Impact of the Precipitation of Boric Acid and its Salts on the Operability of Passive Safety Systems During Serious Accidents in NPP

Abstract

One of the problems of accidents in NPP with VVER is the evaporation of the primary coolant in the containment. Boric acid H₃BO₃ can ingress into the containment together with steam and crystallize, independently or in the form of salts, on heat-exchange and other surfaces of equipment placed in the containment, thereby lowering the efficiency of passive systems removing heat from the containment and the removal of hydrogen. The results of an experimental investigation of the deposition of insoluble aerosols and salts of boric acid on heat-exchange surfaces of the passive heat-removal system and the surfaces of autocatalytic hydrogen recombiners during serious accidents in NPP are reported. It is shown that the impact of crystallization of boric acid and its salts on the operability of these systems is very small.