The invention is a process of repairing cracked or microstructurally damaged portions of irradiated materials, such as nuclear reactor pressure vessels and shrouds. A damaged portion of the irradiated substrate is first removed, such as by electrical discharge machining (EDM). After removing the damaged portion, the recast layer inherent in the EDM process is then removed. Once the repair area substrate material has been removed to a calculated depth, the created cavity is then filled without releasing transmutated elements within the irradiated material. A chamber may be placed on the irradiated material surrounding the repair area to create an isolated work space.

A method for manufacturing a core barrel according to the embodiment includes: welding one end part of a short ring to a lower core support plate; and machining the lower core support plate to which the short ring is welded. The machining of the lower core support plate includes forming a placement surface on which the fuel assembly is to be placed; and forming a fuel alignment pin hole, in which a fuel alignment pin for positioning the fuel assembly is to be inserted. After the machining of the lower core support plate, a main body barrel is welded to the other end part of the short ring, where the main body barrel covers the reactor core including the fuel assembly to be placed on the placement surface.

A method for manufacturing a core barrel according to the embodiment includes: welding one end part of a short ring to a lower core support plate; and machining the lower core support plate to which the short ring is welded. The machining of the lower core support plate includes forming a placement surface on which the fuel assembly is to be placed; and forming a fuel alignment pin hole, in which a fuel alignment pin for positioning the fuel assembly is to be inserted. After the machining of the lower core support plate, a main body barrel is welded to the other end part of the short ring, where the main body barrel covers the reactor core including the fuel assembly to be placed on the placement surface.

A nuclear reactor core (1) for a molten salt nuclear reactor (100). The nuclear reactor core (1) has a tubular cylindrical center moderator vessel (10) for passage of a liquid moderator (11), a cylindrical fuel salt jacket surrounding the center moderator vessel (10), and a cylindrical neutron reflector jacket surrounding the cylindrical fuel salt jacket, wherein the cylindrical center moderator and neutron reflector vessel (10) has a largest inner cross-sectional area medially between a liquid moderator and neutron reflector inlet (12) of the center moderator and neutron reflector vessel (10) and a liquid moderator and neutron reflector outlet (13) of the moderator and neutron reflector vessel (10).

A method for the inner-contour passivation of steel surfaces of a nuclear reactor consists in filling a first contour of a nuclear reactor with a liquid metal coolant, introducing a reagent into the liquid metal coolant, said reagent interacting with the material of elements of the first contour, forming a protective film, and heating the liquid metal coolant, having the reagent introduced therein, to a temperature allowing for conditions for forming the protective film. The liquid metal coolant having the reagent introduced therein is kept at said temperature until a continuous protective film is formed on the surface of the material of the elements of the first contour. The liquid metal coolant having reagent introduced therein is heated by means of the friction thereof against rotating vanes of a vane pump, which is submerged in the liquid metal coolant. The present invention thus provides for a simpler passivation process, a more reliable passivation mode, an increase in the safety thereof and a simpler control over the process of passivation of steel surfaces.

A method for the inner-contour passivation of steel surfaces of a nuclear reactor consists in filling a first contour of a nuclear reactor with a liquid metal coolant, introducing a reagent into the liquid metal coolant, said reagent interacting with the material of elements of the first contour, forming a protective film, and heating the liquid metal coolant, having the reagent introduced therein, to a temperature allowing for conditions for forming the protective film. The liquid metal coolant having the reagent introduced therein is kept at said temperature until a continuous protective film is formed on the surface of the material of the elements of the first contour. The liquid metal coolant having reagent introduced therein is heated by means of the friction thereof against rotating vanes of a vane pump, which is submerged in the liquid metal coolant. The present invention thus provides for a simpler passivation process, a more reliable passivation mode, an increase in the safety thereof and a simpler control over the process of passivation of steel surfaces.

According to a first aspect, there is provided a nuclear fission reactor. The nuclear fission reactor comprises a core, a tank surrounding the core, and a cooling system located outside the tank. The cooling system comprises one or more structures configured to absorb thermal radiation emitted from an outer wall of the tank. The structures are not substantially thermally coupled to the tank except by radiation. The cooling system further comprises a cold air inlet and a hot air outlet, positioned such that air flows from the cold air inlet to the hot air outlet over, around and/or through the one or more structures.

Nuclear reactors have very few systems for significantly reduced failure possibilities. Nuclear reactors may be boiling water reactors with natural circulation-enabling heights and smaller, flexible energy outputs in the 0-350 megawatt-electric range. Reactors are fully surrounded by an impermeable, high-pressure containment. No coolant pools, heat sinks, active pumps, or other emergency fluid sources may be present inside containment; emergency cooling, like isolation condenser systems, are outside containment. Isolation valves integral with the reactor pressure vessel provide working and emergency fluid through containment to the reactor. Isolation valves are one-piece, welded, or otherwise integral with reactors and fluid conduits having ASME-compliance to eliminate risk of shear failure. Containment may be completely underground and seismically insulated to minimize footprint and above-ground target area.

Nuclear reactors have very few systems for significantly reduced failure possibilities. Nuclear reactors may be boiling water reactors with natural circulation-enabling heights and smaller, flexible energy outputs in the 0-350 megawatt-electric range. Reactors are fully surrounded by an impermeable, high-pressure containment. No coolant pools, heat sinks, active pumps, or other emergency fluid sources may be present inside containment; emergency cooling, like isolation condenser systems, are outside containment. Isolation valves integral with the reactor pressure vessel provide working and emergency fluid through containment to the reactor. Isolation valves are one-piece, welded, or otherwise integral with reactors and fluid conduits having ASME-compliance to eliminate risk of shear failure. Containment may be completely underground and seismically insulated to minimize footprint and above-ground target area.

A nuclear reactor is constructed in sub-modules and super modules which are manufactured, packaged, and shipped to a construction site. At least some of the modules are packaged in suitable shielding containers or portions of containers, which may be steel. The modules are assembled on-site, and some of the modules remain within their respective shipping containers after assembly. One or more of the shipping containers may be used as concrete forms to support the pouring of concrete in between selected modules. The concrete may be used for structural support, shielding, or both.