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 that circulates through the steam generator. 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.

An opening and closing device that opens and closes an access port opened from a substantially cylindrical working platform disposed inside a reactor vessel and used to access a nozzle stub of the reactor vessel from the inside of the working platform, the opening and closing device includes: a cover that is slidable along an outer peripheral surface or an inner peripheral surface of the working platform from a closing position where the access port is closed to an opening position where the access port is opened; and moving device for sliding the cover.

An opening and closing device that opens and closes an access port opened from a substantially cylindrical working platform disposed inside a reactor vessel and used to access a nozzle stub of the reactor vessel from the inside of the working platform, the opening and closing device includes: a cover that is slidable along an outer peripheral surface or an inner peripheral surface of the working platform from a closing position where the access port is closed to an opening position where the access port is opened; and moving device for sliding the cover.

A nuclear reactor vessel structure includes an inner peripheral tube-shaped steel plate, an outer peripheral tube-shaped steel plate, and an intermediate tube-shaped steel plate disposed between the inner and outer peripheral tube-shaped steel plates, and is configured to support a nuclear reactor vessel on the inner peripheral side of a tube-shaped structure with concrete placed between the steel plates. The nuclear reactor vessel structure includes a support having a tube-shaped plate disposed on the inner peripheral side of the intermediate tube-shaped steel plate, and an annular plate which protrudes to the inner peripheral side of the tube-shaped plate and to which a connection section is affixed. The support is affixed to the concrete, which is placed between the inner peripheral and the intermediate tube-shaped steel plates, by first bar members, and the support is also affixed to the inner peripheral tube-shaped steel plate by second bar members.

A transportable nuclear power generator unit is provided. The transportable nuclear power generator unit includes a container configured to be transportable by a vehicle, and nuclear power module disposed inside the container. The nuclear power module includes a sealed pressure vessel and a nuclear core disposed inside the sealed pressure vessel. The transportable nuclear power generator unit also includes a plurality of radiation shields provided at a plurality of interior walls inside the container to surround the sealed pressure vessel. The radiation shields are configured to shield radiation generated by the nuclear power module. The radiation shields include a movable shield configured to be movable between a position inside the container and a position on an exterior wall of the container.

A transportable nuclear power generator unit is provided. The transportable nuclear power generator unit includes a container configured to be transportable by a vehicle, and nuclear power module disposed inside the container. The nuclear power module includes a sealed pressure vessel and a nuclear core disposed inside the sealed pressure vessel. The transportable nuclear power generator unit also includes a plurality of radiation shields provided at a plurality of interior walls inside the container to surround the sealed pressure vessel. The radiation shields are configured to shield radiation generated by the nuclear power module. The radiation shields include a movable shield configured to be movable between a position inside the container and a position on an exterior wall of the container.

A nuclear reactor is designed to allow efficient packing of components within the reactor vessel, such as by offsetting the core, and/or vertically stacking components. The in-vessel storage system can be separate from the support cylinder and these components can be fabricated and shipped separately and coupled together at the construction site. Furthermore, the in-vessel storage system can be located adjacent to the core rather than being located circumferentially around it, and may also be located beneath the heat exchanger to further improve packing of components within the vessel. Through these, and other changes, the delicate components can be manufactured in a manufacturing facility, assembled, and shipped by commercial transportation options without exceeding the shipping envelope.

A pressurizer valve device comprising: a valve housing disposed in a reactor vessel accommodated in a containment vessel, and having a communication hole through which steam in the reactor vessel is introduced, a discharge hole, through which the steam introduced into an interior of the reactor vessel is discharged to the containment vessel, and a connection hole, through which a control fluid is introduced; and a valve piston disposed to be movable in one direction in the interior of the valve housing, and configured to open and close the communication hole depending on a change in a vessel pressure in the reactor vessel.