05000271/FIN-2014005-03
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Finding | |
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| Title | Failure to Follow Procedure Results in Inoperable Emergency Diesel Generator |
| Description | The inspectors identified a self-revealing Green NCV of Title 10 of the Code of Federal Regulations (10 CFR) 50, Appendix B, Criterion V, Instructions, Procedures, and Drawings, because Entergy did not properly implement the prescribed maintenance instructions during the installation of the copper o-ring to the Kiene valve adapter of cylinder number six of the A emergency diesel generator (EDG) on June 25, 1992. Entergys corrective actions included initiating condition report CR-VTY-2014-3503, performing a root cause evaluation, and removing and reinstalling the number six cylinder adapters using new copper o-ring gaskets with the correct applied torque. Entergy restored the A EDG to operable status on October 2, 2014. Entergy also performed cylinder air testing of all cylinders on both A and B EDGs to ensure no other leaks existed. This finding is more than minor because it is associated with the equipment performance attribute of the Mitigating Systems cornerstone and affected the cornerstone objective of ensuring the availability of systems that respond to initiating events to prevent undesirable consequences. Specifically, the failure to properly install the Kiene valve adapter on June 25, 1992, resulted in the A EDG failing to start on September 29, 2014, during a quarterly surveillance. Using IMC 0609, Significance Determination Process, Appendix A, Exhibit 2, Mitigating Systems Screening Questions, the inspectors determined that this finding required a detailed risk evaluation (DRE) because the failure of the A EDG to start on September 29, 2014, represented an actual loss of function of a single train of emergency alternating current power for greater than the technical specification allowed outage time. The Region I senior reactor analyst (SRA) used the Systems Analysis Programs for Hands-On Evaluation (SAPHIRE) Revision 8.1.0 and the Standardized Plant Analysis Risk (SPAR) Model for VY, Version 8.19, to conduct the internal events DRE and VYs Individual Plant Examination (IPE) for Severe Accident Vulnerabilities and the Individual Plant Evaluation External Events (IPEEE) to assess the external events risk contribution for this performance deficiency. The SRA made the following assumptions and SPAR model changes to best represent the condition of the A EDG: The exposure time was estimated using T/2 because the actual date and time the EDG became inoperable is indeterminate based upon the uncertainty of gasket coolant leak rate into the cylinder. The time between the last successful operation of the EDG and the observed failure was 36 days. Therefore, T/2 most accurately approximates the postulated exposure time, T/2 = 36/2= 18 days. Adding the unavailability time due to corrective maintenance, the total exposure time for this finding is 21 days. Basic event EPS-DGN-FS-DGA, Diesel Generator A Fails to Start, was set to True, consistent with the Risk Assessment Standardization Project guidance, to reflect the potential for a common cause failure mechanism of both the A and B EDGs. Based upon the observed success of plant staff to recover the EDG following the failure to start event on September 29, 2014, and the available procedure guidance and training, the SRA assumed recovery of the A EDG could reasonably be achieved under accident conditions. Accordingly, the EDG recovery basis event, EPS-XHE-XL-NR01H, nominal probability (8.71E-1) was revised to 0.1 (1 in 10 chance of not successfully recovering the EDG). Based upon the above stated assumptions, the increase in internal risk core damage frequency (delta CDF) associated with this performance deficiency is in the mid E-7 range, or very low safety significance (Green). The SRA examined the IPEEE and associated fire safe shutdown analysis/procedures to determine the external event risk contribution due to this finding. The SRA determined that the A EDG is credited for safe shutdown in the event a fire compromises the West Switchgear Room. Assuming worst case fire conditions, without suppression, the external fire contribution per IPEEE, Table 4.10.1 would be approximately 3.4E-7 (5.9E-6 X 21/365). The SRA also determined that the unavailability of the A EDG has no appreciable impact on seismic, flooding, and high winds associated mitigation capability. Combining the internal and external risk contributions yields a total delta CDF of high E-7 (Green). Based upon a review of the dominant cutsets (loss of offsite power initiating events with subsequent failures of high pressure injection and depressurization), the unavailability of the A EDG may result in an increased risk associated with a Large Early Release Frequency (LERF). The SRA used a 0.1 LERF factor to account for the probability that operators would procedurally take action to mitigate the consequences of a potential containment breach due to these postulated high pressure accident sequences. Consequently, the delta LERF for this finding is high E-8 (Green). The inspectors determined that the finding did not have a cross-cutting aspect because the performance deficiency did not occur within the last three years and would not likely occur today under similar circumstances. |
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
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| Report | IR 05000271/2014005 Section 4OA3 |
| Date counted | Dec 31, 2014 (2014Q4) |
| Type: | NCV: Green |
| cornerstone | Mitigating Systems |
| Identified by: | Self-revealing |
| Inspection Procedure: | IP 71153 |
| Inspectors (proximate) | B Scrabeck J Brand J Furia N Day R Mckinley S Rich S Rutenkroger |
| Violation of: | 10 CFR 50 Appendix B Criterion V Technical Specification Technical Specification - Procedures |
| INPO aspect | |
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Finding - Vermont Yankee - IR 05000271/2014005 | |||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Vermont Yankee) @ 2014Q4
Self-Identified List (Vermont Yankee)
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