ENS 45812
ENS Event | |
|---|---|
17:45 Apr 4, 2010 | |
| Title | Both Trains of Residual Heat Removal (Rhr) Inoperable |
| Event Description | On 4/4/10 at 1245 [CDT], three RHR system snubbers were declared inoperable due to visual inspection identifying empty reservoirs for the snubbers. The inoperability of the snubbers rendered both trains of RHR cooling inoperable. On 4/4/10 at 1545, ultrasonic testing identified voided piping on the common RWST [Refueling Water Storage Tank] suction line to the RHR pumps. This condition also resulted in inoperability of both trains of RHR for the ECCS [Emergency Core Cooling System] mode of operation.
At the time of these discoveries, Unit 2 was in mode 4, proceeding to mode 5 for a refueling outage. The inoperability of both trains of RHR represents a condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to remove residual heat and mitigate the consequences of an accident. Replacement of the snubbers is in progress. Following completion of snubber replacement, Unit 2 will proceed to mode 5 at which point ECCS capability is not required. Resolution of the voided piping will be accomplished following mode 5 entry. The snubbers are in containment and were last checked during the previous refueling outage. The voiding in the RHR suction line only affects suction from the RWST and not when suction is aligned to the Reactor Coolant System. The licensee will notify the NRC Resident Inspector.
An eight hour report (EN #45812) per 10CFR50.72(b)(3)(v)(B) and 10CFR50.72(b)(3)(v)(D) was conservatively reported because both trains of Residual Heat Removal (RHR) system were thought to be inoperable based on the initial visual inspection of three hydraulic snubbers. In addition, initial ultrasonic testing at the RHR suction line to the refueling water storage tank (RWST) identified what was thought to be voided piping. Subsequent visual inspections and testing demonstrated that all three snubbers had adequate oil to ensure that the snubbers would perform their intended function. In addition, the ultrasonic testing was reviewed and determined that the technique for the coupling gel application between the ultrasonic detector and piping was not adequate for an accurate test. The ultrasonic inspection was performed again using the correct detector to piping coupling technique and it was determined that the RHR piping had adequate water level. Therefore, based on more accurate subsequent results of snubber and ultrasonic testing, the RHR system was never inoperable. The three snubbers thought to be inoperable were removed and replaced with snubbers previously verified to be operable. After removal, the snubbers were visually inspected and tested. Two of the three hydraulic snubbers share a common oil reservoir. This common reservoir was found to be completely full of clear oil which made it difficult to determine reservoir oil level while installed in the plant. The third snubber oil reservoir was one-third full. The removed snubbers have been tested to confirm they would have operated as designed. The ultrasonic testing of RHR piping was started as a result of SNC's response to NRC Generic Letter 2008-01. This testing requires a coupling gel to be used between the ultrasonic detector and the RHR piping to ensure accurate water level results. Based on the initial ultrasonic test results it was thought that the RHR piping had voids. However, when the coupling process was reexamined, it was determined that additional coupling gel was needed for accurate results. When the ultrasonic test was performed again with the proper coupling process, it was determined that the RHR piping had adequate water and that voiding did not exist. The second ultrasonic inspection technique was reviewed and confirmed the coupling process utilized was correct. In summary, a loss of safety function on both trains of RHR did not exist and the 50.72(b)(3)(v)(B) and 50.72(b)(3)(D) report (EN # 45812) is retracted. The licensee notified the NRC Resident Inspector. Notified R2DO (Moorman). |
| Where | |
|---|---|
Farley  Alabama (NRC Region 2) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | |
| Time - Person (Reporting Time:+3.18 h0.133 days <br />0.0189 weeks <br />0.00436 months <br />) | |
| Opened: | Bill Arens 20:56 Apr 4, 2010 |
| NRC Officer: | Mark Abramovitz |
| Last Updated: | Apr 5, 2010 |
| 45812 - NRC Website | |
Unit 2 | |
|---|---|
| Reactor critical | Not Critical |
| Scram | No |
| Before | Hot Shutdown (0 %) |
| After | Hot Shutdown (0 %) |
Farley with 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat, 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | |
WEEKMONTHYEARENS 524142016-12-07T19:43:0007 December 2016 19:43:00
[Table view]10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident, 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Discovery of Non-Conforming Conditions During Tornado Hazards Analysis ENS 458122010-04-04T17:45:0004 April 2010 17:45:00 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat, 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident Both Trains of Residual Heat Removal (Rhr) Inoperable ENS 456732010-02-03T02:15:0003 February 2010 02:15:00 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident Two of Three Trains of Auxiliary Feed Water Declared Inoperable ENS 443582008-07-22T01:58:00022 July 2008 01:58:00 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident, 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown Loss of Accident Mitigation Capabilities Due to Two Emergency Diesel Generators Out of Service ENS 441422008-04-15T13:49:00015 April 2008 13:49:00 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat Residual Heat Removal System Declared Inoperable ENS 431062007-01-18T22:00:00018 January 2007 22:00:00 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat Battery Charger Room Cooler Inoperable 2016-12-07T19:43:00 | |