Effects of reflected neutrons on the reactivity measurement of metal Assemblies

The kinetic equation including the reflected neutron effect is established based on the time-dependent two-region kinetic model. Different reactivity measurement methods are simulated by using the equation. The simulation results show the difference of estimated reactivity values between the prompt neutron decay constant method and the positive period method. It illustrates the principle of reactivity difference in measured value by using different measurement methods, that is, the time scale of the measurement method determines the contribution rate of the reflected neutrons in the experiments. The contribution rate influences the measured value of reactivity.