Transmutation Of ~(126)sn In Spallation Targets Of Accelerator-driven Systems

摘要

The practical feasibility of ~(126)Sn transmutation in spallation targets of accelerator-driven systems was evaluated from the viewpoints of accumulation of radioactive spallation products and neutron production as well as transmutation amount of ~(126)Sn. A cylindrical liquid ~(126)Sn target whose length depends on proton beam energy was described, based on a Pb-Bi target design of accelerator-driven system being developed in JAEA. A proton beam of 1.5 GeV-20 mA was estimated to give the transmutation rate of ~(126)Sn 6.4 kg/ yr, which corresponds to the amount of ~(126)Sn annually discharged in 27 LWRs of 1 GWt and 33 GWd/ THM. The equilibrium radioactivity of spallation products would reach 9% of that of ~(126)Sn transmuted in the spallation target, and the equilibrium toxicity would be just 3%. Some parametric analyses showed that the effective half-life of ~(126)Sn could be reduced through a proper reduction of the target size. The ~(126)Sn target was calculated to produce 40 neutrons per proton of 1.5 GeV and give a neutron spectrum very similar to that of the reference Pb-Bi target. As a result, the transmutation of ~(126)Sn in the spallation target has a high feasibility in terms of better transmutation performance and comparable target performance.