The team identified a Green non-cited violation of Title 10 Code of Federal Regulations 50, Appendix B, Criterion III, Design Control. Specifically, Exelon did not correctly verify the capability of alternating current motor-operated valves (
MOVs) at a degraded voltage corresponding to the lowest voltage allowed by plant Technical Specification setpoints for the degraded grid voltage relays. Exelon initiated issue report 1642720 to evaluate the adequacy of their design and determined that 9 out of the 130 alternating current
MOV program valves required further evaluation. The licensee performed an operability evaluation of the affected
MOVs, assuming the appropriate voltage, and determined that, although significant design margin was lost, all
MOVs remained
operable. The finding was more than minor because the finding was associated with the
Mitigating Systems Cornerstone attribute of design control and adversely affected the cornerstone objective of ensuring the capability of the 480 volt alternating current (
AC)
MOVs to respond to
initiating events to prevent undesirable consequences. The team determined the finding was of very low safety significance because it was a design deficiency confirmed not to result in a loss of operability. The team assigned a cross-cutting aspect associated with this finding, because the deficient
AC MOV operability evaluations were completed in November 2011 and were reflective of current performance. The finding had a cross-cutting aspect in the area of Problem Identification and Resolution, Evaluation (
PI.2), because Exelon did not thoroughly evaluate the issue addressed in a previous
NCV contained in NRC Inspection Report 2010004, during 2011, for
PBAPS such that, the resolution addressed causes and extent-of-condition commensurate with the safety significance. Specifically, the affected
MOVs were not evaluated at the required voltage in operability evaluations performed following receipt of a non-cited violation.
