US NRC Generic Issue (GI-199) and its Impact on Analysis/Design of Independent Spent Fuel Storage Installation (ISFSI) in CEUS

摘要

The U. S. Nuclear Regulatory Commission (NRC) Generic Issues Program (GIP) evaluates technical issues that apply to two or more facilities and that may not be covered by existing regulatory processes or criteria. Issues are evaluated for their effect on safety, security, and/or the environment. The GIP is a program by which these issues can be formally assessed to see if they can be dis-positioned by existing regulatory processes or if not, to determine their safety and/or risk significance and how best to treat them. NRC issued Information Notice (IN) 2010-018 [1] in September, 2010 to all current holders of a license to operate a Nuclear Power Plant, addressing the Generic Issue 199 (GI-199) [2], "Implications of Updated Probabilistic Seismic Hazard Estimates in Central and Eastern United States on Existing Plants." In the continental USA, geographic areas located east of the Rocky Mountain Front (East of approximately 104° west longitude) are generally known as the Central and Eastern United States (CEUS). GI-199 investigates the safety and risk implications of updated earthquake-related data and models that suggested that the probability for earthquake ground shaking above the seismic design basis for some nuclear power plants in the CEUS is still low, but larger than previous estimates. Spent Nuclear Fuel storage, using an NRC approved Dry Cask Storage System (DCSS) is an acceptable means of spent fuel management. The Independent Spent Fuel Storage Installations (ISFSIs) are required to satisfy the safety objectives of Title 10 of the Code of Federal Regulations (10 CFR) Part 72 [3]. Regulatory Guides (RGs), NUREGs, Standard Review Plans (SRPs) and other guidance documents are available to assist an applicant in complying with the regulations. Although not specifically evaluated as part of GI-199 a preliminary screening review was performed by the NRC Office of Nuclear Material Safety and Safeguards (NMSS). Design Earthquakes (DE), and the Safe Shutdown Earthquake (SSE) used for the cask designs at the existing ISFSI locations in the CEUS were compared. This review indicated that the safety margin defined for ISFSIs as: the ratio of DE/SSE was adequate and, these ISFSIs can continue to operate safely while the licensees investigate the issue using their site specific detailed information. Even so, holders of an operating license for ISFSIs were included among addressees in the IN 2010-018. Currently there are 48 operating ISFSIs in the CEUS. Except for a wet storage facility at G. E. Morris located in Illinois, these ISFSIs are co-located at operating reactor sites, and a few at permanently shutdown reactor sites. The IN includes ISFSIs that are co-located at the reactor sites, which use the plant SSE as their design/licensing basis, as well as ISFSIs located away from the reactor site, which have their own location-specific licensing/design-basis earthquake. The NRC expects that recipients of the IN will review the information, when available, related to potential increase in seismic demand for applicability to their facilities and consider actions, as appropriate. This paper will provide an overview of some of these issues that NRC licensed facilities will address in the near future to establish adequacies of these ISFSI facilities within the framework of existing 10 CFR Part 72 regulations.