Nuclear reactor (alternatives), fuel assembly of seed-blanket subassemblies for nuclear reactor (alternatives), and fuel element for fuel assembly

Abstract

The invention relates to light water reactor designs in which thorium is used as fuel and in particular to designs of jacketless fuel assemblies, which make up the cores of pressurized water reactors (PWRs) such as the VVER-1000. Nuclear reactor cores containing seed and blanket subassemblies that make up the fuel assemblies are used to burn thorium fuel together with conventional reactor fuel that includes nonproliferative enriched uranium, as well as weapons-grade and reactor-grade plutonium. In the first alternative, the reactor core is fully 'nonproliferative,' since neither the reactor fuel nor the wastes generated can be used to produce nuclear weapons. In the second version of the invention, the reactor core is used to burn large amounts of weapons-grade plutonium together with thorium and provides a suitable means to destroy stockpiles of weapons-grade plutonium and convert the energy released to electric power. The cores in both embodiments of the invention are made up of a set of seed-blanket assemblies, which have central seed areas surrounded by annular blanket areas. The seed areas contain uranium or plutonium fuel rods, while the blanket areas contain thorium fuel rods. The volume ratio of moderator to fuel and the relative sizes of the seed area and the blanket area have been optimized so that neither embodiment of the invention generates wastes that can be used to produced nuclear weapons. A new refueling system is also used for the first embodiment of the invention to maximize recycling of the seed fuel; the system also ensures that the spent nuclear fuel cannot be used to produce nuclear weapons.