DOE REPORT ON RAD-WASTES

DOE REPORT ON RAD-WASTES

U.S. Nuclear Waste Technical Review Board: Report to the U.S. Congress and the Secretary of Energy - January to December 1996

Executive Summary

The Department of Energy's (DOE) Program Plan officially introduced a new program milestone, the viability assessment (VA). The VA is to be completed by September 30, 1998. According to the DOE, the viability assessment will include four components: "(1) the preliminary design concept for the critical elements for the repository and waste package; (2) a total system performance assessment, based upon the design concept and the scientific data and analysis available by September 30, 1998, describing the probable behavior of the repository in the Yucca Mountain geological setting relative to the overall system performance standards; (3) a plan and cost estimate for the remaining work required to complete a license application; and (4) an estimate of the costs to construct and operate the repository in accordance with the design concept."

Perhaps the single most important technical decision facing this program is determining the suitability of Yucca Mountain as a site for a repository. The Board believes "that the VA will not provide adequate information for that decision. Rather, it is an assessment that the site continues to be a candidate that requires additional study, leading to a determination whether it is suitable to be recommended to the President for repository development in 2001. Nothing has been found to date to indicate that the site is unsuitable. ...

.... However, the Board also realizes that the planned VA may trigger other significant decisions such as selecting the location of a centralized facility for storing spent fuel. ...

About four years would elapse between selection of a site for a centralized storage facility and the first receipt of commercial spent fuel there. ...

Characterization of Yucca Mountain during 1996 produced a great deal of scientific information which substantially improved the understanding of the site. Until recently, Yucca Mountain was thought to have very little water available at depth to affect repository performance. During 1996, analysis and synthesis of several types of data suggested that more water flows through the proposed repository level than was previously expected. ...

The safety of a proposed repository can be assessed by using a total system performance assessment (TSPA), that is, a predictive model of the repository's ability to contain and isolate waste. ...

Although there is no formal requirement that the public accept the TSPA, to proceed without acknowledging the importance of such acceptance is condescending at best and a prescription for failure at worst. The likelihood of public acceptance of a TSPA will be significantly affected by its transparency. If the perception is that the TSPA is like a large black box whose results can be dictated by some manipulator arbitrarily adjusting hidden knobs, then no matter how good the underlying rationale, public acceptance will not be attainable. ...

An important element in designing and constructing the underground repository is ground support for the waste emplacement tunnels. Providing and maintaining stable tunnels for waste emplacement will be a major item in the cost of the repository. After the repository is closed, the waste packages are to provide containment for "thousands of years."...

Recommendations of the Board

The recommendations in this report are summarized below:

• A decision to locate the nation's primary centralized storage facility for spent fuel at or near Yucca Mountain should be deferred until the suitability of the site as a repository location has been determined.

• To the extent possible under the market-driven initiative, efforts to develop storage and transportation casks should retain the advantages (e.g., standardization) previously offered by the multipurpose canister concept.

• Before making a determination of the suitability of the Yucca Mountain site for a repository, the DOE should complete additional studies of the area west of the current exploratory studies facility, where wastes would be emplaced, to determine its geologic, hydrologic, and geochemical properties. The best way to obtain the needed information is excavation of a tunnel westward across the proposed repository block.

• The DOE should make a concerted effort to ensure that future TSPAs are transparent and valid, that uncertainty is treated properly, and that any peer review of performance assessment elicitation of expert judgment is objective.

• The DOE should consider ways of increasing public understanding and acceptance of TSPAs. One possibility is to establish processes, modeled on the lines suggested in a recent report by the congressionally chartered Commission on Risk Assessment and Risk Management, for involving and engaging the public.

• The DOE should develop and examine alternative concepts to the proposed remote underground repository operations, for example, ventilation of emplacement tunnels and shields for waste packages. Some alternatives should be developed in time for consideration in the viability assessment.

• The DOE should evaluate alternative design assumptions to determine whether enhanced repository performance or improved operations can be achieved cost effectively.

• The DOE should evaluate the use of precast or cast-in-place concrete tunnel liners to achieve adequate long-term tunnel support. The evaluation should consider cost and possible effects on waste isolation.

• Given the inevitable uncertainties about repository performance, more attention to defense-in-depth (multiple, redundant barriers) is needed in the waste package and repository designs. In particular, comprehensive studies of alternative engineered barriers - such as fillers, backfill materials, drip shields, and engineered inverts - should be completed.

• The DOE should learn that Low-Energy Nuclear Reaction Systems can be developed that will provide technology for ON-SITE REMEDIATION of high-level nuclear wastes.

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Oct. 29, 1997.