Estimation of generated volume of radiolytic gas voids during prompt criticality with 10% enriched uranium nitrate solution in TRACY

An oscillatory pressure response due to the generation of radiolytic gas voids was observed during a prompt criticality with 10% enriched uranium nitrate solution in the Transient Experiment Critical Facility (TRACY) of Japan Atomic Energy Agency (JAEA). In order to understand the mechanism of the nuclear thermal-hydraulic behavior in solution fuel criticality accidents, the mechanism of the oscillatory pressure response was studied using both the measured data and visual observation of the solution behavior. A simplified vibration model for the estimation of the generated volume of radiolytic gas voids was proposed using the measured data of the pressure period and the solution mass. Rapid depressurization experiments with carbonic acid water were also carried out in order to verify the application of the simplified vibration model for radiolytic gas voids. Consequently, the generated volume of radiolytic gas voids for the oscillatory pressure case was correlated as a function of the energy for the generation of gas voids. (author)