Water Chemistries of VVER-SCW Nuclear Power Plants: The Choice and Justification (Review)

The article discusses the potential problems that have to be solved in the framework of development and justification of the water chemistry (WC) conditions required to ensure corrosion resistance of the structural materials used in the core and coolant circuit of the power-generating reactor used in the supercritical water cooled VVER-SCW nuclear power plant (NPP). In reactors cooled with water at supercritical temperature and pressure, the integrity of their physical barriers (fuel-rod claddings and reactor coolant circuit boundaries) depends in many respects on the possibility of maintaining the necessary water chemistry conditions that will guarantee the corrosion resistance of equipment and pipeline structural materials for the power unit’s entire service life. The most complex challenge in this regard is to inhibit corrosion and flow-accelerated corrosion processes and to minimize the formation of deposits on the surface of equipment operating in the domain of near-critical and supercritical conditions. The article formulates the limitations that are suggested to be considered in transferring the experience gained from the standardization of water chemistry in supercritical pressure (SCP) power units at thermal and nuclear power plants to the VVER-SCW NPPs. An analysis is carried out that makes it possible to estimate the effect the chemical composition of a supercritical water coolant has on the corrosion state of candidate structural materials for fuel-rod claddings with the aim to get better insight in the main processes occurring in aqueous solutions and for developing (elaborating) a WC conduction technology as applied to ensuring the integrity of the VVER-SCW NPP physical safety barriers.