05000277/FIN-2011003-01
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Finding | |
|---|---|
| Title | Licensee-Identified Violation |
| Description | In Mode 1, with the HPCI system inoperable for more than 14 days, TS Limiting Condition for Operation 3.5.1 requires the unit to be in Mode 3 within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. Contrary to the above, the Unit 2 HPCI system was determined to be inoperable from approximately January 20 to March 18, 2011, with the reactor in Mode 1, due to a leaking relief valve (RV-2-238-066) on the HPCI cooling water header. With HPCI aligned to the normal, non-safety-related, Condensate Storage Tank (CST) suction source, no voiding would occur in the HPCI discharge piping due to the higher elevation of the CST. However, during a subset of design basis events where HPCI suction would be transferred to the suppression pool, its alternate and safety-related suction source, and the HPCI pump secured, voiding could develop in the discharge piping. The licensee concluded that if HPCI was then restarted, a water hammer condition could potentially result and render Unit 2 HPCI unable to perform its deterministic design function. The voiding in the HPCI discharge piping had been discovered by PBAPS personnel during a ST while transferring Unit 2 HPCI suction from the CST to the suppression pool to support an l&C surveillance. The relief valve was replaced, and subsequent to testing, HPCI was declared operable on March 18, 2011. The inspectors reviewed this condition using IMC 0609, Attachment 4, and in consultation with a Region I Senior Reactor Analyst (SRA), concluded the Unit 2 HPCI system would likely have been able to perform its Significance Determination Process safety function, given the numerous postulated equipment failures and specific system configurations that would have to occur to cause a system failure. Therefore, and as such this issue screened to very low safety significance. A Region I SRA also confirmed the very low significance (mid E-9 increase in core damage frequency) with a conservative analysis. This analysis assumed the HPCI system would have failed if the operators failed to refill the CST, and HPCI switched over to the torus suction, for the 58 day exposure period. The licensee documented the event in their CAP as lRs 1 1 88457 and 1 188987. The LER associated with this event was documented in Section 4OA3. |
| Site: | Peach Bottom  |
|---|---|
| Report | IR 05000277/2011003 Section 4OA7 |
| Date counted | Jun 30, 2011 (2011Q2) |
| Type: | NCV: Green |
| cornerstone | Mitigating Systems |
| Identified by: | Licensee-identified |
| Inspection Procedure: | |
| Inspectors (proximate) | R Nimitz F Bower A Ziedonis J Nicholson P Krohn N Lafferty D Molteni B Dionne |
| INPO aspect | |
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Finding - Peach Bottom - IR 05000277/2011003 | |||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Peach Bottom) @ 2011Q2
Self-Identified List (Peach Bottom)
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