Abstract: A light water reactor to safely convert depleted uranium into a fuel source that could be used as a sustainable source of energy for centuries. The reactor is a type of breed-burn reactor uniquely combined with a proliferation-resistant fuel cycle with no uranium enrichment and no plutonium isolation. It is comprised of a compact factory-produced fast region and a thermal region that produces about 95% of the core power and contains the passageways for transports of delayed-neutron emitters to the fast region, where they can provide additional neutrons (source-based mode) or all the necessary excitation without an external neutron source (self-regulating mode). A second embodiment of the invention is a small unit driven by a neutron source with beam recycling for propulsion, electrical power or radioisotope production. It could also serve as a demonstration facility for the transmutation reactor with fission-fusion fuel.

Abstract: A core of a nuclear reactor wherein the core is provided with a new fuel part at which new fuel is loaded and a burning part where the fuel burns, plutonium which is produced from uranium fissions to generate output, and the burning part moves from the beginning to end of the burning cycle, wherein when dividing the core, which is substantially circular when viewed by a plan view, into a center part and a peripheral part, the new fuel part is formed so that the weight of uranium per unit volume at the center part becomes smaller than the weight of uranium per unit volume at the peripheral part.

Abstract: Exemplary embodiments provide automated nuclear fission reactors and methods for their operation. Exemplary embodiments and aspects include, without limitation, re-use of nuclear fission fuel, alternate fuels and fuel geometries, modular fuel cores, fast fluid cooling, variable burn-up, programmable nuclear thermostats, fast flux irradiation, temperature-driven surface area/volume ratio neutron absorption, low coolant temperature cores, refueling, and the like.

Abstract: To provide a fast reactor having improved structural reliability and excellent safety. A fast reactor 1 comprises: a reactor vessel 7 accommodating therein a reactor core 2 and a primary coolant 5; an intermediate heat exchanger 15 disposed in the reactor vessel 7, for transferring a heat energy of the primary coolant 5 heated in the reactor core 2 to a secondary coolant 45; an intermediate heat exchanger upper drum 15a disposed above the intermediate heat exchanger 15. Disposed above the intermediate heat exchanger upper drum 15a is an upper plug 10 having a neutron shielding function and a heat shielding function. A thermal-expansion absorbing unit 46 is disposed between the intermediate heat exchanger upper drum and the upper plug, for absorbing a thermal expansion of the intermediate heat exchanger upper drum in an axial direction and a radial direction of the intermediate heat exchanger upper drum, and defining a reactor cover gas boundary.

Abstract: Exemplary embodiments provide automated nuclear fission reactors and methods for their operation. Exemplary embodiments and aspects include, without limitation, re-use of nuclear fission fuel, alternate fuels and fuel geometries, modular fuel cores, fast fluid cooling, variable burn-up, programmable nuclear thermostats, fast flux irradiation, temperature-driven surface area/volume ratio neutron absorption, low coolant temperature cores, refueling, and the like.

Abstract: Exemplary embodiments provide automated nuclear fission reactors and methods for their operation. Exemplary embodiments and aspects include, without limitation, re-use of nuclear fission fuel, alternate fuels and fuel geometries, modular fuel cores, fast fluid cooling, variable burn-up, programmable nuclear thermostats, fast flux irradiation, temperature-driven surface area/volume ratio neutron absorption, low coolant temperature cores, refueling, and the like.

Abstract: A preventive maintenance method and apparatus for a structural member in a reactor pressure vessel according to the present invention reduce a tensile residual stress on a surface of the structural member by impinging a water jet from a nozzle onto a plane surface of a deflector to thereby change direction of flow of the water jet, and impinging the water jet after being deflected onto the surface of the structural member. This method and apparatus are applicable to a narrow space portion, and can improve a residual stress on the surface of the structural member and can also prevent damage such as stress corrosion cracking.

Abstract: The internal structure comprises a bed (5) supporting the core (3) of the reactor and supplying liquid metal to the core, plating (6) resting on the bottom of the main vessel (1) of the reactor and an internal vessel (8) separating the hot collector (12) from the cold collector (13) of the liquid metal. The internal vessel (8) is directly fixed to the upper part of the bed (5) which rests on the plating (6) through the medium of slidable bearing means (21), (22). The bed (5) is connected to means (18) for supplying cooling liquid metal in a zone located at its periphery and outside the internal vessel (8) and the plating (6). Assemblies (31) providing a lateral neutronic protection are fixed to the bed (5) at the periphery of the fuel core (3).

Abstract: Fresh fuel bundles are inserted into core locations with small coolant flow orifices, while mid-life fuel bundles are inserted into core locatiosn with large coolant flow locations. Thus, fissile fuel production is promoted at the expense of fissioning early in a bundle lifetime, increasing the effective quantity of fuel available for energy production. Moreover, fissioning is promoted at the expense of conversion later in the bundle lifetime to enhance reactivity of the remaining fissile material and to minimize the further production of fissile fuel. The net result is longer fuel lifetimes and reduced radioactive waste.

Abstract: A light water cooled and moderated nuclear reactor for breeding fissile material on a uranium-plutonium cycle and also a method of operating a light water cooled and moderated reactor having a prebreeder section fueled from plutonium extracted from fuel discharged by a uranium burner or converter burner core. Subsequently, the prebreeder section, together with a breeder section, operated as coupled cores or modules, becomes self-sustaining and able to breed fissile plutonium fuels at a relatively high rate of gain.

Abstract: An integral nuclear fuel element assembly utilizes longitudinally finned fuel pins. The continuous or interrupted fins of the fuel pins are brazed to fins of juxtaposed fuel pins or directly to the juxtaposed fuel pins or both. The integrally brazed fuel assembly is designed to satisfy the thermal and hydraulic requirements of a fuel assembly lattice having moderator to fuel atom ratios required to achieve high conversion and breeding ratios.