Technical reliability of active fire protection features – generic database derived from German nuclear power plants

Abstract

For Probabilistic Fire Safety Analysis fire event and fault trees specific to the conditions of the nuclear power plant need to be established to estimate the corresponding branch point probabilities and end states for core damage frequency. That also requires applying technical and human reliability data for fire specific event sequences. The technical reliability of fire detection systems, fire and smoke extraction dampers, fire doors and fire extinguishing systems and equipment including extinguishing media supplies has been estimated by means of their failure rates. To account for epistemic uncertainties Bayesian estimation methods have been used, depending on homogeneity of the studied components.The data has been evaluated by analyzing the documentation of periodic in-service inspections as well as additional information and reports which resulted from the inspection findings. For more complex systems, in addition to the components’ failure rates, fault trees are presented to calculate the systems reliability.This type of data now covers up to 111 plant operational years of six power reactor units of different age and type. The generic data may also be applied as a-priori information for estimating the reliability of components with similar design and equivalent inspection and maintenance practice for other nuclear power plants.