Publications
Repository performance confirmation
Repository performance confirmation links the technical bases of repository science and societal acceptance. This paper explores the myriad aspects of what has been labeled performance confirmation in U.S. programs, which involves monitoring as a collection of distinct activities combining technical and social significance in radioactive waste management. This paper is divided into four parts: (1) A distinction is drawn between performance confirmation monitoring and other testing and monitoring objectives; (2) A case study illustrates confirmation activities integrated within a long-term testing and monitoring strategy for Yucca Mountain; (3) A case study reviews compliance monitoring developed and implemented for the Waste Isolation Pilot Plant; and (4) An approach for developing, evaluating and implementing the next generation of performance confirmation monitoring is presented. International interest in repository monitoring is exhibited by the European Commission Seventh Framework Programme 'Monitoring Developments for Safe Repository Operation and Staged Closure' (MoDeRn) Project. The MoDeRn partners are considering the role of monitoring in a phased approach to the geological disposal of radioactive waste. As repository plans advance in different countries, the need to consider monitoring strategies within a controlled framework has become more apparent. The MoDeRn project pulls together technical and societal experts to assimilate a common understanding of a process that could be followed to develop a monitoring program. A fundamental consideration is the differentiation of confirmation monitoring from the many other testing and monitoring activities. Recently, the license application for Yucca Mountain provided a case study including a technical process for meeting regulatory requirements to confirm repository performance as well as considerations related to the preservation of retrievability. The performance confirmation plan developed as part of the Yucca Mountain license application identified a broad suite of monitoring activities. A revision of the plan was expected to winnow the number of activities down to a manageable size. As a result, an objective process for the next stage of performance confirmation planning was developed as an integral part of an overarching long-term testing and monitoring strategy. The Waste Isolation Pilot Plant compliance monitoring program at once reflects its importance to stakeholders while demonstrating adequate understanding of relevant monitoring parameters. The compliance criteria were stated by regulation and are currently monitored as part of the regulatory rule for disposal. At the outset, the screening practice and parameter selection were not predicated on a direct or indirect correlation to system performance metrics, as was the case for Yucca Mountain. Later on, correlation to performance was established, and the Waste Isolation Pilot Plant continues to monitor ten parameters originally identified in the compliance certification documentation. The monitoring program has proven to be effective for the technical intentions and societal or public assurance. The experience with performance confirmation in the license application process for Yucca Mountain helped identify an objective, quantitative methodology for this purpose. Revision of the existing plan would be based on findings of the total system performance assessment. Identification and prioritization of confirmation activities would then derive from performance metrics associated with performance assessment. Given the understanding of repository performance confirmation, as reviewed in this paper, it is evident that the performance confirmation program for the Yucca Mountain project could be readily re-engaged if licensing activities resumed.