Non-linear dependency of the voiding effect on the coolant density in RBMK-1500 reactors of Ignalina NPP

The article presents an analysis of non-linear dependency of the voiding effect on reactor coolant density. Having the aim to confirm the existing non-linear profile of this dependency, independent calculations of the voiding effect of RBMK-1500 reactors of Ignalina NPP were performed, using the three-dimensional model of the reactor core, modeled by QUABOX/CUBBOX code. Afterwards, the calculational results were compared to the newest data presented by other authors. Calculational results confirmed the existing non-linear dependency of the voiding effect on the coolant density for different operational conditions of the reactor. Reactor operation at the power level of 240 MW is notable among the other operational regimes of the reactor for the negative and the smallest, by its absolute value, voiding effect. (author)