Initial results of neutronics experiments for evaluation of tritium production rate in solid breeding blanket

In order to examine the accuracy of the tritium production rate (TPR) calculations, neutronics experiments have been performed with D-T neutrons at Fusion Neutronics Source (FNS) of JAERI by using a mockup of the solid breeder blanket consisting of F82H blocks, Li₂TiO₃ blocks with a ⁶Li enrichment of 40 and 95 %, and beryllium blocks. Pellet detectors made of Li₂CO₃ and Li₂TiO₃ enriched to the proper ⁶Li volume concentration were embedded in stacks in a hole of each Li₂TiO₃ layer. After D-T neutron irradiation, the amount of tritium produced in the pellets was measured by liquid scintillation counting methods, of which accuracy was 10%. The TPR was calculated by the Monte Carlo codes MCNP-4B with the nuclear data libraries JENDL-3.2, JENDL-FF, ENDF-VI and FENDL-2. The C/E values of the TPR were 1.15 on average. To clarify the accuracy of the macroscopic absorption cross section for beryllium blocks, the low energy neutron transport was investigated by pulsed D-T neutron injection into the beryllium assembly. The macroscopic absorption cross section of beryllium blocks was about 40 % larger than that of pure beryllium. However, it is found that such amount of impurities does not affect TPR significantly.