A depressurisation valve for a cooling system comprising: a main chamber having a main valve, a pilot line having a secondary valve and a blowdown line; the main valve being located to seal a path of the coolant system of the nuclear reactor. The main chamber is connected to the cooling circuit via the pilot line allowing coolant to enter the main chamber, and the blowdown line allows coolant to escape from the main chamber, the pilot line having a lower fluid resistance than the blowdown line. The pressure of coolant in the main chamber maintains the main valve in a closed position, and under elevated temperature and/or pressure conditions fluid is prevented from entering the main chamber via a closure of the secondary valve on the pilot line and reduce the pressure from the valve, moving it to its open position.

A nuclear reactor head (12) comprising a vessel top head (14), a penetration (36) extending through the vessel top head (14) along a penetration axis (B) for allowing passage of a control shaft (34) of a control rod drive mechanism (32) through the vessel top head (14) and to a corresponding control guide tube (30) of the nuclear reactor (2), the penetration (36) comprising a penetration tube (38) extending through the vessel top head (14) and a thermal sleeve (40) extending inside the penetration tube (38) and coaxially with the penetration tube (38) with an axial play between the thermal sleeve (40) and the penetration tube (38), wherein the nuclear reactor head further comprises a spacer (60) attached to a lower end of the thermal sleeve (40) for maintaining minimal spacing with the upper end of the corresponding control rod guide tube (30).

A closed loop heat convection cooling system for nuclear reactors. The cooling system is formed outside the containment structure of the nuclear reactor and the structure of the cooling system prevents gas that is not in the closed circuit to approach the reactor within neutron radiation distance. The cooling systems has cooling assemblies that are housed in protective structures, which shield the cooling assemblies for projectile impact. Air inlet and outlet apertures are formed in the protective structures to cause outside air to be drawn into the protective structures to cool the cooling assemblies.

A mobile modular reactor, in particular, a graphite-moderated fission reactor, has an active core region and at least a portion of control region(s) that are located within an interior volume of a pressure vessel. Flow annulus features located in the flow annulus between an outer surface of the control rod/fuel rod and an inner surface of the cladding of the channel in which the rod is located stabilizes the flow annulus and maintains a reliable concentricity between the inner and outer claddings that envelope the flow annulus. Flow annulus features are equally circumferentially spaced at longitudinally separated locations and the flow annulus features at successive, longitudinally separated locations are rotationally offset relative to each other. For purposes of transportability, the pressure vessel is sized for mobile transport using a ship, train or truck, for example, by fitting within a shipping container.

A mobile modular reactor, in particular, a graphite-moderated fission reactor, has an active core region and at least a portion of control region(s) that are located within an interior volume of a pressure vessel. Flow annulus features located in the flow annulus between an outer surface of the control rod/fuel rod and an inner surface of the cladding of the channel in which the rod is located stabilizes the flow annulus and maintains a reliable concentricity between the inner and outer claddings that envelope the flow annulus. Flow annulus features are equally circumferentially spaced at longitudinally separated locations and the flow annulus features at successive, longitudinally separated locations are rotationally offset relative to each other. For purposes of transportability, the pressure vessel is sized for mobile transport using a ship, train or truck, for example, by fitting within a shipping container.

The present invention provides an integrated passive reactor system comprising a pressure vessel, a containment vessel arranged outside the pressure vessel and a reactor core arranged inside the pressure vessel, wherein the primary loop operates in full natural circulation. The integrated reactor system is also provided with a secondary side passive residual heat removal system comprising primary loop heat exchanger(s) arranged inside the pressure vessel and passive residual heat removal heat exchanger(s) arranged outside the containment vessel, wherein the primary loop heat exchanger(s) is/are arranged above the reactor core, the passive residual heat removal heat exchanger(s) is/are arranged inside water tank(s) which is/are fixed outside the containment vessel, and the primary heat exchanger(s) and the passive residual heat removal heat exchanger(s) are connected by heat exchanger inlet pipelines and heat exchanger outlet pipelines. By adopting passive safety technology and passive residual heat removal system, and with the help of top double-layer structure of pressure vessel and break isolation measures, the integrated reactor system according to the present invention can reduce the loss of coolant to the greatest extent, thus meeting the requirements for mitigating design basis accidents, ensuring reactor safety and simplifying the design of the system.

A modular nuclear reactor system includes a lift-out, replaceable nuclear reactor core configured for replacement as a singular unit during a single lift-out event, such as rather than lifting and replacing individual fuel assemblies and/or fuel elements. The system includes a reactor vessel and a power generation system configured to convert thermal energy in a high temperature working fluid received from the reactor vessel into electrical energy. The reactor vessel includes: a vessel inlet and an adjacent vessel outlet arranged near a bottom on the vessel; a vessel receptacle configured to receive a unified core assembly; locating datums in the base of the vessel receptacle and configured to constrain a core assembly in multiple degrees of freedom; and an interstitial zone surrounding the vessel receptacle and housing a set of control or moderating drums.

Provided is an apparatus for generating electricity, mechanical energy, and/or process and district heat using a gas propellant chamber fueled with fissile material and enclosed in a sealed containment vessel which also contains an operating gas. The system allows for the operating gas to be compressed as it enters the nuclear fuel chamber where it is heated. As the operating gas exits the nuclear fuel chamber, the kinetic energy of the gas is converted to rotational energy by a variety of methods. The rotational energy is further converted to electricity, mechanical energy, and/or process and district heat. The operating gas circulates in the containment vessel and is cooled prior to re-entering the gas propellant chamber. The apparatus thereby provides a simpler and safer design that is both scalable and adaptable. The apparatus is easily and safely transportable and can be designed to be highly nuclear-proliferation-resistant.

Provided is an apparatus for generating electricity, mechanical energy, and/or process and district heat using a gas propellant chamber fueled with fissile material and enclosed in a sealed containment vessel which also contains an operating gas. The system allows for the operating gas to be compressed as it enters the nuclear fuel chamber where it is heated. As the operating gas exits the nuclear fuel chamber, the kinetic energy of the gas is converted to rotational energy by a variety of methods. The rotational energy is further converted to electricity, mechanical energy, and/or process and district heat. The operating gas circulates in the containment vessel and is cooled prior to re-entering the gas propellant chamber. The apparatus thereby provides a simpler and safer design that is both scalable and adaptable. The apparatus is easily and safely transportable and can be designed to be highly nuclear-proliferation-resistant.

A simple nuclear reactor in which most of the reflector material is outside of the reactor vessel is described. The reactor vessel is a cylinder that contains all of the fuel salt and a displacement component, which may be a reflector, in the upper section of the reactor vessel. Other than the displacement component, the reflector elements including a radial reflector and a bottom reflector are located outside the vessel. The salt flows around the outside surface of the displacement component through a downcomer heat exchange duct defined by the exterior of the displacement component and the interior surface of the reactor vessel. This design reduces the overall size of the reactor vessel for a given volume of salt relative to designs with internal radial or bottom reflectors.