Inspectors identified an unresolved item (
URI) associated with how the site calculated fire frequencies of electrical cabinets in the fire
PRA. The site retained floor-mounted electrical cabinets characterized as well-sealed and robustly-secured as ignition sources in the fire
PRA. The guidance of
NUREG-6850, which the site is committed to, instructs that electrical cabinets housing voltages less than 400V, and that are characterized as well-sealed and robustly secured not be counted as ignition sources. This is because the fire
PRA should only consider fires that can propagate to other combustibles and targets, and by including ignition sources that cannot propagate to other combustibles and targets, the frequency of fires in other electrical cabinets that can actually propagate could be erroneously lowered. Inspectors noted that retaining floor-mounted cabinets characterized as well-sealed and robustly-secured appeared to not be in alignment with the sites
NFPA 805 submittal, and associated
SE, which each contain information specific to the question about how well-sealed robustly secured cabinets were treated in the fire
PRA. The
SE states, Regarding the counting of well-sealed, robustly-secured electrical cabinets having circuits less than 440V, the licensee stated in its response to
PRA RAI 03.b.01 that it updated the FPRA to remove cabinets meeting this definition. The site has asserted that this statement in the
SE is incorrect, and does not align with what the site submitted on the docket as a part of their
NFPA 805 submittal. Planned Closure Action(s): This issue is being characterized as a
URI, pending a decision from
NRR as to the interpretation of the sites submittal regarding treatment of floor-mounted well-sealed and robustly-secured cabinets, and the accuracy of the associated
SER