Hysteresis in Coolant Radiolysis in a Pressurized-Water Reactor and its Effect on the Critical Hydrogen Concentration

Mathematical modeling is used to investigate the effect of the thermophysical non-uniformity of the core in a reactor on the behavior of radiation-chemical processes in the first-loop water coolant of pressurizedwater power reactors. The problem of determining the critical hydrogen concentration in coolant that is sufficient to maintain the concentration of oxidizers in the coolant at a corrosion safe level is used as an example. It is shown that in a reactor the critical hydrogen concentration may not have a definite value but rather a range of values dependent on the radiation-chemical process and the reactor's thermo- and neutron-physical parameters. Calculations also showed that the conditions under which oxidizer formation is suppressed can be determined accurately only with detailed three-dimensional modeling of thermophysical phenomena and radiation-chemical transformations in the entire core volume.