ENS 40905
ENS Event | |
|---|---|
13:42 Jul 29, 2004 | |
| Title | Plant Entered Lco Action Statement Due to Malfunction of a Suppression Chamber-To-Drywell Vacuum Breaker. |
| Event Description | On July 29, 2004, at approximately 0351 hours0.00406 days <br />0.0975 hours <br />5.803571e-4 weeks <br />1.335555e-4 months <br />, testing of Suppression Chamber-to-Drywell vacuum breakers commenced in accordance with Periodic Test 0PT02.3.1, "Suppression Chamber-to-Drywell Vacuum Breaker Operability Test." At 0357 hours0.00413 days <br />0.0992 hours <br />5.902778e-4 weeks <br />1.358385e-4 months <br />, it was determined that vacuum breaker 2-CAC-X18D had an open indication. Technical Specifications (TS) Limiting Condition for Operation (LCO) 3.6.1.6, "Suppression Chamber-to-Drywell Vacuum Breakers," Condition B was entered for one suppression chamber-to-drywell vacuum breaker (2-CAC-X18D) not indicating closed. Required Action B.1 of TS LCO 3.6.1.6 provides 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> to verify the vacuum breaker closed. Attempts to confirm the vacuum breaker closed were unsuccessful and at 0757 hours0.00876 days <br />0.21 hours <br />0.00125 weeks <br />2.880385e-4 months <br />, TS LCO 3.6.1.6 Condition C was entered. Required Action C.1 is to be in Mode 3 (Hot Shutdown) in 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and Required Action C.2 is to be in Mode 4 (Cold Shutdown) in 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />. Initiation of the plant shutdown required by TS LCO 3.6.1.6 commenced at 0942 hours0.0109 days <br />0.262 hours <br />0.00156 weeks <br />3.58431e-4 months <br />.
This condition is being reported in accordance with 10 CFR 50.72(b)(2)(i) as the initiation of any nuclear plant shutdown required by the plant's TS. INITIAL SAFETY SIGNIFICANCE EVALUATION The initial safety significance of this condition is considered to be minimal. The actual position of the vacuum breaker cannot be confirmed, however if one vacuum breaker was not closed, communication between the drywell and suppression chamber air space could occur, and as a result, there is a potential, for primary containment overpressurization due to this bypass leakage if a loss of coolant accident were to occur. The plant is currently proceeding to hot shutdown with all Emergency Core Cooling systems operable. CORRECTIVE ACTIONS Determine the required corrective actions after entry into the drywell following shutdown. The safety significance of the event will be reviewed when the actual condition of the vacuum breaker is known. The NRC Resident Inspector has been notified.
On July 29, 2004, at 1517 hours0.0176 days <br />0.421 hours <br />0.00251 weeks <br />5.772185e-4 months <br />, a manual scram was inserted to shut down the Unit 2 reactor from approximately 23 percent of rated thermal power. The reactor shutdown was implemented to meet the requirements of Technical Specification (TS) Limiting Condition for Operation (LCO) 3.6.1.6 Required Action C.1 to be in Mode 3 in 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. All control rods fully inserted into the core and no ECCS actuation occurred or relief valves lifted. Following the scram, an expected reactor vessel coolant level shrink occurred causing coolant level to decrease below the Low Level 1 setpoint. This coolant level decrease resulted in a Primary Containment Isolation Valve isolation signal to Group 2 (Drywell Equipment and Floor Drain, Traversing In-core Probe, Residual Heat Removal (RHR) Discharge to Radwaste, and RHR Process Sample), Group 6 (Containment Atmosphere Control/Dilution, Containment Atmosphere Monitoring, and Post Accident Sampling System), and Group 8 (RHR Shutdown Cooling Suction and RHR Inboard Injection) isolation valves. The isolation signal closed all of the valves that were open at the time of the expected initiation. The plant is currently in mode 3 and proceeding with a normal cooldown to Mode 4. The NRC Resident Inspection was informed. Notified Reg 2 RDO (Tom Decker). |
| Where | |
|---|---|
Brunswick  North Carolina (NRC Region 2) | |
| Reporting | |
| 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown | |
| Time - Person (Reporting Time:+-1.47 h-0.0613 days <br />-0.00875 weeks <br />-0.00201 months <br />) | |
| Opened: | Ken Chism 12:14 Jul 29, 2004 |
| NRC Officer: | Chauncey Gould |
| Last Updated: | Jul 29, 2004 |
| 40905 - NRC Website
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Unit 2 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (88 %) |
| After | Power Operation (46 %) |
WEEKMONTHYEARENS 546032020-03-24T16:05:00024 March 2020 16:05:00
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