An austenitic stainless steel includes a mixed grain structure composed of a columnar crystal having an average crystal grain size of 20 μm or less and an equiaxed crystal having an average crystal grain size of 5.0 μm or less, in which an area proportion of the columnar crystal in the mixed grain structure is 20% or more, and an average crystal grain size of the whole mixed grain structure is 5.0 μm or less. Accordingly, it is possible to provide a material having excellent irradiation resistance and mechanical properties.

A conduit housing includes a top face, a pair of side faces disposed opposite each other and adjacent to the top face, a front side, and a rear side. The top face includes a plurality of vertical conduit ports arranged in a plurality of rows. The front side is positioned between the pair of side faces and defines a plurality of stepped faces. The rear side is disposed opposite the front side and adjacent the top face. The stepped faces include a plurality of downward faces and each of the plurality of downward faces defines a downward face plane. The stepped faces also include a plurality of upward faces, where each of the plurality of upward faces defines an upward face plane. Each upward face includes a plurality of pitched conduit ports.

A welding system of cylindrical structures which welds a welding end surface of an upper cylindrical structure and that of a lower one in an axial direction thereof, includes: two or more welding apparatuses opposite to the welding end surfaces and disposed at equal arrangement intervals in the circumferential direction thereof; a moving device configured to rotate the upper and lower cylindrical structures relative to the welding apparatuses in a circumferential direction thereof; and a control device configured to control the welding apparatuses and the moving device. The welding apparatus has a filler metal and a heating source therefor, and melts and fuses the filler metal on the welding end surfaces to weld them, and the control device is configured to continuously rotate the upper and lower cylindrical structures an angle of the arrangement interval by the moving device, while welding the welding end surfaces with the welding apparatuses.

A welding system of cylindrical structures which welds a welding end surface of an upper cylindrical structure and that of a lower one in an axial direction thereof, includes: two or more welding apparatuses opposite to the welding end surfaces and disposed at equal arrangement intervals in the circumferential direction thereof; a moving device configured to rotate the upper and lower cylindrical structures relative to the welding apparatuses in a circumferential direction thereof; and a control device configured to control the welding apparatuses and the moving device. The welding apparatus has a filler metal and a heating source therefor, and melts and fuses the filler metal on the welding end surfaces to weld them, and the control device is configured to continuously rotate the upper and lower cylindrical structures an angle of the arrangement interval by the moving device, while welding the welding end surfaces with the welding apparatuses.

Illustrative embodiments provide modular nuclear fission deflagration wave reactors and methods for their operation. Illustrative embodiments and aspects include, without limitation, modular nuclear fission deflagration wave reactors, modular nuclear fission deflagration wave reactor modules, methods of operating a modular nuclear fission deflagration wave reactor, and the like.

Illustrative embodiments provide modular nuclear fission deflagration wave reactors and methods for their operation. Illustrative embodiments and aspects include, without limitation, modular nuclear fission deflagration wave reactors, modular nuclear fission deflagration wave reactor modules, methods of operating a modular nuclear fission deflagration wave reactor, and the like.

Provided is a method for manufacturing a cylindrical member which includes end bending of respective end portions of a plate material in a longitudinal direction, primary grooving of respective end surfaces of the plate material subjected to end bending, bending of the plate material to a ring shape, secondary grooving of respective end surfaces of the plate material subjected to bending in a ring shape, and joining of respective end surfaces of the plate material. Therefore, it is possible to manufacture a high-quality cylindrical member.

Disclosed embodiments include nuclear fission reactors, nuclear fission fuel pins, methods of operating a nuclear fission reactor, methods of fueling a nuclear fission reactor, and methods of fabricating a nuclear fission fuel pin.

A reactor unit cell is disclosed including a graphite moderator structure, a heat pipe positioned in the graphite moderator structure, and a fuel assembly positioned in the graphite moderator structure. The fuel assembly comprises a beryllium-oxide sleeve and nuclear fuel positioned in the beryllium-oxide sleeve.

A reactor unit cell is disclosed including a graphite moderator structure, a heat pipe positioned in the graphite moderator structure, and a fuel assembly positioned in the graphite moderator structure. The fuel assembly comprises at least one fuel rod. Each fuel rod comprises a beryllium-oxide sleeve and nuclear fuel positioned in the beryllium-oxide sleeve.