Accident Analysis for Aircraft Crash into Hazardous Facilities: A Statistical Primer (ANRCP-1998-20)

The DOE Standard 3014-96, Accident Analysis for Aircraft Crash into Hazardous Facilities provides a robust statistical framework useful for assessing the release frequency for hazardous materials used in many industrial operations. The formulae and the verbal instructions for calculating screening quantities and frequencies in the DOE Standard are consistent with an unstated underlying six-term expression for estimating the annual number of aircraft-impact-related releases. The six-term formula is here shown to result from iterated application of Bayes’ rule. The statistical concepts underlying this formula are explained; the six-term model is then developed and its components related to the corresponding elements of the four-factor model presented in the Standard. The sixterm model is shown to be consistent with the instructions given in the Standard for calculating the screening and evaluation quantities using the four-factor model. The difference between screening and evaluation of release frequencies is clarified. Discussion of the six-term model shows clearly how conservative approximations to its conditional probability terms lead to simple and efficient screening formulae. A numerical example is provided to demonstrate a screening calculation.