The use of an efficient frontier in evaluating physical protection system designs

Recent discussions of metrics suitable for evaluating the proliferation resistance and physical protection of Generation IV nuclear energy systems (GenIV) included the concept of an efficient frontier.2 It was suggested that this metric might be the curve defined by a set of points {Ti, Ci} that characterize the times and costs associated with different, rational system design alternatives. This concept is similar to the idea of an efficient environment used in describing the relationship that exists between system performance and risk.3 An operating environment is said to be efficient when it is optimal in terms of throughput or output as a function of resource consumption and assumed risk. For any particular system there exists a set of environments—the efficient set—within which it can operate at maximum efficiency; risk will range from none to very high between the different environments. The risk efficiency principle suggests that system operators will be rational and risk averse, and thus they will only run a system in efficient environments. In the area of physical protection of nuclear facilities, one possible application of this concept would be as a performance metric where a threat agent (adversary) serves as the operator and the removal (theft) or release (sabotage) of nuclear or radiological material is the system output. An initial, brief inquiry into such an application is discussed below.