ENS 42680
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ENS Event | |
|---|---|
04:37 Jul 1, 2006 | |
| Title | Common Cause Degradation to Rhr Service Water Pump Motor Cooling Coils |
| Event Description | At 2337 of 06/30/2006, it was determined that 3 out of 4 Residual Heat Removal Service Water (RHRSW) pumps were inoperable due to a common cause. Each of the 3 affected RHRSW pumps contained motor cooling coils that had experienced flow induced erosion which had significantly reduced the wall thickness of the cooling coil material. In some cases, the thinning was sufficient to cause through wall leakage of water into the upper motor bearing oil reservoir and subsequently displace oil out of the reservoir. Currently, 2 of the 3 affected RHRSW pumps have been removed from service for repairs. 1 of those pumps is expected to be returned to service shortly. The 3rd affected pump remains available for use, but has been conservatively declared inoperable based on Engineering evaluation that indicates a common cause failure mechanism likely exists, based on common fabrication methods used for all RHRSW pump motor cooling coils. The 4th (unaffected) RHRSW pump remains Operable because its cooling coil was replaced approximately 1 month ago. Under these conditions, sufficient confidence that the affected RHRSW pumps could perform their post LOCA mission does not exist. With only 1 of the 4 RHRSW pumps remaining Operable, the RHRSW System is not capable of performing its safety function. This event is reportable under 10CFR50.72(b)(3)(v)(B) and 50.73(a)(2)(v)(B).
With 3 out of the 4 RHRSW pumps considered inoperable, the licensee is currently in an 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> Tech Spec LCO action statement. However, with expected the return of one of these pumps to operable status within the next hour, the LCO will convert to a 7 day action statement. The licensee notified the NRC Resident Inspector. |
| Where | |
|---|---|
Duane Arnold  Iowa (NRC Region 3) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat | |
| Time - Person (Reporting Time:+-2.97 h-0.124 days <br />-0.0177 weeks <br />-0.00407 months <br />) | |
| Opened: | Tim Erger 01:39 Jul 1, 2006 |
| NRC Officer: | Bill Huffman |
| Last Updated: | Jul 1, 2006 |
| 42680 - NRC Website
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Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (96 %) |
| After | Power Operation (96 %) |
WEEKMONTHYEARENS 475112011-12-02T19:11:0002 December 2011 19:11:00
[Table view]10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat Low Pressure Coolant Injection Inoperable ENS 474482011-11-16T22:22:00016 November 2011 22:22:00 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat Rhr Capability Affected Due to Both Trains of River Water Supply Hvac Systems Inoperable ENS 471422011-08-11T08:27:00011 August 2011 08:27:00 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat, 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown Initiation of Technical Specification Required Shutdown ENS 464102010-11-10T11:18:00010 November 2010 11:18:00 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat Rhr Pump Tripped While Operating in Shutdown Cooling Mode ENS 431852007-02-24T23:56:00024 February 2007 23:56:00 10 CFR 50.72(b)(3)(v)(A), Loss of Safety Function - Shutdown the Reactor, 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Loss of Normal Electrical Lineup Due to Grid Instability from Adverse Weather Conditions ENS 426802006-07-01T04:37:0001 July 2006 04:37:00 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat Common Cause Degradation to Rhr Service Water Pump Motor Cooling Coils 2011-08-11T08:27:00 | |
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