Abstract: A liquid metal cooled nuclear reactor includes a reactor vessel, a containment, an air flow path, and an injection unit. The vessel has a reactor core and a coolant for the reactor core. The containment surrounds an outside of the vessel. The air flow path removes heat by flowing air around the containment. The injection unit injects filler in a gap between the vessel and the containment.

Abstract: A reactor core is immersed in a liquid metal coolant in a core barrel of a liquid metal cooled reactor. The reactor core includes a plurality of fuel assemblies contained in the core barrel, a neutron absorber that absorbs a neutron in the reactor core, and a neutron moderator that moderates a neutron therein so as to control a reactivity of the reactor core. The neutron absorber and the neutron moderator constitute a mixture contained in reactivity control assemblies of the reactor core in the liquid metal coolant prior to immersion of the reactor core. The neutron moderator is composed of zirconium hydride.

Abstract: A fast reactor performing reflector control to control reactivity of the core by moving a neutron reflector in the vertical direction, including: a core fuel assembly; a neutron absorption assembly in the middle of the core fuel assembly; a reflector assembly at the circumference of the core fuel assembly; plural inner neutron shields at the circumference of the reflector assembly; a cylindrical core barrel surrounding entirety of the plural neutron shields; and a drive mechanism controlling the reflector. The reflector assembly includes: a reflector element that reflects neutrons from the core fuel assembly towards the core; a cavity section, arranged thereabove, that permits leakage of neutrons to outside the core; a linkage mechanism that links the reflector element and the cavity section; a guide tube that defines a space for removal/insertion of these; and a connecting section that connects the drive mechanism and the cavity section.

Abstract: A liquid metal cooled nuclear reactor includes a reactor vessel, a containment, an air flow path, and an injection unit. The vessel has a reactor core and a coolant for the reactor core. The containment surrounds an outside of the vessel. The air flow path removes heat by flowing air around the containment. The injection unit injects filler in a gap between the vessel and the containment.

Abstract: A fast reactor having a reactivity control reflector has a reactor vessel in which a coolant is accommodated, a reactor core which is installed in the reactor vessel and dipped with the coolant, and a reflector installed outside of the reactor core so as to be movable in a vertical direction for controlling the reactivity of the reactor core. The reflector of the fast reactor has a lower neutron reflecting portion having a neutron reflection capability higher than that of the coolant and an upper cavity portion located above the neutron reflecting portion and having a neutron reflection capability lower than that of the coolant. The cavity portion is composed of a plurality of cylindrical hermetically-sealed vessels.

Abstract: In a nuclear reactor in which a primary coolant is contained, the primary coolant moves upwardly from the core by an operation thereof. An annular steam generator is arranged in an upper side of the core into which the upwardly moving primary coolant flows and transfers heat in the primary coolant into water therein to generate a steam. A passage structure defines a coolant passage for the primary coolant to an outside of the core. The heat-transferred primary coolant in the annular steam generator flows downwardly in the coolant passage so as to flow into the core, thereby moving upwardly. A reactor vessel is arranged to surround the coolant passage so as to contain the core, the annular steam generator and the passage means therein.

Abstract: A fast reactor having a reflector control system is provided which decreases the change in reactivity of the reactor core with time without performing control of a reflector lifting speed and that of a water flow rate. The above fast reactor has a liquid metal coolant, a reactor core immersed therein, and a neutron reflector which is provided outside the reactor core and which is moved in a vertical direction for adjusting leakage of neutrons therefrom for controlling the reactivity of the reactor core. The neutron reflector described above is gradually moved in an upward direction with the change in reactivity caused by fuel burn-up, and at least a part of a lower region of the neutron reflector is a high reflection region having a high neutron reflection ability as compared to that of the other region. The high reflection region is located from the bottom to a place between one fourth and one half of the height of the neutron reflector from the bottom end thereof.

Abstract: A fuel assembly is charged in a reactor core of a nuclear reactor using a liquid metal as a coolant, and includes a wrapper tube storing a plurality of fuel pins and including an entrance nozzle for introducing the coolant and an operation handling head, grids disposed in the wrapper tube to support the fuel pins in the radial direction of the wrapper tube, liner tubes inserted in the wrapper tube to fixedly hold the respective grids in the axial direction of the wrapper tube, and a fixing device for fixing the grids and the liner tubes in the radial direction of the wrapper tube.

Abstract: A fuel assembly is charged in a reactor core of a nuclear reactor using a liquid metal as a coolant, and includes a wrapper tube storing a plurality of fuel pins and including an entrance nozzle for introducing the coolant and an operation handling head, grids disposed in the wrapper tube to support the fuel pins in the radial direction of the wrapper tube, liner tubes inserted in the wrapper tube to fixedly hold the respective grids in the axial direction of the wrapper tube, and a fixing device for fixing the grids and the liner tubes in the radial direction of the wrapper tube.

Abstract: In a nuclear reactor in which a primary coolant is contained, the primary coolant moves upwardly from the core by an operation thereof. An annular steam generator is arranged in an upper side of the core into which the upwardly moving primary coolant flows and transfers heat in the primary coolant into water therein to generate a steam. A passage structure defines a coolant passage for the primary coolant to an outside of the core. The heat-transferred primary coolant in the annular steam generator flows downwardly in the coolant passage so as to flow into the core, thereby moving upwardly. A reactor vessel is arranged to surround the coolant passage so as to contain the core, the annular steam generator and the passage means therein.

Abstract: A fuel assembly is charged in a reactor core of a nuclear reactor using a liquid metal as a coolant and includes a wrapper tube storing a plurality of fuel pins and including an entrance nozzle at a lower end thereof for introducing the coolant and an operation handling head at an upper end thereof, grids for supporting the plurality of fuel pins in the wrapper tube in the radial direction of the wrapper tube, liner tubes inserted in the wrapper tube for fixedly holding the grids in the axial direction of the wrapper tube, and peripheral flow suppressing members disposed in a peripheral flow passage extending between peripherally disposed ones of the fuel pins and the wrapper tube over a length corresponding to a heat generation length, which is a length range in the axial direction of the fuel pins storing a radioactive fuel material.

Abstract: A fuel assembly is charged in a reactor core of a nuclear reactor using a liquid metal as a coolant and includes a wrapper tube storing a plurality of fuel pins and including an entrance nozzle at a lower end thereof for introducing the coolant and an operation handling head at an upper end thereof, grids for supporting the plurality of fuel pins in the wrapper tube in the radial direction of the wrapper tube, liner tubes inserted in the wrapper tube for fixedly holding the grids in the axial direction of the wrapper tube, and peripheral flow suppressing members disposed in a peripheral flow passage extending between peripherally disposed ones of the fuel pins and the wrapper tube over a length corresponding to a heat generation length, which is a length range in the axial direction of the fuel pins storing a radioactive fuel material.

Abstract: A fast reactor having a reflector control system is provided which decreases the change in reactivity of the reactor core with time without performing control of a reflector lifting speed and that of a water flow rate. The above fast reactor has a liquid metal coolant, a reactor core immersed therein, and a neutron reflector which is provided outside the reactor core and which is moved in a vertical direction for adjusting leakage of neutrons therefrom for controlling the reactivity of the reactor core. The neutron reflector described above is gradually moved in an upward direction with the change in reactivity caused by fuel burn-up, and at least a part of a lower region of the neutron reflector is a high reflection region having a high neutron reflection ability as compared to that of the other region. The high reflection region is located from the bottom to a place between one fourth and one half of the height of the neutron reflector from the bottom end thereof.

Abstract: A fast reactor including a reactivity control assembly including a reactor shutdown rod and neutron absorbers, a reactor shutdown rod drive mechanism, and units of neutron absorber drive mechanism. The reactor shutdown rod drive mechanism causes an inner extension tube to fall and release the reactor shutdown rod by a gripper section by turning off the power supply to a holding magnet at the time of scram. When grasping the neutron absorbers, an outer extension shaft is pulled up to allow both of the extension shafts to be inserted. After the outer extension tube gets to a handling head section of the neutron absorber, the outer extension shaft is pushed down to grasp the neutron absorber externally by latch fingers of the gripper section so that the neutron absorber can be moved up and down.

Abstract: A fast reactor having a reflector control system is provided which decreases the change in reactivity of the reactor core with time without controlling a reflector lifting speed and a water flow rate. The fast reactor has a neutron reflector provided outside the reactor core and which is moved in a vertical direction for adjusting neutron leakage to control the reactivity of the reactor core. The neutron reflector is moved in an upward direction with the change in reactivity caused by fuel burn-up. At least a part of a lower region of the neutron reflector may be a region having a high neutron reflection ability as compared to that of the other region. The high reflection region is located at the bottom of the neutron reflector and extends from between one fourth and one half of the height of the neutron reflector.

Abstract: A fast reactor having a reflector control system is provided which decreases the change in reactivity of the reactor core with time without controlling reflector lifting speed and a water flow rate. The reactor has a liquid metal coolant, a reactor core immersed therein, and a neutron reflector provided outside the core and is moved in a vertical direction for adjusting leakage of neutrons therefrom for controlling the reactivity of the core. The reflector described above is gradually moved in an upward direction with the change in reactivity caused by fuel burn-up, and at least a part of a lower region of the reflector is a high reflection region having a high neutron reflection ability as compared to that of the other region. The high reflection region is located between the bottom and one fourth and one half of the height of the neutron reflector.

Abstract: In a nuclear reactor in which a primary coolant is contained, the primary coolant moves upwardly from the core by an operation thereof. An annular steam generator is arranged in an upper side of the core into which the upwardly moving primary coolant flows and transfers heat in the primary coolant into water therein to generate a steam. A passage structure defines a coolant passage for the primary coolant to an outside of the core. The heat-transferred primary coolant in the annular steam generator flows downwardly in the coolant passage so as to flow into the core, thereby moving upwardly. A reactor vessel is arranged to surround the coolant passage so as to contain the core, the annular steam generator and the passage means therein.

Abstract: A fast reactor having a reactivity control reflector has a reactor vessel in which a coolant is accommodated, a reactor core which is installed in the reactor vessel and dipped with the coolant, and a reflector installed outside of the reactor core so as to be movable in a vertical direction for controlling the reactivity of the reactor core. The reflector of the fast reactor has a lower neutron reflecting portion having a neutron reflection capability higher than that of the coolant and an upper cavity portion located above the neutron reflecting portion and having a neutron reflection capability lower than that of the coolant. The cavity portion is composed of a plurality of cylindrical hermetically-sealed vessels.

Abstract: A fast reactor has a reactivity control assembly including a reactor shutdown rod of a backup reactor shutdown system and neutron absorbers to suppress the initial surplus reactivity, a reactor shutdown rod drive mechanism for releasing the reactor shutdown rod and units of neutron absorber drive mechanism capable of moving the respective neutron absorbers up and down. The reactor shutdown rod and the neutron absorbers are arranged in a wrapper tube. The reactor shutdown rod drive mechanism causes an inner extension tube to fall and release the reactor shutdown rod by means of a gripper section at the lowermost end of an outer extension tube by turning off the power supply to a holding magnet at the time of scram. Each of the units of neutron absorber drive mechanism has a dual tube type drive shaft including an outer extension shaft and an inner extension shaft. When grasping the neutron absorbers, the outer extension shaft is pulled up to allow both of the extension shafts to be inserted.

Abstract: In a nuclear reactor in which a primary coolant is contained, the primary coolant moves upwardly from the core by an operation thereof. An annular steam generator is arranged in an upper side of the core into which the upwardly moving primary coolant flows and transfers heat in the primary coolant into water therein to generate a steam. A passage structure defines a coolant passage for the primary coolant to an outside of the core. The heat-transferred primary coolant in the annular steam generator flows downwardly in the coolant passage so as to flow into the core, thereby moving upwardly. A reactor vessel is arranged to surround the coolant passage so as to contain the core, the annular steam generator and the passage means therein.