BWR severe accident sequence analyses at ORNL - some lessons learned Page: 2 of 13
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BWR SEVERE ACCIDENT SEQUENCE ANALYSES AT ORNL
- SOME LESSONS LEARNED*
S. A. Hodge
SASA Project Manager
Oak Ridge National Laboratory
The Severe Accident Sequence Analysis (SASA) Program was estab-
lished in October 1980 by the Division of Accident Evaluation of the
Office of Nuclear Regulatory Research, U.S. Nuclear Regulatory Com-
mission (NRC) to study the possible effects of potential nuclear power
plant accidents. Under the auspices of the program, boiling water
reactor (BWR) studies are being conducted at the Oak Ridge National
Laboratory (ORNL) using Browns Ferry Unit 1 as the model plant. As-
sistance and complete cooperation is provided by the plant owners and
operators, the Tennessee Valley Authority (TVA).
The function of the SASA program at ORNL is to conduct detailed
analyses of the dominant (most probable) BWR accident sequences, which
have been identified by probabilistic risk assessments (PRAs). The SASA
studies complement the PRA studies, which use fault-tree and event-tree
analytical methods to identify the candidate dominant sequences in an
effort to consider all possible accident sequences that might occur at a
particular plant. The SASA study objectives include determination of
the sequence of events and the magnitude and timing of the associated
fission product releases; the results of this more detailed study can
subsequently be fed hack into an improved PRA.
Experience has shown that both PRA and SASA studies must be plant-
specific to induce confidence in the applicability of the results. It
has been generally accepted that separate studies are required to cover
the broad plant classifications such as the differing PWR designs fur-
nished by the yarious yendors and for the three basic BWR containment
concepts. Beyond this, the PRA and SASA studies show that relatively
small differences in plant design can have a large effect on the acci-
dent progression and its. consequences; some examples for the BWR design
are given in this, paper.
All ORNL studies to date have concerned Unit 1 of the Browns Ferry
Nuclear Plant, a BWR-4 with MK-1 containment design, which is typical of
Research sponsored by the U.S. Nuclear Regulatory Commission
Office of Nuclear Regulatory Research under Interagency Agreements
DOE 40-551-75 and 4Q-552-75 with the U.S. Department of Energy under
contract W.-.7405-eng-26 with the Union Carbide Corporation.
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Hodge, S.A. BWR severe accident sequence analyses at ORNL - some lessons learned, article, January 1, 1983; Tennessee. (https://digital.library.unt.edu/ark:/67531/metadc1071248/m1/2/: accessed April 25, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.