Study Questions DOE's Plans For Cleanup Of Tank Wastes

While the U.S. Department of Energy's (DOE) overall plan for cleaning up radioactive waste in 246 underground tanks at three defense-related sites is workable, some important challenges should be addressed, according to a report released on April 4 by the National Academies' National Research Council.

The tanks are located at DOE's Savannah River Site in South Carolina, the Hanford Site in Washington state, and the Idaho National Laboratory. DOE plans to remove the waste from the tanks and separate out high-level radioactive waste, which will eventually be shipped to an off-site geological repository. The remaining radioactive waste will be disposed of on-site, and residual waste in the tanks will be covered by grout. So far, only two of the 246 tanks have been cleaned out and backfilled with grout, and none has had a permanent cover installed.

DOE faces technical hurdles, such as retrieving waste from tanks with significant obstructions at the Savannah River Site and from tanks with leaks at the Hanford Site, noted the committee that wrote the report. In addition, the committee expressed concern that more radioactive material than planned could remain in the waste to be disposed on-site of at the Savannah River Site after the waste-separation process. It also questioned the large volume of radioactive material that DOE plans to place in saltstone vaults there. To reduce the amount of radioactive material to be disposed of at the Savannah River Site, DOE should develop alternatives or enhancements to one of its planned interim waste-processing techniques. The committee also had serious reservations about some of the assumptions the agency made regarding how much waste will remain in closed tanks at Savannah River after cleanup.

The safety and reliability of a proposal to immobilize large amounts of the Hanford Site's non-high-level radioactive waste in glass before on-site disposal were also of concern. This process, known as bulk vitrification, needs to undergo a more detailed transparent and independent technical review of its likely performance and safety, the committee said. The Idaho facility, on the other hand, is making good progress in tank cleanup and closure, the committee found, although there are fewer tanks at the site and they are simpler to clean.

Deciding how much waste to retrieve from the tanks and how much of it should be disposed of on-site -- answering the question "How clean is clean enough?" -- is difficult, the committee acknowledged. DOE must consider the feasibility of technologies to retrieve and separate waste, the risk to workers, the potential risks posed by wastes left on-site, and costs. Making these assessments would be easier if DOE pursued a more consistent risk-informed process with greater participation by other stakeholders, especially the public. The committee applauded the increased transparency in some of DOE's recent waste assessments.

It is not practical to remove all of the waste from the tanks, the committee said. It reiterated a finding from an interim report issued last year, however, that DOE should decouple the schedules for cleaning tanks likely to hold significant residual waste and permanently closing them. This would allow more time for the development of technologies that could remove even more wastes from those tanks. Given that DOE is in the early stages of the tank cleanup process, there is time to pursue a research and development program to improve waste retrieval, tank stabilization, and immobilization of low-level radioactive waste, the committee added. It concluded that a 10-year program supported by $10 million to $50 million per year would be appropriate for generating improved knowledge about tank waste management and disposal. In addition, DOE should begin planning for how it will monitor tanks after they are closed so monitoring systems can be built in and around tanks before they are covered.

Additional information about the report, Tank Waste Retrieval, Processing, and On-site Disposal at Three Department of Energy Sites: Final Report is available at http://www.nap.edu.

This article originally appeared in the 04/01/2006 issue of Environmental Protection.

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