ENS 47873
ENS Event | |
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11:00 Apr 30, 2012 | |
Title | Both Trains of Residual Heat Removal System Declared Inoperable |
Event Description | At 1742 CDT on 04/27/2012, while in Mode 5, both trains of Residual Heat Removal were declared inoperable due to a through wall leak in a 3/4-inch pipe socket weld connection. The leak developed in an ASME Section XI, Code Class 2 weld upstream of a sample isolation valve. The leak is not isolable from the common 10-inch Residual Heat Removal discharge piping. However, the leakage is isolable from the Reactor Coolant System and is therefore not considered RCS pressure boundary leakage per Technical Specification LCO 3.4.13, RCS Operational Leakage. Currently, with both trains of RHR in service for decay heat removal, the leakage impacts redundant equipment required to fulfill a safety function. In the current condition, both trains are required to be operable to meet Technical Specification LCO 3.4.7, RCS Loops - Mode 5, Loops Filled. This event was reported per EN #47871.
At 0600 CDT on 04/30/2012 during the subsequent repair of the leaking weld a second leak of approximately 0.03 gallons per minute developed. The second leak occurred down stream of the original leak while welding a temporary clamp to the 3/4-inch sample line. The cause of the second leak is being directly attributed to the welding activity and not degradation of the pipe. The structural integrity of the pipe in the area of the second leak was verified to be acceptable. Both trains of Residual Heat Removal remain in service removing decay heat from the core. No other equipment is being affected by the leak. Repair options are currently being evaluated. The new leak is being reported under 50.72(b)(3)(v)(B), 'Any event that at the time of discovery could have prevented the fulfillment of the safety function of structures or systems that are needed to: (B) Remove residual heat.' Actions continue in accordance with Technical Specification LCO 3.4.7 Required Action C.2 to restores one RHR loop to operable status. The licensee has notified the NRC Resident Inspector. |
Where | |
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Kewaunee Wisconsin (NRC Region 3) | |
Reporting | |
10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat | |
Time - Person (Reporting Time:+-0.08 h-0.00333 days <br />-4.761905e-4 weeks <br />-1.09584e-4 months <br />) | |
Opened: | Craig Neuser 10:55 Apr 30, 2012 |
NRC Officer: | John Knoke |
Last Updated: | Apr 30, 2012 |
47873 - NRC Website | |
Unit 1 | |
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Reactor critical | Not Critical |
Scram | No |
Before | Cold Shutdown (0 %) |
After | Cold Shutdown (0 %) |