Hazard and operability study using approximate reasoning in light-water reactors passive systems

In this paper, a risk evaluation approach is applied on Hazard and Operability Study (HAZOP). First, the concept of the traditional failure mode and effects analysis (FMEA) for the risk priority number (RPN) has been adapted and applied to HAZOP study. Then, a HAZOP_rpn concept was created. The HAZOP_rpn enables evaluation of the risk level over the system caused by an abnormality on the physical phenomena. The approach created from the fusion between the HAZOP and the traditional RPN has been named hybrid HAZOP. Following this, a fuzzy inference was established over hybrid HAZOP system defining another approach to safety assessment and risk estimation. As an example case, a passive system designed for removing the decay heat of an advanced light-water reactor, was used. The set of results demonstrated the great adherence of the hybrid HAZOP approach in this class of problems. It endorses also the advantages of using of a fuzzy inference system to model the uncertainty parameters levels in risk analysis.