Feasibility study of large-scale production of iodine-125 at the high temperature engineering test reactor

The feasibility of a large-scale iodine-125 production from natural xenon gas at high-temperature gas-cooled reactors (HTGRs) was investigated. A high-temperature engineering test reactor (HTTR), which is located in Japan at Oarai-machi Research and Development Center, was used as a reference HTGR reactor in this study. First, a computer code based on a Runge-Kutta method was developed to calculate the quantities of isotopes arising from the neutron irradiation of natural xenon gas target. This code was verified with a good agreement with a reference result. Next, optimization of irradiation planning was carried out. As results, with 4 days of irradiation and 8 days of decay, the 125I production could be maximized and the 126I contamination was within an acceptable level. The preliminary design of irradiation channels at the HTTR was also optimized. The case with 3 irradiation channels and 20-cm diameter was determined as the optimal design, which could produce approximately 1.8 × 105GBq/y of 125I production. •The HTGRs have large space available for thermal neutron irradiation applications.•The feasibility of a large-scale 125I production at the HTGRs was investigated.•The Runge-Kutta method was used to calculated quantities of various isotopes.•Four days of irradiation is the optimal irradiation planning of 125I at the HTTR.•The optimal HTTR design could produce 1.8 × 105GBq/y of 125I activity.