A layer protecting the surface of zirconium alloys used as materials for nuclear reactors is formed by a homogenous polycrystalline diamond layer prepared by chemical vapor deposition method. This diamond layer is 100 nm to 50 m thick and the size of the crystalline cores in the layer ranges from 10 nm to 500 nm. Maximum content of non-diamond carbon is 25 mol %, total content of non-carbon impurities is maximum up to 0.5 mol %, RMS surface roughness of the polycrystalline diamond layer has a value less than 40 nm and thermal conductivity of the layer ranges from 1000 to 1900 Wm.sup.1K.sup.1. Coating of the zirconium alloys surface with the described polycrystalline diamond layer serves as a zirconium alloys surface protection against undesirable changes and processes in the nuclear reactor environment.

A system for continuously preparing coated particles in a large scale comprises: a coating furnace, a cooling facility, a solid by-product treatment device, and a gas by-product treatment device connected in sequence. The coating furnace is used for coating particles. The cooling facility is used for cooling the coated particles. The solid by-product treatment device is used for treating solid by-products generated in the coating furnace during the particle coating process. The gas by-product treatment device is used for treating gas by-products generated in the coating furnace during the particle coating process. The system for continuously preparing coated particles resolves the problem that a system in the prior art, aiming at batch production, has a time interval between two batches, wherein a temperature increase process and a temperature decrease process both exist, and is small in scale, does not completely break through laboratory research and cannot achieve real industrial continuous preparation.

A system for continuously preparing coated particles in a large scale comprises: a coating furnace, a cooling facility, a solid by-product treatment device, and a gas by-product treatment device connected in sequence. The coating furnace is used for coating particles. The cooling facility is used for cooling the coated particles. The solid by-product treatment device is used for treating solid by-products generated in the coating furnace during the particle coating process. The gas by-product treatment device is used for treating gas by-products generated in the coating furnace during the particle coating process. The system for continuously preparing coated particles resolves the problem that a system in the prior art, aiming at batch production, has a time interval between two batches, wherein a temperature increase process and a temperature decrease process both exist, and is small in scale, does not completely break through laboratory research and cannot achieve real industrial continuous preparation.

A nuclear reactor core includes a plurality of core assemblies. The core assemblies have a cooperating structure formed at one or more load pads that mechanically couple the plurality of core assemblies together to limit relative motion between core assemblies in a kinematically determinate way. A shear key on one core assembly is configured to fit in a tab slot on an adjacent core assembly. Motion of one core assembly is transferred to a second core assembly and the core assemblies move together.

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.

The invention pertains to a nuclear fuel assembly grid or a portion or a part of the grid, such as a grid strap and/or an integral flow mixer that is at least partially constructed of a composition containing one or more ternary compounds of the general formula I:
M.sub.n+1AX.sub.n(I) wherein, M is a transition metal, A is an element selected from the group A elements in the Chemical Periodic Table, X is carbon or nitrogen, and n is an integer from 1 to 3. The invention further pertains to a method of making the nuclear fuel assembly grid or a portion of a part of the grid, by employing a sintering process to sinter the composition containing one or more ternary compounds in powder form such that the resulting grid or a portion of or a part of the grid includes a plurality of sintered layers.

The invention pertains to a nuclear fuel assembly grid or a portion or a part of the grid, such as a grid strap and/or an integral flow mixer that is at least partially constructed of a composition containing one or more ternary compounds of the general formula I:
M.sub.n+1AX.sub.n(I) wherein, M is a transition metal, A is an element selected from the group A elements in the Chemical Periodic Table, X is carbon or nitrogen, and n is an integer from 1 to 3. The invention further pertains to a method of making the nuclear fuel assembly grid or a portion of a part of the grid, by employing a sintering process to sinter the composition containing one or more ternary compounds in powder form such that the resulting grid or a portion of or a part of the grid includes a plurality of sintered layers.

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.

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.