Analysis of reactivity insertion accident for MTR reactor

The reactivity insertion accident for MTR reactor is analyzed. Different conditions are considered namely; slow and fast reactivity insertions; controlled and uncontrolled transients; with and without coolant flow. The slow reactivity insertion (<1$/s) may be initiated due to different reasons e.g. inadvertent control rod withdrawal from the core with the nominal control rod drive speed, sudden decrease in reactor inlet temperature or the presence of voids in the reflector. Two different eases were analyzed for reactor power; in the startup range (1W) and in the full power range. The specific assumptions for the ram rates, trip setting, and time delays before shutdown reactivity insertion were considered. Different cases with a reactivity insertion rate of the values 0.198$/ s, 0.14$/s and 0.1$/s were assumed in order to account for the control rod worth variation with position in the core or the worth for different cores starting from fresh up to the equilibrium core. The peak fuel centerline temperature, clad surface temperature and peak coolant exit temperature were evaluated in each case. No situations were found to initiate melting to the cladding or severe environmental consequences