05000400/LER-2012-002
| Shearon Harris Nuclear Power Plant, Unit 1 | |
| Event date: | 05-31-2012 |
|---|---|
| Report date: | 07-30-2012 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 4002012002R00 - NRC Website | |
Energy Industry Identification System (EIIS) codes are identified in the text as [XX].
Event Description
An investigation in May 2012 revealed that surveillance tests for containment penetration overcurrent protection devices had not been properly scheduled and had not been performed as required by Technical Specification (TS) 4.8.4.1. Testing was performed on the components with missed surveillances over the next several weeks. On May 31, 2012, the Harris Nuclear Plant was in Mode 5 with the Reactor Coolant System [AB] at 100 to 105 degrees F and depressurized. The breaker [BKR] for Pressurizer Heater Bank C could not be tested due to a broken handle, which precluded demonstration of acceptable performance. Subsequently on June 2, 2012, the B Reactor Coolant Pump (RCP) [P] overcurrent protection timing relay [RLY] did not meet acceptance criteria for its surveillance test. An extent of condition evaluation resulted in the testing of 30 breakers and six timing relays, with all but the subject two components described above passing the subsequent surveillance testing. Missed surveillances are required to be reported if subsequent testing does not demonstrate acceptable results.
The failure of the two overcurrent protection devices to pass their overdue surveillances constitutes missed surveillances and are reportable per 10 CFR 50.73(a)(2)(i)(B). Following discovery of the missed surveillances, the two overcurrent protective devices were replaced and tested satisfactorily.
Cause of Failures Procedures were developed in the late 1980's to implement surveillance requirements. MST-E0048, RCP 1A-SN, 1B-SN, 1C-SN Current Relay Calibration was written to implement Surveillance Requirement 4.8.4.1.a.1.a (Channel Calibration of RCP relays) Timing relays (2-50F) for RCP breakers were inadvertently left out of MST-E0048 resulting in not performing a required surveillance.
The root and primary contributing cause was determined to be historical in that the subject overcurrent protection devices were never added to the surveillance test procedure when it was developed. In addition, some inconsistencies were identified in a number of plant documents which led to confusion on the testing requirements for the overcurrent protection devices.
Safety Consequences Both safety related and non-safety related containment penetrations are protected against overcurrent.
Primary and backup overcurrent protection meets the requirements of IEEE 279-1971 with regard to testing and independence. As part of the plant's maintenance procedures, circuit breakers are inspected and tested periodically, based on vendor recommendations and/or industry standards. Testing includes manually operating and/or electrically tripping circuit breakers and calibration of associated relays. In all cases, the penetration circuit protection has been designed so that the primary and back-up disconnecting devices can each limit the maximum current at the containment penetration to a value less than that required for thermal damage to the penetration conductor.
There were no adverse safety consequences as result of this event. During the time the missed surveillance was identified, the plant was shut down and in Mode 5 (Cold Shutdown) for a refueling outage. There were 36 overcurrent protective devices that missed their surveillance. The two that could not pass (either could not be tested or failed the acceptance criteria) their surveillance test were replaced and tested.
For the RCP relay, there is redundancy in the breaker circuitry so a loss of function did not occur.
Corrective Actions
Completed Corrective Actions
- The breaker and relay were replaced and tested satisfactorily.
- A comprehensive review was performed on Tech Spec 3/4.8.4.1 surveillance requirements.
- Surveillance procedure MST-E0048 was revised to add the subject overcurrent protection devices.
Planned Corrective Actions
- Calculation 0030-PKR, Electrical Penetration Protection (Reg. Guide 1.63) will be revised to correct the identified discrepancies.
- Plant Procedure PLP-106, Technical Specification Equipment List Program and Core Operating Limits Report will be revised to correct the identified discrepancies.
Previous Similar Events
A review of LERs for the previous five years did not identify any missed surveillance events.
Commitments This report contains no regulatory commitments.