Evaluation of the Water Radiolysis in the Serpentinite Concrete of the VVER-1200 Reactor Shielding

The first (inner) layer of a VVER-1200 reactor shielding is made of serpentinite concrete, which is heat-treated (dried) for 10–12 days after concrete placement (installation). Currently, the possibility of eliminating the heat treatment is discussed. In this regard, an estimate is made of the water radiolysis rate in serpentinite concrete during the reactor operation. Calculations are made of the field of the absorbed dose rate for neutrons and gamma radiation in the water of serpentinite concrete after the first reactor power start, when the neutron leakage from the core loaded with fresh fuel assemblies is the highest. The estimate of the hydrogen yield due to the radiolysis of free and bound water in serpentinite concrete is carried out for the cases where the concrete is dried or not dried after the placement.