Abstract:
Prompt neutron decay constant
αis an important parameter to determine the reactivity of subcritical assemblies. Randomly pulsed neutron measurements were performed to obtain α of a subcritical assembly composed of cylindrical uranium. Monte Carlo simulations, with its flexibility of recording neutrons of different origins and different energy, were used to analyze the influence of directly transmitted source neutrons on the prompt neutron decay. The simulation results show that the influence of directly transmitted source neutrons to the prompt neutron decay can be neglected after 100 ns for the cylindrical assembly. According to the simulation results, the initial channel of the experimental prompt neutron decay curves was selected as 100 ns and the data were fitted to a single exponential decay. The experimental results ofαfor the uranium metal subcritical assembly is 15.5 μs-1.
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