05000458/FIN-2012009-04
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Finding | |
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| Title | Corrective Action Program Implementation for Prior Lockout Relay Failure in February 2011 |
| Description | The team identified an unresolved item associated with the implementation of corrective actions developed as a result of the failure of a General Electric Type HEA61 lockout relay in 13.8 kV circuit breaker NPS-SWG1A ACB05 in February 2011. This failure resulted in a fire in bus ducting connecting 480 V transformer NJS-X2C to Cooling Tower 1C Load Center NJS-SWG2C. On February 12, 2011, an electrical fault resulted in an overcurrent condition through 13.8 kV circuit breaker NPS-SWG1A ACB05 and a subsequent bus duct fire. The licensee entered this issue into their corrective action program as Condition Report CR-RBS-2011-02209. The licensee performed an apparent cause evaluation for this issue and determined that the 86 lockout relay associated with the circuit breaker had failed to operate due to mechanical binding in the latching mechanism, preventing the circuit breaker from tripping on overcurrent. The evaluation determined that the binding was the result of aging and a lack of relay maintenance and testing. The relay was sent to the vendor for additional forensics analysis and guidance on maintenance requirements to prevent recurrence of the failure. The vendor response identified guidance in General Electric document GEH-2058, General Electric Instructions Auxiliary Relays Type HEA61, EA62, which recommended that this type of relay be periodically tested, including electrically tripping the relay to ensure it works and verifying that all attached circuits are complete so that the affected circuit breaker can be tripped. The apparent cause evaluation documented industry operating experience reviews, including General Electric Service Advisory Letter 165 published in 1981 concerning HEA relay failures due to mechanical binding. The apparent cause evaluation concluded that the overall summary of external operating experience was that mechanical binding was a common cause of 86 lockout relay failures. The apparent cause evaluation documented an extent-of-condition review for the 86 lockout relay failure for relays classified as non-critical relays and run-to-failure relays; however, these relays are also installed in circuit breakers for safety-related Division III equipment. As corrective action for the February 2011 lockout relay failure, the licensee had updated Preventive Maintenance Template E418, Maintenance Template for HEA Relays, to add actions to include functional testing of 86 lockout relays. The team reviewed an updated copy of this maintenance template, but could find no instances in which it had been implemented since being revised. On May 24, 2012, an electrical fault occurred, resulting in an overcurrent condition through 13.8 kV circuit breaker NPS-SWG1B ACB028 for main feedwater pump B. Circuit Breaker ACB028 did not open to isolate the fault as expected, resulting in the trip of upstream supply breaker NPS-SWG1B ACB027. This resulted in the loss of bus NPS-SWG1B and a plant scram. The licensees preliminary investigation identified that circuit breaker ACB028 failed to trip due to the failure of the associated 86 lockout relay. The team concluded the failure mode associated with the May 2012 failure appeared to be the same as the failure in February 2011. Following the May 2012 event, the licensees extent of condition review and testing identified nine additional failures of the older-style General Electric HEA61 relays installed in non-safety related equipment. The licensees investigation also determined that similar 86 lockout relays were installed in safety-related Division III equipment, but no failures were identified for these relays. The team determined that additional inspection is required to assess the effectiveness of the licensees corrective actions from the February 2011 event |
| Site: | River Bend  |
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| Report | IR 05000458/2012009 Section 4OA5 |
| Date counted | Sep 30, 2012 (2012Q3) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 93800 |
| Inspectors (proximate) | S Graves S Garchow G Miller S Alferink V Gaddya Barrettb Tindell E Uribe B Hagar |
| INPO aspect | |
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Finding - River Bend - IR 05000458/2012009 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (River Bend) @ 2012Q3
Self-Identified List (River Bend)
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