ML20196B380
| ML20196B380 | |
| Person / Time | |
|---|---|
| Issue date: | 11/24/1998 |
| From: | Rossi C NRC OFFICE FOR ANALYSIS & EVALUATION OF OPERATIONAL DATA (AEOD) |
| To: | Gillespie F, Roe J, Shao L NRC (Affiliation Not Assigned), NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES) |
| Shared Package | |
| ML20196B356 | List: |
| References | |
| NUDOCS 9812010092 | |
| Download: ML20196B380 (4) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION f
l WASHINGTON, D.C. 20555 0001
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- ,o Novertxr 24,1998 MEMORANDUM TO:
Jack W. Roe, Acting Director, DRPM.NRR Frank P. Gillespie, DISP:NRR Lawrence C. Shao, Director, DET:RES Thomas L. King, Director, DST:RES John W. Craig, Director, DRA:RES l
Jack E. Rosenthal, Chief, B:SPD:AEOD
/*
g FROM:
Charles E. Rossi, OfiN!
Z Safety Programs Division Office for Analysis and Evaluation of Operational Data
SUBJECT:
REQUEST FOR REVIEW OF SPECIAL REPORT - GENERAL ELECTRIC REACTOR PROTECTION SYSTEM UNAVAILABILITY, 1984-1995 (DRAFT 2) l Attached for your information and review is the draft report on the General Electric reactor protection system (RPS) unavailability at U.S. commercial boiling water reactors. This study is part of our ongoing evaluation of the reliability of risk-significant safety systems. Using data l
obtained from licensee event reports and the Nuclear Plant Reliability Data System (NPRDS),
the study provides an estimate of the associated system unavailability based on actual and test demands between 1984 and 1995 and identifies dominant contributors to potential system unavailability. The report also includes a comparison with RPS reliability estimates published in l
probabilistic risk assessments (PRAs) and individual plant examinations (IPEs), and an evaluation of the most significant trends.
This is the first major evaluation of the reliability of the General Electric RPS 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 j
collection of common cause failure (CCF) data related to the RPS.
l l
CONTACT:
Hossein G. Hamzehee (HGH), RRAB:SPD:AEOD (301) 415-6228 l
1 4
9812010092 981124 DR TOPRP ENVGENE i
Multiple addressees 2
Major findings from this study are the following:
The mean unavailability of the General Electric RPS was estimated to be 3.8 x 104 The 4
lower 5* percentile and upper 95* percentile values are 7.5 x 10 and 1.1 x 10-5 respectively. There were no complete failures of the reactor protection system during the period of 1984 through 1995.
Essentially 100% of the RPS unavailability is from CCF events. The independent failures contribute less than 0.1%. CCFs of the hydraulic control units (HCUs) and backup scram solenoid operated valves (SOVs) contribute 50% to total system unavailability, channel relay and trip unit CCF events contribute 39%, control rod CCF events contribute 7%, and trip system relay CCFs contribute 4%. The requirement to test 10% of the control rods every four months was a significant factor in detecting CCF events before they became more significant by causing complete failures of larger numbers of redundant components.
i The backup scram portion of the RPS is an important contributor to the RPS reliability.
However, the backup scram SOVs are not safety-related equipment and, therefore, are not part of the NPRDS reportable scope. Their failure characteristics were assumed to be similar to the HCU SOVs. In addition, since there are not any surveillance test requirements for these backup SOVs, this study assumes that they are tested every refueling outage. (A sensitivity analysis without credit for the backup scram function 4
4 resulted in an increase from 3.8 x 10 to 4.6 x 10 for RPS unavailability).
The RPS mean unavailability estimates in IPEs range from approximately 1,7 x 104 to 8.6 x 10" However, most of the IPE studies referenced the NUREG-0460 RPS 5
unavailability of 3 x 10 RPS quantification models in IPEs are generally limited in scope.
The trends in time of RPS component failure probabilities and the number of CCF events are generally flat over the study period. There are no indications of performance degradation or improvement in these components over the period of 1984 through 1995.
We are specifically interested in your comments regarding:
The technical adequacy of the modeling and data analysis, The appropriateness of the findings and conclusions of the study, and How the information contained in the report can be presented in order to better help you in your regulatory activities.
It is our understanding that NRR will coordinate the review by and receipt of comments from the regions.
s Multiple Addressees 3
We intend to have a review meeting on Wednesday, January 6,1999, at 1:30pm in room T4B3 to discuss any comments or recommendations you might have before we issue the report.
Attachment:
As stated cc w/att:
C.W. Hehl, RGN-l J.T. Wiggins, RGN-l J.R. Johnson, RGN-il B.S. Mallett, RGN-II G.E. Grant, RGN-ill J.A. Grobe, RGN-Ill T.P. Gwynn, RGN-IV A.T. Howell, RGN-IV R. Zimmerman, NRR l
B. Sheron, NRR B. Boger, NRR G. Holahan, NRR l
G. Lainas, NRR L. Spessard, NRR l
E. Adensam, NRR '
Distribution w/att File Center JStolz, NRR GParry, NRR SCollins, NRR RRAB RF ARubin, RES LMarsh, NRR MMarkley, ACRS (15)
SPD RF MMayfield, RES JFlack, RES AThadani, RES l
TTMartin.
REmrit, RES MRubin, NRR FCongel MCunningham, RES AEl-Bassioni, NRR KRaglin NSiu, RES TOMartin, RES DHickman HVanderMolan, RES MKnapp, DEDE MDrouin, RES RSavio, ACRS JMitchell, OEDO DOCUMENT NAME: H:\\HGH\\GEDIST.WPD l
- See previous concurrence To receive a copy of this document Indicated in the box: "C"= Copy wo/attlenci "E"=Co n wlattlenct"N"=No cop f l
OFFICE RRAS/RRAB C
RRAS/RRAB C
RRAB C
SPD g
NAME HHamzehee*
SMays*
PBaranowsky*
CERo @ gef{
s DATE 11/10/98 11/10/98 11/10/98
// / 2.t)/98 OFFICIAL RECORD COPY 4
P
e Multiple Addressees 3
We intend to have a review meeting on Wednesday, January 6,1999, at 1:30pm in om T483 to discuss any comments or recommendations you might have before we issue th report.
1 i
j
Attachment:
As stated cc w/att:
F. Gillespie, NRR R. Zimmerman, NRR B. Sheron, NRR B. Boger, NRR G. Holahan, NRR G. Lainas, NRR L. Spessard, NRR E. Adensam, NRR Distribution w/att:
File Center JStolz, NRR GParry, NRR SCollins, NRR RRAB RF ARubin, RES LMarsh, NRR MKnapp, NMSS SPD RF MMayfield, RES JFlack, RES MMarkley, ACRS (15)
TTMartin REmrit, RES MRubin, NRR FCongel MCunningham, ES AEl-Bassioni, NRR KRaglin NSiu, RES TOMartin, RES DHickman HVanderMo n, RES DEDE MDrouin, RES RSavio, A RS JMitchell, OEDO 1
DOCUMENT NAME: H:\\
H\\GEDIST.WPD
- See prev us concurrence To receiv a copy of this document. Indicated in the box: "C"= Copy wo/attlenci "E"aCoay wlattlenct"N"=No copy OFF[CE RRAS/RRAB C
RRAS/RRAB C
RRAB C
SPD l
t)dME HHamzehee*/)Sg SMays$h PBaranowsky f-CERossi
[DATE 11/10/98 11/10/98 11/10/98
/
/98 OFFICIAL RECORD COPY l