Neutronics Integral Experiments of Lithium-Oxide Fusion Blanket with Heterogeneous Configurations Using Deuterium-Tritium Neutrons

Neutronics experiments for two types of heterogeneous blankets are performed in the Phase-IIC experiments of the Japan Atomic Energy Research Institute/U.S. Department of Energy collaborative program on fusion blanket neutronics. The experimental system uses the same geometry as the previous Phase-IIA series, which was a closed geometry that used a neutron source enclosure of lithium carbonate. The heterogeneities selected for testing are the beryllium edge-on and the water coolant channel assemblies that appear in typical blankets. In the former, the beryllium and the lithium-oxide (Li₂O) layers are piled up alternately in the front part of the test blanket. In the latter, the two simulated water cooling channels are emplaced vertically in the Li₂O blanket. These channels produce a steep gradient of neutron flux and a significant spectrum change around the material boundary. The calculation accuracy and measurement method for these transient regions are key areas of interest in the experiments. The measurements are performed for the tritium production rate and the other nuclear parameters as well as the previous experiments. The void effect is found to not be negligible around the heterogeneous region for the detector with a low-energy response. At the same time, enhancements of tritium production are seen near the beryllium and hydrogenous material. However, the current Monte Carlo calculation shows good agreement with the experiment even in such a boundary.