A NRC-identified
NCV of
10 CFR 50, Appendix B, Criterion III, was identified in that the installed
emergency diesel generator (
EDG) fuel oil storage tank vents did not meet the design basis of bending without crimping. The licensee completed corrective actions to install
tornado missile protection to prevent crimping of the vents. The licensees failure to correctly translate the licensing basis into specifications for the vent piping was a performance deficiency. The performance deficiency was determined to be more than minor because it was associated with the
Mitigating Systems cornerstone design control attribute and adversely impacted the cornerstone objective in that the vent piping could bend and completely crimp on impact of a tornado generated soft missile. A Phase 3 analysis was required because the finding involved the loss or degradation of equipment or function specifically designed to mitigate a severe weather initiating event. A qualitative assessment was performed to determine the risk significance because factors required for determining the risk were not easily quantifiable. Based on the qualitative assessment, the finding was determined to be of very low safety significance (Green). A cross-cutting aspect for this issue was not identified as it was determined to be a legacy design issue and not indicative of current licensee performance
