Provided herein is a fuel rod and a fuel assembly for light water reactors in which crack penetration to a fuel cladding tube or an end plug can be prevented even when cracking occurs at the joint between the fuel cladding tube and the end plug for which a ceramic base material is used. A fuel rod 10a for light water reactors includes: a cylindrical cladding tube 11 formed of a ceramic base material; a connection 21 formed of the same or similar material to the cladding tube 11; and an end plug 12a having a concave portion 12f of a continuously curved surface shape adapted to house the connection 21. The end plug 12a is formed of the same or similar material to the cladding tube 11. A slanted surface 11a formed at an end portion of the cladding tube 11, and a slanted surface 12d formed at an end portion of the end plug 12a are joined in contact with each other with a metallic joint material 20. The joint is supported by the connection 21.

Micro encapsulated fuel particles enhance safety in high-temperature gas cooled reactors by employing multiple barriers to fission product release. Microencapsulated fuel particles also have the potential to do the same in other reactor platforms. The present disclosure provides a method for enhancing the ability of microencapsulated fuel particles to retain radionuclides and thereby further enhance safety in nuclear reactors. Specifically, a nuclear fuel particle including a fuel kernel; a buffer graphitic carbon layer; an inner pyrolytic carbon layer; a multilayer pressure vessel; and an outer pyrolytic carbon layer is disclosed. The multilayer pressure vessel includes alternating layers of silicon carbide and pyrolytic carbon.

Micro encapsulated fuel particles enhance safety in high-temperature gas cooled reactors by employing multiple barriers to fission product release. Microencapsulated fuel particles also have the potential to do the same in other reactor platforms. The present disclosure provides a method for enhancing the ability of microencapsulated fuel particles to retain radionuclides and thereby further enhance safety in nuclear reactors. Specifically, a nuclear fuel particle including a fuel kernel; a buffer graphitic carbon layer; an inner pyrolytic carbon layer; a multilayer pressure vessel; and an outer pyrolytic carbon layer is disclosed. The multilayer pressure vessel includes alternating layers of silicon carbide and pyrolytic carbon.

Disclosed is an automatic welding apparatus for an end plug of a nuclear fuel rod, which is used to perform resistance welding on a cladding tube and the end plug in a welding chamber. The automatic welding apparatus includes a welding chamber configured to perform resistance welding on an end plug and a cladding tube, a cladding tube transfer unit that has a cladding tube clamp fixedly clamping the cladding tube and a first servo motor for driving the cladding tube clamp in a horizontal direction and that horizontally transfers the cladding tube to the welding chamber, end plug welding electrodes gripping the end plug fed from an end plug feeder, an end plug transfer driver for driving the end plug welding electrodes toward the welding chamber in a forward/backward direction, and a position control module for controlling driving of the first servo motor and the end plug transfer driver.

Disclosed is an automatic welding apparatus for an end plug of a nuclear fuel rod, which is used to perform resistance welding on a cladding tube and the end plug in a welding chamber. The automatic welding apparatus includes a welding chamber configured to perform resistance welding on an end plug and a cladding tube, a cladding tube transfer unit that has a cladding tube clamp fixedly clamping the cladding tube and a first servo motor for driving the cladding tube clamp in a horizontal direction and that horizontally transfers the cladding tube to the welding chamber, end plug welding electrodes gripping the end plug fed from an end plug feeder, an end plug transfer driver for driving the end plug welding electrodes toward the welding chamber in a forward/backward direction, and a position control module for controlling driving of the first servo motor and the end plug transfer driver.

A reduced-temperature method for treatment of a fuel element is described. The method includes molten salt treatment of a fuel element with a nitrate salt. The nitrate salt can oxidize the outer graphite matrix of a fuel element. The method can also include reduced temperature degradation of the carbide layer of a fuel element and low temperature solubilization of the fuel in a kernel of a fuel element.

A method of monitoring in real time pressure resistance welding of a cladding tube and an end plug. The method includes: a first step of detecting welding information including voltage, current, and welding force in a process of pressure resistance welding of a cladding tube and an end plug; a second step of comparing static factors obtained by calculating effective values for the welding information with predetermined reference values, respectively; a third step of calculating dynamic factors for the welding information including the gradient of instantaneous welding force, when the reference values are satisfied in the second step; and a fourth step of determining whether there is defect or not in welding quality by comparing the dynamic factors.

A fuel pellet visual inspection device for manufacturing a nuclear fuel rod improves convenience and workability of visual inspection of a plurality of pellets by simultaneously turning over the pellet. The fuel pellet visual inspection device for manufacturing a nuclear fuel rod includes: a rotary shaft; a pair of seats hinged to the hinge shaft, arranged at both sides from the rotary shaft, and seated with a tray thereon; and a dust-collecting unit disposed under the pair of seats and collecting dust scattered from pellets.

A fuel pellet visual inspection device for manufacturing a nuclear fuel rod improves convenience and workability of visual inspection of a plurality of pellets by simultaneously turning over the pellet. The fuel pellet visual inspection device for manufacturing a nuclear fuel rod includes: a rotary shaft; a pair of seats hinged to the hinge shaft, arranged at both sides from the rotary shaft, and seated with a tray thereon; and a dust-collecting unit disposed under the pair of seats and collecting dust scattered from pellets.

A method of manufacturing nuclear fuel elements may include: forming a graphite base portion of the fuel element; depositing a first layer of graphite spheres on the base portion; depositing a first layer of fuel, burnable poison and/or breeder particles on the first layer of graphite spheres; forming a second layer of graphite spheres on the first layer of particles; depositing a second layer of fuel, burnable poison and/or breeder particles on the second layer of graphite spheres; and forming a graphite cap portion of the fuel element. Fuel, burnable poison and/or breeder particles of the first layer may be are spaced apart by substantially the same distance, and fuel, burnable poison and/or breeder particles of the second layer may be spaced apart by substantially the same distance. The fuel element may be a spherical fuel pebble. The fuel particles may be tri-structural-isotropic (TRISO) particles without an overcoat.