HPSA presents environmental benefits, it also creates opportunities for supply chain efficiencies.