Probability analysis as a tool for assessing reliability of electrical systems of WWER type nuclear power plants

The possibilities are discussed of a system approach to technological reliability of WWER type nuclear power plants. The theory of the Markov processes is compared with the failure tree and the critical section method. The results are reported of the assessment of category I consumer power supply in nuclear popwer plants. The results obtained are only informative. To increase the importance of probability analysis, input data on the frequencies of failures of the individual system elements should be rendered more accurate. (J.C.)