05000266/LER-2015-004
| Point Beach Nuclear Plant | |
| Event date: | 06-04-2015 |
|---|---|
| Report date: | 08-03-2015 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability |
| 2662015004R00 - NRC Website | |
Description of the Event:
Eslimaled burden per response to comply wilh this mandatory colleclion request: 80 hours9.259259e-4 days <br />0.0222 hours <br />1.322751e-4 weeks <br />3.044e-5 months <br />.
Reported lessons learned are incorporated into the licensing process and fed back to industry.
Send comments regarding burden eslimate to the FOIA, Privacy and Information Colleclions Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001,or by internet e-mail to lnfocollects.Resource@nrc.gov, and to the Desk Officer, Office of I nfonmalion and Regulatory Affairs, NEOB-1 0202, (3150-01 04), Office of Management and Budget, Washington, DC 20503. If a means used to impose an informalion collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the informalion colleclion.
6. LER NUMER
On June 4, 2015 with both units at full power, it was identified that removal of the W-185A(B), G-03(04) EDG Switchgear Room Exhaust Fan from service may result in the inability to maintain switchgear room temperatures below that required to maintain equipment operable.
This 60-day licensee event report is being submitted in accordance with the requirements of 10 CFR 50. 73(a)(2)(i)(B), and 10 CFR 50.73(a)(2)(vii).
Cause of the Event:
The cause of the event prohibited by Technical Specification is less than adequate understanding of the design support function of the EDG Switchgear Room Exhaust Fan resulting in less than adequate administrative controls for its removal from service.
Analysis of the Event:
The 4160V system provides the primary means to interconnect the onsite and offsite power sources and distribute the power to the 480V AC system. Buses A-05 and A-06 supply the safety-related loads (4160V and 4160V/480V transformers). Buses A-05 and A-06 each serve one of the two 4160/480V station service transformers for the unit's 480V safeguards equipment. Buses A-05 and A-06 are supplied emergency power by four EDGs. Each EDG has sufficient power capacity to safely shut down the unaffected unit at the same time adequate power is provided to engineered safety features of the affected unit.
Subsequent engineering evaluation has determined that room temperature could have exceeded the environmental conditions at which the components would be reasonably expected to function for their respective mission times with the G-03(04) EDG Switchgear Room Exhaust Fan(s) out of service. This condition resulted in five instances of a condition prohibited by Technical Specifications, Technical Specification 3.8.9. Distribution Systems- Operating, where the A-06 bus was inoperable on April 29, 2013, May 29, 2013, October 28, 2013, May 5, 2014 and April 27, 2015. Additionally, the declaration of the associated A-06 bus required feature(s) inoperable as a result of Technical Specification 3.8.9 required action A.1 would have resulted in exceeding the respective A-06 bus safety related load allowed out of service times.
No opposite train plant systems were affected by this condition.
Corrective Actions:
The identified condition of the fan out of service has been corrected by restoration of the fan. The less than adequate administrative controls and understanding of W-185A(B), G-03(04) EDG Switchgear Room Exhaust Fan is being addressed in the corrective action program. It is not anticipated that a supplemental LER will be required.
Safety Significance:
The fans were taken out of service for short durations of time. For example, during the last year, one fan was out of service for approximately 13 hours1.50463e-4 days <br />0.00361 hours <br />2.149471e-5 weeks <br />4.9465e-6 months <br /> and the other fan was taken out of service at a different time for approximately 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />. During these durations, there was a heightened awareness of the condition of the fan and the supported area environment. Additionally, the other three safety busses were operable at the time. Worst case engineering evaluations demonstrate that the switchgear could perform its specified safety function without its room exhaust fan running for nearly three days. There would be sufficient time to detect a malfunction and correct it prior to the buses not being able to perform its specified safety function. Additionally, recovery of offsite power any time during this period would allow non- safety related room ventilation to be restored to limit the temperature rise. Operations also had the capability of managing EDG loading and restoring the non-safety related room ventilation if offsite power was not available. The redundant EDG Train B was operable during this time. The affected A06 bus could have been transferred to this redundant EDG Train B.
This would be at a point in the post-accident transient that would not be as critical for decay heat removal. Therefore, based on the duration of inoperability and the design redundancy there is reasonable assurance that this condition is of very low safety significance.
Similar Events:
Reported lessons learned are incorporated into the licensing process and fed back to industry.
Send comments regarding burden estimate to the FOIA, Privacy and lnfonmation Collections Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or byintemet e-mail to lnfocollects.Resource@nrc.gov, and to the Desk Officer, Office of I nfonmation and Regulatory Affairs, NEOB-1 0202, (3150-01 04), Office of Management and Budget, Washington, DC 20503. If a means used to impose an information collection does not display a currently valid OMS control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
6. LERNUMER
There have been similar events where operation or conditions prohibited by technical specifications were reported.
condition or event but had a different cause. There have been similar events or conditions with the causes of less than adequate administrative controls and less than adequate understanding of plant design functions. One of the corrective actions for those conditions was to provide training to all personnel with respect to improving questioning attitude, which directly led to identification of this condition.
Component Failure Data:
None