05000220/FIN-2014007-03
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Finding | |
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| Title | Deficient Design Control of Protective Device Sizing for Unit 1 Core Spray Injection Motor-Operated Valves |
| Description | The team identified a Green NCV of 10 CFR Part 50, Appendix B, Criterion III, Design Control, because Exelon did not verify the design adequacy of Nine Mile Point Unit 1 electrical power to safety-related MOVs to support their design function during design basis events. Specifically, Exelon did not verify that the thermal/magnetic breaker (TMB) protection on core spray (CS) loop injection MOV circuits 1V-40-01, 1V-40-09, 1V-40-10, and 1V-40-11 were properly sized to support the design function of repetitive MOV operation (throttling) in response to a design basis loss-of-coolant accident (LOCA). Routine throttling operation of the CS injection valves could potentially cause a TMB trip and loss of power to the MOV leading to the valve failing in an indeterminate position and not being capable of performing its design function to control reactor pressure vessel (RPV) level. Immediate corrective action included guidance to control room operators to close three of the MOVs when required to maintain RPV level and only use MOV 1V-40-09 which had a TMB tripping design of 17 seconds Exelon entered this issue into its corrective action program as issue report 2393386. The finding was more than minor because it is associated with the design control attribute of the Mitigating Systems Cornerstone and adversely affected the cornerstone objective of ensuring the availability, reliability, and capability of systems that respond to initiating events to prevent undesirable consequences. The team determined that the finding was of very low safety significance (Green) because it was a design deficiency confirmed not to result in loss of operability or functionality. The team determined that the central cause of this finding was not reflective of current performance or current plant modification processes. Therefore no cross-cutting aspect was assigned. |
| Site: | Nine Mile Point  |
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| Report | IR 05000220/2014007 Section 1R21 |
| Date counted | Dec 31, 2014 (2014Q4) |
| Type: | NCV: Green |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.21 |
| Inspectors (proximate) | C Edwards D Kern F Arner J Ayala J Brand J Nicely N Floyd W Sherbin |
| Violation of: | 10 CFR 50 Appendix B Criterion III, Design Control |
| INPO aspect | |
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Finding - Nine Mile Point - IR 05000220/2014007 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Nine Mile Point) @ 2014Q4
Self-Identified List (Nine Mile Point)
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