Description and status of BWR water radiolysis model

A water radiolysis model for boiling water reactor primary coolant circuits has been developed jointly with Harwell Laboratories. Hydrogen water chemistry plant tests, on which the model is based, started in 1982. Since then, ten plant tests have been completed. Test results indicate that: (1) oxygen concentrations in the steam from plant to plant decreases fairly uniformly with increasing hydrogen concentration; (2) oxygen concentrations in the recirculating water varies widely with increasing hydrogen concentration in the feedwater; and (3) copper significantly suppresses the reduction of oxygen. The radiolysis model was developed to provide predictive conditions in the BWR primary circuit including the core. The objectives of the work are: (1) to develop and calibrate the model against experimental data; (2) to predict the concentration of various radiolytic species and oxygen suppression in various parts of the primary system under hydrogen water chemistry conditions; and (3) to define the role of copper on the reactions. The model considers the thermodynamics and kinetics of homogeneous chemical reactions in eight regions of the reactor and its external circuit. From initial concentrations, the model constructs a set of simultaneous equations to calculate hydrogen, hydrogen peroxide, and oxygen concentrations in various regions. Pilgrim data were used for the initial calibration. The model includes neutron and gamma dose rates in the core region and gamma dose rates in the other various regions, as well as temperature, power levels, heat transfer, steam quality, and gas/liquid transport in the core region, etc. The results of calculations for the oxygen concentrations in the recirculation water as a function of hydrogen concentration in the feedwater show good agreement with the experimental data obtained in a number of reactor tests