05000272/LER-2002-006
| Salem Generating Station Unit 1 | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 2722002006R00 - NRC Website | |
DOCKET (2) SEAU3mBENTEIRAL REVISION
PLANT AND SYSTEM IDENTIFICATION
Westinghouse — Pressurized Water Reactor Main Steam/Safety Valves {SB/RV}* Pressurizer/Safety Valves {AB/RV}* *Energy Industry Identification System (EIIS) codes and component function identifier codes appear as {SS/CC}
CONDITIONS PRIOR TO OCCURRENCE
The plant was in the shutdown condition for refueling outage 1R15. No structures, systems, or components were inoperable at the time of discovery that contributed to the event.
DESCRIPTION OF OCCURRENCE
On October 15, 2002 with Unit 1 in Mode 6 (Refueling) one of five Main Steam Safety Valves (MSSV) {SB/RV} that were tested failed the as-found actuation pressure surveillance test, required by ASME OM-1987, Part 1, Requirements for lnservice Performance Testing of Nuclear Power Plant Pressure Relief Devices. The Technical Specification (TS) acceptance band for the as-found actuation pressure is ± 3% of the nameplate setpoint pressure. The as-found actuation pressure for MSSV 12MS11{SB/RV} was above the upper limit of plus 3% of the nameplate setpoint. Also, on October 16, 2002 the as found actuation pressure for Pressurizer Safety Valve (PSV) 1PR3 {AB/RV} was below the lower limit of minus 3% of the nameplate setpoint.
The actual test results of the failed valves are:
Valve Id As found (psig) TS Setpoint (psig) Acceptable band (psig) % Difference 12MS11 1178 1125 1091.25 - 1158.75 + 4.71 1PR3 2398 2485 2410.45 - 2559.55 - 3.50 Because the actual lift set point of the 12MS11 and 1PR3 were not within 3% of set point, expanded testing scope was performed in accordance with the In-Service Test (1ST) program. Two MSSVs and two PSVs were tested and met the Technical Specification required acceptance criteria.
CAUSE OF OCCURRENCE
The apparent cause of the MSSV failing to meet the Technical Specification acceptance criteria was attributed to the valve spindle rubbing the spindle guide during lift due to misalignment. The apparent DOCKET (2)
SEQUENTIA
of SALEM GENERATING STATION UNIT 1 05000272 2002 0 0 6 00 3 4 CAUSE OF OCCURRENCE (Cont'd) cause of the misaligned valve internals is inappropriate handling. Although changes have been made for the handling of these valves, such as storage/shipping position, the removal and installation procedure will be enhanced to provide additional handling precautions.
The apparent cause of the PSV failing to meet the Technical Specification acceptance criteria is that this was an original assembly valve and some parts, such as the spring, spring caps and spindle mating surfaces, may not have been lapped in place during manufacture. During valve disassembly, all internal parts were inspected for dimensional acceptance and damage. All internal parts were satisfactory. The only work performed was the lapping of the mating surfaces of the spring, spring caps and spindle. The as-left test was satisfactory. Although the offsite test procedure provides specific direction to inspect these mating surfaces, there is no instruction to lap them during reassembly. The offsite repair procedure will be revised to perform the lapping of these parts if the valve is required to be disassembled.
PRIOR SIMILAR OCCURRENCES
A review of 2000 and 2001 LERs for Salem identified two occurrences where MSSVs exceeded the Technical Specification acceptance of ± 1%; however, these occurrences would have met the current acceptance criteria of ± 3%. Hope Creek LERs were not reviewed since the valves are two stage and any corrective action would not have been applicable.
Corrective actions associated with these LERs would not have prevented this event, since both previous failures were due to seat leakage.
SAFETY CONSEQUENCES AND IMPLICATIONS
Regarding MSSVs, the UFSAR Chapter 15 events that tend to most challenge the allowable peak main steam system design pressure criterion are as follows: Loss of External Electrical Load and/or Turbine Trip (UFSAR Section 15.2.7), Loss of Normal Feedwater (UFSAR Section 15.2.8), and Loss of Power to the Station Auxiliaries (UFSAR Section 15.2.9). The calculated results for each of these three events were reviewed, and it was found that in all instances, the fifth safety was not actuated at all in protection against the over-pressurization of the main steam system. Even though this valve did not open in these events, all acceptance criteria were met. Thus, the one out of tolerance MSSV has no affect on the calculated results for the above listed MSS limiting transients.
With respect to PSVs, they are typically credited in the UFSAR Chapter 15 safety analyses for their pressure relief benefits, and these valves are modeled at the setpoint plus 3% tolerance. Thus, having one of these valves out of tolerance in the negative direction would be a direct benefit to all analyses that credit these valves for protection. However, one UFSAR Chapter 15 safety analysis, DOCKET (2) T.
Spurious Operation of the Safety Injection System at Power, assumes that the valve could have opened at 2398 psig, thus, increasing the potential of liquid relief through the pressurizer safety valves. The calculated results for this transient were reviewed. The lower lift pressure of the one out- of-tolerance PSV has no affect on the calculated results, since it will not open given a spurious operation of the safety injection system. Therefore, the calculated results for UFSAR Section 15.2.14 remain bounding.
Based upon this analysis, there were no safety consequences or implications involved as a result of these valves exceeding the allowable tolerance. Therefore, the public health and safety was not affected.
A review of this condition determined that a Safety System Functional Failure (SSFF) has not occurred as defined in Nuclear Energy Institute (NEI) 99-02.
CORRECTIVE ACTIONS:
MSSV
1. Expanded scope of MSSV testing to include an additional 2 MSSVs from another header in accordance with the IST Program. The two additional valves tested satisfactorily.
2. Valve was disassembled, inspected, repaired, retested satisfactorily and reinstalled.
3. The removal and installation procedure will be enhanced to provide additional handling precautions.
PSV
1. Expanded scope of PSV testing to include an additional 2 PSVs in accordance with the IST Program. The two additional valves tested satisfactorily.
2. Valve was disassembled, inspected, reassembled, and retested satisfactorily.
3. Review the test performance of this style valve from its initial installation to present to determine if any downward trend in set point exists.
4. The offsite repair procedure will be revised to perform the lapping of the spring, spring caps and spindle mating surfaces if the valve is required to be disassembled.
COMMITMENTS
The corrective actions cited in this LER are voluntary enhancements and do not constitute commitments.