Risk Informed Assessment of Regulatory and Design Requirements for Future Nuclear Power Plants (Cooperative Agreement DE-FC03-99SF21902, Am. M004) Final Technical Report

OAK-B135 Research under this project addresses the barriers to long term use of nuclear-generated electricity in the United States. It was agreed that a very basic and significant change to the current method of design and regulation was needed. That is, it was believed that the cost reduction goal could not be met by fixing the current system (i.e., an evolutionary approach) and a new, more advanced approach for this project would be needed. It is believed that a completely new design and regulatory process would have to be developed--a ''clean sheet of paper'' approach. This new approach would start with risk-based methods, would establish probabilistic design criteria, and would implement defense-in-depth only when necessary (1) to meet public policy issues (e.g., use of a containment building no matter how low the probability of a large release is) and (2) to address uncertainties in probabilistic methods and equipment performance. This new approach is significantly different from the Nuclear Regulatory Commission's (NRC) current risk-informed program for operating plants. For our new approach, risk-based methods are the primary means for assuring plant safety, whereas in the NRC's current approach, defense-in-depth remains the primary means of assuring safety. The primary accomplishments in the first year--Phase 1 were (1) the establishment of a new, highly risk-informed design and regulatory framework, (2) the establishment of the preliminary version of the new, highly risk-informed design process, (3) core damage frequency predictions showing that, based on new, lower pipe rupture probabilities, the design of the emergency core cooling system equipment can be simplified without reducing plant safety, and (4) the initial development of methods for including uncertainties in a new integrated structures-systems design model. Under the new regulatory framework, options for the use of ''design basis accidents'' were evaluated. It is expected that design basis accidents would be an inherent part of the Probabilistic Safety Assessment for the plant and their evaluation would be probabilistic. Other first year accomplishments include (1) the conversion of an NRC database for cross-referencing NRC criteria and industry codes and standards to Microsoft 2000 software, (2) an assessment of the NRC's hearing process which concluded that the normal cross-examination during public hearings is not actually required by the U.S. Administrative Procedures Act, (3) the identification and listing of reliability data sources, and (4) interfacing with other industry groups (e.g., NEI and IAEA) and NRC at workshops for risk-informing regulations. The major accomplishments during the second year consisted of (1) issuance of the final report for Subtask 1.1, ''Identify Current Applicable Regulatory Requirements [and Industry Standards],'' (2) issuance of the final report for Subtask 1.2,'' Identify Structures, Systems, and Components and Their Associate d Costs for a Typical Plant,'' (3) extension of the new, highly risk-informed design and regulatory framework to non-light-water-reactor technology, (4) completion of more detailed thermal-hydraulic and probabilistic analyses of advanced conceptual reactor system/component designs, (6) initial evaluation and recommendations for improvement of the NRC design review process, and (7) initial development of the software format, procedures and statistical routines needed to store, analyze and retrieve the available reliability data. Final reports for Subtasks 1.1 (regulatory and design criteria) and 1.2 (costs for structures, systems, and components) were prepared and issued. A final report for Subtask 1.3 (Regulatory Framework) was drafted with the aim to issue it in Phase 3 (Year 3). One technical report was produced for Subtask 1.4 (methods development) and two technical reports were produced for Subtask 1.6 (sample problem analysis). An interim report on the NRC design review process (Subtask 1.7) was prepared and issued. Finally, a report on Subtask 2.2 (database weaknesses) addressed the initial development of a new database to track reliability data. During the third and final year (Phase 3), work was completed on Subtasks 1.3 (regulatory framework), 1.6 (sample problem analysis), Subtask 1.7 (regulatory analysis), Subtask 1.8 (industry and NRC coordination), and Subtask 2.3 (reliability data improvements)