Dependence of Control-Rod Efficiency on the Initial Conditions of Rod Motion

Resumo

The effectiveness of control rods is measured in a nonstationary regime at minimum reactor power. The measurement algorithm entails a buildup of reactor power caused by lifting of the measured or any other rod followed by its release, which is due to the need to maintain a detector signal above the background level up to the end of the experiment. It is known that some fission neutrons (the prompt neutrons) are created directly during nuclear fission while others are formed from the decay of the precursors of delayed neutrons, which possess a low-energy spectrum or lower average energy. For fast reactors, this can be reflected on the efficiency of the control rods during measurements and during the development of the processes occurring during an accident. This work is devoted to determining the effect of the conditions preceding the movement of control rods on their effectiveness and the discrepancy between the efficiency of the rods realized in practice and the efficiency calculated on the basis of stationary states.