The prompt neutron decay constant of the MOATA reactor and related coupled-core assemblies

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Australian Atomic Energy Commission
The correlation functions of the neutron noise have been used to determine the prompt neutron decay constant, α, for the AAEC reactor Moata - a Universities1 Training Reactor (UTR). The basic characteristics of the UTR system are two coupled 235u fuel cores, hydrogen moderated and graphite reflected. To investigate this type of reactor in greater detail, a series of 'mockup' assemblies was constructed on the AAEC Split-table Zero-power Critical Facility. A value of α was experimentally determined for each assembly, and the effects on α of core separation, fuel arrangements, perturbations to the coupling region, and detector positions were investigated. A comparison with previous results for the Moata reactor and with results for similar UTR systems was carried out. Using a two-dimensional neutron diffusion and kinetics computer code, the prompt neutron generation time, Λ, and the effective delayed neutron fraction, β, were calculated for each assembly. The results from the two-dimensional calculations were consistent with experiment, but the difficulty of modelling the neutron leakage limited the accuracy of the calculated α. Improved agreement with experiment was obtained using a three-dimensional diffusion calculation.
Prompt neutrons, Neutron diffusion equation, MOATA Reactor, Decay
Knott, R. B., & Harries, J. R. (1976). The prompt neutron decay constant of the MOATA reactor and related coupled-core assemblies. AAEC/E380). Lucas Heights, NSW: Australian Atomic Energy Commission.