05000395/FIN-2011006-01
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Finding | |
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Title | |
Description | The team identified a non-cited violation (NCV) of 10 CFR 50.63, Loss of all Alternating Current Power, for failure to ensure Regulatory Guide 1.155, Station Blackout, (SBO) requirements were implemented. Specifically, the licensee failed to develop procedures to provide starting air to the emergency diesel generators (EDG) to restore emergency AC power during the recovery from a SBO. The licensee entered this issue into their corrective action program as CR-11-00746 and CR-11-00738, and initiated compensatory measures which included the development of procedure EMP-100.011, Restoring Power to Emergency Diesel Generator Air Start Compressor, Rev. 0. The licensees failure to establish procedures to provide starting air to the EDGs to restore emergency ac power in the event of a SBO was a performance deficiency. The finding was more than minor because it was associated with the Design Control attribute of the Mitigating System Cornerstone and affected the cornerstone objective to ensure the availability, reliability, and capability of systems that respond to initiating events to prevent undesirable consequences. Specifically, the failure to develop procedures to provide starting air to the EDGs resulted in a lack of reasonable assurance that the licensee could provide adequate starting air to restore emergency ac power in the event of a SBO. The conditions necessary for the condition would be a loss of offsite power (LOOP), two failed start attempts of both EDGs, and failure to recover an EDG or offsite power within the four hour SBO coping period. Using Manual Chapter Attachment 0609.04, Phase 1 Initial Screening and Characterization of Findings, the inspectors determined the finding would represent a loss of the core heat removal safety function within the mitigating systems cornerstone conditional upon establishing these SBO circumstances. The pre-solved significance determination process (SDP) Phase 2 worksheet for VC Summer did not have an appropriate surrogate to evaluate these specific conditions, therefore an SDP phase 3 risk evaluation was performed by a regional SRA. The SDP phase 3 risk evaluation was performed using failure data from the NRC VC Summer SPAR model using a one year exposure period. The risk was mitigated by the number and likelihood of the conditions required to establish the circumstances necessary for the performance deficiency. The result of the SDP phase 3 risk analysis was a risk increase in core damage frequency of < 1E- 6/year. The performance deficiency is characterized as GREEN, a finding of very low safety significance. A cross-cutting aspect was not identified because the finding does not represent current performance. |
Site: | Summer ![]() |
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Report | IR 05000395/2011006 Section 1R21 |
Date counted | Jun 30, 2011 (2011Q2) |
Type: | NCV: Green |
cornerstone | Mitigating Systems |
Identified by: | NRC identified |
Inspection Procedure: | IP 71111.21 |
Inspectors (proximate) | D Jones D Mas-Penaranda M Yeminy S Sandal B Desai J Eargle |
INPO aspect | |
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Finding - Summer - IR 05000395/2011006 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Summer) @ 2011Q2
Self-Identified List (Summer)
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