29 Analysis of Human Actions in the Framework of Dynamic Reliability Analysis (PSAM-0040)

An essential element of a PSA is the analysis of operator performance. Plant operators, system components and the physical process are interacting parts of a complex system like a nuclear power plant that has to respond to specific conditions and events. The traditional methods of fault tree and event tree analysis are not capable of explicitly treating the time dependent interactions of the plant process variables (temperature, pressure etc.), system components and operator actions.

For that reason, a module (‘Crew Module’) was developed which can be applied in the framework of a dynamic reliability analysis. The ‘Crew Module’ allows simulating human performance as a separate dynamic process, which evolves in parallel and interacts dynamically with the system process. The Crew Module can operate in combination with the probabilistic dynamics tool MCDET /1/, /2/ and any deterministic dynamics code simulating the process and system dynamics. This combination allows to consider mutual dependencies between system components, physical process quantities, human actions and any relevant random events influencing the man-machine-system.

In the ‘Crew Module’ alternative operator strategies, communications between crew members, time durations of actions, recovery of failures, the influence of any performance shaping factors (i.e. stress, complexity of task etc.) , errors of omission as well as errors of commission in principal can be modelled. Stochastic events regarding the performance of human actions can be taken into account.

Applying the ‘Crew Module’ in the framework of a dynamic reliability analysis allows a more realistic modelling of dynamic operator plant interactions and can be important, for instance, in assessing the efficiency and relevance not only of emergency operating procedures (EOP) but also of maintenance, repair and any other human performances.

It is emphasized that the ‘Crew Module’ does not intend to model the mental or cognitive processes of plant operators.

The objective of this paper is to describe the intention and the concept of the ‘Crew Module’.