Severe accident in-vessel stage subcriticality evaluation
28th Symposium of AER on VVER Reactor Physics and Reactor Safety (2018, Olomouc, Czechia)
Reactor dynamics and safety analysis
The development of severe accidents is possible for a large number of scenarios with the reactor core damage. The severe accidents, taking into account impacts introduced by NPP emergency systems (for instance, water injection into the primary circuit) make it necessary to perform a calculational analysis of criticality for the number of severe accident scenarios. Reaching criticality can drastically change scenarios and consequences of the accidents of this type.
For the typical base states of severe accidents, calculational models of scenarios of accident situations are formed, that take into account the following: chemical composition of molten materials, distribution of coolant parameters, temperature distribution of the core components and the core internals, change in the configuration of the elements of the basic state model developed for normal operation conditions. In preparation of calculational models, the design characteristics of RP with V-320 are used as well as the thermal-hydraulic characteristics obtained during the analysis of various stages of the scenarios of severe accidents.
Impossibility of realization of repeated criticality is demonstrated based on the analysis of the neutron multiplication factor for base states.