The document “General Provisions for Ensuring Safety of Nuclear Power Plants” (NP-001-15) contains a new regulatory requirement on necessity to provide measures in nuclear power plant (NPP) design aimed at eliminating the cliff-edge effect. The article analyzes (with involvement of both Russian and credible international sources) the content of the concept of “cliff-edge effect” used in this requirement.
It is shown that the manifestation of the cliff-edge effect should include situations when a small change in the NPP parameter leads to a loss of effectiveness of two or more levels of defence-in-depth or to a significant change in the magnitude of radiation exposure to personnel, the population, and the environment, or to a situation where the probability of such consequences significantly increases. The interpretations of the concepts of “significant deterioration in safety”, “parameter”, “small change in parameter”, “discontinuity” used in NP-001-15 when defining the term “cliff-edge effect” are considered.
Based on the results of the analysis, for subsequent discussion among specialists, a matrix is proposed for determining the necessity of taking measures in NPP design aimed at cliff-edge effect exclusion.
Keywords: nuclear power plant, cliff-edge effect, defence-in-depth.
Article language: Russian. Pp. 24–41. DOI: 10.26277/SECNRS.2021.102.4.003.