ENS 45586
ENS Event | |
|---|---|
13:45 Dec 22, 2009 | |
| Title | Loss of Water Seal to Secondary Containment |
| Event Description | On December 22, 2009, at 0845 hours0.00978 days <br />0.235 hours <br />0.0014 weeks <br />3.215225e-4 months <br />, with the reactor at 100% core thermal power and steady state conditions, Pilgrim Nuclear Power Station (PNPS) declared Secondary Containment inoperable due to the loss of a water seal on two 14 inch drain lines in the Torus Compartment designed to mitigate the consequences of a flood in the Reactor Auxiliary Bay. An initial assessment of the condition indicates that the cross-sectional area of pipes, as found, have the potential to exceed the analytical value of allowable Secondary Containment leakage pathway size documented in the design calculations. The Limiting Condition for Operation (LCO) for Technical Specification (TS) 3.7.C.2.a, was immediately entered at 0845 until the condition was corrected. The TS LCO was subsequently exited at 0945 hours0.0109 days <br />0.263 hours <br />0.00156 weeks <br />3.595725e-4 months <br /> at which time Secondary Containment was declared operable.
As background, each Reactor Auxiliary Bay (2) is equipped with a sump containing two 14 inch drain lines that discharge into separate trough in the Torus Compartment in the event of a flooding condition. The trough is approximately 4 feet by 4 feet by 4 feet deep and is equipped with a high and low level alarm which annunciates in the Control Room. One of the functions of the alarm is to indicate a low level condition prior to the pipes losing their water seal which maintains Secondary Containment for those penetrations. When the water level in the trough dropped below the low level setpoint, the alarm failed to annunciate. This condition was discovered during an engineering walk down of the Torus Compartment. Immediate actions taken were to refill the trough to the correct level, initiate repairs to the level switch, which was found to be defective, and to enhance the weekly tour requirement of the Torus Compartment performed by plant operations. This notification has no impact on the health and safety of the public. The NRC Resident Inspector is onsite and has been notified. This is an 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> notification made in accordance with 50.72(b)(3)(v)(C). |
| Where | |
|---|---|
| Pilgrim Massachusetts (NRC Region 1) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material | |
| Time - Person (Reporting Time:+2.75 h0.115 days <br />0.0164 weeks <br />0.00377 months <br />) | |
| Opened: | Francis Clifford 16:30 Dec 22, 2009 |
| NRC Officer: | Charles Teal |
| Last Updated: | Dec 22, 2009 |
| 45586 - NRC Website | |
Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |