05000282/FIN-2010005-05
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Finding | |
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| Title | Potential for Common Mode Failure of Safety-Related Battery Chargers |
| Description | On September 21, 2010, the licensee initiated CAP 1250561 to document that a grid disturbance of sufficient voltage and time duration could cause all of the safety-related battery chargers to lock up until the chargers were manually turned off and restarted. While the CAP stated that this type of event was unlikely, the exact grid voltage and time required to cause the chargers to cease to operate was unknown. The CAP also stated that based upon recent battery discharge test results, operations personnel would have at least 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> and 20 minutes to restart the battery chargers. The licensees corrective action screening team reviewed CAP 1250561 on September 28, 2010. The screening team recommended that the Engineering Department review previous testing data and the apparent cause report for CAP 1238842 (discussed above) to determine if additional actions were needed. This review was required to be completed by October 29, 2010. On October 8, 2010, the NRC participated in a conference call to discuss issues related to the 12 battery charger (discussed above) and the licensees evaluation o
CAP 1250561. During this call, the licensee stated that CAP 1250561 was continuing to be evaluated. As a result, no additional actions had been taken. On October 15, 2010, the NRC formally asked the licensee to address the potential for a common mode failure of all of the safety-related battery chargers as part of a request for information to support the exigent TS change to TS SR 3.8.1.10c. The inspectors reviewed the licensees formal response to the NRC and the evaluation of the condition contained in CAP 1250561. The CAP evaluation contained information which indicated that each of the safety-related battery chargers may be susceptible to a lock up condition during specific design basis events including a loss of offsite power and a loss of coolant event with the grid voltage above operability limits. The licensee established a designated operator to perform manual actions to address the potential battery charger lock up condition to ensure there is no current safety concern. The licensee was continuing to evaluate this condition at the conclusion of the inspection period. As a result, this item was considered unresolved until the NRC reviews the results of the licensees completed evaluation. |
| Site: | Prairie Island  |
|---|---|
| Report | IR 05000282/2010005 Section 1R15 |
| Date counted | Dec 31, 2010 (2010Q4) |
| Type: | URI: Green |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.15 |
| Inspectors (proximate) | C Brown J Giessner K Stoedter L Kozak P Zurawski S Lynchc Brownd Mcneil J Dalzell J Giessner K Stoedter L Kozak P Zurawski R Lerch |
| INPO aspect | |
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Finding - Prairie Island - IR 05000282/2010005 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Prairie Island) @ 2010Q4
Self-Identified List (Prairie Island)
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