ENS 42478
ENS Event | |
|---|---|
20:15 Apr 5, 2006 | |
| Title | High Pressure Coolant Injection Declared Inoperable (Hpci) |
| Event Description | During performance of a Unit 3 High Pressure Coolant Injection System (HPCI) Logic System Functional Test, the High Pressure Coolant Injection (HPCI) system was found to be inoperable. The inoperability is due to a logic failure that would prevent the automatic opening of MO-3-23-015, 'HPCI TURBINE STEAM LINE INBOARD ISOLATION VAVLE'. MO-3-23-015 is a normally open valve located inside Primary Containment. The HPCI system initiates upon receipt of a reactor low water level (level 3) signal or a high drywell pressure signal. Upon a HPCI system initiation MO-3-23-015 is required to automatically open, if closed, with no isolation signal present. The automatic opening of MO-3-23-015 is required to ensure the design function of HPCI is fulfilled. The design function of HPCI is to assure that the reactor is adequately cooled to limit fuel-clad temperature in the event of a small break in the nuclear system and loss of coolant, which does not result in rapid depressurization of the reactor vessel. HPCI permits the nuclear plant to be shut down while maintaining sufficient reactor vessel water inventory until the reactor vessel is depressurized.
The HPCI system inoperability has no immediate impact on plant operations. The inoperability places Unit 3 in a 14-day shutdown Tech Spec Action Statement. The 14-day shutdown Tech Spec Action Statement commenced on 04/05/06 @ 0824 when the Logic System Function Test was started. A troubleshooting and repair team has been initiated to determine a cause and repair of the deficiency. The licensee notified the NRC Resident Inspector.
The purpose of this notification is to retract a previous report made on 4/5/06 at 1643 hours0.019 days <br />0.456 hours <br />0.00272 weeks <br />6.251615e-4 months <br /> (EN# 42478). On 4/5/06, the High Pressure Coolant Injection (HPCI) system was removed from service and declared inoperable for the performance of a Logic System Functional Test (LSFT). During the LSFT, a condition was discovered in the open control logic circuit of the MO-3-23-015 (HPCI Turbine Steam Line Inboard Isolation Valve) that would have inhibited automatic opening of the valve on a HPCI initiation signal. Notification of this issue to the NRC on 4/5/06 was initially made as a result of the belief that the MO-3-23-015 may not have been capable of being opened for design events. It was subsequently determined that a relay contact exhibited high resistance during the LSFT. The relay was replaced on 4/6/06 (IR 475307). Since the initial report, Engineering has performed an operability review that evaluated the impact that the relay contact high resistance condition had on the ability of the HPCI system to perform its safety function. It was determined that the relay contact degradation did not cause the HPCI system to be inoperable. The MO-3-23-015 is a normally open Primary Containment Isolation Valve. MO-3-23-015 would only isolate for conditions where HPCI would be rendered inoperable. Automatically re-opening the MO-3-23-015 valve is not a safety related function. Therefore, HPCI was capable of performing its safety function with the degraded relay contact. Notified the R1DO (Dimitriadis). The licensee notified the NRC Resident Inspector. |
| Where | |
|---|---|
Peach Bottom  Pennsylvania (NRC Region 1) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | |
| Time - Person (Reporting Time:+-3.53 h-0.147 days <br />-0.021 weeks <br />-0.00484 months <br />) | |
| Opened: | Todd Strayer 16:43 Apr 5, 2006 |
| NRC Officer: | John Mackinnon |
| Last Updated: | May 11, 2006 |
| 42478 - NRC Website | |
Unit 3 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |