NUREG-1537, Part 2 - NRC

13 ACCIDENT ANALYSES
Other chapters of the SAR should contain discussions and analyses of the reactor
facility as designed for normal operation. The discussions should include the
considerations necessary to ensure safe operation and shutdown of the reactor to
avoid undue risk to the health and safety of the public, the workers, and the
environment. -The analyses should include limits for operating ranges and reactor
parameters within which safety could be ensured. The bases for the technical
specifications should be developed in those chapters.
In this chapter the applicant should present a methodology for reviewing the
systems and operating characteristics of the reactor facility that could affect its safe
operation or shutdown. The methodology should be used to identify limiting
accidents, analyze the evolution of the scenarios, and evaluate the consequences.
The analyses should start with the assumed initiating event. The effects on
designed barriers, protective systems, operator responses, and mitigating features
should be examined. The endpoint should be a stable reactor., The potential
radiological consequences to the public, the facility staff, and the environment
should be analyzed. The information and analyses should show that facility system
designs, safety limits, limiting safety system settings, and limiting conditions for.;
operation'were selected to ensure thatfthe consequences of analyzed accidents do
not exceed acceptable limits. -
The applicant should also'discuss and analyze postulated accident scenario
whose potential consequences are shown to exceed and bound all credible
accidents. For non-power reactors, this accident is called the maximum
hypothetical accident (MHA). Because the accident of greatest consequence at a
non-power reactor would probably include the release of fission products, the
MHA, in most cases, would be expected to contain such a scenario involving fuel
or a fueled experiment and need not be entirely credible. The review and
evaluation should concentrate on the evolution of the scenario and analyses of the
consequences, rather than on the details of the assumed initiating event.
Because"the consequences of the postulated MHA lhould exceed those of any.
credible accident at the facility, the accident is not likely to occur during the life of
the facility. The MHA is used to demonstrate that the maxinum consequences of
operating'the reactor at a specific site are ithin acceptable limits. The applicant
may choose to perform sensitivity analysis of the assumptions of the MHA. For
example, reactor operating time before accident initiation mnay be examined to
determine the change in MHA outcome if a more realistic assumption is made.
Assumptions made in the accident analysis may form the basis for technical
specification limits on the operation of the facility For example, if the accident
analysis assumes that the reactor operates for 5 hours a day, 5 days a week, this
may become a limiting condition for operation.
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