resolution of uncertainties does not create greater offsetting risks to health and the environment or other costs. Actions that would eliminate important options should be delayed when possible because options have value.

By structuring the path toward a final end state as a sequence of decisions (e.g., a tank closure decision or a saltstone processing decision), one can start to separate the decisions into decisions that clearly should be taken as soon as possible and those that potentially may be delayed until important uncertainties can be reduced (allowing a better choice to be made) or until new options become available (e.g., through operational experience, research, and technological innovation) that may make the decision easier (reduced risk at lower cost) and better informed.

The committee’s findings and recommendations address four major issues: (1) near-term and long-term risks; (2) tank space crisis; (3) Class C limits and performance objectives; and (4) research and development needs. The following findings and recommendations are based on information available to the committee at the time of writing this interim report and may be extended if new information becomes available at the time the final report is written.

Near-Term Versus Long-Term Risks

Finding 1a: By far the greatest reductions in near-term probability and quantity of radionuclide and hazardous chemical releases to the environment are achieved by bulk removal and immobilization of liquid, salt, and sludge from the noncompliant high-level waste tanks. The tank heels that remain after bulk removal contain a smaller quantity of waste that is less mobile and constitutes a much lower near-term probability of release.

Finding 1b: The Savannah River Site Federal Facility Agreement has schedules for waste removal from and closure of the noncompliant tanks. For some tanks, the tank-closure step immediately follows the waste-removal step, making them appear to be coupled. This coupling could limit the time available for tank-waste removal and consequently could determine how much waste can be removed to “the maximum extent practical.” A decoupled schedule is already planned for a limited number of tanks, as shown in Appendix F. Decoupling allows the consideration of a wider set of options for removing and/or immobilizing residual waste (especially for tanks that have significant obstructions that complicate waste removal), which could reduce long-term risks.

Recommendation 1: DOE should decouple tank waste removal and tank closure actions on a case-by-case basis where there are indications that near-term (5-10 years) techniques could become available to remove tank heels more effectively, safely, or at a lower cost. In evaluating schedules for each tank, DOE should consider the risks from postponing tank closure compared with the risk reductions that could be achieved if the postponement improves heel removal. Although the committee believes that postponing tank closure need not extend the closure dates of the tank farms, DOE should work with the State of South Carolina to revise the schedule for closure of a limited number of the tanks that contain significant heels, if necessary.

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