Transmutation of Elemental Cesium by a Fusion Neutron Source

Abstract

Transmutation of radioactive Cs from fission products of nuclear reactors without the potentially dangerous and expensive operation of isotopic separation is addressed. Transmutation is proposed to be performed in the blanket of a fusion neutron source with the plasma performance characteristics inherent in the current research on fusion reactors. The domain of Cs transmutation is quantitatively determined with detailed neutronics analysis of hard and softened neutron spectra, the effect of first wall loading, and two reprocessing modes. One is continuous on-line reprocessing; another one deals with a multicycle option in which a substantially long irradiation period is assumed before reprocessing. Transmutation efficiency is estimated in terms of the effective lifetime of ¹³⁵Cs, which is the key characteristic governing the approach to equilibrium and the fraction of power associated with cesium transmutation in a nuclear energy system as a whole. In a contrast to fast reactors and accelerator-driven systems, fusion-driven transmutation reveals time to approach equilibrium that is comparable with the lifetime of transmuter and power associated with transmutation lies well within 5% of the total power of the nuclear energy system composed of fission reactors and transmuters.