ANALYSIS OF THE EFFECT OF ACTUAL THERMAL-HYDRAULIC MODEL CRITICALITY EXCURSION TRANSIENT BASED ON THE COUPLING OF POINT KINETICS AND CFD

抄録

The aqueous solution, as a form of fissile material, is particularly common in reprocessing, where the possibility of criticality exists. The simplified thermal-hydraulic model coupled with point kinetics typically results in the advantages that are relatively easier to solve and lower computational cost compared to more fundamentally based modeling. In consequence, this makes simplified thermal-hydraulic models coupled with point kinetics widely used to track critical accident transients which may have significant durations. This is usually considered lumped model or diffused model (also known as the heat conduction model) with a modified thermal diffusivity coefficient. However, the difference in temperature spatial distribution between the actual natural convection due to buoyancy and simplified thermal-hydraulic models may lead to different calculation results of reactivity feedback. Therefore, this paper simulates the R100 experiment on the TRACY facility to study the spatial distribution characteristics of solutions temperature to provide a reference for improving the accuracy of the thermal-hydraulic models as much as possible, based on the coupling of point kinetics and computational fluid dynamics (CFD). The results indicate that the thermal-hydraulic model should be considered as a natural convection model rather than a heat conduction model in the simulation of criticality excursion transient in solution, in the case of taking into account the spatial effect of temperature feedback.