Configurations of molten fuel salt reactors are described that utilize neutron-reflecting coolants or a combination of primary salt coolants and secondary neutron-reflecting coolants. Further configurations are described that circulate liquid neutron-reflecting material around a reactor core to control the neutronics of the reactor. Furthermore, configurations which use the circulating neutron-reflecting material to actively cool the containment vessel are also described. A further configuration is described that utilizes a core barrel between a reactor core volume of molten fuel salt and a reflector volume, in which the reflector volume contains a plurality of individual reflector elements separated by an interstitial space filled with molten fuel salt.

A nuclear reactor (10) includes a vessel (12) containing a primary liquid, a core (14) comprising nuclear fuel and arranged in the internal volume of the vessel (12), at least one primary pump generating a main primary flow (56) of primary liquid in the vessel (12), at least one control member (16) for controlling the reactivity of the core (14), at least one movement mechanism (18) for moving the control member (16), arranged in the internal volume of the vessel (12) and linked to the control member (16), and a pressurizer (20) situated in a top portion of the vessel (12). The movement mechanism (18) comprises an electrical actuator and a transmission mechanism. The electrical actuator is completely immersed in the primary fluid and situated outside the main primary flow (56).

A nuclear reactor is configured with an intermediate coolant loop for transferring thermal energy from the reactor core for a useful purpose. The intermediate coolant loop includes a bypass flowpath with an air heat exchanger for dumping reactor heat during startup and/or shutdown. A fluidic diode along the bypass flowpath asymmetrically restricts flow across the bypass flowpath, inhibiting flow in a first flow direction during a full power operating condition and allowing a relatively uninhibited flow in a second direction during a startup and/or shut down low power operating condition.

Configurations of molten fuel salt reactors are described that allow for active cooling of the containment vessel of the reactor by the primary coolant. Furthermore, naturally circulating reactor configurations are described in which the reactor cores are substantially frustum-shaped so that the thermal center of the reactor core is below the outlet of the primary heat exchangers. Heat exchanger configurations are described in which welded components are distanced from the reactor core to reduce the damage caused by neutron flux from the reactor. Radial loop reactor configurations are also described.

The present disclosure provides a stopped cooling system including: a steam line connecting portion connected to a steam line so as to receive cooling water through the steam line connected to an outlet of a steam generator; a stopped cooling heat exchanger for receiving cooling water that enters the stopped cooling system through the steam line connecting portion, and discharging same through a passage of the heat exchanger; a stopped cooling pump activated to perform stopped cooling of the nuclear reactor upon normal stoppage of the nuclear reactor after primary cooling of the nuclear reactor cooling system or when an accident occurs, and for forming a circulating flow of cooling water that circulates between the steam generator and the stopped cooling heat exchanger; and a water supplying pipe connecting portion connected to the heat exchanger passage and a water supplying pipe, which is connected to the inlet of the steam generator, so as to supply the cooling water cooled in the stopped cooling heat exchanger to the steam generator through the water supplying pipe.

Configurations of molten fuel salt reactors are described that include an auxiliary cooling system which shared part of the primary coolant loop but allows for passive cooling of decay heat from the reactor. Furthermore, different pump configurations for circulating molten fuel through the reactor core and one or more in vessel heat exchangers are described.

Disclosed is a nuclear power plant which drives a Stirling engine by means of heat generated in nuclear power plant safety systems during an accident, uses the resulting power directly or generates electric power so as to supply the power to the safety systems, and thus can improve economic efficiency as well as the reliability of safety systems, such as a passive safety system, by operating the safety systems without an emergency diesel generator or external electric power.

Configurations of molten fuel salt reactors are described that utilize neutron-reflecting coolants or a combination of primary salt coolants and secondary neutron-reflecting coolants. Further configurations are described that circulate liquid neutron-reflecting material around an reactor core to control the neutronics of the reactor. Furthermore, configurations which use the circulating neutron-reflecting material to actively cool the containment vessel are also described.

An in-vessel cooling and power generation system according to the present disclosure may include a small scale reactor vessel, a heat exchange section provided inside the reactor vessel, and formed to supply supercritical fluid to receive heat from a reactor coolant system in the reactor vessel, an electric power production section comprising a supercritical turbine formed to produce electric energy using the energy of the supercritical fluid whose temperature has increased while receiving heat from the reactor coolant system, a cooling section configured to exchange heat with the supercritical fluid discharged after driving the supercritical turbine to shrink a volume of the supercritical fluid, wherein the supercritical fluid that has received heat from the reactor coolant system in the heat exchange section is formed to circulate through the electric power production section, and the cooling section. The in-vessel cooling and power generation system according to the present disclosure may be continuously operated not only during a normal operation but also during an accident to perform in-vessel cooling, and produce emergency power, thereby improving the system reliability. In addition, the in-vessel cooling and power generation system according to the present disclosure may facilitate the application of a safety class or seismic design with a small scale facility, thereby improving the reliability due to the application of the safety class or seismic design.

A compact pressurized water nuclear reactor having connected to the reactor pressure vessel a plurality of horizontal pressure vessels, with all the horizontal pressure vessels connected to the reactor pressure vessel by a single connection between the respective nozzle of the reactor pressure vessel with the respective nozzle of each horizontal pressure vessel.