A licensee-identified violation was discovered on April 16, 2011, for Unit 2
TS 3.6.1.1 which states that
primary containment shall be
operable during Modes 1, 2 and 3.
TS 5.5.12 requires
primary containment overall leakage rate acceptance criteria be less than or equal to La (allowable leakage). Contrary to this requirement, on April 16, 2011, the licensee discovered during the Unit 2 refueling outage that
primary containment isolation valves
2T48-F309 and
2T48-F324 exceeded the as-found local leak rate requirements and resulted in an overall leak rate through
penetration 2T23X205 greater than La. The inspectors screened the significance of this violation using
IMC 0609 Appendix H. The Appendix H Phase 2 screening results required a more detailed analysis by an NRC senior risk analyst (
SRA). A regional
SRA reviewed the Appendix H Phase 2, and requested that NRC headquarters risk analysts perform an analysis to determine the impact of the finding given the potential for scrubbing of the fission products prior to release. The analysts used
NUREG-1765, and concluded that this was a Type B
LERF finding which involves leakage through the torus and not a drywell bypass. Section 3.2.1 of
NUREG-1765 states that for such cases, fission product scrubbing through the suppression pool can be credited and that this type of finding does not contribute significantly to
LERF. Therefore, the finding is GREEN. Corrective actions taken by the licensee included repairs to valves
2T48-F309 and
2T48-F324 and satisfactory post-maintenance testing to verify leakage was within limits prior to plant restart. This issue was captured in the licensees corrective action program as CR 2011105213 and was documented in
LER 05000366/2011-001.
