Some thoughts on allocation of reliability

The technical feasibility of allocating reliability to reactor systems, subsystems, components, and structures is discussed in this paper. The basic premise for this analysis is that a set of objective functions or safety variables has been defined on a global basis for a class of nuclear power plants. The decision variables, which represent the system, subsystem, component, and structural reliabilities are related to the global objective functions by a risk model obtained from an existing plant-specific probabilistic risk assessment (PRA). A multiobjective optimization technique is employed to obtain the set of decision variables which optimize (minimize) all of the objective functions. A cost function is introduced (and incorporated in the optimization scheme) which measures the cost of increasing reliability. Illustrative calculations were performed for a BWR with an existing PRA. (orig./HP)