Production of transuranic elements in the SM-2 and mir reactors

Abstract

The relative rates of accumulation of the individual isotopes of the transuranic elements (and hence also the isotopic compositions of these elements) may vary over a wide range in accordance with the conditions of irradiation of the initial materials. The effective cross sections for the capture of the neutrons by even-even and odd-even nuclei increase substantially as the proportion of resonance neutrons in the reactor spectrum incrases. Hence the irradiation of the original materials in the hard spectrum of the active zone of the SM-2 leads to the formation of elements with a high concentration of isotopes having an odd number of neutrons. This enables us to produce elements with sharply differing isotopic compositions, which in turn eases the study of the nuclear properties of individual isotopes. The successful combination of the high thermal-neutron flux in the trap of the SM-2 reactor, the hard neutron spectrum in the active zone of this reactor, and the large spaces available for irradiation in the MIR enables us to accumulate the desired isotopes under almost optimum conditions in every case.