By Helge Gabert
Although depleted uranium (DU) once constituted a small percentage of the low-level radioactive waste (LLRW) generated in the United States, increased production in recent years has led to a growing need to find sites that are best suited for its long-term disposal.
EnergySolutions, a commercial LLRW company in Utah, is seeking a license amendment from the Department of Environmental Quality (DEQ) to dispose of large quantities of DU at its Clive facility. Federal and state law require the company to conduct an extensive analysis called a performance assessment (PA) to determine whether DU can be safely stored at EnergySolutions’ West Desert site.
Characteristics of Depleted Uranium
Depleted uranium is what remains after U-235, the isotope used to release energy for nuclear power, is extracted from naturally occurring uranium. Because nuclear reactors need a higher concentration of this particular isotope, enrichment facilities concentrate it, leaving behind material that contains less U-235 and more U-238, another uranium isotope.
While depleted uranium is initially less radioactive than naturally occurring uranium, it becomes significantly more radioactive over time. The reduction of U-235 relative to U-238 in DU makes the material very unstable. As DU decays, it generates daughter products that increase, rather than decrease, its radioactivity. Eventually the decay products reach equilibrium and turn into lead, but this process takes millions of years. This particular characteristic of DU — increasing radioactivity over a long period of time — makes safe disposal very challenging.
Performance Assessment (PA)
State regulations require EnergySolutions to conduct a PA before it can accept large quantities of DU for disposal. The PA includes a quantitative, probabalistic analysis to demonstrate that the waste disposal will meet performance objectives for a minimum of 10,000 years, with additional qualitative, deep-time analyses for the period during which the DU reaches peak radiation activity, or approximately 2 million years. The technical document must provide reasonable assurance that the disposal plan will:
- Protect the public from radiation exposure through air, soil, ground water, surface water, and plant and animal pathways
- Protect inadvertent human intruders
- Protect individuals during operations
- Ensure the long-term stability of the disposal site
On June 1, 2011, EnergySolutions submitted a 960-page, site-specific performance assessment that identified critical data, facility design, and modeling procedures for DU disposal at its facility. In August 2013, DEQ hired an outside contractor from Virginia, SC&A, to evaluate the PA for adequacy.
Safety Evaluation Report (SER)
DEQ and its contractor SC&A reviewed the PA for completeness and asked EnergySolutions additional questions, or interrogatories, about its analyses. EnergySolutions revised the initial design of the DU disposal cell and resubmitted the portion of the modeling report related to cell performance, as well as an updated compliance report, in June and July of 2014.
Upon completion of supplemental interrogatories, including a dune study and enhanced deep time analysis in late 2014 and early 2015, DEQ and SC&A prepared a Safety Evaluation Report (SER) that summarizes the analyses they performed to determine whether the PA meets federal and state regulatory performance criteria for DU disposal sites.
The DEQ evaluation found that that the DU PA met some of the required regulatory criteria or could meet the requirements under an applicable condition(s).
There were eight issues that DEQ determined were not satisfied in the PA and must be subject to further analysis. EnergySolutions is also required to meet seven additional conditions before DEQ can reach a decision on the the proposed license amendment to accept depleted uranium at Clive.
Next Steps
DEQ released the SER for public comment on April 13, 2015. EnergySolutions requested and was granted additional time to address the issues that, according to the SER, were not resolved in the PA. The public comment period has been placed on hold for a limited period of time.
DEQ will proceed with the public meetings that were originally scheduled for May 6 and 7 to provide the public with an opportunity to learn more about the current SER and its findings. Additional public information meetings may be held at the time of the final proposal, and public hearings to take comments will be held during the comment period for the final proposal.
The assessment and review process, although lengthy, is designed to provide decision-makers with the best information available. DEQ has not made a formal recommendation or determination at this time regarding EnergySolutions’ proposal. The director of the Division of Radiation Control will make the final decision on whether to issue a license amendment to EnergySolutions for the disposal of DU.
We encourage the public to participate in the process by visiting our website to learn more about DU, attending our upcoming informational meetings, and providing comments on the final proposal. Please join us at one of the two meetings being held this week.
Wednesday, May 6, 2015
5:00 PM. to 8:00 PM.
Tooele County Courthouse
47 South Main Street
Tooele, Utah
Thursday, May 7, 2015
5:00 PM. to 8:00 PM.
Utah Department of Environmental Quality, Board Room #1015
195 North 1950 West
Salt Lake City, Utah
I was born in Germany but raised in East Africa. I received a Master’s in Hydrology from the University of Freiburg, Germany, with minors in Mathematics and Statistics, in 1985. I subsequently worked as an environmental consultant in Salt Lake City, and started with the Division of Solid and Hazardous Waste at DEQ in 1995. As a hydrologist, I work mostly on ground water corrective action issues at Tooele Army Depot, Grassy Mountain, and ATK-Bacchus. Apart from having been involved with national issues at the EPA ground water forum, and the ITRC ground water statistics and monitoring compliance group, in the past year and a half, I have been the DEQ project manager for EnergySolutions’ proposal to dispose of large quantities of depleted uranium. I enjoy hiking, bicycling, motorcycling, swimming, classical music, and dabbling in number theory.