05000361/FIN-2008013-07
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Finding | |
|---|---|
| Title | Degraded Electrical Connections |
| Description | Following NRC inspectors initial review of AR 080301117 that discussed the loose electrical connections affecting the 125 Vdc battery breaker the inspectors questioned whether other degraded electrical connection issues had been identified by the licensee. Based on these questions additional examples were identified consisting of: (1) on June 25, 2005, emergency supply Fan 3A276 failed due to a loose wire, which resulted in the inoperability of the emergency diesel generator (EDG) 3G003; (2) on September 17, 2007, loose electrical bolt connections were identified affecting 125 Vdc Bus 2D2; (3) in 2007, a loose electrical connection was identified affecting emergency chiller supply Breaker E336; and (4) on July 9, 2008, a loose electrical connection was found affecting EDG 3G002 cooling fan supply breaker. Based on these examples having the generic potential to adversely affect the safety function of multiple safety systems used for accident mitigation the NRC concluded that a special inspection was warranted. The special inspection team performed a review of plant corrective action documents, procedures, and work orders, associated with deficient electrical connections to determine whether the existing processes for control of electrical connection integrity were adequate. From January 2005, to July 2008, the team noted that over 30 loose electrical connection events occurred, with thirteen events occurring in equipment important to safety. Loose electrical connections that were identified and evaluated included the following: Item Equipment Description Condition The team reviewed documentation associated with training in the establishment and maintenance of electrical connections. Documents describing the training program for torquing mechanical bolted connections and instrumentation and control connections were provided. While training programs existed for mechanical bolted connections, formal training related to electrical connections was limited to instrumentation and control connections. No training documents related to general electrical connection integrity was provided. The team determined that formal training on torquing electrical connections was not provided, and the reliance on skill of the craft, does not appear adequate to ensure uniform application of proper techniques for making electrical connections. The team determined that these electrical deficiencies resulted in configurations where structures, systems, or components, may not have been able to perform their design function during a seismic event. The integrity of electrical connections is a key element in the reasonable assurance of operability. The failure to ensure that appropriate measures were maintained to assure that systems specified in the design basis were maintained in a configuration which provided a reasonable assurance of operability during design basis events is being considered an unresolved item pending further NRC review: URI 05000361;05000362/2008013-07, Degraded Electrical Connections |
| Site: | San Onofre  |
|---|---|
| Report | IR 05000361/2008013 Section 4OA5 |
| Date counted | Dec 31, 2008 (2008Q4) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 93812 |
| Inspectors (proximate) | B Collins G Skinner G Warnick M Baquera S Gravesl Ricketsong Guerra R Lantz P Elkmann J Adams J Reynoso G Warnick C Osterholtz A Fairbanks M Bloodgood R Schmitts Gravesg Skinner G Warnick M Baquera B Collins |
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Finding - San Onofre - IR 05000361/2008013 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (San Onofre) @ 2008Q4
Self-Identified List (San Onofre)
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