Following the flooding of the 1A
DG room that occurred on May 22, 2006, the licensees
PRA staff worked with the Region II
SRAs to determine the risk significance that resulted from this event. The flooding event was documented as Unresolved Item (
URI)
05000413/2006009-03 in the
AIT report issued on June 29, 2006. The
URI was opened to review the root and contributing causes, the extent of condition, and the corrective actions associated with the failure to seal conduits into manholes and the 1A
DG room as required by design and construction documents. The issue was dispositioned as a Green
NCV in Inspection Report 05000413,414/2006-04. It was determined to be of very low safety significance (Green) based on the results of the
Significance Determination Process Phase 1 screening, the Phase 2 evaluation using the Catawba Plant Notebook, and the Phase 3 evaluation. The team identified Unresolved Item 05000413,414/2006010-01 to re-quantify the station risk resulting from the cumulative effect of the missing conduit seals, degraded conduit seals and water ingress paths that have been identified as being present over the time period of April 6, 2005 and May 22, 2006.
