05000298/FIN-2010005-05
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Finding | |
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| Title | Diesel Generator Overspeed Governor Loose Bolting Issue |
| Description | The inspectors identified an unresolved item associated with the loose bolting issue on the over speed governor of diesel generator two. Specifically, the issue concerns past operability of the diesel, adequacy of previous evaluations and corrective actions taken by the licensee, and procedure quality and use. On September 8, 2009, while performing a monthly surveillance run of diesel generator two, the overspeed governor trip mechanism was observed to be vibrating significantly. The licensee secured the diesel generator, and during subsequent inspection found that all eight nuts that that were used to retain the governor were loose (less than finger tight). The licensee determined that this event had been caused by gasket creep and thermal cycle effects, and had this been occurring over a very long period of time, approximately 30 years. The licensee took corrective actions based on these identified causes. Subsequently, on August 17, 2010, while performing bolt tightness checks the licensee discovered six of eight nuts that were used to retain the diesel generator two overspeed governor drive unit were loose (less than finger tight), and one bolt was at a reduced torque (48 ft-lbs). The licensee determined that the cause of this event was improper torque being applied to the nuts when they had been reassembled following the September 2009 issue along with thermal cycle effects. During review of the root cause report for the loose bolting issue found on diesel generator two in August 2010, the inspectors noted that this condition appeared to be a repeat occurrence of what had been found in September 2009, and as such, questioned the licensees determined cause for the 2010 issue. The inspectors also questioned key assumptions used by the licensee when evaluating this issue. Furthermore, the inspectors noted that the past operability evaluation that the licensee performed failed to consider all pertinent conditions that could have affected the equipments ability to perform its design basis function, specifically elevated vibrations associated with the asfound condition. As such, the inspectors determined that more inspection was necessary to resolve this issue. Accordingly, this issue is being considered an unresolved item pending further review. An unresolved item is an issue requiring further information to determine if it is acceptable, if it is a finding, or if it constitutes a violation of NRC requirements. As such, no analysis of this issue has occurred. Additional information was needed to determine whether a violation of regulatory requirements occurred. Pending further review of additional information provided by the licensee, this issue is being treated as an Unresolved Item 05000298/2010005-05, Diesel Generator Overspeed Governor Loose Bolting Issue. |
| Site: | Cooper  |
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| Report | IR 05000298/2010005 Section 4OA2 |
| Date counted | Dec 31, 2010 (2010Q4) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71152 |
| Inspectors (proximate) | G Pick J Josey L Ricketson M Chambers M Young N Greene V Gaddyg Guerrap Elkmann J Josey V Gaddy M Chambers E Ruesch |
| INPO aspect | |
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Finding - Cooper - IR 05000298/2010005 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Cooper) @ 2010Q4
Self-Identified List (Cooper)
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