SBIR-STTR Award

Techniques have recently been developed to analyze the 'seismic margin' of a nuclear power plant using the HCLPF concept (high confidence of a low probability of failure). Starting with an earthquake level chosen for margin review, the technique determines whether the plant can or cannot withstand the review-earthquake without core damage here 'withstand means withstand with a high confidence of low probability of failure'. This HCLPF-based method can screen a plant's seismic 'margin' without undertaking a full-scope seismic PRA. However, the insights from the method are limited, partly because those accident sequences that dominate the HCLPF-based analysis are not themselves analyzed further. In this proposed project, the feasibility of carrying the HCLPF-based analysis one step further will be explored. If this 'one step further' is feasible, each key seismic accident sequence could be assigned a plant damage state (containing information about offsite release magnitude, timing, and probability) and the role of human factors and of non-seismic-induced failures could be better understood, without the need or expense of a full-scope seismic PRAM -

Anticipated Results:
If The Proposed Research Is Successful, The Usefulness Of Nrc's New Hclpf-Based Methodology For 'seismic Margin Reviews' Of Nuclear Power Plants Will Be Significantly Enhanced, And At Only Slightly Greater Cost. Decision-Makers In Both The Nrc And The Utility Will Have Great Use For The Additional Information Produced (About Source Terms, Non-Seismic- Induced Contributors, And The Role Of Human Factors In The Key Accident Sequences.) Several Commercial Firms That Have The Capability To Perform Seismic Margin Reviews Would Benefit From This Improved Methodology.

Techniques have recently been developed to analyze the 'seismic margin' of a nuclear power plant using the HCLPF concept (high confidence of a low probability of failure). This HCLPF-based approach can screen a plant's seismic 'margin' without undertaking a full-scope PRA. However, insights from the method are limited, partly because those accident sequences that dominate the HCLPF-based analysis are not themselves analyzed further. In Phase I of this project, the feasibility of carrying the HCLPF-based analysis one step further was explored, additional insights in the areas of non-seismic-induced failures, human interactions, and the potential for severe offsite consequences were found to be available using an expanded methodological approach. In the proposed Phase II, the expanded methodology will be applied in three test cases: by reanalyzing the recently completed margins reviews of Maine Yankee and Catawba, and by a trial application for the upcoming BWR margin review that NRC and EPRI are planning together. If the expanded methodology is shown to be effective and inexpensive, it should be feasible to use It for routine application in seismic margin reviews.

Anticipated Results:
If the proposed research is successful, the usefulness of NRC's new HCLPF-based methodo-logy for seismic margin reviews of nuclear power plants will be significantly enhanced, and at only slightly greater cost. Decision-makers in both the NRC and the utility will have great use for the additional information produced (about the potential for severe offsite consequences, non-seismic-induced failures, and the role of human interactions in the key seismic accident sequences.) Several commercial firms that have the capability to perform seismic margin reviews would benefit from this improved methodology.