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 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.

The present disclosure relates to a passive safety system which uses a heat exchanger together with a thermoelectric element, and a nuclear power plant comprising the same. Disclosed are a passive safety system and a nuclear power plant comprising the same, the passive safety system comprising: a heat exchanger; a thermoelectric element; and a fan unit. The heat exchanger is formed at a space inside or outside a sealed housing, and in the heat exchanger, atmosphere is introduced and heat exchange is carried out in order to lower the pressure or temperature of the atmosphere inside the housing if an accident occurs in a reactor coolant system or a secondary system disposed inside the housing. The thermoelectric element is disposed in the heat exchanger, and when a cooling fluid, for performing heat exchange with the atmosphere, performs heat exchange with the atmosphere, the thermoelectric element is configured to generate electricity due to a temperature difference between the atmosphere and the cooling fluid. The fan unit is connected to the thermoelectric element via an electricity path so as to receive electricity generated by the thermoelectric element, and is configured to increase the flow rate of the atmosphere or the cooling fluid which passes through the heat exchanger such that the heat exchange of the atmosphere and the cooling fluid can be smoothly carried out.

A nuclear reactor comprises a nuclear reactor core disposed in a pressure vessel. An isolation valve protects a penetration through the pressure vessel. The isolation valve comprises: a mounting flange connecting with a mating flange of the pressure vessel; a valve seat formed into the mounting flange; and a valve member movable between an open position and a closed position sealing against the valve seat. The valve member is disposed inside the mounting flange or inside the mating flange of the pressure vessel. A biasing member operatively connects to the valve member to bias the valve member towards the open position. The bias keeps the valve member in the open position except when a differential fluid pressure across the isolation valve and directed outward from the pressure vessel exceeds a threshold pressure.

A power conversion system for converting thermal energy from a heat source to electricity is provided. The system includes a chamber including an inner shroud having an inlet and an outlet and defining an internal passageway between the inlet and the outlet through which a working fluid passes. The chamber also includes an outer shroud substantially surrounding the inner shroud. The chamber includes a source heat exchanger disposed in the internal passageway, the source heat exchanger being configured to receive a heat transmitting element associated with the heat source external to the chamber, and to transfer heat energy from the heat transmitting element to the working fluid. The system also includes a compressor disposed adjacent the inlet of the inner shroud and configured to transfer energy from the compressor to the working fluid, and an expander disposed adjacent the outlet of the inner shroud.

A power conversion system for converting thermal energy from a heat source to electricity is provided. The system includes a chamber including an inner shroud having an inlet and an outlet and defining an internal passageway between the inlet and the outlet through which a working fluid passes. The chamber also includes an outer shroud substantially surrounding the inner shroud. The chamber includes a source heat exchanger disposed in the internal passageway, the source heat exchanger being configured to receive a heat transmitting element associated with the heat source external to the chamber, and to transfer heat energy from the heat transmitting element to the working fluid. The system also includes a compressor disposed adjacent the inlet of the inner shroud and configured to transfer energy from the compressor to the working fluid, and an expander disposed adjacent the outlet of the inner shroud.

A pressurized water reactor (PWR) includes a vertical cylindrical pressure vessel having a lower portion containing a nuclear reactor core and a vessel head defining an integral pressurizer. A reactor coolant pump (RCP) mounted on the vessel head includes an impeller inside the pressure vessel, a pump motor outside the pressure vessel, and a vertical drive shaft connecting the motor and impeller. The drive shaft does not pass through the integral pressurizer. The drive shaft passes through a vessel penetration of the pressure vessel that is at least large enough for the impeller to pass through.

A pressurized water reactor (PWR) includes a vertical cylindrical pressure vessel having a lower portion containing a nuclear reactor core and a vessel head defining an integral pressurizer. A reactor coolant pump (RCP) mounted on the vessel head includes an impeller inside the pressure vessel, a pump motor outside the pressure vessel, and a vertical drive shaft connecting the motor and impeller. The drive shaft does not pass through the integral pressurizer. The drive shaft passes through a vessel penetration of the pressure vessel that is at least large enough for the impeller to pass through.

A nuclear reactor comprises a nuclear reactor core disposed in a pressure vessel. An isolation valve protects a penetration through the pressure vessel. The isolation valve comprises: a mounting flange connecting with a mating flange of the pressure vessel; a valve seat formed into the mounting flange; and a valve member movable between an open position and a closed position sealing against the valve seat. The valve member is disposed inside the mounting flange or inside the mating flange of the pressure vessel. A biasing member operatively connects to the valve member to bias the valve member towards the open position. The bias keeps the valve member in the open position except when a differential fluid pressure across the isolation valve and directed outward from the pressure vessel exceeds a threshold pressure.

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.