An integrated passive cooling containment structure for a nuclear reactor includes a concentric arrangement of an inner steel cylindrical shell and an outer steel cylindrical shell that define both a lateral boundary of a containment environment of the nuclear reactor that is configured to accommodate a nuclear reactor and an annular gap space between the inner and outer steel cylindrical shells, a concrete donut structure at a bottom of the annular gap space, and a plurality of concrete columns spaced apart azimuthally around a circumference of the annular gap and extending in parallel from a top surface of the concrete donut structure to a top of the annular gap space. The outer and inner steel cylindrical shells and the concrete donut structure at least partially define one or more coolant channels extending through the annular gap space.

An integrated passive cooling containment structure for a nuclear reactor includes a concentric arrangement of an inner steel cylindrical shell and an outer steel cylindrical shell that define both a lateral boundary of a containment environment of the nuclear reactor that is configured to accommodate a nuclear reactor and an annular gap space between the inner and outer steel cylindrical shells, a concrete donut structure at a bottom of the annular gap space, and a plurality of concrete columns spaced apart azimuthally around a circumference of the annular gap and extending in parallel from a top surface of the concrete donut structure to a top of the annular gap space. The outer and inner steel cylindrical shells and the concrete donut structure at least partially define one or more coolant channels extending through the annular gap space.

A pressure vessel includes a pressure vessel body provided with a flow channel through which a fluid is caused to flow, having a rectangular cross-sectional shape, and formed to extend in a direction of flow of the fluid, a body flange provided at at least one end side of the pressure vessel body in a longitudinal direction and having a circular cross-sectional shape, and a connecting member connecting the pressure vessel body and the body flange to each other, and the connecting member has a body-flange connected portion connected to the body flange, having a circular cross-sectional shape, and formed in a cylindrical shape, a pressure-vessel-body connected portion connected to the pressure vessel body, being larger in outer shape than the body-flange connected portion, and formed in a cylindrical shape, and a connecting portion connecting the body-flange connected portion and the pressure-vessel-body connected portion to each other and formed in a cylindrical shape with a shape changing to be gradually smaller from the pressure-vessel-body connected portion toward the body-flange connected portion.

A metal gasket includes: a metal gasket body having, in the outer circumferential surface thereof, a recessed circumferential groove; and an elastic body. An elastic body is inserted into the circumferential groove of the gasket body; in a vertical cross-section of the metal gasket, an arc-shaped upper seal surface having an upward-facing bulge is formed on the top surface of the gasket body which contacts a material to be sealed, and an arc-shaped lower seal surface having a downward-facing bulge is formed on the bottom surface of the gasket body which contacts the material to be sealed; and an upper flat surface or an upper notched section is provided to the upper seal surface, and a lower flat surface or a lower notched section is provided to the lower seal surface.

A nuclear reactor comprises a nuclear reactor core disposed in a pressure vessel. An isolation valve protects a penetration through the pressure vessel. The isolation valve comprises: a mounting flange connecting with a mating flange of the pressure vessel; a valve seat formed into the mounting flange; and a valve member movable between an open position and a closed position sealing against the valve seat. The valve member is disposed inside the mounting flange or inside the mating flange of the pressure vessel. A biasing member operatively connects to the valve member to bias the valve member towards the open position. The bias keeps the valve member in the open position except when a differential fluid pressure across the isolation valve and directed outward from the pressure vessel exceeds a threshold pressure.

A nuclear fuel assembly is constructed with fuel assembly components that are wire wrapped and positioned in hexagonal rings within a fuel assembly duct. The fuel assembly components positioned in an outermost ring of the fuel assembly are wire wrapped with a pitch that is shorter than fuel assembly components positioned at an interior ring of the fuel assembly. The shorter pitch at the outer ring of the fuel assembly increases pressure drop of a coolant fluid at the edge and corner subchannels and thereby reduces the temperature gradient across the fuel assembly, which provides a higher output temperature of the nuclear reactor without substantially increasing peak temperature of the fuel cladding.

A nuclear fuel assembly is constructed with fuel assembly components that are wire wrapped and positioned in hexagonal rings within a fuel assembly duct. The fuel assembly components positioned in an outermost ring of the fuel assembly are wire wrapped with a pitch that is shorter than fuel assembly components positioned at an interior ring of the fuel assembly. The shorter pitch at the outer ring of the fuel assembly increases pressure drop of a coolant fluid at the edge and corner subchannels and thereby reduces the temperature gradient across the fuel assembly, which provides a higher output temperature of the nuclear reactor without substantially increasing peak temperature of the fuel cladding.

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.

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.

The present disclosure is directed to systems and methods useful for the construction and operation of a Modular Integrated Gas High-Temperature Reactor (MIGHTR). The MIGHTR includes a reactor core assembly disposed at least partially within a core baffle within a first high-pressure shell portion, a thermal transfer assembly disposed at least partially within a flow separation barrel within a second high-pressure shell portion. The longitudinal axes of the first high-pressure shell portion and the second high-pressure shell portion may be collinear. The reactor core assembly may be accessed horizontally for service, maintenance, and refueling. The core baffle may be flexibly displaceably coupled to the flow separation barrel. Coolant gas flows through the reactor core assembly and into the thermal transfer assembly where the temperature of the coolant gas is reduced. A plurality of coolant gas circulators circulate the cooled coolant gas from the thermal transfer assembly to the reactor core assembly.