Transmutation of Massive Loadings of Cesium-137 in the Blanket of a Controlled Thermonuclear Reactor

Calculations have been performed which indicate the possibility of reducing below ten years the effective half-life for transmutation of massive loadings of ¹³⁷Cs placed in the blanket of a controlled thermonuclear reactor (CTR). The calculations assume the cylindrical “standard blanket” geometry and neutron source (which yields a vacuum wall loading of 10 MW/m² of 14-MeV neutrons). Significant thermal flux enhancement is obtained by (n,2n) reactions in a beryllium moderator. Gas production and induced radioactivity problems in the beryllium moderator are not much worse than in a graphite moderator. For an 80% target-zone loading of ¹³⁷Cs, a transmutation rate of 290 kg per year per meter of CTR length is obtained. At this loading, the transmutation rate in roughly 1% of the length of a CTR blanket would balance the production rate in a fission reactor of the same power. Constraint of the CTR source strength to yield a wall loading of 1 MW/m² would increase the effective half-life for ¹³⁷Cs to more than 20 years.