Improvements of radiation shielding designs on advanced liquid blankets for fusion reactor FFHR

Improvements of radiation shielding designs for the Flibe-cooled and Li-cooled blanket systems have been performed in the design activity of the helical-type fusion reactor FFHR2 based on 3-D Monte Carlo neutronics calculations. Evaluations of the fast neutron fluxes with a simple torus calculation model indicate that the Flibe-cooled blanket systems would achieve adequate shielding abilities within the blanket space of ∼100 cm by adjusting the ratios of JLF-1 (Reduced Activation Ferritic Steel) and B₄C in the radiation shield. For the Li-cooled blanket system, enhancement with a heavy density material such as WC would be needed for reducing the blanket space to ∼100 cm. Nuclear heating in the superconducting magnet regions was lower than the allowable level for all the blanket systems. In the optimization of the shielding configuration with a 3-D reactor geometry, neutron streaming through the divertor pumping areas and neutron reflection are the issues to be improved by further design modification. (author)