Safety evaluation of nuclear transmission lines using fuzzy relations

In this paper, we deal with the performance evaluation of transmission lines of nuclear installations. We argue that the traditional assessment process based on a single parameter is inappropriate. Instead, it should take several related factors like isolation damage, rust, resistance change etc. into account to determine the degradation degree of a transmission line properly. Therefore, we regard the safety analysis of transmission lines as a comprehensive evaluation process associated with multiple parameters. Another feature of the process is the difficulty in quantifying the involved parameters due to existence of the subjective judges in determining the degradation degree and the sufficient knowledge about the evaluation parameters. In view of these difficulties, fuzzy set method, specifically use of fuzzy relations and linguistic expressions, can provide an approximate but efficient performance descriptions of a transmission line. With the known linguistic expressions, Bellman and Zadeh's original fuzzy decision model is employed for the final evaluation. Sometimes we should consider different parameters unequally. For instance, the resistance change is the most important factor whereas the rust is relatively less important when we pay attention to the consideration of protection from fire of a transmission line. In this situation, we assign the different weight for the different parameter, depending on the importance. The corresponding method is from Yager's multiple objectives decision model. In this way, we get a systematic evaluation model while taking into account multiple parameters and the subjectivity as well.