Consideration of the combined damage of several sources of radioactivity in level 2 probabilistic safety assessment for a NPPs unit

Consideration of the combined damage of several sources of radioactivity in level 2 probabilistic safety assessment for a NPPs unit

The issues related to the application of recommendations of safety guide in the use of atomic energy RB-044-18 of Rostechnadzor (hereinafter – RB-044-18) and the IAEA Specific Safety Guide SSG-4 (rev. 1) (hereinafter – SSG-4 (rev. 1) for accounting of damage of several sources of radioactivity in the probabilistic safety assessment of level 2 (PSA-2) performed to assess the compliance of the NPP unit design with the requirement of i. 1.2.17 of federal rules and regulations NP-001-15, are discussed.
The concept of “state with damage to radioactivity sources” for several sources is characterized. It is shown under what conditions and how the releases from several radioactivity sources should be taken into account in the estimation of large accidental release probability.
The analyses of the approaches for assessing the probability of a large accidental release from several sources of radioactivity at a NPPs unit, recommended by RB-044-18 and SSG-4 (rev. 1), was performed. A method for assessing the probability of a large accidental release in its absence from individual sources of radioactivity is given.
An algorithm for analyzing the joint damage of radioactivity sources is presented. The recommendations for improving the RB-044-18 in terms of considerations of several radioactivity sources are provided.

► Keywords: level 2 probabilistic safety assessment, state with damage to radioactivity sources, radioactivity source, joint damage, nuclear fuel.

Article language: Russian. Pp. 15–23. [in Russian]. DOI: 10.26277/SECNRS.2025.117.3.002.