This invention relates to a structure to surround the fusion plasma of a fusion reactor, or other fusion plasma containing device, said structure commonly called a blanket.
Fusion reactors of all varieties produce energetic neutrons which can advantageously be captured in a blanket region or structure substantially or completely surrounding the reactor core. In a fusion-fission hybrid reactor, the blanket contains a fertile fuel intended to breed fissile fuel and to produce energy by neutron induced fission. In a pure fusion reactor, the blanket contains fertile species which capture neutrons to form valuable isotopes. In both reactor types, the blanket is cooled by a coolant by which means heat is transferred away to cool the reactor, and perhaps generate useful power.
While many nuclear transformations are possibly of interest in a fusion reactor blanket, the generation of tritium from a neutron-induced nuclear reaction of lithium nuclei is especially important since tritium is a fusion reactor fuel.
The design of a suitable blanket is considered a significant obstacle to the development of a practical fusion power reactor. Several concepts have been proposed encompassing liquid lithium or solid lithium compounds for tritium breeding, solid fertile fuel for fissile element breeding, and gas, liquid, and even pebble bed coolants. All have technical handicaps. A solid blanket must be replaceable for isotope recovery and for blanket repair which, it develops, is a difficult task. A liquid lithium blanket can be continually or intermittently processed for tritium recovery and can readily be used to recover heat deposited therein by conventional means. However, liquid lithium and other liquid metals in the presence of the strong magnetic fields (in magnetic confinement fusion reactors) experience magnetohydrodynamic forces which limit the serviceability of that type of blanket. Gas cooled blankets have intrinsically lower material densities which reduce the efficiencies of heat transfer. Pebble bed blankets generally require high coolant pumping power.
Consequently, it is desired to provide a blanket for a fusion reactor which can be refueled on-line, has high density, and is well adapted for power and isotope production.