Progress of the ST-VNS study

Progress is given on the investigation of a low cost, scientifically attractive, and technologically feasible volumetric neutron source (VNS) based on the spherical torus (ST) concept. The ST-VNS has a major radius of 1.07 m, an aspect ratio of 1.4, and a plasma elongation 3. It can produce a neutron wall loading ultimately up to 5 MW/m² averaged over the outboard test section when the fusion power reaches 380 MW. Initial operation of this device can be at a level of 1 MW/m² or lower. Higher performance blanket components can be developed to raised the neutron wall loading. Using staged high wall loading operation scheme and optimistic availability projected for the VNS device, a neutron fluence of more than 30 MW-y/m² can be expected to accumulate within 20 years of operation. Assessments of lifetime and reliability of fusion core components will thus be allowed in a power reactor relevant environment. A full-function testing of fusion core components may also become possible because of the high neutron wall loading capability. Integrated testing of tritium breeding in such a full scale power reactor relevant VNS device can be very useful to verify the self-sufficiency of fuel cycle in candidate power blanket concepts.