ENS Event | |
|---|---|
20:15 Apr 15, 2005 | |
| Title | Invalid Actuation During Excess Flow Check Valve Testing |
| Event Description | At 1515 hours0.0175 days <br />0.421 hours <br />0.0025 weeks <br />5.764575e-4 months <br /> on April 15, 2005, while conducting excess flow check valve testing in conjunction with a reactor vessel pressure test during a scheduled refueling outage, Unit 1 received an invalid Anticipated Transient Without Scram (ATWS) Channel A trip signal and invalid reactor Lo-Lo water level trips on the A and C channels for ECCS. The operating Reactor Recirculation pump (1 A) tripped and both Emergency Diesel Generators (Unit 1 and Unit 0) auto-started and ran unloaded. RCIC received an initiation signal, which resulted in proper valve repositioning for the system but no injection due to the steam supply being isolated to support the reactor vessel pressure test. In addition, all appropriate running equipment tripped due to load shedding. Reactor pressure was 787 psig at the time of the event and no pressure transient or vessel injection occurred. All equipment responded to the actuation as expected for plant conditions. The excess flow check valve testing was stopped and the reactor vessel pressure test was terminated as a result of this invalid actuation.
It was subsequently determined that a leaking drain valve at the instrument rack where the excess flow check valve testing was being performed caused a slow depressurization of the high-pressure side sensing line for the level transmitters associated with ATWS Channel A and the A and C channels for ECCS, resulting in an erroneous level signal and the invalid actuation. The instrument rack drain valve is scheduled for replacement. The NRC Resident Inspector was notified |
| Where | |
|---|---|
Quad Cities  Illinois (NRC Region 3) | |
| Reporting | |
| 10 CFR 50.73(a)(1), Submit an LER, Invalid Actuation | |
| Time - Person (Reporting Time:+1433.5 h59.729 days <br />8.533 weeks <br />1.964 months <br />) | |
| Opened: | Eric Marks 13:45 Jun 14, 2005 |
| NRC Officer: | Chauncey Gould |
| Last Updated: | Jun 14, 2005 |
| 41770 - NRC Website
Loading map... | |
Unit 1 | |
|---|---|
| Reactor critical | Not Critical |
| Scram | No |
| Before | Cold Shutdown (0 %) |
| After | Cold Shutdown (0 %) |
WEEKMONTHYEARENS 478752012-03-25T00:36:00025 March 2012 00:36:00
[Table view]10 CFR 50.73(a)(1), Submit an LER Invalid Protection System Actuation During Station Electrical Transient ENS 417702005-04-15T20:15:00015 April 2005 20:15:00 10 CFR 50.73(a)(1), Submit an LER Invalid Actuation During Excess Flow Check Valve Testing 2012-03-25T00:36:00 | |