Characterization of irradiation fields for fuel and material irradiation in the experimental fast reactor Joyo

The Joyo MK-III core is a worldwide fast neutron irradiation field not only for FBR development but also for use in other fields such as light water reactor (LWR) and fusion reactor studies, and in the non-nuclear industry. The characterization of these neutron and gamma ray fields is most important to utilize for irradiation tests. This paper describes the details of distributions of neutron flux, reaction rate and gamma heating in the MK-III core. The calculation accuracy of the core management codes HESTIA, TORT and MCNP, was also evaluated by the measured data. The calculated results in neutron calculation agreed well with the measured one. The calculation method was validated and correction factors were identified. In case of gamma heating evaluation, the calculated result is underestimated with respect to the experimental value especially in the upper and lower SS reflector region. Further investigations in gamma heating evaluation are needed. (author)