Information Notice No. 90-74: Information on Precursors to Severe Accidents
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555
December 4, 1990
Information Notice No. 90-74: INFORMATION ON PRECURSORS TO
SEVERE ACCIDENTS
Addressees:
All holders of operating licenses or construction permits for nuclear power
reactors.
Purpose:
This information notice is intended to alert addressees to the existence of
reports that examine events that have occurred at commercial nuclear power
plants and that quantify how close these events were to causing severe core
damage. This information notice does not contain NRC requirements;
therefore, no specific action or written response is required.
Discussion:
The Office for Analysis and Evaluation of Operational Data and its
consultants at the Oak Ridge National Laboratory have published a series of
accident sequence precursor study reports ("Precursors to Potential Severe
Core Damage Accidents: [year] A Status Report"). The studies reviewed
licensee event reports (LERs), for the period from January 1969 through
December 1989, to identify and categorize precursor events to potential
severe core damage accidents. Accident sequences considered in these
studies were those associated with the failure of one or more safety
systems, the degradation of two or more safety systems, or the occurrence of
an initiator; such as loss-of-offsite power, loss of coolant accident, steam
line break, or a transient with complications. When coupled with one or
more other postulated events, precursor events may result in a plant
condition in which core cooling is inadequate. Study of accident precursors
has indicated that the causes of the most safety significant events are
essentially the same as those of minor events and can reveal areas of a
plant's design, procedures, or operation that potentially could contribute
to a severe core damage accident. The accident sequence precursor study
reports estimate the conditional probability of core damage, given the
occurrence of precursor events.
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IN 90-74
December 4, 1990
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The accident sequence precursor study reports may be obtained from the
Superintendent of Documents, U.S. Government Printing Office, P.O. Box
37082, Washington, D.C. 20013-7082. The following reports are available:
Year(s) Document Number
1969 to 1979 (NUREG/CR-2497, vol. 1 and 2)
1980 to 1981 (NUREG/CR-3591, vol. 1 and 2)
1984 (NUREG/CR-4674, vol. 3 and 4)
1985 (NUREG/CR-4674, vol. 1 and 2)
1986 (NUREG/CR-4674, vol. 5 and 6)
1987 (NUREG/CR-4674, vol. 7 and 8)
1988 (NUREG/CR-4674, vol. 9 and 10)
1989 (NUREG/CR-4674, vol. 11 and 12)
This information notice requires no specific action or written response. If
you have any questions about the information in this notice, please contact
one of the technical contacts listed below or the appropriate NRR project
manager.
Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical Contacts: Adel El-Bassioni, NRR
(301) 492-1094
Fred Manning, AEOD
(301) 492-4426
Attachment: List of Recently Issued NRC Information Notices
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