A Neutronic Assessment of Strontium-90 Transmutation in Fusion Reactors

Abstract

Transmutation of ⁹⁰Sr using fusion neutrons has been suggested as a possible technique for disposing of this waste nuclide. For transmutation to be attractive, high transmutation rates relative to natural decay are required. “Effective” half-lives for ⁹⁰Sr were computed for fusion reactor blankets constructed of various materials. To obtain satisfactory transmutation rates, fusion reactors with high first wall neutron currents and with highly moderating blankets were found to be necessary. An effective half-life for ⁹⁰Sr of <5 yr was extremely difficult to achieve with the fusion concepts and blankets studied.

A waste management system was formulated to determine the reduction in the ⁹⁰Sr inventory and the number of burners required for various fission usage scenarios. Efficient and fast chemical separations were needed to reap the benefits of a short effective half-life. For the fusion burners considered, it was found that the ⁹⁰Sr inventory could not be reduced to less than one-fourth of the inventory without transmutation if fission usage continued at a constant rate. Such a reduction is not sufficient to justify the transmutation disposal of ⁹⁰Sr.