A pressurized water reactor (PWR) includes a vertical cylindrical pressure vessel having a lower portion containing a nuclear reactor core and a vessel head defining an integral pressurizer. A reactor coolant pump (RCP) mounted on the vessel head includes an impeller inside the pressure vessel, a pump motor outside the pressure vessel, and a vertical drive shaft connecting the motor and impeller. The drive shaft does not pass through the integral pressurizer. The drive shaft passes through a vessel penetration of the pressure vessel that is at least large enough for the impeller to pass through.

Fission reactor has a shell encompassing a reactor space within which are a central longitudinal channel, a plurality of axially extending rings with adjacent rings defining an annular cylindrical space in which a first plurality of primary axial tubes are circumferential located. Circumferentially adjacent primary axial tubes are separated by one of the plurality of secondary channels and a plurality of webbings connects at least a portion of the plurality of primary axial tubes to adjacent structure. A fissionable nuclear fuel composition is located in at least some of the plurality of secondary channels and a primary coolant passes thorough at least some of the primary axial tubes. Additive and/or subtractive manufacturing techniques produce an integral and unitary structure for the fuel loaded reactor space. During manufacturing and as-built, the reactor design can be analyzed using a computational platform that integrates and analyzes data from in-situ monitoring during manufacturing.

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 designed to allow efficient packing of components within the reactor vessel, such as by offsetting the core, and/or vertically stacking components. The in-vessel storage system can be separate from the support cylinder and these components can be fabricated and shipped separately and coupled together at the construction site. Furthermore, the in-vessel storage system can be located adjacent to the core rather than being located circumferentially around it, and may also be located beneath the heat exchanger to further improve packing of components within the vessel. Through these, and other changes, the delicate components can be manufactured in a manufacturing facility, assembled, and shipped by commercial transportation options without exceeding the shipping envelope.

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 system for sensing a UF.sub.6 gas leak in a nuclear fuel manufacturing process is proposed. The system is configured to sense whether or not there is a UF.sub.6 gas leak by optically detecting UO.sub.2F.sub.2 in a solid state generated due to a reaction with outside air, and thus to allow prevention of damage to a detection apparatus by means of sensing in a non-contact manner whether or not there is a UF.sub.6 gas leak, and to realize extension of mechanical life and reduction of the maintenance and repair cost for the detection apparatus.

A system for sensing a UF.sub.6 gas leak in a nuclear fuel manufacturing process is proposed. The system is configured to sense whether or not there is a UF.sub.6 gas leak by optically detecting UO.sub.2F.sub.2 in a solid state generated due to a reaction with outside air, and thus to allow prevention of damage to a detection apparatus by means of sensing in a non-contact manner whether or not there is a UF.sub.6 gas leak, and to realize extension of mechanical life and reduction of the maintenance and repair cost for the detection apparatus.

The present disclosure relates to a pellet containing an oxide additive to improve a nuclear-fission-gas-adsorption ability of a uranium-dioxide pellet used as nuclear fuel and increase the grain size thereof, and to a method of manufacturing the same. A La.sub.2O.sub.3—Al.sub.2O.sub.3—SiO.sub.2 sintering additive is added to uranium dioxide so that mass movement is accelerated due to the liquid phase generated during sintering of the uranium-dioxide pellet, which promotes the growth of grains thereof. Further, since less volatilization occurs during sintering due to the low vapor pressure of the liquid phase, efficient additive performance is exhibited, so the liquid phase surrounding the grain boundary effectively adsorbs cesium, which is a nuclear fission gas.

A cross-over fluid coupling includes a first coupling end and a second coupling end. A plurality of first conduits have inner ends disposed toward the first coupling end and outer ends spaced apart from the inner end toward the second coupling end and being outboard of the inner end. A plurality of second conduits have outer ends that are disposed toward the first coupling end and positioned laterally outboard of the inner end of at least one of the first conduits, and inner ends that are spaced apart from the outer end toward the second coupling end in the axial direction and is laterally inboard of the outer end of the at least one of the first conduits.

A cross-over fluid coupling includes a first coupling end and a second coupling end. A plurality of first conduits have inner ends disposed toward the first coupling end and outer ends spaced apart from the inner end toward the second coupling end and being outboard of the inner end. A plurality of second conduits have outer ends that are disposed toward the first coupling end and positioned laterally outboard of the inner end of at least one of the first conduits, and inner ends that are spaced apart from the outer end toward the second coupling end in the axial direction and is laterally inboard of the outer end of the at least one of the first conduits.