NUREG/CR-4674, Forwards NUREG/CR-4674,Vols 9 & 10, 1988 Accident Sequence Precursor Rept. Rept Describes & Evaluates Significant Operational Events Reported by LERs for CY88. W/O Encl
| ML20055C387 | |
| Person / Time | |
|---|---|
| Issue date: | 02/27/1990 |
| From: | Jordan E NRC OFFICE FOR ANALYSIS & EVALUATION OF OPERATIONAL DATA (AEOD) |
| To: | Beckjord E, Murley T Office of Nuclear Reactor Regulation, NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES) |
| References | |
| RTR-NUREG-CR-4674 NUDOCS 9003080204 | |
| Download: ML20055C387 (2) | |
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IEB 27 890-MEMORANDUM FOR:
Thomas E. Murley, Director Office of Nuclear Reactor Regulation Eric S. Beckjord, Director Office of Nuclear Regulatory Research FROM:
Edward L. Jordan, Director Office for Analysis and Evaluation of Operational Data
SUBJECT:
1988 ASP ANNUAL REPORT Enclosed for your information and use is the 1988 Accident Sequence Precursor ti (ASP) report, NUREG/CR-4674, Vol. 9 and 10.
This report describes and
[
evaluates significant operational events reported by licensee event reports.
t (LERs) during the calendar year 1988.
For your information, our plans. call for the 1989 ASP annual report to be published and distributed by the end of August of this year.
l This report provides a-risk significance perspective of operational data reported by commercial nuclear power plants in the United States during the 1988 calendar year. The ASP Program evaluates' LERs of plant problems, equipment failures, or other operational incidents that are required to be reported by--
the operators of the nuclear plants.
The ASP Program identifies and evaluates operational occurrences that: involve portions of postulated core damage sequences.
The ASP Program uses-event tree i
models and probabilistic risk assessment techniques to put the data in:
perspective for evaluation. The event trees model plant equipment that could -
affect or be used to mitigate the event being evaluated. This allows-quantitative-estimates of the significance of the event or condition in terms of core damage likelihood.
The ASP evaluations described and shown in this report differ from-those of' previous ASP annual reports. The following differences need to be noted if the-data from this report is compared with prior ASP annual reports for " trending" precursor events:
(1) The event tree models have been changed somewhat from-prior reports.
These changes involve simplification of the event tree models and improved modeling of station blackout scenarios. -(2) The ASP Program L'
redirection in 1989 called for the ASP Program contractor,-0ak Ridge National Laboratory (ORNL), to concentrate the search for precursors among those LERs-
- l Contacts:
Frederick Manning h
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Peter Lam
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i 9003000204 900227 PDR NUREO
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Thomas E. Murley Eric S. Beckjord 1
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a determined to be significant by the Reactor Operations Analysis Branch, j
Division of Safety Programs. Prior to this redirection, ORNL independently reviewed all LERs for precursors. While the ASP-and Reactor Operations Analysis Branch screening and selection criteria are similar, they are not identical.
The precursor events provide and highlight significant portions of accident or l
incident sequences.
As such, they can increase our' understanding of nuclear -
l plants, and the margins provided by the assumptions we make regarding these-plants. The enclosed report indicates that four of the seven highest core damage probability precursors (i.e., precursors having estimated conditional-core damage probability greater than IE-4) involved common mode failures.
Additionally, our review also identifies the Zion event (LER 295/88-019) as-J one that involves potential common mode failures.
These events illustrate-l the importance of common mode failures and the need for continued vigilance in.
'7 the areas of maintenance, inspection, and testing.
Oii hl Signed.Ry:
G oi C. J. Hehmes, Jr.,
Edward L. Jordan,' irector Office for Analysis'and Evaluation
_of Operational Data
Enclosure:
As stated cc:
E. Rossi, NRR A. Thadani, NRR B. Sheron, RES Distribution:
PDR TNovak KBlack Central File VBenaroya MTaylor, EDO ROAB R/F CHeltemes PBaranowsky, NRR DSP R/F LSpessard HFaulkner, IP ACRS SRubin FManning GZech Plam KRaglin, TTC JRosenthal MWilliams
- (see previous concurrence)
OFC :ROAB *
- ROAB*
- ROAB *
- DSP *
- AE0D
- AE00 NAME :FManning
- Plam
- JRosental
- TNovak'-
- CHel es
- EJ an DATE$2/23/90sr
$2/23/90.
$2/23/90
$2/ 23/90
$2/W90
$ 2/L'y90 OFFICIAL RECORD COPY m
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