Accident sequence dynamic simulation versus event trees

An event tree is a powerful tool for delineating accident scenarios as representatives of classes of events for probabilistic safety assessment purposes. It is, however, a modelling technique which hardly gives an adequate account of dynamic processes interacting with systems' states, which is what an operator is in reality confronted with. Petri nets or other similar approaches model fairly well timed sequences of events: they fail again in giving an account of the process physics. On the other hand, the DYLAM (dynamic logical analytical methodology) technique is shown to present significant advantages, especially for developing stochastic models of dynamic systems, and therefore is a powerful aid for the design of decision support systems to assist the operator in the control of hazardous processes. (author)