Study of dependence of ⁶³Ni and ²³⁸Pu efficiency production on the energy structure of neutron flux density

At present, the existing approaches to the production of artificial isotopes are mostly based on the development experience of previous years. In the present work, the task is to develop an algorithm for selecting the most effective irradiation modes for target materials. The study is based on the sequential simulation of irradiation of target isotopes by neutrons of different "single-group" fluxes at the same value of their densities. In this study, a flux density equal to 2·10¹⁵ n/cm²·s was used for all energy groups. This approach will help in "designing" and selecting the real neutron spectrum that has the highest efficiency compared to the alternatives. The study considers the production efficiency of ⁶³Ni (⁶³Cu, ⁶²Ni irradiation), ²³⁸Pu (²³⁷Np, ²⁴¹Am irradiation). The most effective groups in terms of specific activity are selected and their behaviour is analysed. For ⁶³Ni production from ⁶²Ni, group 25 (1-2.15 eV) is preferable among all groups, based on its specific activity of ~ 15.8 Ci/g. In the case of ⁶³Ni production from copper, such high specific activity values are not achieved. With the increase of irradiation duration and/or neutron flux value, the values of specific activity will increase. The maximum specific activity will be in group 2 (1.05·107-1.4·107 eV) and is ~ 0.45 Ci/g. The most preferable for production of ²³⁸Pu from ²³⁷Np is group 19 (100-215.44 eV), specific activity is ~ 15.7 Ci/g. In case of production of ²³⁸Pu from ²⁴¹Am the most preferable groups for the production are 21 (21.54-46.42 eV) and 23 (4.64-10 eV), specific activity is ~ 6.5 Ci/g.