Application of fuzzy-sets methods for calculating the reliability of safety systems of NPP

For the analysis of reliability of the elementary components devices or such analysis for whole systems many methods based on probabilistic calculations were created. One of the most interesting methods is the fuzzy-sets method. Its particular advantage lay in the possibility of reliability calculations in situations where the adequate determination of device failure is impossible. In practice, often the change in working mode of one component implies the worsening of system operation but is not yet considered as a failure. This is often encountered in nuclear power plants (NPP). The analysis is based on the determination of functions which should be fulfilled by the system