05000282/FIN-2012004-02
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Finding | |
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| Title | Unit 1 Required Shutdown Due to D1 and D2 Emergency Diesel Generator Exhaust Fires |
| Description | The inspectors evaluated outage activities for an unscheduled Unit 1 shutdown to affect repairs to EDGs D1 and D2. The outage began on August 14, 2012, and continued through August 20, 2012. The inspectors reviewed activities to ensure that the licensee considered risk in developing, planning, and implementing the outage schedule. The inspectors observed or reviewed the reactor shutdown, outage equipment configuration and risk management, electrical lineups, personnel fatigue management, startup, and identification and resolution of problems associated with the outage. This event follow-up review constituted one operational sample as defined in IP 71153-05. On August 13, 2012 at 9:39 a.m., operations personnel performed a scheduled monthly surveillance run of the D1 EDG. During this surveillance, the operators identified a small candle sized flame at the exhaust manifold. The D1 EDG was immediately shutdown. The shift supervisor entered TS 3.8.1 due to the D1 EDG being inoperable. Subsequent troubleshooting performed by the maintenance determined that the flame appeared to be caused by a gasket leak at the exhaust extension joint between the ring collector and the turbocharger. As part of the ongoing review of this issue, TS 3.8.1 required the license to determine whether the remaining operable EDG was potentially inoperable due to a common cause failure. On August 14, 2012 at 2:30 a.m., the licensee ran the D2 EDG to verify whether a common cause failure existed. At 3:12 a.m., the Shift Manager reported a small candle sized fire on the exhaust manifold for the D2 EDG. The D2 EDG was subsequently declared inoperable and was shutdown. With both Unit 1 EDGs inoperable, TSs required that one EDG be returned to an operable status within 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />. If this was unable to be completed, the TSs directed that the Unit 1 reactor be shut down within six hours. The inspectors monitored the licensees EDG restoration efforts. However, the licensee was unable to restore either the D1 or the D2 EDG to an operable status within two hours. As a result, operations personnel commenced shutting down the Unit 1 reactor at 4:30 a.m. on August 14, 2012. The licensee documented the details regarding the D1 EDG fire in CAP 1348044. The inspectors monitored the licensees corrective actions which included replacing the exhaust extension joint gaskets and removing/replacing the adjacent insulation. The licensee documented the D2 EDG exhaust fire in CAP 1348106. Corrective actions for this issue included torquing the exhaust extension joint flange bolts to reduce the amount of leakage and removing/replacing the adjacent insulation. Lastly, the licensee documented the D1 and D2 EDG common cause failure and the associated Unit 1 shutdown in CAP 1348310. Since both EDGs experienced similar fires, the inspectors were concerned that the condition of the exhaust extension joints/gaskets could have constituted a maintenance related issue. However, the licensees evaluation regarding the cause of the fires had not been completed at the conclusion of the inspection. As a result, the inspectors were unable to conclude whether a performance deficiency existed. This issue was determined to be unresolved pending a review of the licensees causal evaluations and a determination regarding whether a performance deficiency existed |
| Site: | Prairie Island  |
|---|---|
| Report | IR 05000282/2012004 Section 4OA3 |
| Date counted | Sep 30, 2012 (2012Q3) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71153 |
| Inspectors (proximate) | A Dunlop C Moore D Passehl J Bozga K Riemer K Stoedter M Holmberg M Learn M Phalen P Zurawski T Bilikb Kemkerk Riemer K Stoedter P Zurawski T Bilik A Shaikh |
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Finding - Prairie Island - IR 05000282/2012004 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Prairie Island) @ 2012Q3
Self-Identified List (Prairie Island)
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