Thermal–hydraulic modeling of reactivity insertion in a research reactor

Highlights: ► A thermal–hydraulic model for reactivity insertion in a research reactor is presented. ► The proposed model is used to analyze reactivity insertion for a IAEA 10-MW research reactor. ► No safety limits are exceeded for slow reactivity insertion. ► A brief localized boiling is predicted for fast reactivity insertion. ► Comparison of the simulation results with the PARAT code proved to be satisfactory. - Abstract: Transient reactivity insertion for a pool type research reactor with scram enabled is numerically investigated. The analyses were performed by developing a coupled kinetic–thermal–hydraulics code, with continuous feedback due to coolant and fuel temperature effects. A modified Runge–Kutta method was adopted for a better solution to a system of stiff point kinetic equations. Transient thermal–hydraulics during the process of slow and fast reactivity insertion were considered for a IAEA 10-MW research reactor. The code was used to carry out transient thermal–hydraulics analysis for both high-enriched uranium (HEU) and low enriched uranium (LEU) fuel. Reactor power, fuel, clad and coolant temperatures, MDNBR, reactor period, energy released for slow and fast reactivity insertion transients were predicted. The model prediction was verified through comparison with the PARET code and other institution results reported in the literature for detailed simulations of reactivity insertion. The comparison of simulation results and the PARET code showed good agreement for the main thermal–hydraulic parameters.