ML17331A278
| ML17331A278 | |
| Person / Time | |
|---|---|
| Site: | Cook  |
| Issue date: | 04/12/1993 |
| From: | Fitzpatrick E INDIANA MICHIGAN POWER CO. (FORMERLY INDIANA & MICHIG |
| To: | Murley T NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| AEP:NRC:1170E, NUDOCS 9304190199 | |
| Download: ML17331A278 (4) | |
Text
A.CCELERA"I'ED DOCUMENT DlSTRLSUTlON SYSTEM REGULATC INFORMATION DISTRIBUTION+STEM (RIDE) rrP ACC'ESSION NSR:9304190199 DOC.DATE: 93/04/12 NOTARIZED: NO DOCKET FACIL:50-315 Donald C.
Cook Nuclear Power Plant, Unit 1, Indiana M
05000315 50-316 Donald C.
Cook Nuclear Power Plant, Unit 2, Indiana M
05000316 AUTH.NAME AUTHOR AFFILIATION FITZPATRICK,E.
Indiana Michigan Power Co. (formerly Indiana a Michigan Ele RECIP.NAME RECIPIENT AFFILIATION Document Control Branch (Document Control Desk)
SUBJECT:
Provides description of findings during that outage as well 1992 Unit 1 refueling outage.
DISTRIBUTION CODE:
A001D COPIES RECEIVED:LTR ENCL 'IZE:
TITLE: OR Submittal: General Distribution NOTES:
RECIPIENT ID CODE/NAME PD3-1 LA DEANFW COPIES LTTR ENCL RECIPIENT ID CODE/NAME PD3-1 PD COPIES LTTR ENCL INTERNAL: NRR/DE/EELB NRR/DRCH/HICB NRR/DSSA/SPLB NUDOCS-ABSTRACT OGC/HDS2 EXTERNAL: NRC PDR NRR/DORS/OTSB NRR/DSSA/SCSB NRR/DSSA/SRXB OC/j FMB REG FICE Ol NSIC 1
1 1
1 1
NOTE TO ALL"RIDS" RECIPIENTS:
PLEASE HELP US TO REDUCE WASTE! CONTACT TIIE DOCUMENI'ONTROL DI SI',
ROOM Pl-37 (EXT. 504-2065) TO ELIMINATEYOUR NAME FROM DISCI'RIDUT)ON LISTS FOR DOCUMENTS YOU DON'T NEED!
TOTAL NUMBER OF COPIES REQUIRED:
LTTR 16 ENCL
Indiana Michigan Power Company P.O. Box 16631 Coiumbus, OH 43216 AEP:NRC:1170E Donald C. Cook Nuclear Plant Units 1 and 2
Docket Nos.
50-315 and 50-316 License Nos.
DPR-58 and DPR-74 PRESSURIZER SAFETY VALVE POSITION INDICATOR ACOUSTIC MONITORING SYSTEM ROOT CAUSE ANALYSIS AND DESIGN REVIEW RESULTS U. S. Nuclear Regulatory Commission Document Control Desk Washington, D.C.
20555 Attn:
T. E. Murley April 12, 1993
Dear Dr. Murley:
Zn the safety evaluation report (SER) issued by the NRC staff as Amendment No.
161 to the facility operating li.cense for the Donald C.
Cook Nuclear Plant Uni.t 1, it was noted that we would be performing a detailed root cause analysis and desi.gn review of the pressurizer safety valve position indicator acoustic monitoring system (or acoustic valve monitoring system@
AVMS)g during the February 1992 Uni.t 2 refueling outage.
Contai.ned in this letter is a description of our findings during that outage as well as the 1992 Uni.t 1 refueling outage.
The root cause of our recent AVMS difficulties is the method of the monthly surveillance test.
The test (channel check) relies on the detection of low level vibrations by a monitoring system which is designed to detect flow-induced vibrations of orders of magnitude higher than the vibrations present during normal plant operation.
Normal background vibration levels in the vicinity of the AVMS accelerometers are typically at or below the system's detection threshold.
If a background signal i.s not observed on an AVMS channel during the monthly channel check, that channel is declared i.noperable.
This leads to AVMS channels being declared inoperable although it is likely that the channels would perform their intended function should a pressurizer safety valve open.
To improve channel
- checks, an investigation is currently bei.ng performed to determine the feasibility,
- scope, and installation schedule of a new channel check test circuit.
The system currently under consideration involves placement of one or more oscillators'ear the AVMS sensors.
This test circuit is still under development by the equipment vendor and is not immediately available.
Other solutions, including one in which the AVMS is replaced with a system that would provide direct pressurizer safety valve position indication, are also being evaluated.
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Dr. T. E. Murley AEP:NRC:1170E As an interim measure, we have modified the surveillance test procedure to cycle a block valve for the power operated relief valves (PORV) if necessary, as this event produces a low level noise or vibration in proximity to the AVMS accelerometers that is somewhat higher than normal background vibration.
In addition to the low background signal detection
- problems, the Unit 2 pressurizer safety valve acoustic monitor 2-QR-107C had spurious alarms.
The spurious alarms were caused by the combination of a loose signal cable and a charge converte'r (amplifier) found performing outside the vendor specification.
To correct the loose
- cable, lock wire is being used to secure the cable to the accelerometer and insulation was ad)usted to reduce interference with the accelerometers and cabling.
The charge converter in this circuit had been in service for five years.
The charge converter had passed operational tests during the previous outages and was within the specified replacement frequency.
As a conservative measure, all AVMS charge converters in both units were replaced.
In previous correspondence (letter number AEP:NRC:1170D, dated August 12, 1992),
we have requested changes to the Cook Nuclear Plant Technical. Specifications (T/Ss) which would permit continued operation with any two of the three AVMS channels operable.
Any one of the existing three AVMS channels is capable of detecting the open position of any of the three pressurizer safety valves (i.e.,
if one pressurizer safety valve opens, all three AVMS channels will indicate valve opening in the control room).
Operator response to an open pressurizer safety valve does not require the operator to know which valve or how many valves are open.
The proposed T/S
- changes, therefore, would improve plant availability, through decreased vulnerability to a
single AVMS channel failure or malfunction, without compromising safety.
In light of the above,,we request expedited approval of the T/S change request submitted to the NRC Staff in our letter AEP:NRC:1170D.
Approval of the T/S change request would provide a reduction in the monthly risk of shutdown.
Sincerely, E'E'.
E. Fit patrick Vice President dr cc:
A. A. Blind Bridgman J.
R. Padgett G. Charnoff NFEM Section Chief A. B. Davis Region III NRC Resident Inspector Bridgman