A study of nuclear transmutation of Th and ^natU with neutrons produced in a Pb target and U blanket irradiated by 1.6 GeV deuterons

Abstract

The spallation lead target in the “Energy plus Transmutation” set-up, covered with uranium blanket, was irradiated by the 1.6GeV deuteron beam from the Nuclotron accelerator at the Joint Institute for Nuclear Research in Dubna. The neutrons generated in the subcritical uranium blanket are used to activate the radioactive uranium and thorium samples outside the blanket. Rates of the (n,$\gamma$) , (n, f) and (n, 2n) reactions are determined for some residual nuclei. The ratio of the reaction rates R(n, 2n)/R(n, f) is estimated to be 27(9)%. Contributions of the neutrons with energy E _n > 20 MeV to the (n, f) reaction rate is ∼ 57% for ²³²Th and ∼ 37% for ^natU , respectively. To compare with the experimental results, the reaction rates are simulated by generating the neutron fluxes employing two different models, the beam shapes by the MCNPX 2.6.c code and making use of the appropriate libraries of cross-sections. The transmutation power of the set-up is estimated using the average (n,$\gamma$) and (n, 2n) reaction rates and compared with some of the results of the TARC experiment.