Study on risk-informed safety classification in VVER nuclear power plant

With the development of probability safety assessment (PSA) and the application of risk-informed technology, a risk-informed safety classification method of Structures, Systems and Components for nuclear power plants has been developed. The risk-informed safety classification does not replace the existing safety classification, but further subdivides the two levels of "safety related" and "non-safety related" in the existing safety classification according to the safety significant of components to the risk. The SSCs is subdivided into high safety significant (HSS) and low safety significant (LSS) according to the safety significant of components to the risk. This paper focuses on the methods of risk-informed safety classification. In the analysis, the typical system of nuclear power plant is studied as a risk-informed safety classification, and according to the analysis results, the optimization of special treatment requirements for RISC-3 components is proposed. The analysis results show that among the components classified as safety related by traditional deterministic analysis method, a relatively high proportion of the components can be classified as safety related components with low safety significant through analysis. Exempting or reducing the special treatment requirements for these components can effectively improve the economy of nuclear power plant under the premise of ensuring safety.