Effect of compositional variation in plutonium on process shielding design

Radiation dose rate from plutonium with a high 239Pu content varies with initial nuclidic content, radioactive decay time, and impurity elemental content. Large variations in photon dose rate may result from variations in the 241Pu and 236Pu initial contents. The high-intensity, low-energy gamma emission from 241Am, the first daughter of 241Pu, may cause large doses for unshielded processing of bare plutonium. The high-energy gamma emission from 208Tl, a daughter in the 236Pu decay chain, may be the primary photon dose contributor for heavily shielded processes. Variations in neutron dose rate result from variations in impurity (α, n) reactions and spontaneous fission, as a result of variations in the 241Am and 240Pu contents, respectively. Because dose variation implies shielding variation, knowledge of the composition of the plutonium to be processed should be incorporated in shielding design analysis