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Please refer to Docket ID NRC-2012-0261 when contacting the NRC about the availability of information regarding this document. You may access information related to this document by any of the following methods:
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The NRC staff developed draft JLD-ISG-2012-06 to provide guidance and clarification to assist nuclear power licensees and holders of construction permits in active or deferred status with the performance of an integrated assessment. This ISG is being issued in draft form for public comment to involve the public in development of the implementation guidance.
On March 11, 2011, a magnitude 9.0 earthquake struck off the coast of the Japanese island of Honshu. The earthquake resulted in a large tsunami, estimated to have exceeded 14 meters (45 feet) in height that inundated the Fukushima Dai-ichi nuclear power plant site. The earthquake and tsunami produced widespread devastation across northeastern Japan and significantly affected the infrastructure and industry in the northeastern coastal areas of Japan. When the earthquake occurred, Fukushima Dai-ichi Units 1, 2, and 3, were in operation and Units 4, 5, and 6, were shut down for routine refueling and maintenance activities. The Unit 4 reactor fuel was offloaded to the Unit 4 spent fuel pool (SFP). Following the earthquake, the three operating units automatically shut down and offsite power was lost to the entire facility. The emergency diesel generators started at all six units providing alternating current (ac) electrical power to critical systems at each unit. The facility response to the earthquake appears to have been normal. Approximately 40 minutes following the earthquake and shutdown of the operating units, however, the first large tsunami wave inundated the site, followed by additional waves. The tsunami caused extensive damage to site facilities and resulted in a complete loss of all ac electrical power at Units 1 through 5, a condition known as station blackout. In addition, all direct current electrical power was lost early in the event on Units 1 and 2 and after some period of time at the other units. Unit 6 retained the function of one air-cooled EDG; Despite their actions, the operators lost the ability to cool the fuel in the Unit 1 reactor after several hours, in the Unit 2 reactor after about 70 hours, and in the Unit 3 reactor after about 36 hours, resulting in damage to the nuclear fuel shortly after the loss of cooling capabilities.
Following the events at the Fukushima Dai-ichi nuclear power plant, the NRC established a senior-level agency task force referred to as the Near-Term Task Force (NTTF). The NTTF was tasked with conducting a systematic and methodical review of the NRC's regulations and processes, and determining if the agency should make additional improvements to these programs in light of the events at Fukushima Dai-ichi. As a result of this review, the NTTF developed a comprehensive set of recommendations, documented in SECY-11-0093, “Near-Term Report and Recommendations for Agency Actions Following the Events in Japan,” dated July 12, 2011 (ADAMS Accession No. ML11186A950). These recommendations were enhanced by the NRC staff following interactions with stakeholders. Documentation of the staff's efforts is contained in SECY-11-0124, “Recommended Actions to be Taken Without Delay from the Near-Term Task Force Report,” dated September 9, 2011 (ADAMS Accession No. ML11245A158) and SECY-11-0137, “Prioritization of Recommended Actions to be Taken in Response to Fukushima Lessons Learned,” dated October 3, 2011 (ADAMS Accession No. ML11272A111).
As directed by the Commission's Staff Requirement Memorandum (SRM) for SECY-11-0093 (ADAMS Accession No. ML112310021), the NRC staff reviewed the NTTF recommendations within the context of the NRC's existing regulatory framework and considered the various regulatory vehicles available to the NRC to implement the recommendations. SECY-11-0124 and SECY-11-0137 established the staff's prioritization of the recommendations based upon the potential for each recommendation to enhance safety.
As part of the SRM for SECY-11-0124, dated October 18, 2011, the
In addition to Commission direction, the Consolidated Appropriations Act, Public Law 112-074, was signed into law on December 23, 2011. Section 402 of the law directs the NRC to require licensees to reevaluate their design basis for external hazards.
In response to the aforementioned Commission and Congressional direction, the NRC issued a request for information to all power reactor licensees and holders of construction permits under 10 CFR part 50 on March 12, 2012. The March 12, 2012, letter includes a request that licensees reevaluate flooding hazards at nuclear power plant sites using updated flooding hazard information and present day regulatory guidance and methodologies. The letter also requests the comparison of the reevaluated hazard to the current design basis at the site for each potential flood mechanism. If the reevaluated flood hazard at a site is not bounded by the current design basis, licensees are requested to perform an Integrated Assessment. The Integrated Assessment will evaluate the total plant response to the flood hazard, considering multiple and diverse capabilities such as physical barriers, temporary protective measures, and operational procedures. The NRC staff will review the licensees' responses to this request for information and determine whether regulatory actions are necessary to provide additional protection against flooding.
By this action, the NRC is requesting public comments on draft JLD-ISG-2012-06. This draft JLD-ISG provides guidance and clarification to assist nuclear power reactors applicants and licensees with performing a flooding hazard reanalysis in response to enclosure 2 of the information request. The NRC staff will make a final determination regarding issuance of the JLD-ISG after it considers any public comments received in response to this request.
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