05000354/LER-2021-001, Safety Relief Valve (SRV) As-Found Setpoint Failures
| ML21225A038 | |
| Person / Time | |
|---|---|
| Site: | Hope Creek  (NPF-057) |
| Issue date: | 08/13/2021 |
| From: | Poorman S Public Service Enterprise Group |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LR-N21-0062 LER 2021-001-00 | |
| Download: ML21225A038 (4) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3542021001R00 - NRC Website | |
text
PSEG Nuclear LLC P.O. Box 236, Hancocks Bridge, New Jersey 08038-0236 0 PSEG Nuclear LLC LR-N21-0062 13 August 2021 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-001
Subject:
Hope Creek Generating Station Renewed Facility Operating License No. NPF-57 Docket No. 50-354 Licensee Event Report 2021-001-00, Safety Relief Valve (SRV) As-Found Setpoint Failures 10CFR50.73 In accordance with 10 CFR 50.73(a)(2)(i)(B), PSEG Nuclear LLC is submitting Licensee Event Report (LER) Number 2021-001-00, "Safety Relief Valve (SRV) As-Found Setpoint Failures."
There are no regulatory commitments contained in this letter.
Should you have any questions regarding this submittal, please contact Mr. Francis D.
Possessky at (856) 339-1160.
Steven R. Poorman Plant Manager Hope Creek Generating Station Attachment: Licensee Event Report 2020-001-00 cc:
Regional Administrator - Region I, NRC US NRC NRR Project Manager US NRC Senior Resident Inspector - Hope Creek Manager NJ Bureau of Nuclear Engineering Corporate Commitment Coordinator, PSEG Nuclear LLC
Abstract
On June 14, 2021, Hope Creek Generating Station (HCGS) received results that two as-found setpoint tests for safety relief valve (SRV) pilot stage assemblies (A and J) had exceeded the lift setting tolerance of +/- 3% of the nominal setpoint value prescribed in Technical Specification (TS) 3.4.2.1. Additionally, one SRV (R) did not lift when tested.
This is a condition reportable under 10 CFR 50.73(a)(2)(i)(B).
Setpoint exceedance for two of the SRV pilot stage assemblies is attributed to corrosion bonding between the pilot discs and seating surfaces, which is consistent with industry experience. This conclusion is based on previous cause evaluations and the repetitive nature of this condition at HCGS and within the BWR industry. The cause of the R SRV not lifting was main disc and piston thread wear. This conclusion is based on a failure analysis performed at the vendor.
The affected SRV pilot assemblies were replaced with pre-tested, certified spare assemblies. The R SRV was replaced.
PLANT AND SYSTEM IDENTIFICATION
General Electric - Boiling Water Reactor (BWR/4)
Main Steam - EIIS Identifier {SB}*
Safety Relief Valves - EIIS Identifier {SB/RV}*
- Energy Industry Identification System {EIIS} codes and component function identifier codes appear as {SS/CCC}
IDENTIFICATION OF OCCURRENCE Event Date: June 14, 2021 Discovery Date: June 14, 2021 CONDITIONS PRIOR TO OCCURRENCE When the reports of the as-found results were received, Hope Creek was in Operational Condition (OPCON) 1, Operation at Power, at 100 percent rated thermal power. No other structures, systems or components that could have contributed to the event were inoperable at the time of the event.
DESCRIPTION OF OCCURRENCE During the twenty-third refueling outage (H1RF23) at Hope Creek Generating Station (HCGS), seven 2-stage Main Steam safety relief valve (SRV) assemblies {SB/RV}, and one 3-stage SRV assembly were removed and tested at NWS Technologies. The SRVs are Target Rock Model 7567F two-stage SRVs and Target Rock Model 0867F 3-stage SRVs. On June 14, 2021, HCGS received the results of the 2-stage as-found set pressure testing required by Technical Specification (TS) Surveillance Requirement (SR) 4.4.2.2. A total of two of the seven SRV pilot stage assemblies had setpoint drift outside of the required TS 3.4.2.1 tolerance values of +/-3% of nominal value.
The as-found test results for the two 2-stage SRVs not meeting the TS requirements are as follows:
Valve ID As Found (psig)
TS Lift Setting (psig)
Acceptable Band (psig)
% Difference Actual F013A 1167 1130 1096.1 - 1163.9 3.27%
F013J 1161 1120 1086.4 - 1153.6 3.66%
During SRV Main Stage assembly testing required by TS SR 4.4.2.3 at NWS Technologies it was identified that the R SRV main valve did not lift.
Technical Specification (TS) 3.4.2.1 requires that the safety function of at least 13 of 14 SRVs be operable with a specified code safety valve function lift setting, within a tolerance of +/- 3%. Action (a) of TS 3.4.2.1 specifies With the safety valve function of two or more of the above listed fourteen safety/relief valves inoperable, be in at least HOT SHUTDOWN within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and in COLD SHUTDOWN within the next 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. Therefore, this is a condition reportable under 10 CFR 50.73(a)(2)(i)(B).
CAUSE OF EVENT
Setpoint exceedance for two of the SRV pilot stage assemblies (A and J) is attributed to corrosion bonding between the pilot discs and seating surfaces, which is consistent with industry experience. This conclusion is based on previous cause evaluations, the second lift test being within the acceptable band and the repetitive nature of this condition at HCGS and within the BWR industry.
The cause of the R SRV Main failing to actuate is attributed to the main disc and piston thread wear, resulting in side-loading of the main piston within the guide. This allowed slight grooves to form in the guide in which the piston and rings could bind. This conclusion is based on a failure analysis performed at NWS Technologies.
SAFETY CONSEQUENCES AND IMPLICATIONS
There were no instances during operating cycle 23 that resulted in any of the fourteen SRVs being declared inoperable and there were no events during that cycle that required operation of the SRVs. The industry has recognized that corrosion bonding occurs during the operating cycle. Once an SRV lifts, the corrosion bond breaks and subsequent openings occur very close to the set point as demonstrated during testing. The deviations observed following H1RF23 testing of SRVs are bounded by margins which exist in current Hope Creek design analyses; thus, the aggregate effect of this condition has no safety significance.
The R SRV was installed in H1RF20 and without firm evidence of the time that the R SRV would not actuate, this LER assumes for a safety consequence review, that the R SRV was inoperable since it was installed in H1RF20. A review was performed of the additional SRVs that were inoperable in Cycle 21 (B, D, F, G, H, L, M, P - setpoint failures) and Cycle 22 (A, C, D, H, J, K-setpoint failures) and determined that the ASME overpressure protection and core thermal limits would not have been exceeded.
PREVIOUS EVENTS Similar events occurred during the 2016 (H1RF20) 2018 (H1RF21) and 2020 (H1RF22) Hope Creek refueling outages when multiple SRVs were found out of the TS required limits of +/- 3%. These events were reported as LER 354/2016-003-00, LER 354/2018-002-01 and LER 354/2019-002-00.
A three-year review was performed for other SRVs that failed to lift - no previous failures to lift were identified.
CORRECTIVE ACTIONS
1.
All seven 2-stage SRV assemblies were removed and replaced with pre-tested, certified 3-stage SRV assemblies (H1RF23).
2.
The R SRV was replaced with a 3-stage SRV model.
COMMITMENTS
There are no regulatory commitments contained in this LER.Page 3 of 3