Assessing aircraft hazards to nuclear facilities

The methodology and selected models used for assessing the frequency of aircraft crashes to critical surface facilities are examined. The DOE Standard model is the basis for comparing other models, particularly those used to assess risk to DOE facilities. The NRC methodology is relevant for nuclear power plants. A rigorous physical model that describes the Markov chain of events and their related probabilities that lead to aircraft hazards to ground facilities is developed. The chain of events is then quantified to provide a basis for comparison and evaluation of mathematical models. The model has a form similar to the standard transport equation for a particle at a given position in space moving with a given velocity under the influence of various force fields, e.g., engine thrust, drag, lift, and gravity. It is evident that all quantitative models for aircraft crash frequency assessments are constrained by the limited statistical database available for supporting such risk assessments. Aircraft crashes to critical facilities are rare events, and this condition limits experimental data and verification efforts. Most existing models are very conservative and employ assumptions that overestimate actual risks