A nuclear reactor in one embodiment includes a cylindrical body having an internal cavity, a nuclear fuel core, and a shroud disposed in the cavity. The shroud comprises an inner shell, an outer shell, and a plurality of intermediate shells disposed between the inner and outer shells. Pluralities of annular cavities are formed between the inner and outer shells which are filled with primary coolant such as demineralized water. The coolant-filled annular cavities may be sealed at the top and bottom and provide an insulating effect to the shroud. In one embodiment, the shroud may comprise a plurality of vertically-stacked self-supported shroud segments which are coupled together.

A system for attenuating seismic forces includes a reactor pressure vessel containing nuclear fuel and a containment vessel that houses the reactor pressure vessel. Both the reactor pressure vessel and the containment vessel include a bottom head. Additionally, the system includes a base support to contact a support surface on which the containment vessel is positioned in a substantially vertical orientation. An attenuation device is located between the bottom head of the reactor pressure vessel and the bottom head of the containment vessel. Seismic forces that travel from the base support to the reactor pressure vessel via the containment vessel are attenuated by the attenuation device in a direction that is substantially lateral to the vertical orientation of the containment vessel.

A system for attenuating seismic forces includes a reactor pressure vessel containing nuclear fuel and a containment vessel that houses the reactor pressure vessel. Both the reactor pressure vessel and the containment vessel include a bottom head. Additionally, the system includes a base support to contact a support surface on which the containment vessel is positioned in a substantially vertical orientation. An attenuation device is located between the bottom head of the reactor pressure vessel and the bottom head of the containment vessel. Seismic forces that travel from the base support to the reactor pressure vessel via the containment vessel are attenuated by the attenuation device in a direction that is substantially lateral to the vertical orientation of the containment vessel.

A system for fighting a fire includes a plurality of containers containing liquid nitrogen. Thermally activated release mechanisms are each connected to one of the containers. Each thermally activated release mechanism is configured to release the liquid nitrogen from a connected container when a predetermined safety threshold temperature is reached, so that the released liquid nitrogen produces an expanding volume of cold nitrogen vapor. A central storage container stores liquid nitrogen. The central storage container is connected to each of the plurality of containers. A sensor system activates refilling of a respective container with liquid nitrogen from the central storage container when the amount of liquid nitrogen in the respective container is below a predetermined threshold.

A system for fighting a fire includes a plurality of containers containing liquid nitrogen. Thermally activated release mechanisms are each connected to one of the containers. Each thermally activated release mechanism is configured to release the liquid nitrogen from a connected container when a predetermined safety threshold temperature is reached, so that the released liquid nitrogen produces an expanding volume of cold nitrogen vapor. A central storage container stores liquid nitrogen. The central storage container is connected to each of the plurality of containers. A sensor system activates refilling of a respective container with liquid nitrogen from the central storage container when the amount of liquid nitrogen in the respective container is below a predetermined threshold.

A system for attenuating seismic forces includes a reactor pressure vessel containing nuclear fuel and a containment vessel that houses the reactor pressure vessel. Both the reactor pressure vessel and the containment vessel may include a bottom head. Additionally, the system may include a base support that is configured to contact a support surface on which the containment vessel is positioned in a substantially vertical orientation. An attenuation device may be located between the bottom head of the reactor pressure vessel and the bottom head of the containment vessel. Seismic forces that travel from the base support to the reactor pressure vessel via the containment vessel may be attenuated by the attenuation device in a direction that is substantially lateral to the vertical orientation of the containment vessel.

A system for attenuating seismic forces includes a reactor pressure vessel containing nuclear fuel and a containment vessel that houses the reactor pressure vessel. Both the reactor pressure vessel and the containment vessel may include a bottom head. Additionally, the system may include a base support that is configured to contact a support surface on which the containment vessel is positioned in a substantially vertical orientation. An attenuation device may be located between the bottom head of the reactor pressure vessel and the bottom head of the containment vessel. Seismic forces that travel from the base support to the reactor pressure vessel via the containment vessel may be attenuated by the attenuation device in a direction that is substantially lateral to the vertical orientation of the containment vessel.

A passive fire response system is configured to suppress a metallic fire. The system includes a reservoir containing an ionic liquid, at least one outlet in communication with the reservoir, a valve arranged between the reservoir and the outlet, a sensor configured to sense at least one of a hydrogen concentration and a temperature and/or heat, and a controller configured to open the valve and release the ionic liquid if an output from the sensor indicates that the at least one of the hydrogen concentration and the temperature equals or exceeds at least one of a threshold hydrogen concentration and a threshold temperature.

Disclosed is a digital twin platform provision system for detecting and responding to a fire in an installation region of electrical equipment in a nuclear power plant, which includes: a digital twin build unit for building an initial digital twin by digitally modeling target objects including equipment and subsidiary materials related to fire outbreak and damage spread; an attribute information application unit for applying fire reactivity information received from an outside and serves as attribute information about fire outbreak and spread factors to the initial digital twin, thereby building a digital twin; and a simulation information provision for unit generating simulation information, which is information fire outbreak about prediction, fire spread simulation upon fire break, and fire response and evacuation scenarios upon the fire break, by using the digital twin according to a user input and outputting the simulation information to a user terminal.

Disclosed is a digital twin platform provision system for detecting and responding to a fire in an installation region of electrical equipment in a nuclear power plant, which includes: a digital twin build unit for building an initial digital twin by digitally modeling target objects including equipment and subsidiary materials related to fire outbreak and damage spread; an attribute information application unit for applying fire reactivity information received from an outside and serves as attribute information about fire outbreak and spread factors to the initial digital twin, thereby building a digital twin; and a simulation information provision for unit generating simulation information, which is information fire outbreak about prediction, fire spread simulation upon fire break, and fire response and evacuation scenarios upon the fire break, by using the digital twin according to a user input and outputting the simulation information to a user terminal.