A nuclear fission power plant

Abstract

A nuclear fission power plant (10) comprising: a gas-cooled moderated nuclear reactor core (20), the gas-cooled moderated nuclear reactor core comprising: a fuel (30); a moderator (35); and at least one core inlet (46) and outlet (48); a neutron reflector (70); a plurality of primary neutronic control elements (50); a secondary neutronic control element (60); a containment vessel (40) substantially surrounding the gas-cooled moderated nuclear reactor core comprising a containment vessel inlet (42) and outlet (44) defining a flow path therebetween such that gas following the flow path flows from the containment vessel inlet towards the containment vessel outlet via the gas-cooled moderated nuclear reactor core; a fluid circuit (90) configured to receive hot gas from the containment vessel outlet and deliver cooled gas to the containment vessel inlet; and a Rankine power system connected to a generator (108) to generate electrical power.

Description

A NUCLEAR FISSION POWER PLANTTECHNICAL FIELD

[0001] This disclosure relates to a nuclear fission power plant configured for use in a terrestrial environment and a kit of parts and method for a nuclear fission power plant configured for use in a terrestrial environment.BACKGROUND

[0002] It is desirable to have a reliable and low-carbon power source capable of deployment in a terrestrial environment. Terrestrial environments may include deserts, tundra, temperate climates, tropical rainforests, the Arctic, Antarctica, etc. Solar panels are often used as a means to generate electricity in terrestrial environments. However, their power density is low and they are limited to applications in sunlight. This is a particular problem for expeditions where a facility could be in darkness or in shadow for prolonged periods of time, e.g. a facility located in or substantially towards the Antarctic circle during the winter solstice, or a facility located beneath a tree canopy in a forest or jungle. The low power density of solar panels further limits their application. In particular, a facility in a terrestrial environment may have a high power requirement for which solar panels are not suited. Similarly, wind turbines may not be effective in locations with too low or too high an average wind speed for effective use of the turbine. Wind turbines also suffer from increased complexity in transportation and logistics, especially with regards to transporting the turbine blades, which may make it difficult to rapidly deploy a wind turbine to a terrestrial environment. On the other hand, diesel or gas generators are high-carbon energy sources, emit greenhouse gases, and may be highly noise polluting.

[0003] The high-power density of a nuclear fission power plant and its ability to generate electricity independently from environmental conditions (e.g. sunlight or wind) make nuclear fission power plants an attractive option for use in terrestrial environments. However, it is desirable for a nuclear fission power plant to withstand harsh environmental conditions, require minimal maintenance, and be sufficiently robust to withstand damage in transit to a terrestrial environment. Weight and size are also issues as any power plant would likely need to fit within the confines of a container or containers in a transport vessel(s) capable of journeying to possibly remote and harsh environments.

[0004] The present disclosure seeks to address these issues.SUMMARY

[0005] According to a first aspect there is provided a nuclear fission power plant configured for use in a terrestrial environment, the nuclear fission power plant comprising: a gas-cooled moderated nuclear reactor core, the gas-cooled moderated nuclear reactor core comprising: a fuel; a moderator; and at least one core inlet and at least one core outlet; a neutron reflector disposed around a periphery of the gas-cooled moderated nuclear reactor core; a plurality of primary neutronic control elements, each primary neutronic control element being configured to be selectively inserted into the gas-cooled moderated nuclear reactor core; a secondary neutronic control element configured to be selectively inserted into the gas- cooled moderated nuclear reactor core; a containment vessel substantially surrounding the gas-cooled moderated nuclear reactor core, the containment vessel comprising a containment vessel inlet and a containment vessel outlet, and being configured to define a flow path between the containment vessel inlet and the containment vessel outlet, such that gas following the flow path flows from the containment vessel inlet towards the gas-cooled moderated nuclear reactor core, into the gas- cooled moderated nuclear reactor core via the at least one core inlet, out of the gas-cooled moderated nuclear reactor core via the at least one core outlet, and towards the containment vessel outlet; a fluid circuit configured to receive hot gas from the containment vessel outlet and deliver cooled gas to the containment vessel inlet; and an electricity-generating system coupled to the fluid circuit so as to generate an electrical current.

[0006] A plurality of voids may be formed in the gas-cooled moderated nuclear reactor core. The plurality of voids may correspond to the plurality of primary neutronic control elements, such that each primary neutronic control element may be selectively inserted into a respective void. Similarly, the secondary neutronic control element may be selectively inserted into a corresponding void formed in the gas-cooled moderated nuclear reactor core.

[0007] The fuel may comprise High Assay Low Enriched Uranium (HALEU). The fuel may be enriched to substantially 19.75% uranium-235. The fuel may comprise uraniumdioxide, UO2. The fuel may alternatively comprise a different ceramic fuel, such as uranium carbide (UC), uranium nitride (UN) etc.

[0008] The fuel may comprise pellets of fuel stacked within a metal tube.

[0009] The neutron moderator may comprise graphite.

[0010] The neutron reflector may comprise graphite or aluminium oxide.

[0011] The plurality of primary neutronic control elements may comprise a plurality of linearly movable control rods. The secondary neutronic control element may comprise a linearly movable control rod.

[0012] The electricity-generating system may be coupled to the fluid circuit via a heat exchanger boiler. The electricity-generating system may be a Rankine power system comprising a pump, a condenser, a turbine, and a generator. The Rankine power system may be arranged such that a working fluid pumped by the pump flows through the condenser, the heat exchanger boiler, and the turbine. The condenser may be configured to condense the working fluid. The heat exchanger boiler may be configured to permit heat in the gas flowing through the fluid circuit to be transferred to the working fluid to thereby evaporate the working fluid. The turbine may be configured to drive the generator.

[0013] The working fluid in the power conversion system may comprise water (e.g. liquid water and / or steam).

[0014] The power conversion system may further comprise a fan. The condenser may comprise a duct. The duct may be configured to fluidical ly couple the fan to a cool side of the condenser and to fluidically couple the cool side of the condenser to a hot side of the condenser. As such, air blown by the fan may flow from the cool side of the condenser to the hot side of the condenser before being exhausted into the environment.

[0015] The primary neutronic control elements may be a primary form of control to control a reactivity level of the gas-cooled moderated nuclear reactor core. The primary neutronic control elements may be used for fine control, such as during a normal operation mode. The secondary neutronic control element may be a secondary form of control to control a reactivity level of the gas-cooled moderated nuclear reactor core. The secondary neutronic control elements may be used for coarse control, such as in an emergency or shut-down mode.

[0016] The primary and / or secondary neutronic control elements may comprise boron carbide, B4C.

[0017] The nuclear fission power plant may further comprise a neutron shield disposed around a periphery of the neutron reflector.

[0018] The neutron shield may comprise boron carbide.

[0019] The nuclear fission power plant may comprise at least one further fluid circuit and at least one further electricity-generating system, the further fluid circuit being configured to be coupled to the electricity-generating system or the further electricity-generating system.

[0020] The nuclear fission power plant may comprise at least one further fluid circuit and at least one further Rankine power system. The further fluid circuit may be configured to transfer heat from the gas-cooled moderated nuclear reactor core via the heat exchanger boiler or via further heat exchanger boilers to the Rankine power system or the further Rankine power system.

[0021] According to a second aspect there is provided a kit of parts for a nuclear fission power plant configured for use in a terrestrial environment, the kit of parts being configured at least partially for assembly at the terrestrial environment and comprising: a gas-cooled moderated nuclear reactor core, the gas-cooled moderated nuclear reactor core comprising: a fuel; a moderator; and at least one core inlet and at least one core outlet; a neutron reflector configured to be disposed around a periphery of the gas-cooled moderated nuclear reactor core; a plurality of primary neutronic control elements, each primary neutronic control element being configured to be selectively insertable into the gas-cooled moderated nuclear reactor core; a secondary neutronic control element configured to be selectively insertable into the gas-cooled moderated nuclear reactor core; a containment vessel which is configured to substantially surround the gas-cooled moderated nuclear reactor core, the containment vessel comprising a containment vessel inlet and a containment vessel outlet, and being configured to define a flow path between the containment vessel inlet and the containment vessel outlet, such that gas following the flowpath flows from the containment vessel inlet towards the gas-cooled moderated nuclear reactor core, into the gas-cooled moderated nuclear reactor core via the at least one core inlet, out of the gas-cooled moderated nuclear reactor core via the at least one core outlet, and towards the containment vessel outlet; a fluid circuit configured to be able to receive hot gas from the containment vessel outlet and deliver cooled gas to the containment vessel inlet; and an electricity-generating system configured to be coupled to the fluid circuit so as to generate an electrical current.

[0022] The Rankine power system of the kit of parts may further comprise a fan, and the condenser may further comprise a duct, the duct being configured to fluidically couple to the fan and to a cool side of the condenser and to fluidically couple the cool side of the condenser to a hot side of the condenser, such that when the kit of parts is assembled, air blown by the fan can flow from the cool side of the condenser to the hot side of the condenser before being exhausted into the environment.

[0023] The kit of parts may further comprise a neutron shield configured to be disposed around a periphery of the neutron reflector.

[0024] According to a third aspect there is provided a method for a nuclear fission power plant configured for use in a terrestrial environment, the method comprising controlling the nuclear fission power plant to: generate heat with a gas-cooled moderated nuclear reactor core, the gas-cooled moderated nuclear reactor core comprising a fuel, a moderator, at least one core outlet, and at least one core inlet, wherein: a neutron reflector is disposed around a periphery of the gas-cooled moderated nuclear reactor core; a plurality of primary neutronic control elements are configured to be selectively inserted into the gas-cooled moderated nuclear reactor core; a secondary neutronic control element is configured to be selectively inserted into the gas-cooled moderated nuclear reactor core; and a containment vessel is arranged to substantially surround the gas-cooled moderated nuclear reactor core, the containment vessel comprising a containment vessel inlet and a containment vessel outlet, and being configured to define a flow path between the containment vessel inlet and the containment vessel outlet, such that gas following the flow path flows from the containment vessel inlet towards the gas-cooled moderated nuclearreactor core, into the gas-cooled moderated nuclear reactor core via the at least one core inlet, out of the gas-cooled moderated nuclear reactor core via the at least one core outlet, and towards the containment vessel outlet; receive hot gas from the containment vessel outlet to a fluid circuit; deliver cooled gas to the containment vessel inlet via the fluid circuit; and generate electricity with an electricity-generating system coupled to the fluid circuit.

[0025] The electricity-generating system of the method may further comprise a Rankine power system, the Rankine power system being coupled to the fluid circuit via a heat exchanger boiler, the Rankine power system comprising a pump, a condenser, a turbine, and a generator, and being arranged such that a working fluid pumped by the pump flows through the condenser, the heat exchanger boiler, and the turbine, wherein the condenser is configured to condense the working fluid, the heat exchanger boiler is configured to permit heat in the gas flowing through the fluid circuit to be transferred to the working fluid to thereby evaporate the working fluid, and the turbine is configured to drive the generator to generate electricity.

[0026] The skilled person will appreciate that except where mutually exclusive, a feature described in relation to any one of the above aspects may be applied mutatis mutandis to any other aspect. Furthermore, except where mutually exclusive any feature described herein may be applied to any aspect and / or combined with any other feature described herein.BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Embodiments will now be described by way of example only with reference to the accompanying drawings, which are purely schematic and not to scale, and in which:

[0028] Figure 1 is a schematic diagram showing an example nuclear fission power plant configured for use in a terrestrial environment;

[0029] Figure 2 is a schematic diagram showing another example nuclear fission power plant configured for use in a terrestrial environment;

[0030] Figure 3 is a schematic diagram showing another example nuclear fission power plant configured for use in a terrestrial environment; and

[0031] Figure 4 is a flowchart depicting an example method for a nuclear fission power plant configured for use in a terrestrial environment.DETAILED DESCRIPTION

[0032] With reference to Figures 1 to 3, the present disclosure relates to a nuclear fission power plant 10 configured for use in a terrestrial environment. The nuclear fission power plant 10 is configured to be sufficiently robust, reliable, deployable, and rugged to be transported to and used anywhere on the Earth’s surface, including remote and harsh environments such as desert regions, tropical rainforests, tundra, etc. Transportation / deployment to such environments may use any of ground / land-based vehicles (e.g. trucks, trains, etc.), aircraft (e.g. helicopters, airplanes, etc.), watercraft (e.g. boats, ships, etc.), or any other form of transportation. The nuclear fission power plant 10 may be fully assembled prior to transportation or may be at least partially assembled before transportation. Alternatively, the nuclear fission power plant 10 may be configured as a kit of parts to be assembled where it is intended to be operated. For example, the nuclear fission power plant 10 may be transported in modular components or in sub-assemblies. Each module or subassembly may be transported, and the nuclear fission power plant 10 may subsequently be assembled.

[0033] The nuclear fission power plant 10 may be a micro-reactor. The micro-reactor may have a power output in the range of 1 - 5MW. The nuclear fission power plant 10 may be readily transportable, e.g. in a standard shipping container, or in a plurality of shipping containers for the distinct modules / sub-assemblies of the nuclear fission power plant 10.

[0034] As depicted, the nuclear fission power plant 10 comprises a nuclear reactor core 20. The nuclear reactor core 20 comprises a fuel 30. The fuel 30 may comprise High Assay Low Enriched Uranium (HALEU), e.g., with the concentration of the fissile isotope uranium-235 (U-235) being between 5% and 20% of the mass of uranium. In particular, the fuel 30 may be enriched to substantially 19.75% uranium-235. This level of enrichment allows for better energy density whilst maintaining a safe level of enrichment.

[0035] The fuel may comprise uranium dioxide, UO2. Such fuels are sufficiently hard and strong, with a high enough melting point and resistance to radiation damage that allows them to be used in the extreme conditions of a nuclear reactor core. The fuel 30 may be in pellet form and may be clad, e.g. in plated metal or a tubular cladding. The fuel pellets may be stacked within a tube 32. The tube 32 may be a metal tube. For example, pellets of fuel may be stacked within the metal tube, before being welded closed with a gap at the top to trapfission gases. The fuel may alternatively comprise any other suitable ceramic fuel, such as e.g. uranium carbide (UC), uranium oxycarbide (UO), and uranium nitride (UN).

[0036] The nuclear reactor core 20 may be moderated and may comprise a moderator 35. The moderator may improve the neutron economy of the nuclear reactor core 20. The moderator 35 may be provided within the nuclear reactor core 20 and may be interspersed throughout the nuclear reactor core. The moderator 35 may slow down the neutrons within the nuclear reactor core 20. The moderator 35 may comprise graphite. Graphite may possess a sufficient neutron slowing power and may be more rugged than other moderator materials. The moderator 35 may alternatively comprise any of zirconium hydride, aluminium oxide, or yttrium hydride. However, graphite may be a good compromise for deployable applications as it has a sufficient ability to slow neutrons and may better withstand the forces associated with transportation.

[0037] The nuclear reactor core 20 may be gas cooled. The nuclear reactor core 20 may comprise at least one core inlet 46. The nuclear reactor core may comprise at least one core outlet 48. Heat may therefore be extracted from the nuclear reactor core 20 by virtue of a cooling gas that flows within the nuclear reactor core 20. The cooling gas may be configured to enter the nuclear reactor core 20 via the at least one core inlet 46. The cooling gas may be configured to exit the nuclear reactor core 20 via the at least one core outlet 48. The cooling gas may be helium, nitrogen, hydrogen, or any other appropriate cooling gas. A gas cooling system may allow higher core temperatures to be reached, as coolant evaporation issues (which can inflict pressurised water reactors) are eliminated. This, in turn, may allow for a greater thermodynamic efficiency of the nuclear fission power plant by creating a greater temperature difference between the reactor core 20 and heat sink.

[0038] The nuclear fission power plant 10 further comprises a plurality of primary neutronic control elements 50. The primary neutronic control elements 50 may be controlled to vary their neutron-absorbing effect on the core and thereby control reactivity levels in the nuclear reactor core 20. The primary neutronic control elements 50 may comprise linearly movable control rods that may be selectively inserted into corresponding primary neutronic control element voids 56 (i.e., cavities) in the nuclear reactor core 20. Movement of the control rods by one or more first actuators 52 may vary the neutron-absorbing effect on the core of the primary neutronic control elements 50. The one or more first actuators 52 may be controlled by a suitable controller, which may receive data from one or more sensors. For example, the one or more first actuators 52 may be controlled by a first controller 54. The firstcontroller 54 may be in communication with any suitable reactivity sensor system of the nuclear fission power plant 10, which may determine a rate of fission in the nuclear reactor core 20. The primary neutronic control elements 50 may be used for fine control, such as during a normal operating mode of the nuclear fission power plant 10. For example, the control rods of the primary neutronic control elements 50 may be incrementally inserted or retracted from the nuclear reactor core 20. One or more first actuators 52 may cause the control rods to be gradually / incrementally inserted or retracted in response to a determined rate of fission in the core 20 and operating instructions stored in the first controller 54. It is noted that the one or more first actuator(s) 52 may additionally be configured to cause the control rods of the primary neutronic control elements 50 to be rapidly inserted into the primary neutronic control element voids 56. For example, the control rods may be rapidly inserted into the primary neutronic control element voids 56 in the case of an emergency.

[0039] It is noted that the nuclear fission power plant 10 may comprise any number of primary neutronic control elements 50. Thus, although two primary neutronic control elements 50 are shown in Figure 1 , the nuclear fission power plant 10 is not limited to comprising only two primary neutronic control elements. It is envisaged that two or more independent first actuators 52 may be provided (per primary neutronic control element) for redundancy, and / or that the linearly movable control rods may be arranged in two or more independent sets of linearly movable control rods with each set having its own first actuator. The linearly movable control rods within a particular set may alternate with linearly movable control rods from another set. For example, there may be two independent sets of six linearly movable control rods interspersed with one another about the circumference of the nuclear reactor core 20. Therefore, although only one first controller 54 is shown, there may be two or more independent control systems. For example, an independent control system may be provided for each set of linearly movable control rods. Therefore, to achieve a desired level of reactivity in the nuclear reactor core 20, the first controller 54 or more than one independent first controller 54 may operate the one or more first actuators 52 to either cause each linearly movable control rod of the nuclear fission power plant 10 to be selectively inserted / retracted, or cause a set of linearly movable control rods of the nuclear fission power plant 10 to be selectively inserted / retracted, or cause individual rods of the nuclear fission power plant 10 to be selectively inserted / retracted.

[0040] The nuclear fission power plant 10 further comprises a secondary neutronic control element 60. The secondary neutronic control element 60 may comprise a linearly movable control rod that may be selectively inserted into a corresponding secondary neutroniccontrol element void 66 (i.e., a cavity) in the nuclear reactor core 20. Movement of the control rod by a second actuator 62 may vary the neutron absorbing properties of the secondary neutronic control element 60. The second actuator 62 may be controlled by a second controller 64. The second controller 64 may be part of or separate from the first controller 54. The second controller 64 may be in communication with any suitable reactivity sensor system of the nuclear fission power plant 10, which may determine a rate of fission in the nuclear reactor core 20. The secondary neutronic control element 60 may be used for coarse control, such as in an emergency or shut-down mode of the nuclear fission power plant 10. The control rod of the secondary neutronic control element 60 may be inserted quickly into the nuclear reactor core 20, e.g., in the event of an emergency. An emergency event may be determined by the suitable reactivity sensor system of the nuclear fission power plant 10. The second controller 64 may be configured to cause the second actuator 62 to rapidly insert the secondary neutronic control element 60 into the nuclear reactor core 20 when the reactivity sensor system determines that a rate of fission has reached a predetermined threshold.

[0041] The primary / secondary neutronic control elements 50, 60 may comprise boron carbide, B4C, as the neutron absorbing material.

[0042] The nuclear fission power plant 10 may further comprise a neutron reflector 70 disposed around the nuclear reactor core 20. The neutron reflector 70 may be configured to reflect neutrons back towards the core. The neutron reflector 70 may at least partially surround the nuclear reactor core 20. In particular, the neutron reflector 70 may surround or substantially surround the nuclear reactor core. For instance, the neutron reflector may be disposed around a periphery of the nuclear reactor core 20. The neutron reflector 70 may comprise rod through holes to permit primary / secondary neutronic control elements 50, 60 to be inserted into a corresponding primary neutronic control element void 56 or secondary neutronic control element void 66 of the nuclear reactor core 20. In addition, a plurality of channels may be formed in the neutron reflector 70. At least some of the plurality of channels (such as channel 43) may be configured to permit a cooling gas to flow through the neutron reflector 70 and around the nuclear reactor core 20. Additionally, at least some of the plurality of channels may be configured to permit the cooling gas to enter and / or exit the nuclear reactor core 20. For example, the at least one core inlet 46 and the at least one core outlet 48 may be formed by virtue of a plurality of channels formed in the neutron reflector 70. The neutron reflector 70 may be formed from graphite or aluminium oxide. Nuclear-grade graphite may be used as a reflection material, as it provides acceptable neutron reflection properties for its mass.Aluminium oxide (AI2O3) exhibits similar properties and could therefore also be used as the reflection material.

[0043] The nuclear fission power plant 10 may further comprise a containment vessel 40. The containment vessel 40 may be disposed around the nuclear reactor core 20. In particular, the containment vessel 40 may at least partially surround the neutron reflector 70, the plurality of primary neutronic control elements 50, the secondary neutronic control element 60, and the nuclear reactor core 20. For instance, the containment vessel 40 may be disposed around a periphery of the neutron reflector 70. The containment vessel 40 may be configured to contain a cooling gas. The cooling gas may be configured to cool the nuclear reactor core 20. The containment vessel may comprise an inlet 42. The containment vessel may comprise an outlet 44. The containment vessel inlet 42 may be configured to permit a cooling gas into the containment vessel 40. The containment vessel outlet 44 may be configured to permit the cooling gas out of the containment vessel 40. The containment vessel 40 may define a flow path (see for example block arrows in Figure 1 , Figure 2, and Figure 3) between the containment vessel inlet 42 and the containment vessel outlet 44. For example, the containment vessel 40 may comprise at least one inner surface 45. The at least one inner surface 45, in conjunction with other surfaces, e.g. of the containment vessel 40, may define a passage (i.e. the flow path) along which the cooling gas may flow. Accordingly, cooling gas may flow through the containment vessel 40 in a pre-determined manner. In this way, cooling gas following the flow path may flow from the containment vessel inlet 42 towards the nuclear reactor core 20. The flow path may direct the flow of the gas from the containment vessel inlet 42, through a channel formed in the neutron reflector 70 (such as channel 43), to the at least one core inlet 46. The cooling gas may then flow into the nuclear reactor core 20 via the at least one core inlet 46. The cooling gas may then flow through the nuclear reactor core 20, thereby forcing the gas to flow over components within the nuclear reactor core 20. The cooling gas may subsequently flow out of the nuclear reactor core 20 via the at least one core outlet 48. The flow path may direct the flow of the gas from the at least one core outlet 48 to the containment vessel outlet 44. The gas may then exit the containment vessel 40 via the at least one containment vessel outlet 44.

[0044] With reference to Figure 2, the nuclear fission power plant 10 may further comprise a neutron shield 80 disposed around the nuclear reactor core 20. The neutron shield 80 may be configured to substantially reduce a likelihood of neutrons escaping from the nuclear reactor core 20 and into the surrounding environment. The neutron shield 80 may at least partially surround the containment vessel 40. In particular, the neutron shield 80 maysurround or substantially surround the containment vessel 40. For instance, the neutron shield 80 may be disposed around a periphery of the containment vessel 40. The neutron shield 80 may thus improve a safety of the nuclear fission power plant 10, as neutrons which have not been absorbed by the primary or secondary neutronic control elements 50, 60, or reflected by the neutron reflector 70, may be absorbed by the neutron shield 80. The neutron shield 80 may be formed from boron carbide, or any other suitable neutron absorbing material.

[0045] The neutron shield 80 and the containment vessel 40 may comprise control through holes. The number and location of control through holes formed in the neutron shield 80 and the containment vessel 40 may correspond with the number and location of rod through holes formed in the neutron reflector 70. A first or second neutronic control element 50, 60 may thus be inserted into a corresponding primary or secondary neutronic control element void 56, 66 of the nuclear reactor core 20 through a control through hole. Additionally or alternatively, the control through holes may allow e.g. cables, shafts, actuation systems, sensors, etc. to couple a first or second actuator 52, 62 to a corresponding primary / secondary neutronic control element 50, 60. The neutron shield 80 may further com prise an outlet through hole. The outlet through hole formed in the neutron shield 80 may correspond with the containment vessel outlet 44. As such, cooling gas following the flow path defined by the containment vessel 40 may flow out of the containment vessel 40 and be received by a heat exchanging system.

[0046] The nuclear fission power plant 10 may therefore further comprise a fluid circuit 90 with a gas that flows through the fluid circuit. The fluid circuit 90 may comprise a heat exchanger boiler 92 and a pump 94. The pump 94 may be operated to pump the working fluid (i.e. , the gas) around the fluid circuit. The fluid circuit 90 may be configured to deliver cooling gas to the containment vessel inlet 42 via a fluid circuit outlet 96. The fluid circuit 90 may further be configured to receive hot gas from the containment vessel outlet 44 via a fluid circuit inlet 98. As such, cooling gas may be pumped (by the pump 94) from the fluid circuit 90 into the containment vessel 40 via the containment vessel inlet 42. The gas, guided by the flow path defined by the containment vessel 40, may flow through the core of the nuclear reactor 20. The cooling gas may therefore absorb heat from the nuclear reactor core 20 before flowing out of the containment vessel outlet 44 and being received by the fluid circuit 90. The hot gas may then flow through the heat exchanger boiler 92. The heat exchanger boiler 92 may be configured to transfer heat from the gas of the fluid circuit 90 to the working fluid of a power conversion system 100.

[0047] The power conversion system 100 may comprise a Rankine power system. The power conversion system may therefore comprise a condenser 102, a pump 104, a turbine 106. The condenser 102, pump 104, heat exchanger boiler 92, and turbine 106 may be arranged in a loop 110. Specifically, fluid pumped by the pump 104 may flow from the pump 104 to the heat exchanger boiler 92, from the heat exchanger boiler 92 to the turbine 106, and from the turbine 106 to the condenser 102. The working fluid of the power conversion system 100 may be water. Water (e.g. liquid water) may be pumped into the heat exchanger boiler 92. The heat exchanger boiler 92 may be configured to transfer heat from the working fluid (i.e., the gas) of the fluid circuit 90 to the water, such that the water vaporises into steam (e.g., dry steam). The steam may then drive the turbine 106 before being condensed (in the condenser 102) back into liquid water. The cycle may then repeat.

[0048] The turbine 106 may be coupled to an electrical generator 108, and thus the turbine 106 may drive the generator 108 to generate electrical power. The electrical power may be distributed via a power distribution network 114 to users.

[0049] With reference to Figure 3, an air fan 118 may be coupled to the condenser 102. For example, an intake duct 112 may fluidically couple the air fan 118 to a cool side of the condenser 102. Ambient air may therefore be blown about the cool side of the condenser 102 by the air fan 118. The condenser 102 may comprise ducting that directs the air towards a hot side of the condenser 102 (e.g. such that the air and water are in a counter-flow arrangement). The cool air may therefore flow about the hot side of the condenser 102 before being exhausted back into the atmosphere via an exhaust duct 116. Circulating cool air towards the hot side of the condenser 102 may improve a performance of the condenser 102, as a rate of heat transfer from the steam entering the condenser 102 to the environment may be increased. The air released back into the environment may subsequently act as a heatsink, thereby improving a thermodynamic efficiency of the power conversion system 100.

[0050] Although not depicted, it is envisaged that the nuclear fission power plant 10 may be transported in distinct sub-assemblies. Each sub-assembly may be loaded onto distinct shipping containers, or onto the same container, and may be assembled ‘in-situ’ at the terrestrial location, e.g. where power is required. As an example, a first sub-assembly may comprise the nuclear reactor core 20, the primary neutronic control elements 50, the secondary neutronic control element 60, the neutron reflector 70, the containment vessel 40, and the neutron shield 80. A second sub-assembly may comprise the pump 94, the heat exchanger boiler 92, and any interconnecting piping of the fluid circuit 90. A third sub-assemblymay comprise the power conversion system 100. A fourth sub-assembly may comprise the first controller 54, the second controller 64, and any first or second actuators 52, 62 of the primary / secondary neutronic control elements 50, 60. This is but one example, it will be understood that other sub-assemblies are possible, and that the configuration of subassemblies may be adapted to best suit the means of transport. For example, first actuators 52 of the primary neutronic control elements may be assembled into the first sub-assembly instead of being separately transported in the fourth sub-assembly. It is also possible for the nuclear fission power plant 10 to be completely assembled, loaded onto a container, and transported to the appropriate terrestrial location.

[0051] Although not depicted, it is envisaged that the nuclear fission power plant 10 may comprise at least one further fluid circuit similar to fluid circuit 90. The further fluid circuit may be configured to transfer heat from cooling gas flowing through the further fluid circuit to the working fluid of the power conversion system 100 via the heat exchanger boiler 92 or a further heat exchanger boiler. The further fluid circuit may have a further pump for circulating a gas in the further fluid circuit. The further fluid circuit may effectively be parallel to the fluid circuit 90 and may improve the robustness of the nuclear fission power plant 10 since it can continue to operate in the event of one of the fluid circuits failing.

[0052] Although not depicted, it is envisaged that the nuclear fission power plant 10 may comprise at least one further power conversion system 100. The nuclear fission power plant 10 may thus comprise at least one further Rankine power system (e.g. like that described above). The further Rankine power system may be configured to absorb heat from the working fluid of the fluid circuit 90 or further fluid circuit. The further Rankine power system may therefore be coupled to the heat exchanger boiler 92 or to a further heat exchanger boiler. The further Rankine power system may effectively be parallel to the Rankine power system and may improve the robustness of the nuclear fission power plant 10 since it can continue to operate in the event of one of the Rankine power systems failing.

[0053] The present disclosure also relates to a kit of parts for the nuclear fission power plant 10. The kit of parts may comprise at least some of the above-described components. The kit of parts may be configured for placement within at least one container, such as a standard shipping container to be loaded onto a ship or a truck. The kit of parts may also be configured at least partially for assembly at the desired terrestrial deployment location. Once deployed in the terrestrial environment, the kit of parts may automatically assemble, or may be assembled with the assistance of a robot or any other operative.

[0054] With reference to Figure 4, the present disclosure also relates to a method 200 for the nuclear fission power plant 10. The method 200 comprises controlling the nuclear fission power plant 10. The control of the nuclear fission power plant 10 may be at least partially carried out remotely. For example, the nuclear fission power plant 10 may be controlled from a control facility that is located remote to the location of the nuclear fission power plant 10. Alternatively, control of the nuclear fission power plant 10 may be carried out locally (i.e., at the location of the nuclear fission power plant 10).

[0055] The method 200 controls the nuclear fission power plant 10 such that in a first action 210, the nuclear fission power plant 10 generates heat with the gas-cooled moderated nuclear reactor core 20. In a second action 220, cooled gas is delivered to the containment vessel 40 by the fluid circuit 90. In a third action 230, hot gas from the containment vessel 40 is received by the fluid circuit 90. In a fourth action 240, a working fluid flowing in the power conversion system 100 is heated by virtue of the heat exchanger boiler 92. More specifically, water flowing in the power conversion system 100 is vaporised to steam by virtue of the heat exchanger boiler 92. In a fifth action 250, the generator 108 is driven by the turbine 106. More specifically, the turbine 106 is driven by the steam which in turn drives the generator 108, the steam then flowing into the condenser 102 to be condensed back into water. In a sixth action 260, electricity is generated by the generator 108.

[0056] The present disclosure advantageously provides a highly efficient and reliable nuclear fission power plant. This is at least partly because the ceramic fuel is resilient to high temperatures and a gaseous coolant cannot change state at high temperatures in the way a liquid coolant can. This in turn can improve thermodynamic efficiency by providing a greater temperature gradient across the system.

[0057] A further advantage of the present disclosure is that the use of a tube cladding (to contain the pellets of fuel) may improve a safety and transportability of the nuclear fission power plant. In particular, the tube cladding may protect the fuel from damage when in transportation and may more effectively retain nuclear isotopes.

[0058] Safety of the nuclear fission power plant is improved by reducing a likelihood of neutrons and radioisotopes from being released into the environment. This is at least partly achieved by the neutron shield, which may absorb any neutrons that are not reflected by the neutron reflector, and the fluid circuit, which provides a further barrier between the reactor core and the power conversion system, thereby reducing a risk of radioisotopes beingreleased into the environment. The linearly movable control rods, in combination with the control systems provided, allows both fine and coarse control to be exerted over the rate of fission in the core of the reactor. This further enhances a safety of the nuclear fission power plant.

[0059] The fluid circuit may also provide a thermal buffer between the reactor core and the power conversion system. The fluid circuit may thus reduce the impact of any thermal fluctuations in the reactor core. As an example, the thermal inertia provided by the fluid circuit may reduce a thermal load experienced by components of the power conversion system, and therefore reduce a thermal fatigue of those components. This, in turn, may improve a life span of the nuclear fission power plant, and reduce an amount of maintenance required.

[0060] It is further noted that the Rankine power system provides excellent efficiency and reliability when compared to other power conversion technologies, which further improves a life-expectancy and performance of the nuclear fission power plant.

[0061] A transportability and utility of the nuclear fission power plant is improved through the ability to either transport the nuclear fission power plant in distinct sub-assemblies, or to transport an ‘already’ assembled nuclear fission power plant. As such, if transport constraints (e.g. regulations) demand smaller shipping containers, this may be accommodated by transporting the nuclear fission power plant in sub-assemblies configured to be easily assembled at the environment. Where no such constraints exist, the nuclear fission power plant may be fully or substantially assembled (e.g. at a factory) before being transported to the environment, thereby reducing a complexity for an end operative.

[0062] Various examples have been described, each of which feature various combinations of features. It will be appreciated by those skilled in the art that, except where clearly mutually exclusive, any of the features may be employed separately or in combination with any other features and the disclosure extends to and includes all combinations and subcombinations of one or more features described herein.

Claims

CLAIMS1 . A nuclear fission power plant configured for use in a terrestrial environment, the nuclear fission power plant comprising: a gas-cooled moderated nuclear reactor core, the gas-cooled moderated nuclear reactor core comprising: a fuel; a moderator; and at least one core inlet and at least one core outlet; a neutron reflector disposed around a periphery of the gas-cooled moderated nuclear reactor core; a plurality of primary neutronic control elements, each primary neutronic control element being configured to be selectively inserted into the gas-cooled moderated nuclear reactor core; a secondary neutronic control element configured to be selectively inserted into the gas- cooled moderated nuclear reactor core; a containment vessel substantially surrounding the gas-cooled moderated nuclear reactor core, the containment vessel comprising a containment vessel inlet and a containment vessel outlet, and being configured to define a flow path between the containment vessel inlet and the containment vessel outlet, such that gas following the flow path flows from the containment vessel inlet towards the gas-cooled moderated nuclear reactor core, into the gas- cooled moderated nuclear reactor core via the at least one core inlet, out of the gas-cooled moderated nuclear reactor core via the at least one core outlet, and towards the containment vessel outlet; a fluid circuit configured to receive hot gas from the containment vessel outlet and deliver cooled gas to the containment vessel inlet; and a Rankine power system coupled to the fluid circuit via a heat exchanger boiler, wherein the Rankine power system comprises: a pump; a condenser; a turbine; and a generator; the Rankine power system being arranged such that a working fluid pumped by the pump flows through the condenser, the heat exchanger boiler, and the turbine, and wherein the condenser is configured to condense the working fluid, the heat exchanger boiler is configured to permit heat in the gas flowing through the fluid circuit to betransferred to the working fluid to thereby evaporate the working fluid, and the turbine is configured to drive the generator.

2. The nuclear fission power plant of claim 1 , wherein the fuel comprises High Assay Low Enriched Uranium (HALEU).

3. The nuclear fission power plant of claim 1 or 2, wherein the fuel is enriched to substantially 19.75% uranium-235.

4. The nuclear fission power plant of any preceding claim, wherein the fuel comprises uranium dioxide, UO2.

5. The nuclear fission power plant of any preceding claim, wherein the fuel comprises pellets of fuel stacked within a metal tube.

6. The nuclear fission power plant of any preceding claim, wherein the moderator comprises graphite7. The nuclear fission power plant of any preceding claim, wherein the neutron reflector comprises graphite or aluminium oxide.

8. The nuclear fission power plant of any of the preceding claims, wherein the plurality of primary neutronic control elements comprises a plurality of linearly movable control rods.

9. The nuclear fission power plant of any of the preceding claims, wherein the secondary neutronic control element comprises a linearly movable control rod.

10. The nuclear fission power plant of any of the preceding claims, wherein the working fluid in the Rankine power system comprises water.

11. The nuclear fission power plant of any of the preceding claims, wherein the Rankine power system further comprises a fan, and the condenser comprises a duct, the duct being configured to fluidically couple the fan to a cool side of the condenser and to fluidically couple the cool side of the condenser to a hot side of the condenser, such that air blown by the fanflows from the cool side of the condenser to the hot side of the condenser before being exhausted into the environment.

12. The nuclear fission power plant of any of the preceding claims, wherein the primary neutronic control elements are a primary form of control to control a reactivity level of the gas- cooled moderated nuclear reactor core, and are used for fine control.

13. The nuclear fission power plant of any of the preceding claims, wherein the secondary neutronic control element is a secondary form of control to control a reactivity level of the gas- cooled moderated nuclear reactor core, and is used for coarse control.

14. The nuclear fission power plant of any preceding claim, further comprising a neutron shield disposed around a periphery of the neutron reflector.

15. The nuclear fission power plant of claim 14, wherein the neutron shield comprises boron carbide.

16. A kit of parts for a nuclear fission power plant configured for use in a terrestrial environment, the kit of parts being configured at least partially for assembly at the terrestrial environment and comprising: a gas-cooled moderated nuclear reactor core, the gas-cooled moderated nuclear reactor core comprising: a fuel; a moderator; and at least one core inlet and at least one core outlet; a neutron reflector configured to be disposed around a periphery of the gas-cooled moderated nuclear reactor core; a plurality of primary neutronic control elements, each primary neutronic control element being configurable to be selectively inserted into the gas-cooled moderated nuclear reactor core; a secondary neutronic control element configurable to be selectively inserted into the gas-cooled moderated nuclear reactor core; a containment vessel which, when the kit of parts is assembled, substantially surrounds the gas-cooled moderated nuclear reactor core, the containment vessel comprising a containment vessel inlet and a containment vessel outlet, and being configurable to define aflow path between the containment vessel inlet and the containment vessel outlet, such that gas following the flow path flows from the containment vessel inlet towards the gas-cooled moderated nuclear reactor core, into the gas-cooled moderated nuclear reactor core via the at least one core inlet, out of the gas-cooled moderated nuclear reactor core via the at least one core outlet, and towards the containment vessel outlet; a fluid circuit configurable to receive hot gas from the containment vessel outlet and deliver cooled gas to the containment vessel inlet; and a Rankine power system couplable to the fluid circuit via a heat exchanger boiler, wherein the Rankine power system comprises: a pump; a condenser; a turbine; and a generator; the Rankine power system being arrangeable such that a working fluid pumped by the pump flows through the condenser, the heat exchanger boiler, and the turbine, and wherein the condenser is configurable to condense the working fluid, the heat exchanger boiler is configurable to permit heat in the gas flowing through the fluid circuit to be transferred to the working fluid to thereby evaporate the working fluid, and the turbine is configurable to drive the generator.

17. The kit of parts of claim 16, wherein the Rankine power system further comprises a fan, and the condenser comprises a duct, the duct being configured to fluidically couple to the fan and to a cool side of the condenser and to fluidically couple the cool side of the condenser to a hot side of the condenser, such that air blown by the fan can flow from the cool side of the condenser to the hot side of the condenser before being exhausted into the environment.

18. The kit of parts of claim 16, or 17, further comprising a neutron shield configured to be disposed around a periphery of the neutron reflector.

19. A method for a nuclear fission power plant configured for use in a terrestrial environment, the method comprising controlling the nuclear fission power plant to: generate heat with a gas-cooled moderated nuclear reactor core, the gas-cooled moderated nuclear reactor core comprising a fuel, a moderator, at least one core outlet, and at least one core inlet, wherein:a neutron reflector is disposed around a periphery of the gas-cooled moderated nuclear reactor core; a plurality of primary neutronic control elements are configured to be selectively inserted into the gas-cooled moderated nuclear reactor core; a secondary neutronic control element is configured to be selectively inserted into the gas-cooled moderated nuclear reactor core; and a containment vessel is arranged to substantially surround the gas-cooled moderated nuclear reactor core, the containment vessel comprising a containment vessel inlet and a containment vessel outlet, and being configured to define a flow path between the containment vessel inlet and the containment vessel outlet, such that gas following the flow path flows from the containment vessel inlet towards the gas-cooled moderated nuclear reactor core, into the gas-cooled moderated nuclear reactor core via the at least one core inlet, out of the gas-cooled moderated nuclear reactor core via the at least one core outlet, and towards the containment vessel outlet; receive hot gas from the containment vessel outlet to a fluid circuit; deliver cooled gas to the containment vessel inlet via the fluid circuit; and generate electricity with a Rankine power system, the Rankine power system being coupled to the fluid circuit via a heat exchanger boiler, the Rankine power system comprising a pump, a condenser, a turbine, and a generator, and being arranged such that a working fluid pumped by the pump flows through the condenser, the heat exchanger boiler, and the turbine, wherein the condenser is configured to condense the working fluid, the heat exchanger boiler is configured to permit heat in the gas flowing through the fluid circuit to be transferred to the working fluid to thereby evaporate the working fluid, and the turbine is configured to drive the generator.

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