ML20217L001
| ML20217L001 | |
| Person / Time | |
|---|---|
| Issue date: | 04/29/1998 |
| From: | Rossi C NRC OFFICE FOR ANALYSIS & EVALUATION OF OPERATIONAL DATA (AEOD) |
| To: | Drake A WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP., WESTINGHOUSE OPERATING PLANTS OWNERS GROUP |
| Shared Package | |
| ML20217L006 | List: |
| References | |
| NUDOCS 9805040245 | |
| Download: ML20217L001 (4) | |
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April 29, 1998 Mr. Andrew Drake, Project Manager Westinghouse Ownets Group Westinghouse Electric Corporation Mail Stop ECE 5-16 P.O. Box 355 Pittsburgh, PA 15230-0355
SUBJECT:
REQUEST FOR REVIEW OF SPECIAL REPORT -WESTINGHOUSE i
i REACTOR PROTECTION SYSTEM UNAVAILABILITY,1984--1995 (DRAFT 2)
Dear Mr. Drake:
Attached for your information and review is the draft reliability report of the Westinghouse reactor protection system (RPS) at U.S. commercial pressurized-water reactors. This study is part of our ongoing evaluation of the reliability of risk-significant safety systems. Using data obtained from licensee event reports and the Nuclear Plant Reliability Data System, the study provides an estimate of the associated system unavailability (i.e., the probability the system will fail when demanded including maintenance unavailability) based on actual and test demands between 1984 through 1995 and idenhfies dominant contributors to potential system failure.
The report also includes a comparison with RPS reliability estimates published in probabilistic risk assessments and individual plant examinations (IPEs), and an evaluation of the most significant trends.
This is the first major evaluation of the RPS system by the NRC since the mid 1980s when NRC i
developed simple RPS logic models in support of the anticipated transient without scram rulemaking activities. A major contnbution of this current study is the collection of common-cause failure (CCF) data related to the RPS system.
Major findings from this study are the following:
The mean unavailability of the Westinghouse RPS system was estimated to e
be 1.3 x 104 for the Analog Series 7300 design and 1.1 x 10 for the Eagle-21 design.
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The associated 90 percent uncertainty intervals are about a factor of three around these
. values.
Approximately 95 percent of both RPS unavailabilities are from CCF events. The e
dominant CCF contributors are undervoltage drivers, bistables, analog process modules, solid state protection system universal cards, and mechanical portion of the f
reactor trip breakers. RPS train failures contribute about 60 percent to the total system
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unavailability, channel failures contribute about 30 percent, and reactor trip breakers and control rods each contribute about 5 percent. No complete system failures have j
occurred. No complete channel failures were identified during unplanned reactor trips.
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A. Drcke i RPS unavailability estimates from IPEs and other sources range from approximately e
4 1.0 x 10 to 1.0 x 104 In most of these other sources, the CCF of the reactor trip breakers was identified as a dominant contributor to RPS unavailability. In this study such events contribute about 5 percent to 6 percent.
Four of the 14 components (signal processing modules, bistables, temperature sensors / transmitters, and AT processing modules) had a statistically significant decreasing trend with time in total component failure probability. The other 10 components showed no indication of a trend over the study period.
In accordance with our peer review process prior to the finalization and distribution of this report, we want to provide you with the opportunity to review and comment on the draft report.
We are specifically interested in your comments regarding the technical adequacy of the modeling and data analysis and the appropriateness of the findings and conclusions of the study. To meet our planned publication schedule, we would appreciate receiving your comments within 60 days from receipt of this letter. We plan to perform similar analyses of the RPS for the other vendors. A copy of the draft report is being provided to them for information only.
As you may know, the Office for Analysis and Evaluation of Operational Data studies do not represent an official U.S. Nuclear Regulatory Commission position or the position of the responsible NRC program office. Our reports are one input to an ongoing review and evaluation process.
A copy of this draft report and letter are being placed in the Public Document Room at 2120 L Street NW, Washington, DC 20555.
If you have any questions related to this report, please contact Dr. Dale Rasmuson (301-415-7571) (e-mail: dmr@nrc. gov) of my staff.
Sincerely, Original signed by Charles E. Rossi. Director Safety Programs Division Office for Analysis and Evaluation of Operational Data l
Enclosure:
As stated cc w/ encl.: See attached list 1
Distribution w/o encl.: See attached list H:\\DMR\\RPS-WEST.WPD To receive a copy of this document,Indicata in the tion: "C" = Copy wo/sttacWencle "E" = Copy wfattachtencio *N" m 660 copy OFFICE RRAS/RRAB E
RRAS/RRAB C
RRAB C
SPD C___
NAME DRasmuson:nl*
SMays*
PBaranowsky*
CERo g g DATE 4/28/98 4/28/98 4/28/98 L/-/;t,P/98 OFFICIAL RECORD COPY
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RPS unavailability estimates from IPEs and other sources range from approximately 1.0 x 104 to 1.0 x 10d. In most of these other sources, the CCF of the reactor trip breakers was identified as a dominant contributor to RPS unavailability. In this study such events contribute about 5% to 6%.
Four of the 14 components (signal processing modules. bistables, tenyp'erature sensors / transmitters, and AT processing modules) had a statistically /significant decreasing trend with time in total component failure probability. The other 10 components showed no indication of a trend over the study pepo'd.
In accordance with our peer review process prior to the finalizatiop$nd distribution of this report, we want to provide you with the opportunity to review and comment on the draft report.
We are specifically interested in your comments regarding th echnical adequacy of the modeling and data analysis and the appropriateness of the dings and conclusions of the study. To meet our planned publication schedule, we wou appreciate receiving your comments within 60 days from receipt of this letter. W lan to perform similar analyses of the RPS for the other vendors. A copy of the draft report being provided to them for information i
only.
As you may know, the Office for Analysis and Ev luation of Operational Data studies do not represent an official U,S. Nuclear Regulatory pmmission position or the position of the responsible NRC program office. Our report are one input to an ongoing review and evaluation process.
A copy of this draft report and letter are eing placed in the Public Document Room at 2120 L Street NW, Washington, DC 20555.
If you have any questions related t this report, please contact Dr. Dale Rasmuson (301-415-7571)(e-mail: dmr@nr. gov) of my staff.
J Sincerely, Charles E. Rossi, Director Safety Programs Division Office for Analysis and Evaluation of Operational Data
/
Enclosure:
As stated cc:
J.J. Kelly,fB&W Owners Group Services Gordon,Bischoff, ABB Combustion Engineering Owners Group D. Townsend, G.E. Nuclear Energy Owners Group Distribution: /
RRAB RF SPD RF File Center Public DHickman JRosenthal TTMartin AThadani JMitchell DOCUMENT NAME: H:\\DMR\\RPS-WEST.WPD To recebe a copy of this document, Indicate in the box:"C" = Copy wo/ attach /encis E" = Copy w/ attach /encle "N" = No copy OFFICE RRAS/RRAB 6
RRAS/RRAB C RRAB
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SPD NAME DRasmuson:nif)Hk SMays h PBaranowsk[(/)CERossi
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DATE 4 / 2K /98 f /pt /98 f /M/98
/
/98 OFFICIAL RECORD COPY
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A. Drake cc w/ encl.:
Mr. J. J. Kelly, Manager B&W Owners Group Services Framstome Technologies, Inc.
P.O. Box 10935 Lynchburg, VA 24506-0935 Mr. Dennis Townsend G.E. Nuclear Energy Owners Group G.E. Nuclear Energy 175 Curtner Avenue M/C 187 San Jose, CA 95125 ABB Combustion Engineering Owners Group clo Gordon Bischoff, CEOG Project Manager M.S. 9615-1932 2000 Day Hill Road Windsor, CT 06095 Distnbution w/ encl.-
File Center Public j
l Distnbution w/o encl.
RRAB RF SPD RF DHickman JRosenthal TTMartin I
AThadani, DEDE JMitchell, OEDO l
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