ENS 42651
ENS Event | |
|---|---|
21:55 Jun 18, 2006 | |
| Title | Loss of Onsite Emergency Safety Function - "B" Edg Failed to Start During Test Run |
| Event Description | The following event description is based on information currently available. If through subsequent reviews of this
event, additional information is identified that is pertinent to this event or alters the information being provided at this time, a follow-up notification will be made via the ENS or under the reporting requirements of 10CFR50.73. On June 18, 2006, at approximately 1455 Mountain Standard Time (MST), Palo Verde Nuclear Generating Station Unit 1 was operating at 0% power in Mode 6 with the 'A' Emergency Diesel Generator (EDG) inoperable for troubleshooting of the train 'A' load sequencer, The 'B' EDG failed to start during a test run resulting in a loss of the onsite emergency power safety function required by General Design Criterion (GDC) 17. The offsite power source safety function remains available to the plant. The unit entered Technical Specification 3.8.2, AC Sources - Shutdown Condition B for one required DG inoperable. There was no movement of irradiated fuel assemblies, therefore the unit remained in compliance with the Required Actions. The offsite electrical grid is stable. At 1810 MST the 'A' EDG was declared operable, exiting Technical Specification 3.8.2. With the 'A' EDG operable, the safety function for the onsite emergency power was also restored. There were no structures, systems or components that were inoperable at the start of event that contributed to the event. This condition did not result in any challenges to the fission product barrier or result in any releases of radioactive materials. There were no adverse safety consequences or implications as a result of this event. This condition did not adversely affect the safe operation of the plant or health and safety of the public. The NRC Resident Inspector has been notified of this condition and this ENS notification.
Further evaluation has determined that this event is not reportable. In the 'test' mode, an 'Incomplete Sequence' trip is enabled and functions on an engine start to trip the engine if starting air is not terminated within 15 seconds. Due to a delay in opening the engine fuel racks by the test mode pneumatic control valve loop, the 'Incomplete Sequence' trip actuated. During an emergency start, the electrically operated emergency fuel solenoids control the operation of the engine fuel racks and the 'Incomplete Sequence' trip function is bypassed. Engineering evaluation found none of the equipment required to operate the 'B' EDG in the emergency mode degraded or malfunctioning. The 'B' EDG was still capable of performing its design function and was 'OPERABLE'. Additionally, it was determined that the 'A' EDG was fully functional and in a standby condition, capable of performing its design function at the time the 'B' EDG test run trip occurred. Therefore, this condition is not reportable per 10CFR50.72(2)(b)(v)(B) or (2)(b)(v)(D)." The licensee notified the NRC Resident Inspector. R4DO(Pick) has been notified. |
| Where | |
|---|---|
Palo Verde  Arizona (NRC Region 4) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat | |
| Time - Person (Reporting Time:+2.57 h0.107 days <br />0.0153 weeks <br />0.00352 months <br />) | |
| Opened: | Jim Blasek 00:29 Jun 19, 2006 |
| NRC Officer: | Joe O'Hara |
| Last Updated: | Jul 5, 2006 |
| 42651 - NRC Website | |
Unit 2 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |
Unit 3 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |