Research on the effects of corrosion resistant zinc injection in primary circuit of large-scale PWR plants on core crud amount

In recent years, the number of nuclear plants injecting zinc is increasing worldwide because zinc injection can reduce the corrosion rate of structural materials in the primary coolant circuit. However, at the initial stage of zinc injection, zinc can introduce a large amount of corrosion products entering into the coolant circuit by displacing other divalent species in oxide. These corrosion products will be carried into the core by the coolant and cause unevenness of the crud on fuel cladding surfaces, which can increase the probability of crud induced power shift (CIPS) and damage to fuel claddings. In this paper, the structural material corrosion model with or without zinc injection is built based on a mixed conduction model. The migration model of corrosion products in the primary circuit is established, and the relationship of crud amount with the time is obtained. The mechanism of interactions between zinc and formed oxide layers is analyzed. The extra amount of corrosion products due to zinc injection is calculated according to the different starting times. It is used to revise the crud mass. The influences of zinc injection on the crud amount are achieved, which can be the foundation of further research on the relationship between zinc injection and CIPS.