Optimization of neutron spectrum field for radioisotope production in the experimental fast reactor Joyo

Sasaki, Yuto ; Iwamoto, Nobuyuki  ; Maeda, Shigetaka   ; Takaki, Naoyuki*

In Japan, research is being promoted to improve and achieve domestic preparedness for the production of medical radioisotopes (RI) using existing fission reactors. We investigated the efficient production of Mo/Tc by neutron activation with an alternative method of producing Mo that does not use enriched uranium (HEU, LEU) as a raw material, utilizing the neutron moderator filed around the core of the experimental fast reactor Joyo. As a result, we found that 23133 TBq of Mo can be produced by irradiating the sample for 7 days in an irradiation field using a moderated assembly with a beryllium filling rate of 60%. This amount is enough to meet domestic weekly demand, even if we consider a supply of once every two weeks. However, Joyo has difficulty in continuing production due to annual inspections. Therefore, it would be possible to achieve a stable supply by establishing a supply system that is a best mix of other research reactors and accelerators.