Risk methodologies for offsite hazardous materials

A number of suggestions have been advanced in recent years concerning the risks posed to nuclear power plants by offsite hazardous materials relative to (1) the regulatory approach including considerations of minimum and safe standoff distances, exclusion distances, site acceptance ceilings and floors, screening distances and screening probabilities, plant design, etc., and (2) the analysis and evaluation procedures such as material screening criteria, plant vulnerability, standarized physical models, etc. An evaluation of current analyses and approaches indicates that this complex problem, variety of approaches, and safety concerns may be better accommodated by developing criteria and treatments along the lines of a so-called conditional risk approach. Specifically, the probability (P) of some ultimate consequence (C) occurring from an accident (A) involving hazardous materials is given as P(C) = P(C/A) x P(A). Assuming that the plant to accident site standoff distance is the fundamental independent variable of the risk methodology, certain conditional risk designations and conditions can be made and are presented