05000289/FIN-2009002-02
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Finding | |
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| Title | Decay Heat River Water System Pump (DR-P-1B) Failed to Start |
| Description | On February 12, 2008, decay heat river water pump DR-P-1B failed to start (IRs 735277 and 735778) due to a faulted starting relay (X relay) within electrical circuit breaker DR-P-1B-BK. Station personnel determined one of the coil wires on the X relay was not firmly anchored (deficient solder joint) to the coil beneath the factory-installed electrical seal. Laboratory analysis concluded the apparent cause was an isolated occurrence of a coil manufacturing defect. The control relay was replaced and DR-P-1B was successfully returned to service on February 13. This event was previously documented in NRC Inspection Report 05000289/2008002. Engineers subsequently concluded DR-P-1B had been inoperable from January 25 to February 13, 2008. The inspectors noted that since October 2007, when the breaker containing the defective starting relay was installed, DR-P-1B had started successfully over 20 consecutive times. Maintenance records indicated the breaker had been properly inspected, maintained, and tested prior to installation of DR-P-1B. Based on direct visual inspections and review of the laboratory failure analysis, the inspectors determined the inoperable decay heat river water pump did not result from a licensee performance deficiency. The deficient solder joint weakened during each breaker actuation and eventually broke on February 12, 2008, due to the cumulative fatigue. The equipment failure could not have been avoided or detected by the licensees quality assurance program or other related control measures. The inspectors performed a risk based assessment using the TMI Unit 1 probabilistic risk assessment model. The assessment assumed DR-P-1B was inoperable for 19 days, the likelihood of DR-P-1A being inoperable during this same period was low, and some recovery credit for licensee repair capabilities after identification was applied. The inspectors determined the risk significance of this issue was low to moderate safety significance. TS 3.3.1.4, Cooling Water Systems, requires two decay heat river water pumps be operable. Further, TS 3.3.2 permits one of the two decay heat river water trains to be inoperable temporarily for component maintenance or testing. If the inoperable component and train are not restored to operable status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, the reactor must be placed in a hot shutdown condition within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />. Contrary to these requirements, DR-P-1B was inoperable from January 25 to February 13, 2008, and the reactor was not shutdown. The event had a potential safety consequence in that if the redundant pump (DR-P-1A) failed to operate during an accident, decay river cooling which supports the decay heat removal function would not be available. Corrective actions included: (1) replacing the defective control relay; (2) performing an extent-of-condition review; (3) inspecting all the X relays from the same manufacturing lot; (4) revising applicable electrical inspection and testing procedures; and, (5) incorporating this failure into the manufacturer corrective action program. Because no licensee performance deficiency was identified, no enforcement action is warranted. In accordance with Section VII.B.6 of the NRCs Enforcement Policy, the NRC has chosen to exercise enforcement discretion and not issue a violation for this issue. Further, because licensee actions did not contribute to this violation, it will not be considered in the assessment process or NRCs Action Matrix. (EA-09-011) |
| Site: | Three Mile Island  |
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| Report | IR 05000289/2009002 Section 4OA3 |
| Date counted | Mar 31, 2009 (2009Q1) |
| Type: | Violation: Severity level Enforcement Discretion |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71153 |
| Inspectors (proximate) | J Caruso P Presby J Brand D Kern R Bellamy C Newport |
| INPO aspect | |
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Finding - Three Mile Island - IR 05000289/2009002 | |||||||||||||||||||||||||||||||||||
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Finding List (Three Mile Island) @ 2009Q1
Self-Identified List (Three Mile Island)
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