05000352/FIN-2016001-02
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Finding | |
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| Title | Seismic Qualification of Safety Related Battery not Maintained |
| Description | The inspectors identified a Green NCV of 10 CFR 50, Appendix B, Criterion III, Design Control, and technical specification 3.8.2, D.C. Sources, because Exelon failed to ensure the design control measures for field changes impacting the seismic support of station batteries were commensurate with those applied to the original design requirements. Specifically, during cell replacement of the Class 1E 1A1 125/250 volts direct current (Vdc) safeguards battery, removal of adjacent cells and restraint barriers left the battery in a state in which the seismic qualification was not maintained. Exelon initiated IR 2624349, stopped the battery cell replacement work, and performed a technical evaluation to determine the requirements to maintain the seismic qualification during the cell replacement process. This finding is more than minor because it adversely affected the protection against external factors (seismic) attribute of the mitigating systems cornerstone to ensure the availability and reliability of systems that respond to initiating events to prevent undesirable consequences (i.e. core damage). Specifically, during cell replacement of the Class 1E 1A1 125/250 Vdc safeguards battery, removal of adjacent cells and restraint barriers left the battery in a state in which the seismic qualification was not maintained. In accordance with IMC 0609, Appendix A, Exhibit 4, External Event Screening Questions, the inspectors determined that a detailed risk evaluation was required because the loss of this equipment by itself during the seismic event it was intended to mitigate would degrade one or more trains of a system that supports a risk significant function. The Region I Senior Reactor Analyst referenced the Limerick External Events Notebook to assess the potential increase in plant risk associated with this condition. As referenced in the Notebook, the initiating event frequency for the safe shutdown earthquake (SSE) is approximately 5E-4/year. Based upon the inspectors review of operations logs, the five battery replacement activities that occurred over the past 12 months ranged in duration from between one to six days. Assuming the seismic qualification was compromised the entire duration of these maintenance activities, the consequential increase in risk for any single event would be in the low to mid E-9 delta core damage frequency range. The dominant core damage sequences involve an SSE that results in a loss of offsite power and the subsequent failure to remove heat from containment (via the multi-train residual heat removal system and associated service water cooling trains). This estimated small increase in core damage frequency represents a condition of very low safety significance (Green). The inspectors determined that this finding has a cross-cutting aspect in the area of Human Performance, Avoid Complacency, because Exelon did not recognize and plan for the possibility of latent issues associated with the battery replacement process. [H.12] |
| Site: | Limerick  |
|---|---|
| Report | IR 05000352/2016001 Section 1R18 |
| Date counted | Mar 31, 2016 (2016Q1) |
| Type: | NCV: Green |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.18 |
| Inspectors (proximate) | D Schroeder J Furia J Richmond M Fannon R Nimitz S Barber S Rutenkroger J Schussler |
| Violation of: | 10 CFR 50 Appendix B Criterion III, Design Control Technical Specification |
| CCA | H.12, Avoid Complacency |
| INPO aspect | QA.4 |
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Finding - Limerick - IR 05000352/2016001 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Limerick) @ 2016Q1
Self-Identified List (Limerick)
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