A fire risk analysis method for nuclear installations

A fire safety analysis (FSA) is requested to justify the adequacy of fire protection measures set by the operator of a nuclear facility. An IRSN document outlines a global process for such a comprehensive fire safety analysis and focuses on compliance with performance criteria for fire protection measures. These performance criteria are related to the vulnerability of targets to effects of fire, and not only based upon outside radiological consequences caused by a fire. In his FSA, the operator has to define the safety functions to be preserved in the case of a fire in order to be compliant with nuclear safety objectives. Then, the operator has to justify the adequacy of fire protection measures, defined according to defence in depth principles. One of the key points of the fire analysis is the assessment of possible fire scenarios in the facility. Given the large number of possible fire scenarios, it is then necessary to evaluate ''reference fires'' which are envelope of all possible fire scenarios and which are used by the operator for the design of fire protection measures. (orig.)