Determination of natural uranium fission rate in fast spallation and fission neutron field: An experimental and Monte Carlo study

The “Energy plus Transmutation” experimental setup of the Joint Institute for Nuclear Research (JINR), Dubna, Russia, is a lead target surrounded by a natural uranium blanket. A polyethylene plus cadmium shield is placed around the target-blanket assembly to modify the spallation and fission neutron spectra in the system. In this work the spatial distribution of natural uranium fission rate in the assembly and fission rate in the blanket were determined experimentally and compared with Monte Carlo predictions using the MCNPX 2.6C code. Besides neutron-induced fission the calculations include the reactions NatU(p, f), NatU(π, f) and NatU(γ, f). Good agreements between the experimental and calculations results were obtained. The possible sources of errors in the experiment and calculations are discussed in detail.