ML20217K998
| ML20217K998 | |
| Person / Time | |
|---|---|
| Issue date: | 04/29/1998 |
| From: | Rossi C NRC OFFICE FOR ANALYSIS & EVALUATION OF OPERATIONAL DATA (AEOD) |
| To: | Hastie W INSTITUTE OF NUCLEAR POWER OPERATIONS |
| References | |
| NUDOCS 9805040244 | |
| Download: ML20217K998 (4) | |
Text
i ..
,f f '%y A= y k UNITED STATES
!* { NUCLEAR REGULATORY COMMISSION
- WASHINGTON. D.C. 2055H001 u...l April 29, 1998 Mr. William J. Hastie j i
Institute of Nuclear Power Operations -
700 Galleria Parkway i Atlanta, GA 30339-5957 !
SUBJECT:
REQUEST FOR REVIEW OF SPECIAL REPORT- WESTINGHOUSE REACTOR PROTECTION SYSTEM UNAVAILABILITY,1984-1995 (DRAFT 2)
Dear Mr. Hastie:
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 licencee 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 identifies 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. l This is the first major evaluation of the RPS system by the NRC since the mid 1980s when NRC developed simple RPS logic models in support of the anticipated transient without scram )
rulemaking activities. A major contribution 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:
e' .The mean unavailability of the Westinghouse RPS system was estimated to be 1.3 x 10-5 for the Analog Series 7300 design and 1.1 x 10-5 for the Eagle-21 design.
The associated 90 percent uncertainty intervals are about a factor of three around these
[
M, I values.
e Approximately 95 percent of both RPS unavailabilities are from CCF events. The dominant CCF contributors are undervoltage drivers, bistables, analog process
[h modules, solid state protection system universal cards, and mechanical portion of the reactor trip breakers. RPS train failures contributa about 60 percent to the total system !
unavailability, channel failures contribute about 30 percent, and reactor trip breakers and control rods each contribute'about 5 percent.' No complete system failuies have occurred. No complete channel failures were identified during unplanned reactor trips. _ ;
O :
C i
& - l() 4 l'
- NRC HU CENTFa s.7upy; 9905040244 990429 PDR TOPRP EMVWEST C POR y h;~ he~~ [ LAlf b_ l pm
, J
W. Hastia p o RPS unavailability estimates from IS.Es 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 percent to 6 percent, e 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 indicaiion 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 45 days from receipt of this letter.
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 repor1, please feel free to 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
Enclosure:
As stated
(
Distribution w/ encl.: Distribution w/o encl.:
File Center RRAB R/F DHickman TTMartin JMitchell, OEDO Public SPD R/F JRosenthal AThadani, DEDE Identical letters sent to: See attached list H:\DMR\RPS-OUT.REV
- See previous concurrence To receive a copy of this document, indicate in the box:"C" = Copy wo/ attach /encls "E" = Copy w/ attach /encls "N" = No copy OFFICE RRAS/RRAB E RRAS/RRAB C RRAB C SPD 6-'
NAME DRasmuson* SMays* PBaranowsky" CERosgC;;j s
DATE 4/28/98 4/28/98 4/28/98 y'12 fl98 OFFICIAL RECORD COPY
)
Mr. William J. Hastie
e 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% /
e Four of the 14 components (signal processing modules, bistables, temperature / i sensors / transmitters, and AT processing modules) had a statistically significant decreasingt[end 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 thi eport, we want j to provide you with the opportunity to review and comment on the craft report. We ar specifically interested in your comments regarding the technical adequacy of the modeling and ata analysis and the appropriateness of the findings and conclusions of the study. To meet our plann publication schedule, we would appreciate receiving your comments within 45 days from receipt of t s letter, j As you may know, the Office for Analysis and Evaluation of Operational D a studies do not represent an official U.S. Nuclear Regulatory Commission position or the position of e responsible NRC program office. Our reports are one input to an ongoing review and evaluatio rocess.
A copy of this draft report and letter are being placed in the Publi Document Room at 2120 L Street NW, Washington, DC 20555.
If you have any questions related to this report, please fee ree to contact Dr. Dale Rasmuson (301-415-7571)(e-mail: dmr@nre gov) of my staff.
Sincerely, Charles E. Rossi, Director Safety Programs Division Office for Analysis and Evaluation of Operational Data
Enclosure:
As stated identical letters sent to:
Mr. Ralph E. Beedle Mr. V.K. Chexal. Director Nuclear Energy Institute Nuclear Safety Analysis Center 17761 Street NW, Suite 400 Electric Power Research Institute ;
Wathington, DC 20006-3708 P.O. Box 10412 Palo Alto, CA 94303 Mr. David A. Lochbaum Nuclear Safety Engineer Union of Concerned S ntists
.1616 P Street N.W., ite 310
~ Washington, DC 2 36-1495 Distribution:
RRAB RF SPD RF File Center Public DHickman JRosenthal TTMartin AThadani JMitchell DOCUt NT NAME: H:\DMR\LOSP-OUT.WPD To ceive a copy of ihls da unt, indicate in the box:"C" = Copy wo/ attach /encls "E" = Ccoy w/ attach /encls *N" = No c y I
OFFICE RRAS/RRAB 6 RRAS/RRAB (, RRAB { SPD NAME SMays ' 'AV) CERossi DRasmuson d PBaranows[d.
DATE l 4 / 73 /98 4 / pg /98 y 21798 / /98 OFFICIAL RECORD COPY l
J
i Letter dated 4 / 1 /08
SUBJECT:
REQUEST FOR REVIEW OF SF'ECIAL REPORT - WESTINGHOUSE REACTOR PROTECTION SYSTEM UNAVAILABILITY, 1984-1995 (DRAFT 2)
Identicalletters sent to:
Mr. Ralph E. Beedle
. Nuclear Energy institute 1776 i Street NW, Suite 400 Washington, DC 20006-3708 Mr. V. K. Chexal, Director Nuclear Safety Analysis Center Electric Power Research Institute P.O. Box 10412 Palo Alto, CA 94303 Mr. David A. Lochbaum Nuclear Safety Engineer '
Union of Concerned Scientists 1616 P Street NW, Suite 310 Washington, DC 20036-1495 i
\