ML17059A376
| ML17059A376 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  |
| Issue date: | 07/25/1994 |
| From: | Abbott R NIAGARA MOHAWK POWER CORP. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NMP1L-0839, NMP1L-839, NUDOCS 9408030272 | |
| Download: ML17059A376 (6) | |
Text
REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)
ACCESSION NBR:9408030272 DOC.DATE: 94/07/25 NOTARIZED: NO DOCKET g
FACIL:50-220 Nine Mile Point Nuclear Station, Unit 1, Niagara Powe 05000220 AUTH.NAME AUTHOR AFFILIATION ABBOTT,R.B.
Niagara Mohawk Power Corp.
RECIP.NAME RECXPIENT AFFXLXATION Document Control Branch (Document Control Desk)
SUBJECT:
Special rept:on 940710,re inoperability of Ill containment hydrogen monitoring unit. Caused by air regulator for valve operator set at 73 psig air pressure. Regulator reset to 29 Ps'lg DISTRIBUTION CODE:
IE22D COPXES RECEIVED:LTR ENCL 5 SXZE:
TITLE: 50.73/50.9 Licensee Event Report (LER),
ncident Rpt, etc.
NOTES:
RECXPIENT ID CODE/NAME PD1-1 PD INTERNAL: ACRS AEOD/ROAB/DSP NRR/DE/EMEB NRR/DRCH/HHFB NRR/DRCH/HOLB NRR/DSSA/SPLB NRR/PMAS/IRCB-E RES/DSXR/EIB EXTERNAL EG&G BRYCE g J
COPXES LTTR ENCL RECIPIENT ID CODE/NAME BRINKMAN,D.
AEOD/DSP/TPAB NRR/DE/EELB NRR/DORS/OEAB NRR/DRCH/HICB NRR/DRSS/PRPB
/J3SSA/SRXB REG FIL~
02 RGN1 FILE 01 L ST LOBBY WARD NSIC MURPHY,G.A NUDOCS FULL TXT COPIES LTTR ENCL NOTE TO ALL"RIDS" RECIPIENTS:
PLEASE HELP US TO REDUCE KVASTE!CONTACTTHE DOCUMENTCONTROL DESK, ROOM Pl-37 (EXT. 504-2083 ) TO ELIh!!NATE YOUR VAMEFROM DISTRIBUTIONLISTS FOR DOCUMENTS YOU DON'T NEED!
TOTAL NUMBER OF COPIES REQUIRED:
LTTR 27 ENCL
V NIAGAR U MOHAWK NINE MILEPOINT NUCLEARSTATION/P.O. BOX 63. LYCOMING,NEW YORK 13093/TELEPHONE (315) 343-2110 Richard D. Abbott Plant Manat,cr - Unit EI (315) 349-1812 (315) 3494417 (PAX)
July 25, 1994 NMP1L 0839 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555 RE:
Nine Mile Point Unit 1 Docket No. 50-220 DPR- "
Subject:
Special Report Gentlemen:
In accordance with Nine Mile Point Unit 1 (NMP1) Technical Specification Table 3.6.11-1, "Accident Monitoring Instrumentation," Action Statement 4.a, Niagara Mohawk Power Corporation is submitting the following Special Report concerning the inoperability of the
¹11 Containment Hydrogen Monitoring Unit (HMS).
De cri 'vent On July 10, 1994 at 0930 hours0.0108 days <br />0.258 hours <br />0.00154 weeks <br />3.53865e-4 months <br />, with the reactor mode switch in the "RUN" position and the plant operating at approximately 100 percent of rated thermal power, the ¹11 HMS was removed from service.
During the performance of procedure Nl-ST-Q5, "Primary Containment Isolation Valve Operability Test," on a group of eight primary containment isolation valves on the ¹11 containment monitoring system, the "open to close" time of one of these valves, i.e., valve 201.7-03, as measured in the control room, was 8.9 seconds.
The Inservice Test (IST) limitis ~ 8.5 seconds and the Technical Specification limitis ~60
- seconds, Procedure Nl-S P-Q5 requires tkat a 1 eioht valves be declared inoperabl ifany one of them exceeds the IST limit. Alleight of these valves are controlled by one switch.
At 0930 hours0.0108 days <br />0.258 hours <br />0.00154 weeks <br />3.53865e-4 months <br /> on July 10, 1994, valve 201.7-03 was declared inoperable and closed, as were the seven other primary containment isolation valves, and, consequently ¹11 HMS was also declared inoperable and removed from service.
Number 12 HMS remained in service.
Cause Event Troubleshooting was performed that included the following steps:
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The limitswitches were inspected for signs of sticking or degradation, and none was found.
'tI4080>0-7 ttt4072'5 PDR ADOCK 0 9
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Page 2
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Testing was done to determine ifthe solenoid operated air pilot valves were degraded.
Minor leakage was found, but this was not the cause of the slow stroke time.
The valve actuator was disassembled and inspected for signs of degradation, and none was found.
The valve actuator was reassembled and the valve manually restroked and found to move freely.
However, the air regulator for the valve operator was found to be set at 73 psig air pressure.
This was reset to 29 psig, the correct value, and the valve was found to stroke at 60% open.
The 60% open was determined to be acceptable because this provided more than the required flow for the ¹11 HMS to be operable.
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After troubleshooting, valve 201.7-03 successfully passed its 10 CFR 50 Appendix J local leak rate test and its IST stroke timing test.
None of these troubleshooting steps provided insight into the cause of the failed IST stroke time test.
Corrective Action After successfully restroking and retiming valve 201.7-03, the valve was declared operable and opened, along with the seven other primary containment isolation valves.
Number 11 HMS was started, tested using procedure Nl-ISP-201-020, "Containment H, Atmosphere Monitoring System Functional Verification," and was returned to service at 1048 hours0.0121 days <br />0.291 hours <br />0.00173 weeks <br />3.98764e-4 months <br /> on July 15, 1994.
Because the root cause of the slow stroke time could not be determined by this troubleshooting, and because this valve has failed its IST stroke time testing before (on May 10, 1994; reference Special Report NMP1L 0818, dated May 24, 1994), valve 201.7-03 willremain on an increased stroke time testing frequency of once per month for at least three months, and its operation willbe observed locally. Additional testing willbe performed, by September 30, 1994, which willinclude an actuator benchset.
This testing willisolate the timing problem to the valve/packing assembly or the actuator assembly, and willprovide insight on the valve's stroke limitation. Corrective actions willthen be taken, as appropriate, to resolve any identified problems.
Very truly yours, g8Ci~
R. B. Abbott Plant Manager - NMP1 RBA/JTP/ksj xc:
Mr. Thomas T. Martin, Regional Administrator, Region I Mr. Barry S. Norris, Senior Resident Inspector
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