Upgrading of Regulatory Documents: Probabilistic Safety Analysis in Support of Decision-Making in the Design and Operation of NPP

Matters concerning the improvement of safety guidelines related to the use of risk-informative methods in determining the safety class of elements of nuclear power plants in the process of design and assessment of malfunctions are considered. Clarifi cations of the terms and defi nitions used are proposed. Considerable attention is given to the interpretation and calculation of the conditional probability of a severe accident in the event of a single failure of an NPP element and disruptions characterized by a complex of failures. Relations are given for calculating the indicated probability in terms of signifi cance indicators for the elements (complex of elements) of NPP. Proposals are formulated to clarify the criteria for the classifi cation of disruptions of operation, taking into account the guidelines presented in the top-level regulatory documents. The proposed indicator ensures that the assessment methods used for different types of disturbances are consistent. Recommendations for improving the risk-informative approach to decision-making during NPP operation are described.