A method to obtain radioactivity of non-γ nuclides by 60Co based on Monte Carlo simulations

Source term investigation is a critically important aspect of reactor decommissioning, particularly as the range of nuclides under consideration expands beyond the capabilities of existing analysis methods. In this study, we try to propose a methodology to indirectly determine the radioactivity of long-lived nuclides which are non-γ or low energy in various nuclear waste materials by measuring the radioactivity of 60Co. The critical point of this method is to establish relationship between some easy to measure (ETM) key nuclides, such as certain γ emitters (like 60Co), and the difficult to measure (DTM) nuclides to derive information for the DTM nuclides of interest. To begin, we calculate nuclide bulk densities of 55Fe, 60Co, 63Ni and 152Eu in nuclear waste materials. By constructing inversion matrices and analyzing the intensity matrices of characteristic γ lines emitted by 60Co, we can extract the radioactivity of non-γ radionuclides (55Fe, 63Ni, and 152Eu) present in the nuclear waste materials that are contained within a specific container. Furthermore, our methodology accounts for the influence of voids within the container, thereby ensuring the reliability and validity of the obtained results. This innovative approach offers a promising avenue for efficiently sorting nuclear waste.