05000286/LER-2010-001
| Indian Point Unit 3 | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(v)(A), Loss of Safety Function - Shutdown the Reactor |
| 2862010001R00 - NRC Website | |
Note: The'Energy Industry Identification System Codes are identified within the brackets fl.
DESCRIPTION OF EVENT
On March 2, 2010, at approximately 19:18 hours, while at 100% steady state reactor power, an engineering evaluation of past operability determined that there were instances of past performance that may have affected the operability of the Reactor Coolant System {AB}(RCS) 31 wide range cold leg temperature loop T-413B {IM}. This component is required by Technical Specification (TS) 3.3.4, Remote Shutdown. The event was recorded in the Indian Point Energy Center corrective action program (CAP) as CR-IP3-2009-04823.
The RCS wide range cold leg temperature instrument {TE} TE-413B is located in the remote panel POE {PL} and satisfies the remote shutdown panel function. Surveillance test 3-PC-OLO1B, "RCS Wide Range Temperature Appendix "R" Instruments Calibration and Transfer Switch Check" satisfies the channel calibration requirements of TS Surveillance Requirement (SR) 3.3.4.3 and the results were reviewed by engineering to evaluate the past performance of the temperature loop. The as found condition of the components failed the acceptance criteria repeatedly. Specifically, the failure appeared to be the R/I converter located in the remote panel POE which affects the remote instrumentation TE-413B (tagged as POE-PS2) required by TS 3.3.4. There were also functional test failures evidenced during performance of 3PT-R152, "Operability Test of Safe Shutdown Instrumentation" performed after 3-PC-OLO1B. These were not monitored under the drift monitoring program and a failure would cause an adjustment of the R/I by work order. The temperature instrument PS2 was added to the drift monitoring program in 2001 and failures occurred as follows:
- 2001, PS2 (TI-413B) fails 3PT-R152 with erroneously high as found reading (remote was 650°F and control room was 537°F)
- 2003, PS2 fails 3-PC-OLO1B as found acceptance criteria (Approximately -15% shift for all values).
- 2003, PS2 fails 3PT-R152 with erroneously high as found reading (remote was 660°F and control room was 537°F)
- 2005, PS2 fails 3-PC-OLO1B as found acceptance criteria (top of span value low by
- 2007, PS2 fails 3-PC-OLO1B as found acceptance criteria (Approximately -15% shift for all values).
- 2007, PS2 fails 3PT-R152 with erroneously high as found reading (remote was 670°F and control room was 537°F)
- 2009, PS2 fails 3-PC-OLO1B as found acceptance criteria (Approximately +16% shift for all values).
Cause of Event
The direct cause of this failure is transfer switch high resistance contacts which were not detected during testing due to inadequate steps in the calibration procedure associated with R/I calibrations and proper as found criteria. The failure to identify the adverse trend was poor change management and a lack of commitment to implement the drift monitoring program.
Corrective Actions
The following corrective actions have been or will be performed under Entergy's Corrective Action Program to address the cause and prevent recurrence:
- performed a surveillance to demonstrate the current operability of the instrument on March 2, 2010 when past inoperability was identified.
- Procedure 3-PC-OLO1B was revised to provide adequate steps for performing R/I calibrations, switch contact resistance checks, and proper as found criteria.
- The current set point drift review process provides a timely review of as found calibration results for potential impacts on set point drift.
- Procedure 3-PC-OLO1B will be revised to ensure CR and remote shutdown indications are consistent.
Event Analysis
The event is reportable under 10 CFR 50.73(a)(2)(i)(B). The licensee shall report any operation or condition which was prohibited by the Technical Specifications (TS).
This event meets the reporting criteria because TS 3.3.4 limits the loss of the remote shutdown function to 30 days before shutdown is required. The exact period of time the cold leg temperature loop was out of service could not be determined but it would have exceeded that period. This event is reportable under 10 CFR 50.73(a)(2)(v)(A). The licensee shall report any event or condition that could have prevented the fulfillment of the safety function of structures or systems to shutdown the reactor. The cold leg monitor for the remote shutdown function is limited to the 31 loop and there are no redundant instruments.
Past Similar Events
A review was performed of the past three years for Licensee Event Reports (LERs) reporting a safety system functional failure. LER-2009-009 identified the loss of a neutron flux detector but determined the cause was lack of recurring preventative maintenance. LER-2008-002 identified the loss of 31 pressurizer backup heater transformer but determined the cause was due to insulation breakdown.
Safety Significance
This event had no effect on the health and safety of the public. There were no actual safety consequences for the event because there was no shutdown using the remote shutdown panel. There were no significant potential safety consequences of this event because the remote shutdown instrument is not credited for any accident response in the plant accident analysis.