A welding method includes welding a base material (1) of low alloy steel which is irradiated with neutrons using a welding material (2) of austenitic stainless steel.

A welding method includes welding a base material (1) of low alloy steel which is irradiated with neutrons using a welding material (2) of austenitic stainless steel.

A cooling system for a reactor module includes a reactor pressure vessel that houses primary coolant and a steam generator that lowers a temperature of the reactor pressure vessel by transferring heat from the primary coolant to a secondary coolant. The steam generator releases at least a portion of the secondary coolant as steam. Additionally, the cooling system includes a containment vessel that at least partially surrounds the reactor vessel in a containment region. The containment region is dry during normal operation of the reactor module. A controller introduces a source of water into the containment region in response to a non-emergency shut down of the reactor module. The source of water is located external to the containment vessel, and the water is introduced into the containment region after the steam generator has initially lowered the temperature of the reactor pressure vessel in response to releasing the steam.

A cooling system for a reactor module includes a reactor pressure vessel that houses primary coolant and a steam generator that lowers a temperature of the reactor pressure vessel by transferring heat from the primary coolant to a secondary coolant. The steam generator releases at least a portion of the secondary coolant as steam. Additionally, the cooling system includes a containment vessel that at least partially surrounds the reactor vessel in a containment region. The containment region is dry during normal operation of the reactor module. A controller introduces a source of water into the containment region in response to a non-emergency shut down of the reactor module. The source of water is located external to the containment vessel, and the water is introduced into the containment region after the steam generator has initially lowered the temperature of the reactor pressure vessel in response to releasing the steam.

Structures for forming a module, such as a module for use in a nuclear reactor building, and associated systems and methods are described herein. A representative structure can include a first plate, a second plate spaced apart from and positioned parallel to the first plate, and a support assembly positioned between the first and second plates. The support assembly can include a column, a first beam extending from the column parallel to the first and second plates, and a second beam extending from the column parallel to the first and second plates. The panel structure can further include a plurality of spaced apart joint plates extending between and connecting the first and second plates. The joint plates can support the first beam and the second beam. The panel structure can further include a fill material between the first and second plates and surrounding the support assembly and the joint plates.

A method for manufacturing a core barrel according to the embodiment includes: welding one end part of a short ring to a lower core support plate; and machining the lower core support plate to which the short ring is welded. The machining of the lower core support plate includes forming a placement surface on which the fuel assembly is to be placed; and forming a fuel alignment pin hole, in which a fuel alignment pin for positioning the fuel assembly is to be inserted. After the machining of the lower core support plate, a main body barrel is welded to the other end part of the short ring, where the main body barrel covers the reactor core including the fuel assembly to be placed on the placement surface.

A method for manufacturing a core barrel according to the embodiment includes: welding one end part of a short ring to a lower core support plate; and machining the lower core support plate to which the short ring is welded. The machining of the lower core support plate includes forming a placement surface on which the fuel assembly is to be placed; and forming a fuel alignment pin hole, in which a fuel alignment pin for positioning the fuel assembly is to be inserted. After the machining of the lower core support plate, a main body barrel is welded to the other end part of the short ring, where the main body barrel covers the reactor core including the fuel assembly to be placed on the placement surface.

A power distribution plate (PDP) sits on top of a support plate. Control rod drive mechanism (CRDM) units are mounted on top of the PDP, but the PDP is incapable of supporting the weight of the CRDM units and instead transfers the load to a support plate. The PDP has receptacles which receive cable modules each including mineral insulated (MI) cables, the MI cables being connected with the CRDM units. The PDP may further include a set of hydraulic lines underlying the cable modules and connected with the CRDM units. The cable modules in their receptacles define conduits or raceways for their MI cables and for any underlying hydraulic lines.

A power distribution plate (PDP) sits on top of a support plate. Control rod drive mechanism (CRDM) units are mounted on top of the PDP, but the PDP is incapable of supporting the weight of the CRDM units and instead transfers the load to a support plate. The PDP has receptacles which receive cable modules each including mineral insulated (MI) cables, the MI cables being connected with the CRDM units. The PDP may further include a set of hydraulic lines underlying the cable modules and connected with the CRDM units. The cable modules in their receptacles define conduits or raceways for their MI cables and for any underlying hydraulic lines.

A method for detecting gas leakage from a radioactive material sealed container includes measuring a temperature at a top portion of a metallic sealed container, a temperature at a bottom portion of a lid portion of a concrete-made storage container facing the top portion of the metallic sealed container, or a temperature of a member existing between the bottom portion of the lid portion and the top portion of the metallic sealed container. An inner temperature of the lid portion of the concrete-made storage container is also measured. Presence of leakage of inactive gas is estimated by comparing the temperatures.