Application of High-Temperature Mechanical Filtration of the Primary Coolant at a VVER-SCW Nuclear Power Unit

Abstract

The issues are examined associated with application of high-temperature mechanical filtration of the coolant for rendering proper water chemistry (WC) in the primary circuit of a supercritical water-cooled power reactor (VVER-SCW reactor). A critical analysis of the use of high-temperature filters (HTFs) in a dual-circuit VVER-SCW nuclear power plant is presented. The main challenges associated with the introduction of the high-temperature filtration technology under the primary circuit operating conditions, which was developed and implemented in the design of the unified VVER-1000 unified reactor plant, are outlined. The features of HTF operation under supercritical conditions are examined. The causes responsible for the change in the behavior of corrosion products on transition to operation in the region of near-critical and supercritical parameters are analyzed. The calculated and experimental values of the solubility of corrosion products in the water coolant under near-critical and supercritical conditions are assessed. It has been demonstrated that the transition to near-critical and supercritical operating conditions increases the degree of oversaturation of the coolant with iron and nickel, thereby facilitating further dominance of the fraction of suspended particles in it compared to compounds in a truly dissolved state. The effect the transition to the near-critical and supercritical operating conditions has on the characteristics of suspended particles of corrosion products in the coolant and the HTF efficiency was analyzed. A proposal has been made that the effects of radiolysis in supercritical water enhances the importance of colloidal systems formed from the corrosion products. It has been demonstrated that, if high-temperature mechanical filtration systems of the coolant are used at VVER-SCW power units, one can expect that the problems encountered during their (HTFs) operation at series power units with a VVER-1000 reactor will worsen. Potential ways are proposed for improving the technology of high-temperature filtration in the primary circuit of VVER-SCW nuclear power units.