Tungsten boride shields in a spherical tokamak fusion power plant

Abstract The favourable properties of tungsten borides for shielding the central high temperature superconductor (HTS) core a spherical tokamak fusion power plant are modelled using MCNP code. objectives to minimize deposition into cooled HTS core, and keep radiation damage acceptable levels by limiting neutron gamma fluxes. shield materials compared W 2 B, WB, B 5 WB 4 along with reactively sintered boride 0.329 C 0.074 Cr 0.024 Fe 0.274 0.299 , monolithic WC. Five thicknesses between 253 670 mm were considered, corresponding plasma major radii 1400 2200 mm. gave most results factor ∼10 or greater reduction in flux energy as W. These layered water-cooled shields, giving result that moderating boron, comparable deposition, (in case ) even better performance. Good performance without water-coolant has advantages from reactor safety perspective due risks associated radio-activation oxygen. 10 isotope concentrations 0% 100% considered shields. naturally occurring 20% fraction much lower depositions than fraction, but improvement largely saturated beyond 40%. Thermophysical candidate discussed, particular thermal strain. To our knowledge, is unrivalled other materials. This partly its trigonal crystal structure gives it higher atomic density borides. It also suggested depends on having just enough content maintain constant spectrum across shield.