05000395/FIN-2017003-03
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Finding | |
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| Title | Failure to Adequately Assess the Risk for an Activity with Consequent Loss of Core Cooling |
| Description | The inspectors identified a Green, NCV of 10 CFR 50.65(a)( 4), Requirements for Monitoring the Effectiveness of Maintenance at Nuclear Power Plants, involving the licensees failure to perform an adequate risk assessment for an activity involving restoration of the B train emergency bus to the normal supply and a subsequent loss of the B train residual heat removal (RHR) pump and a consequent loss of core cooling. The issue was entered into the licensees CAP as condition report, CR- 17- 03696 The inspectors reviewed IMC 0612, Appendix B, Issue Screening, dated September 7, 2012, and determined that the PD was more than minor and therefore a finding because it was associated with the Mitigating Systems Cornerstone, and adversely affected the cornerstone objective to ensure in part the availability of systems that respond to initiating events to prevent undesirable consequences. Specifically, the failure to perform an adequate risk assessment resulted in performance of an activity causing a vulnerability to operability of the running RHR pump and a consequent loss of core cooling. The finding was screened for risk significance using NRC IMC 0609.04 and routed to NRC IMC 0609, Appendix G. A detailed shutdown risk assessment was performed by a regional senior risk analyst using NRC IMC 0609 Appendix G and Attachments 1 and 2. The major analysis assumptions included: treatment of the PD as a loss of RHR with an initiating event likelihood of 1.0 using NRC IMC 0609 Appendix G, Attachment 2, worksheet 9 (loss of RHR in plant operating state 2); and recovery credit was applied for closing the alternate feeder breaker. The dominant sequence was a loss of RHR, failure to recover decay heat removal prior to reactor coolant system (RCS) boiling, failure to initiate RCS injection before core damage and failure to restore power to the B train safety bus. The RCS conditions of time to boil and time to core uncovery and availability of mitigating equipment limited the risk. The detailed risk evaluation determined that the PD represented an increase in core damage frequency <1.0E -6 a GREEN finding of very low safety significance. The inspectors reviewed IMC 0310, Aspects Within Cross Cutting Areas, dated December 4, 2014, and determined that this finding had a cross -cutting aspect in the area of Work Management (H.5), because the licensee did not perform an adequate risk assessment in accordance with their procedure. |
| Site: | Summer  |
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| Report | IR 05000395/2017003 Section 1R13 |
| Date counted | Sep 30, 2017 (2017Q3) |
| Type: | NCV: Green |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.13 |
| Inspectors (proximate) | J Reece N Hilton P Heher D Lanyi A Masters |
| Violation of: | 10 CFR 50.65 |
| CCA | H.5, Work Management |
| INPO aspect | WP.1 |
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Finding - Summer - IR 05000395/2017003 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Summer) @ 2017Q3
Self-Identified List (Summer)
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