Overview of Post-Fire Operator Manual Actions
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In response to the Browns Ferry fire, the U.S. Nuclear Regulatory Commission (NRC) created fire protection regulations and guidelines to ensure that nuclear power plants (NPPs) can be safely shut down in the event of a fire. An important requirement of these rules was to require the protection of redundant equipment and cables required to place the plant in a state of safe shutdown. Where separation of redundant equipment could not occur, licensees were permitted (under certain conditions) to use post-fire operator manual actions (OMAs) to safely shut down the reactor.
In 2000, NRC inspections identified that some licensees compensated for the lack of approved separation by relying on OMAs under conditions not permitted by the NRC. The NRC issued Regulatory Issue Summary 2006-10, "Regulatory Expectations with Appendix R Paragraph III.G.2 Operator Manual Actions," in June 2006 to clarify expectations.
With the intention of giving licensees an opportunity to find and fix unapproved post-fire OMAs, the NRC issued enforcement discretion for licensee-identified unapproved post-fire OMAs. This discretion provided a period of time for licensees to self-identify unapproved post-fire OMAs, and also provided time for licensees to bring those unapproved post-fire OMAs into compliance without the NRC taking enforcement action. The NRC expects some of the unapproved post-fire OMAs to be resolved through reanalysis, procedure changes, modifications, or requests for NRC approval. Facilities transitioning to National Fire Protection Association (NFPA) Standard 805, "Performance-Based Standard for Fire Protection for Light-Water Reactor Electric Generating Plants" (NFPA 805), will address OMAs as part of their transition.
The NRC also issued NUREG-1852, "Demonstrating the Feasibility and Reliability of Operator Manual Actions in Response to Fire," to assist NRC staff in reviewing post-fire OMA applications under conditions permitted by the NRC. NUREG-1852 is publicly available so that licensees are able to examine the factors that the NRC staff will review.
According to the Enforcement Guidance Memorandum 07-004, “Enforcement Guidance Memorandum for Post-Fire Manual Actions Used as Compensatory Measures for Fire-Induced Circuit Failures,” licensees should have completed their modifications or submitted exemptions or license amendments to NRC for approval by March 6, 2009. On March 6, 2009, unapproved operator manual actions were considered non-compliances, unless the NRC was, at the time, reviewing an exemption or license amendment for that licensee.
Of the 104 reactor units in operation in the United States, about half are in the process of dispositioning issues relating to unapproved operator manual actions during their transition to the risk-informed alternative rule (NFPA 805). Of the remaining units not transitioning to NFPA 805, 11 units have submitted requests for licensing actions. The NRC staff performed Temporary Instruction 2515-0181 at Vogtle and Millstone. The results of these inspections are documented in Inspection Reports for Millstone Unit 2 and for Vogtle, Units 1 and 2. The inspections concluded that the NRC had stabilized the regulatory framework in a manner that provided licensees with sufficient information to properly disposition the use of post fire OMAs at their stations.