Progress in Neutronics Studies for the Water Cooled Pebble Bed Blanket

Blanket neutronics experiments were conducted for the development of the water-cooled pebble bed type ITER Test Blanket Module (TBM) using the Fusion Neutronics Source (FNS). Slab mockup assemblies based on the water-cooled pebble bed ITER TBM including water panels and/or a breeder pebble layer were irradiated by 14 MeV neutrons. After the irradiation, the amount of tritium produced in the diagnostic Li₂CO₃ pellets or breeder pebbles is measured by liquid scintillation counting method. The C/E ratios for the tritium production rate in those experiments are within 1 ± 0.05. A plan of the neutronics test on ITER-TBM and the neutronic diagnostics in the module are discussed. Micro fission chambers and compact activation foil transfer systems to be embedded in TBM are proposed for the neutron flux and neutron spectrum measurements, respectively.