PHYSICAL FOUNDATIONS OF NUCLEAR POWER SAFETY: EFFECT OF STEAM-PHASE SOLUBILITY ON BORIC ACID ACCUMULATION IN THE CORE OF A VVER REACTOR

This thesis analyzes the risk of boric acid crystallization in the core of a VVER reactor under prolonged beyond-design-basis accident conditions. Unlike conservative approaches, this study uses a refined mathematical model that accounts for the removal of boric acid due to its solubility in steam. The aim is to evaluate the impact of this mechanism on the final concentration of boric acid and to assess the effectiveness of a design solution involving the reduction of initial boron concentration in Stage 3 hydroaccumulators (HA-3). The results indicate that considering steam-phase solubility significantly reduces the crystallization risk; however, additional measures are still required for complete elimination of the hazard.