05000331/LER-1996-007, :on 961203,three MSRVs & One MSSV Failed to Meet TS Setpoints.Caused by Insufficient Tolerance Associated W/Relief Valve Setpoint Acceptance Criteria.Out of Tolerance MSRVs & MSSV Were Restored to within TS LSSS
| ML20141J425 | |
| Person / Time | |
|---|---|
| Site: | Duane Arnold  |
| Issue date: | 08/08/1997 |
| From: | Murrell R IES UTILITIES INC., (FORMERLY IOWA ELECTRIC LIGHT |
| To: | |
| Shared Package | |
| ML20141J420 | List:
|
| References | |
| LER-96-007, LER-96-7, NUDOCS 9708200048 | |
| Download: ML20141J425 (4) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2) |
| 3311996007R00 - NRC Website | |
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On November 27,1996, as found testing was completed at Wyle Labs for the Main Steam Relief Valves (MSRVs)and Main Steam Safety Valves (MSSVs) removed during Refueling Outage 14. The test results were reviewed and documented at the DAEC on December 3,1996. Four of the eight valves failed to meet the setpoint requirements of the Technical Specincation Limiting Safety System Setting. The cause of the event was an insufHcient tolerance associated with the relief valve setpoint acceptance criteria.
The out of tolerance MSRVs and the MSSV were restored to within their Technical Specification (TS)
Limiting Safety System Settings. Improvements previously made to the setpoint test methodology for the MSSVs will be evaluated for effectiveness. The overall system's relief valve function was not impacted by the as found condition. Therefore, the actual and potential safety consequences associated with this condition was minimal.
This event is being reported as a Common Cause Failure pursuant to 10CFR50.73(a)(2)(vii).
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l. DESCRIPTION OF EVENT
On November 27,1996, as found testing was completed at Wyle Labs for the hiain Steam itelief Valves (htSRVs) and hiain Steam Safety Valves (MSSVs) removed during Refueling Outage 14. Four of the eight valves Adled to meet the setpoint requirements of the Technical Specification Limiting Safety System Setting. The plant was in mode 1 operating at 85% power at the time the test results were received.
l At the time of notification of the test results, the out of tolerance h1SRVs and MSSV had aheady been restored to within their Technical Specification Limiting Safety System Settings when the MSSVs and the pilot valves fbr the MSRVs were replaced with pre set spares during Refueling Outage (RFO) 14.
Technical Specification (TS) 4.6.D.! requires once per operating cycle, at least one safety valve and three relief valves shall be removed, set pressure tested and reinstalled or replaced with spares that have been previously set pressure tested. The safety and relief valves shall be rotated, at least once per 40 months, such that both safety and 6 relief valves are removed, set pressure tested and reinstalled or replaced with spares.
Any spare that is installed must have been set pressure tested within the previous 40 months. The setpoint of the safety valves shall be as specified in Specification 2.2 (il%).
Results of as fbund testing fbr the valves removed during RFO-14 completed on November 27,1996, indicated that three htSRVs and one h1SSV failed. The specific component iD numbers were htSRVs PSV4402, PSV4406 and PSV4407 and MSSV PSV4404. Test results for the remaining MSRVs and h1SSV were satisfactory. The following is a summary of the as fbund test results:
Valve lD Specified Pass / Fail As found
% out of Setpoint Setpoint Setpoint spec PSV4400 1130 11 Pass 1123
- - 0.6%
PSV4401 1120 + 11 Pass 1130 40.9%
PSV4402 1130i i1 Fail 1152
+1.9%
PSV4403 1240
- 12 Pass 1232
- - 0.6%
PSV4404 1240
- 12 Fail 1261
+1.7%
PSV4405 1140
- 11 Pass 1140 0.0%
PSV4406 1140
- 11 Fail 1173
+2.9%
PSV4407 1110
- 11 Fail 1138
+2.5%
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II. CAUSE OF EVENT
l The cause of the test failures was insullicient setpoint tolerances. DAEC trending data indicates these valves to be performing acceptably within an expanded setpoint tolerance (average drin of +1.03%),
which is within the 13% nominal value of an industry initiative to expand the tolerances as described in 1.icensing Topleal Report NEDC 31753P. "IlWROG In Service Pressum Relief Technical Specification Revision 1.icensing Topical Report".
lit. ANALYSIS OF EVENT:
Cycle reload analysis (GENE 24A5171) for over pressurization protection for the previous cycle was perfonned with a tolerance of +3%. None of the as found setpoints exceeded the +3%, therefore, this condition was bounded by this analysis and the vessel over pressure function would have perfonned within analyzed limits. The as found condition ofindividual valves exceeded specified tolerances, but the overall system perninnance ensured design margin to vessel over pressurization limits was maintained.
There were no other structures, systems, or components inoperable at the time of discovery that contributed to the event.
IV. CORRECTIVE ACTIONS
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The MSSVs and the MSRV pilot valves were replaced with valves that were previously set pressure tested. Prior to this event, the setpoint test methodology had been improved to account for differences.
between the MSSVs' installed ambient conditions and the test conditions. The effectiveness of that corrective action in reducing the setpoint drin will be reviewed after receipt of the RFO 15 test results.
This action will be completed by July 31,1998.
Expanded setpoint tolerances (+1, -3%) were requested in the DAEC Improved Standard TS submittal in a letter dated October 30,1996 (NG 96 2322). Additional analyses, which are required to further expand the tolerances to the full range of13%, are being considered.
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A. Ells System and Component Codes:
hiain Steam: Sil l
llelief Valve: RV II. hianufacturer and hiodel Number:
MSl(Vs Target Rock, model number 7467F h1SSVs Dresser, model number 3700
C. Previous Similar Events
A review of LERs at DAEC dating back to 1984 did not reveal any previously reported similar events.
This event was initially reported as a voluntary LER. Aller additional review ofindustry reporting practices, it is being repo:1ed as a Common cause Failure pursuant to 10CFR50.73(a)(2)(vil).