05000331/FIN-2013002-01
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Finding | |
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| Title | A Standby Diesel Generator Lube Oil Heat Exchanger Gasket Failure |
| Description | During the Duane Arnold fall 2012 refueling outage, a licensee vendor performed replacements of the A and B SBDG lube oil heat exchanger tube bundle assemblies as part of preventive maintenance activities under WOs 40132858 and 40132849, respectively. These activities included disassembly of the lube oil heat exchangers, removal of the existing tube bundles, installation of the new tube bundles, and reassembly of heat exchangers. Both SBDGs successfully passed TS surveillance testing as part of the work coming out of the refueling outage. On March 7, 2013, the licensee removed the A SBDG from service to perform embedded cable inspections associated with the SBDG. Following these inspections, the licensee performed a required one hour post-maintenance run on March 8, 2013, and identified a 2-3 dpm leak from the lube oil heat exchanger to channel head flange. Because small leaks are not abnormal until engine temperatures normalize after the engine is loaded, the licensee continued with the maintenance run. Throughout the course of the maintenance run, the leak increased to approximately 60 dpm and was constant at the time the engine was secured. Following completion of the maintenance run, the licensee verified minimum acceptable torque of the channel head fasteners and re-started the A SBDG with the intention of increasing the torque on the fasteners to attempt to minimize or eliminate the leak. Within a few minutes of starting the A SBDG, the gasket catastrophically failed, resulting in a significant lube oil leak and spray, and requiring a local manual shutdown of the engine. The licensee declared the A SBDG unavailable and remained in the seven day shutdown limiting condition for operation (LCO), performed an evaluation to rule out a common cause concern for the B SBDG (no prior leaks, acceptable visual inspection, review of past assembly and torque application). On March 9, 2013, the licensee replaced the A SBDG lube oil heat exchanger gasket and declared the engine operable on March 10, 2013, following a successful maintenance run and TS surveillance test. The licensee generated CR 01855032 to evaluate the past operability, reportability, and root cause of the A SBDG lube oil heat exchanger gasket failure. The inspectors noted several issues of concern associated with the as-installed gasket material, adequacy of the gasket installation work order performed during the fall 2012 refueling outage, bolting/torque practices and training, and vendor oversight. However, the licensees evaluation of the cause of the gasket failure was not complete at the end of the inspection period. Based on the unresolved questions surrounding the cause of the gasket failure, the inspectors did not have enough information at the end of the inspection period to screen the issues of concern using IMC 0612, Appendix B, Issue Screening. The inspectors presented the unresolved item to the licensee at the exit meeting. Once the licensee determines the cause of the gasket failure, the inspectors will be able to determine whether any performance deficiencies existed and close this URI (URI 05000331/2013002-01, A Standby Diesel Generator Lube Oil Heat Exchanger Gasket Failure). |
| Site: | Duane Arnold  |
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| Report | IR 05000331/2013002 Section 1R12 |
| Date counted | Mar 31, 2013 (2013Q1) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.12 |
| INPO aspect | |
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Finding - Duane Arnold - IR 05000331/2013002 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Duane Arnold) @ 2013Q1
Self-Identified List (Duane Arnold)
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