ENS 45791
ENS Event | |
|---|---|
19:40 Mar 25, 2010 | |
| Title | High Head Safety Injection Inoperable Due to Voids Identified in Piping |
| Event Description | At 1540 on 3/25/2010, engineering identified a gas void in the Unit 4 B Cold Leg High Head Safety Injection (HHSI) pipe which exceeded the station's allowable gas accumulation acceptance criteria. This condition rendered the cold leg injection flow path inoperable and required entry into Technical Specification 3.0.3 at 1540. The void was immediately vented and Technical Specification 3.0.3 was exited at 1750.
The licensee notified the NRC Resident Inspector.
The licensee is retracting this report based on the following: At 2018 on 3/25/2010, an event notification (#45791) was reported to the NRCOC as follows: 'At 1540 on 3/25/2010, engineering identified a gas void in the Unit 4 B Cold Leg High Head Safety Injection [HHSI] pipe which exceeded the station's allowable gas accumulation acceptance criteria. This condition rendered the cold leg injection flow path inoperable and required entry into Technical Specification 3.0.3 at 1540. The void was immediately vented and Technical Specification 3.0.3 was exited at 1750 [on 3/25/2010].' The decision to enter TS 3.0.3 was based on the plant procedural guidance and the results of ultrasonic testing. Following the discovery of the void, the failure investigation process required that an engineering evaluation be performed. The evaluation performed calculations to determine if, during a hypothetical HHSI pump start with the measured gas void present, the resulting water hammer conditions would cause the Unit 4 HHSI piping design pressure or Unit 4 HHSI piping supports design loading to be exceeded, thereby challenging the integrity of the Unit 4 HHSI discharge flow path to the reactor coolant system (RCS). The engineering evaluation determined that under the specific conditions in the Unit 4 HHSI piping on 3/25/2010: (1) Unit 4 HHSI piping design pressure would not have been exceeded should the HHSI pumps have started. (2) Unit 4 HHSI piping support design loading would not have been exceeded should the HHSI pumps have started. Therefore, the analysis of the void concluded that both the pipe and the support structural integrity would have withstood the pressure and axial loads due to the gas void and the HHSI system would have continued to perform its safety related function. The Unit 4 HHSI system discharge flowpath to the RCS remained operable at all times. Technical Specification 3/4.5.2, ECCS SUBSYSTEMS: Tavg GREATER THAN OR EQUAL TO 350 degrees F, Limiting Condition for Operation was satisfied at all times. Entry into Technical Specification 3.0.3 was not required at any time before or after the void discovery. The Unit 4 HHSI system remained capable of fulfilling the design safety function to mitigate the consequences of an accident on Unit 4, and an immediate notification to the NRCOC, discussed in 10 CFR 50.72(b)(3)(v)(D), was not required. The licensee informed the NRC Resident Inspector. Notified R2DO (Ayres). |
| Where | |
|---|---|
Turkey Point  Florida (NRC Region 2) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | |
| Time - Person (Reporting Time:+0.63 h0.0263 days <br />0.00375 weeks <br />8.62974e-4 months <br />) | |
| Opened: | Roger Montgomery 20:18 Mar 25, 2010 |
| NRC Officer: | Pete Snyder |
| Last Updated: | Apr 23, 2010 |
| 45791 - NRC Website
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Unit 4 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |