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Tank Waste Retrieval, Processing, and On-Site Disposal at Three Department of Energy Sites: Final Report Executive Summary1 The U.S. Congress asked the National Academies to evaluate the Department of Energy’s (DOE’s) plans for retrieval and on-site disposal of certain radioactive wastes2 stored in underground tanks at three DOE sites3 and to make recommendations to improve those plans. The major results of this evaluation are summarized below. Readers are strongly encouraged to read the full report and particularly the findings and recommendations for further details. DOE’s overall approach for management and disposal of tank wastes is workable, but important technical and programmatic challenges remain. In particular, the essential question, How clean is clean enough? applies to all cleanup activities and does not have a unique, numerical solution. The amount of waste to be retrieved from these tanks and how much of that should be disposed on-site is a decision in which DOE must consider a range of technical and nontechnical factors, including technical capabilities for waste retrieval and radionuclide separation from the removed wastes; cost, both in terms of dollars spent and worker doses incurred per increment of risk reduction achieved; and the potential risks from other wastes to be left on-site. DOE should pursue a more risk informed, consistent, participatory, and transparent process for making decisions about how much waste to retrieve from each of its tanks or group of tanks, and how much of that waste to dispose at each of the three sites. Only 2 of the 246 tanks at the three sites have been cleaned out and backfilled with grout, and none has had a permanent cover installed. At this early stage in the process, there is still time to develop tools and processes to address problems described here and in the full report. DOE should initiate a targeted, aggressive, collaborative research program to develop and deploy needed innovative technologies for tank waste retrieval, treatment, closure, and disposal. DOE’s current knowledge of tank waste characteristics is adequate for retrieving waste from tanks at all three sites. DOE needs to know the waste composition in greater detail for processing purposes and to confirm compliance with performance objectives, but this must be done after waste retrieval when mixing makes representative sampling of the retrieved waste possible and when samples of the tank heels can be taken. DOE should decouple its schedule for tank waste retrieval from its schedule for tank closure for those tanks that still contain significant amounts of radioactive material after initial waste retrieval is completed. More broadly, because decisions about planned disposal activities require multiple inputs, DOE should not make decisions based solely on schedule conformance. Decoupling will enhance future opportunities to remove additional radioactive material from these tanks as retrieval technologies are improved. If implemented properly, decoupling for individual tanks need not delay the final closure of the tank farms. There is little technical advantage in the accelerated closure of the tanks. DOE plans to make waste determinations for individual tanks and small groups of tanks. Documents demonstrating compliance with performance objectives will be generated for each draft waste determination. The ongoing review of draft determinations by the U.S. Nuclear Regulatory Commission and host 1 A detailed summary of the committee’s report is presented in the next chapter. 2 These wastes are the result of reprocessing spent fuel and targets from defense reactors and contain radionuclide concentrations above Class C quantities as defined in Title 10, Part 61 of the Code of Federal Regulations (10 CFR 61). 3 The Savannah River Site, South Carolina; Hanford Site, Washington; and Idaho National Laboratory.
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Tank Waste Retrieval, Processing, and On-Site Disposal at Three Department of Energy Sites: Final Report states, as required by the Ronald Reagan National Defense Authorization Act of 2005 (NDAA) and the state-approved closure plans it demands, is improving the technical quality and public transparency of DOE’s planning efforts. DOE should continue to seek transparent, independent peer review of critical data and analyses used to support decisions about tank waste retrieval, processing, and disposal even if review is not required under the NDAA. DOE is just beginning to develop plans for post-closure monitoring of closed tank farms and associated disposal sites. The main objective of this monitoring is to verify compliance with the performance objectives in 10 CFR 61. However, some of the assumptions made in DOE’s waste determinations need to be confirmed. Therefore, DOE should develop plans now for a post-closure monitoring program and begin to build provision for monitoring into its tank closures and disposal facilities. The report provides several site-specific findings and recommendations; these are summarized below: Savannah River Site: The committee has serious reservations about aspects of DOE’s plans for tank closure, including the point of compliance and assumptions about exposure scenarios and waste inventories remaining after tank cleanup. The committee is also concerned about DOE’s plans to dispose of large inventories of radionuclides in the Saltstone Vaults on-site, and that the tank space crisis may lead DOE to dispose of additional radioactive material on-site. To reduce the quantities of radionuclides to be disposed of on-site, DOE should develop alternates or enhancements to the deliquification, dissolution, and adjustment treatment process to solve its tank space problems. Hanford Site: The committee also has reservations about DOE’s plans to use bulk vitrification as a secondary process for treating low-activity waste for on-site disposal. DOE should arrange for a transparent, independent, technical review of the bulk vitrification process to assess its performance and safety. Idaho National Laboratory: DOE is making good progress in tank cleanup and closure. A number of other significant issues will have to be resolved by DOE. The committee did not examine these issues in depth because DOE has not developed detailed plans for them, as yet, but DOE should review and resolve these issues with deliberate speed. These include remediation of plugged and leaking underground pipes and interwall spaces in double-walled tanks; the disposition of calcine bin waste at the Idaho site; regulatory approvals for the off-site disposal of some Hanford tank waste and Idaho sodium-bearing tank waste; the philosophy and methodology for post-closure monitoring; and plans for carrying out long-term stewardship, including how the federal government will maintain control “in perpetuity” at sites unsuitable for unrestricted release.
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