In-vessel natural circulation alkali metal furnace system, purification system, and associated method

Abstract

A method and system for an in-vessel natural circulation alkali metal reactor system, a cleanup system, and associated methods are disclosed. The reactor vessel system includes an inner vessel defining an interior volume sized to at least partially surround a nuclear reactor. The reactor includes a plurality of nuclear fuel elements at least partially surrounded by cladding, and the reactor is cooled by a liquid metal coolant in a primary coolant loop. A pool of immersion fluid occupies a volume inside the inner vessel. The reactor vessel system includes an outer vessel sized to completely or substantially surround the inner vessel. The nuclear reactor power system includes a reactor core including an active fuel region and a rotatable drum including at least one of a neutron absorbing material, a neutron leakage enhancing material, or a neutron reflecting material, the rotatable drum being positioned outside the active fuel region of the reactor core.

Description

Technical Field

[0001] This embodiment generally relates to nuclear reactors, and more specifically to nuclear reactors that use liquid metal.

Background Art

[0002] Global energy growth, as well as the drive to reduce pollution and emissions, is stimulating new activities surrounding the commercialization and design of new nuclear reactor technologies. Some of these technologies include small nuclear reactors designed to provide power that is more distributed, long-lasting, and resilient in a more decentralized manner. Some of these nuclear reactors incorporate liquid metal into their design and cooling due to the favorable heat transfer and neutron characteristics of liquid metal.

Summary of the Invention

Means for Solving the Problems

[0003] This disclosure describes a system and method for a natural circulation alkali metal reactor system within a container, as well as the implementation of a purification system. According to some embodiments, the nuclear reactor may include a fuel containing a fissionable material such as uranium-233, uranium-235, or plutonium-239, a coolant that uses an alkali (e.g., sodium) metal to transport heat away from the fuel, a heat exchanger for transferring heat from the coolant or a cooling device to a power conversion system, as well as measurement equipment, a support structure, and a shielding material.

[0004] According to some embodiments, the fissionable material may be contained within fuel elements. The fuel elements may be held inside a nuclear reactor vessel.

[0005] According to some embodiments, the liquid metal primary coolant transports its heat to a heat exchanger that transfers the heat from the fuel and the heat is transferred to an intermediate coolant or a power conversion working fluid.

[0006] According to some embodiments, an auxiliary heat exchanger is used to remove residual heat and stored energy. These heat exchangers use liquid metal, salt, or gas to remove residual heat, which is then released into ambient air or water.

[0007] According to some embodiments, a decay heat removal auxiliary cooling system is used to passively remove decay heat from the reactor vessel.

[0008] According to some embodiments, external cooling can remove heat from the reactor vessel system via a fluid such as air or liquid.

[0009] According to some embodiments, the liquid metal flows by natural circulation and transfers heat by natural convection.

[0010] According to some embodiments, the liquid metal flows via natural circulation under steady-state conditions within a range of power levels, from reactor startup to full power.

[0011] According to some embodiments, one or more booster pumps are used to facilitate reactor startup by establishing a flow pattern via forced and mixed circulation, which then transitions to natural circulation at a desired power level, at which point the pumps are shut down.

[0012] According to some embodiments, the booster pump is installed inside the vessel at either the heat exchanger outlet or the core inlet. According to some embodiments, the booster pump is installed outside the vessel, within a section of the primary flow loop.

[0013] According to some embodiments, a momentum-based circulator, such as a flywheel, is positioned at the outlet of a booster pump to provide rotational inertia to the coolant.

[0014] According to some embodiments, maintaining adequate control over the chemical properties and purity of the coolant is important to ensure the lifespan of the coolant and its components. A cold trap may be used to control the chemical properties and purity of the liquid metal coolant.

[0015] According to some embodiments, the cold trap is installed within the reactor vessel and in an area where sufficient coolant flow is generated. According to some embodiments, the cold trap is cooled by a pre-cooled bypass flow of intermediate coolant that has been cooled to the cold trap operating temperature. Pre-cooling may be performed by a heat exchanger or a direct cooling device.

[0016] According to some embodiments, the cold trap is cooled by a bypass flow of coolant from a decay heat removal auxiliary cooling system, which is cooled to the cold trap operating temperature.

[0017] According to some embodiments, the core, riser, primary heat exchanger, and support components, including fuel, structures, reflectors, and shielding materials, are cooled by a fluidized loop that is completely housed inside the vessel.

[0018] According to some embodiments, the fluid loop is immersed in a fluid contained inside the reactor vessel. The immersion fluid may be used to provide cooling to the components or system. The immersion fluid may also provide heat storage capacity.

[0019] According to some embodiments, the immersion fluid is the same fluid used as the primary coolant. According to some embodiments, the coolant in the primary coolant loop is hydraulically connected to the fluid in the immersion pool.

[0020] According to some embodiments, the hydraulic connection between the immersion fluid and the primary coolant is made by a flow diode, pressure gate, permeable membrane, or height difference, which is designed to allow flow between the coolant bodies under certain conditions such as a range of flow rates, coolant levels, pressure differences, and temperatures.

[0021] According to some embodiments, a hydraulic connection between the primary coolant and the immersion fluid can enhance the natural circulation characteristics of the system, increase the thermal mass of the fluid available to the system, and provide a thermal coupling to an auxiliary heat removal path for residual heat removal.

[0022] According to some embodiments, fuel elements and other in-core elements are removed from the reactor via conduits or pipelines that reach the top of the pool above each fuel assembly or near the top of its free surface, and the conduits can serve as standpipe-like structures for easier fuel removal.

[0023] According to some embodiments, fuel elements can be handled or removed using temporary fuel handling equipment, which is brought into the plant only when handling equipment is required.

[0024] According to some embodiments, the fuel element has a unique marker column that extends upward through a riser to or near the surface of the free pool. The marker column is structurally connected to the fuel element and acts as an extended lifting handle, reducing or eliminating the need to handle the fuel element through a deep liquid metal pool.

[0025] According to some embodiments, reactor components such as heat exchangers or pumps are integrated into modular packages to enable easier inspection, maintenance, and replacement.

[0026] According to some embodiments, the pump can be packaged with or in proximity to a heat exchanger such that an intermediate coolant flowing into the heat exchanger can be used to cool the pump. In some examples, the intermediate coolant can cool the pump at a temperature below the operating temperature of the primary coolant.

[0027] According to some embodiments, the pump is installed in contact with the container wall so that the pump can be cooled by conduction through the container wall.

[0028] According to some embodiments, the intermediate coolant can be the same coolant as the primary coolant. The coolant can also be a heat transfer fluid with a high specific heat, such as a liquid salt.

[0029] According to some embodiments, the reactor uses absorber rods to control the power level of the reactor, and in some cases, the rods are used alone to shut down the reactor. These rods can be positioned to be inserted into the core within the active fuel region or reflector region.

[0030] According to some embodiments, passive or inherent reactor control devices can be positioned within a removable assembly cartridge that allows for testing, replacement, and inspection. Such devices can include, among others, flow-floating absorbers, fusible latch absorbers, Curie-point latch absorbers, expanding liquid absorbers, or expanding gas-driven absorbers.

[0031] According to some embodiments, rotating drums are used to control neutron leakage and thus the power of the reactor. These drums are positioned outside the active fuel region of the core. These drums contain neutron absorber materials, neutron leakage enhancers, or neutron reflectors.

[0032] According to some embodiments, the drum is suspended via its drive line shaft. According to some embodiments, the drum is mounted on bearings or discs that provide structural support, alignment, and sufficient lubrication to enable rotation, while also being compatible with the coolant. These may be made from metallic or ceramic materials such as nitrides or carbides.

[0033] According to some embodiments, the drum is contained within a cartridge that isolates the drum from the primary coolant.

[0034] According to some embodiments, the power conversion system is connected to an intermediate coolant via a heat exchanger, where the working fluid is heated and then used to drive power conversion turbomachinery.

[0035] According to some embodiments, the power conversion system uses steam, gas, or supercritical fluid.

[0036] According to some embodiments, the power conversion system directly transfers heat from the primary system through the heat exchanger of the power conversion system.

[0037] According to some embodiments, a power plant, including a nuclear reactor, is controlled using an automatic control mechanism. According to some embodiments, advances in compilers enable the training of a system controller to better simulate all control operations from the same program.

[0038] According to some embodiments, automated differential calculus capabilities for use in machine learning techniques are used to create differentiable programs in which the derivative can be obtained through complex code involving loops, branches, and other structures. Various tools are connected to a compiler to create a compiled differential version of a function so that the differential f'(x) for any complex number f(x) can be compiled efficiently.

[0039] According to some embodiments, it can therefore be used to calculate sensitivity studies. According to some embodiments, the ability to find the derivative of an arbitrary complex function for any of its parameters allows the trainable model to be used as part of a differentiable program.

[0040] According to some embodiments, a function is created whose inputs are the current system state and several desired target states. The resulting information is provided to a trainable model, which acts as a controller and is required to bring the system to a target state, giving an interpretable proposal for a control operation. This proposal and the current system state are used to solve differential equations, which determine the actual results of those control operations. The difference between the results of the differential equation solver and the target state provides a metric for the usefulness of the trainable model of the reactor and power plant.

[0041] According to some embodiments, automatic differentiation allows for the direct calculation of the gradient of the loss value with respect to the intrinsic parameters of the controller model. A neural network is one such embodiment. This function is executed in a loop, and the controller parameters are updated, thereby minimizing losses and improving the quality of control proposals derived from models for nuclear reactors and power plants.

[0042] According to some embodiments, the controller is trained by having it repeatedly attempt to bring the system to a target state, without the need to define a reward function or generate any kind of training data. This eliminates the need to implement black-box reinforcement learning algorithms by selecting a differentiable control method to achieve faster convergence to a more effective control scheme for nuclear reactors and power plants.

[0043] In an exemplary implementation, the reactor vessel system includes, within the primary coolant loop, an inner vessel defining an internal volume sized to at least partially enclose a reactor cooled by a liquid metal coolant, and an outer vessel sized to completely or substantially enclose the inner vessel.

[0044] In some aspects that can be combined with exemplary implementations, a nuclear reactor includes multiple nuclear fuel elements.

[0045] In one aspect that can be combined with any of the aforementioned aspects, at least a portion of the multiple nuclear fuel elements are enclosed at least partially within the cladding.

[0046] In one aspect that can be combined with any of the aforementioned aspects, the system includes a heat exchanger configured to transfer heat from a liquid metal coolant to an intermediate coolant.

[0047] In one aspect that can be combined with any of the aforementioned aspects, the system includes a heat exchanger configured to transfer heat from a liquid metal coolant to a power conversion working fluid.

[0048] In one aspect that can be combined with any of the aforementioned aspects, the heat exchanger is a low-pressure drop heat exchanger.

[0049] In one aspect that can be combined with any of the aforementioned aspects, the system includes a cold trap configured to purify a liquid metal coolant.

[0050] In one aspect, which can be combined with any of the aforementioned aspects, the cold trap is located within the coolant loop and is cooled by intermediate coolant flowing from either an intermediate coolant circuit or a passive reactor cooling system.

[0051] In one aspect that can be combined with any of the aforementioned aspects, the cold trap is located at the outlet of the heat exchanger.

[0052] In one aspect that can be combined with any of the aforementioned aspects, the system includes a hot trap located within the primary coolant loop, configured to purify the liquid metal coolant.

[0053] In one aspect that can be combined with any of the aforementioned aspects, during operation, the liquid metal coolant flows through the primary coolant loop by natural circulation.

[0054] In one aspect, which can be combined with any of the aforementioned aspects, the liquid metal coolant flows by natural circulation under steady-state conditions at power levels ranging from reactor startup to full power.

[0055] In one aspect that can be combined with any of the aforementioned aspects, the system includes a booster pump configured to pump liquid metal coolant through a primary coolant loop.

[0056] In one aspect that can be combined with any of the aforementioned aspects, the booster pump is positioned at the outlet of the heat exchanger.

[0057] In one aspect that can be combined with any of the aforementioned aspects, the booster pump is located at the reactor inlet.

[0058] In one aspect that can be combined with any of the aforementioned aspects, the booster pump is located outside the outer vessel, within a section of the coolant loop.

[0059] In one aspect that can be combined with any of the aforementioned aspects, the system includes a momentum-based circulator located at the outlet of the booster pump.

[0060] In one aspect that can be combined with any of the aforementioned aspects, the momentum-based circulation device includes a flywheel.

[0061] In one aspect, which can be combined with any of the aforementioned aspects, the primary coolant loop is hydraulically isolated from the pool of immersion fluid.

[0062] In one aspect, which can be combined with any of the aforementioned aspects, the immersion fluid cools the components of the system.

[0063] In one aspect, which can be combined with any of the aforementioned aspects, the immersed fluid stores the thermal energy generated by the reactor.

[0064] In some aspect that can be combined with any of the aforementioned aspects, the immersion fluid is the same fluid as the liquid metal coolant.

[0065] In one aspect that can be combined with any of the aforementioned aspects, the immersion fluid and the liquid metal coolant are connected by hydraulic pressure.

[0066] In one aspect that can be combined with any of the aforementioned aspects, the immersion fluid and liquid metal coolant are connected by hydraulic pressure by one of the following: a flow diode, a pressure gate, a permeable membrane, or a height difference.

[0067] In one aspect that can be combined with any of the aforementioned aspects, the system includes a modular package of reactor vessel components.

[0068] In some aspect, which can be combined with any of the aforementioned aspects, the modular package is removable from the system.

[0069] In one aspect that can be combined with any of the aforementioned aspects, the modular package includes a heat exchanger and a pump.

[0070] In one aspect that can be combined with any of the aforementioned aspects, the intermediate coolant flowing through the heat exchanger during operation cools the pump.

[0071] In one aspect, which can be combined with any of the aforementioned aspects, the intermediate coolant cools the pump to a temperature below the operating temperature of the liquid metal coolant during operation.

[0072] In one aspect that can be combined with any of the aforementioned aspects, the intermediate coolant contains the same fluid as the liquid metal coolant.

[0073] In one aspect that can be combined with any of the aforementioned aspects, the intermediate coolant contains a liquid salt.

[0074] In another exemplary implementation, the method involves operating one of the reactor vessel systems of the aforementioned implementations to produce electricity.

[0075] In another exemplary implementation, the reactor power system includes a core, which includes an active fuel region, and a rotatable drum, which includes at least one of i) a neutron-absorbing material, ii) a neutron-leaking material, or iii) a neutron-reflecting material, the rotatable drum being located outside the active fuel region of the core.

[0076] In one aspect that can be combined with the exemplary implementation, the rotatable drum is suspended by a drive line shaft.

[0077] In one aspect that can be combined with any of the aforementioned aspects, the rotatable drum is mounted on a bearing, which provides lubrication to enable the rotation of the rotatable drum.

[0078] In one aspect that can be combined with any of the aforementioned aspects, the bearing is made from either a metallic or ceramic material.

[0079] In one aspect that can be combined with any of the aforementioned aspects, the rotatable drum is enclosed within a container that isolates the rotatable drum from the liquid metal coolant.

[0080] In an exemplary implementation, a process is disclosed for refueling a reactor core having a plurality of core elements arranged in a spatial grid, wherein the plurality of core elements include at least a plurality of fuel elements and a plurality of reflector elements. The process includes removing the reflector elements from a first spatial grid position, moving the fuel elements from a second spatial grid position to a first spatial grid position, the first spatial grid position being a different distance from the center of the spatial grid than the second spatial grid position, and inserting the reflector elements into a third spatial grid position, the third spatial grid position being a different distance from the center of the spatial grid than the first and second spatial grid positions.

[0081] In one aspect that can be combined with the exemplary implementation, the fuel element is a first fuel element, and the process involves moving the first fuel element from a second spatial lattice position to the first spatial lattice position, and then inserting the second fuel element into the second spatial lattice position.

[0082] In one aspect that can be combined with any of the aforementioned aspects, the first fuel element is an irradiated fuel element, and the second fuel element is an unirradiated fuel element.

[0083] In one aspect, which can be combined with any of the aforementioned aspects, the fuel elements are not removed from the reactor core.

[0084] In one aspect that can be combined with any of the aforementioned aspects, the core includes a core barrel having at least one aspect, an active fuel region located within the core barrel and containing a plurality of fuel elements, and a reflector region located within the core barrel and containing a plurality of reflector elements. The reflector region is concentric with the active fuel region and has an inner boundary adjacent to the active fuel region and an outer boundary closer to the side of the core barrel than the inner boundary. A first spatial grid position is located at the inner boundary of the reflector region, and a third spatial grid position is located at the outer boundary of the reflector region.

[0085] In one aspect that can be combined with any of the aforementioned aspects, the first lattice position is at a greater distance from the center of the spatial lattice than the second spatial lattice position.

[0086] In one aspect that can be combined with any of the aforementioned aspects, the third lattice position is at a greater distance from the center of the spatial lattice than both the first and second spatial lattice positions.

[0087] In one aspect that can be combined with any of the aforementioned aspects, the third grid position has not been occupied by either a fuel element or a reflector element.

[0088] In one aspect that can be combined with any of the aforementioned aspects, the third grid position is dedicated to either the fuel element or the reflector element.

[0089] An exemplary implementation discloses a process for refueling a reactor core having multiple fuel elements arranged in a spatial grid. This process includes moving a first fuel element from a first spatial grid position to a second spatial grid position, where the first spatial grid position is a distance from the center of the spatial grid that is different from the second spatial grid position, and inserting the second fuel element into the first spatial grid position.

[0090] In one aspect that can be combined with the exemplary implementation, the first fuel element is an irradiated fuel element, and the second fuel element is an unirradiated fuel element.

[0091] In one aspect that can be combined with any of the aforementioned aspects, the first fuel element is not removed from the reactor core.

[0092] In one aspect that can be combined with any of the aforementioned aspects, the second spatial lattice position is at a greater distance from the center of the spatial lattice than the first spatial lattice position.

[0093] In one aspect that can be combined with any of the aforementioned aspects, the core includes a core barrel having at least one aspect, an active fuel region located within the core barrel and containing a plurality of fuel elements, and a reflector region located within the core barrel and containing a plurality of reflector elements. The reflector region is concentric with the active fuel region and includes an inner boundary adjacent to the active fuel region and an outer boundary closer to the side of the core barrel than the inner boundary. The first spatial grid position is located within the active fuel region, and the second spatial grid position is located at or near the inner boundary of the reflector region.

[0094] In one aspect that can be combined with any of the aforementioned aspects, the second spatial grid position has not been occupied by either the fuel element or the reflector element.

[0095] In one aspect that can be combined with any of the aforementioned aspects, the second spatial grid position is dedicated to either the fuel element or the reflector element.

[0096] In one aspect that can be combined with any of the aforementioned aspects, the process includes moving a reflector element from a second spatial grid position to a third spatial grid position, or outside the core, prior to moving a first fuel element from a first spatial grid position to a second spatial grid position.

[0097] Details of one or more embodiments of the subject matter of this specification are described in the accompanying drawings and the following description. Other features, aspects, and advantages of the subject matter will be evident from the description, drawings, and claims. The present invention provides, for example, the following: (Item 1) A reactor vessel system, An inner vessel defining an internal volume sized to at least partially enclose a nuclear reactor, wherein the reactor comprises a plurality of nuclear fuel elements at least partially enclosed within a cladding material, and the reactor is cooled by a liquid metal coolant in a primary coolant loop, the inner vessel and An outer container sized to completely or substantially enclose the inner container and A reactor vessel system equipped with the following features. (Item 2) The reactor vessel system according to item 1, comprising a heat exchanger configured to transfer heat from the liquid metal coolant to an intermediate coolant or to a power conversion working fluid, wherein the heat exchanger is a low-pressure drop heat exchanger. (Item 3) The reactor vessel system according to item 1, comprising a cold trap configured to purify the liquid metal coolant, the cold trap located in the primary coolant loop at the outlet of a heat exchanger and cooled by an intermediate coolant flowing from one of an intermediate coolant circuit or a passive reactor cooling system. (Item 4) The reactor vessel system according to item 1, comprising a hot trap located within the primary coolant loop and configured to purify the liquid metal coolant. (Item 5) The reactor vessel system according to item 1, wherein during operation under steady-state conditions at power levels ranging from reactor startup to full power, the liquid metal coolant flows through the primary coolant loop by natural circulation. (Item 6) The reactor vessel system according to item 1, comprising a booster pump configured to pump the liquid metal coolant through the primary coolant loop, wherein the booster pump is located at one of the following: the outlet of a heat exchanger, the inlet of a reactor, or a section of the primary coolant loop outside the outer vessel. (Item 7) The reactor vessel system according to item 6, comprising a momentum-based circulation device located at the outlet of the booster pump. (Item 8) The reactor vessel system according to item 1, comprising a pool of immersion fluid occupying a certain volume inside the inner vessel. (Item 9) The reactor vessel system according to item 8, wherein the pool of immersed fluid is hydraulically isolated from the primary coolant loop. (Item 10) The reactor vessel system according to item 8, wherein the pool of immersed fluid is hydraulically connected to the primary coolant loop by one of a flow diode, a pressure gate, a permeable membrane, or a height difference. (Item 11) The reactor vessel system according to item 8, wherein the immersion fluid includes the same fluid as the liquid metal coolant. (Item 12) The reactor vessel system according to item 1, comprising a modular package of reactor vessel components, wherein the modular package is removable from the system. (Item 13) The reactor vessel system according to item 12, wherein the modular package comprises a heat exchanger and a pump, and during operation, an intermediate coolant flowing through the heat exchanger cools the pump to a temperature below the operating temperature of the liquid metal coolant. (Item 14) A method comprising operating a reactor vessel system to produce electricity, wherein the reactor vessel system is An inner vessel defining an internal volume sized to at least partially enclose a nuclear reactor, wherein the reactor comprises a plurality of nuclear fuel elements at least partially enclosed within a cladding material, An outer container sized to completely or substantially enclose the inner container and A method comprising, wherein the method includes cooling the reactor using a liquid metal coolant in a primary coolant loop. (Item 15) The method according to item 14, comprising transferring heat from the liquid metal coolant to an intermediate coolant or to a power conversion working fluid by a low-pressure drop heat exchanger. (Item 16) The method according to item 14, comprising purifying the liquid metal coolant with a cold trap, the cold trap being located within the primary coolant loop at the outlet of a heat exchanger and cooled by an intermediate coolant flowing from one of an intermediate coolant circuit or a passive reactor cooling system. (Item 17) The method according to item 14, comprising purifying the liquid metal coolant by a hot trap located within the primary coolant loop. (Item 18) The method according to item 14, wherein during operation under steady-state conditions at power levels ranging from reactor startup to full power, the liquid metal coolant flows through the primary coolant loop by natural circulation. (Item 19) The method according to item 14, comprising pumping the liquid metal coolant through the primary coolant loop by a booster pump, wherein the booster pump is located at one of the following: the outlet of a heat exchanger, the inlet of a reactor, or a section of the primary coolant loop outside the outer vessel. (Item 20) The method according to item 19, wherein the reactor vessel system comprises a momentum-based circulator located at the outlet of the booster pump. (Item 21) The reactor vessel system according to item 14, wherein the reactor vessel system comprises a pool of immersion fluid occupying a certain volume inside the inner vessel. (Item 22) The method according to item 21, wherein the pool of immersion fluid is hydraulically isolated from the primary coolant loop. (Item 23) The method according to item 21, wherein the pool of immersion fluid is hydraulically connected to the primary coolant loop by one of a flow diode, a pressure gate, a permeable membrane, or a height difference. (Item 24) The method according to item 21, wherein the immersion fluid comprises the same fluid as the liquid metal coolant. (Item 25) The method according to item 14, wherein the reactor vessel system comprises a modular package of reactor vessel components, the modular package being removable from the system. (Item 26) The method according to item 25, wherein the modular package comprises a heat exchanger and a pump, and the method includes cooling the pump to a temperature below the operating temperature of the liquid metal coolant by an intermediate coolant flowing through the heat exchanger. (Item 27) A nuclear reactor power system, A reactor core equipped with an active fuel region, i) a neutron-absorbing material, ii) a neutron-leaking material, or iii) a neutron-reflecting material, wherein the rotatable drum is located outside the active fuel region of the reactor core, and A reactor power system equipped with a nuclear reactor. (Item 28) The reactor power system according to item 27, wherein the rotatable drum is enclosed within a container that isolates the rotatable drum from a liquid metal coolant, and is mounted on a bearing, the bearing provides lubrication to enable the rotation of the rotatable drum, and the bearing is made of one of a metallic material or a ceramic material. (Item 29) A method comprising operating a reactor power system to produce electricity, wherein the reactor power system is A reactor core equipped with an active fuel region, i) a neutron-absorbing material, ii) a neutron-leaking material, or iii) a neutron-reflecting material, wherein the rotatable drum is located outside the active fuel region of the reactor core, and A method that includes [a certain feature]. (Item 30) The method according to item 29, wherein the rotatable drum is enclosed within a container that isolates the rotatable drum from a liquid metal coolant, and is mounted on a bearing, the bearing provides lubrication to enable the rotation of the rotatable drum, and the bearing is made of one of a metallic material or a ceramic material. (Item 31) A method for training a controller for controlling a nuclear reactor power system, To provide the controller's control model with data representing the current state of the reactor power system, To provide the control model with data representing the target state of the reactor power system, Receiving data from the control model representing one or more control operations to achieve the target state of the reactor power system, Determining the predicted final state of the reactor power system based on data representing one or more control operations to achieve the target state of the reactor power system, To determine the difference between the predicted final state of the reactor power system and the target state of the reactor power system, Adjusting one or more parameters of the control model based on the difference between the predicted final state of the reactor power system and the target state of the reactor power system. A method that includes this. (Item 32) The control model is the method according to item 31, comprising a neural network model. (Item 33) The aforementioned reactor power system is An inner vessel defining an internal volume sized to at least partially enclose a nuclear reactor, wherein the reactor comprises a plurality of nuclear fuel elements at least partially enclosed within a cladding material, and the reactor is cooled by a liquid metal coolant in a primary coolant loop, the inner vessel and An outer container sized to completely or substantially enclose the inner container and The method according to item 31, comprising: (Item 34) The aforementioned reactor power system is A reactor core equipped with an active fuel region, i) a neutron-absorbing material, ii) a neutron-leaking material, or iii) a neutron-reflecting material, wherein the rotatable drum is located outside the active fuel region of the reactor core, and The method according to item 31, comprising: (Item 35) A method for refueling a reactor core having a plurality of core elements arranged in a spatial grid, wherein the plurality of core elements comprises at least a plurality of fuel elements and a plurality of reflector elements, and the method is Removing the reflector element from the first spatial grid position, The fuel element is moved from a second spatial grid position to the first spatial grid position, wherein the first spatial grid position is a distance from the center of the spatial grid that is different from the second spatial grid position. The reflector element is placed into a third spatial grid position, wherein the third spatial grid position is a distance from the center of the spatial grid that is different from each of the first and second spatial grid positions. Methods that include... (Item 36) The method according to item 35, wherein the fuel element includes a first fuel element, and the method comprises moving the first fuel element from the second spatial grid position to the first spatial grid position, and then introducing the second fuel element into the second spatial grid position. (Item 37) The method according to item 36, wherein the first fuel element is an irradiated fuel element and the second fuel element is an unirradiated fuel element. (Item 38) The fuel element is not removed from the reactor core, as described in item 35. (Item 39) The aforementioned reactor core is A core barrel having at least one side, An active fuel region, which includes the plurality of fuel elements, is located within the core barrel. A reflector region located within the core barrel, comprising the plurality of reflector elements, wherein the reflector region is concentric with the active fuel region, and the reflector region has an inner boundary adjacent to the active fuel region and an outer boundary closer to the side surface of the core barrel than the inner boundary. The method according to item 35, wherein the first spatial grid position is located at the inner boundary of the reflector region, and the third spatial grid position is located at the outer boundary of the reflector region. (Item 40) The method according to item 35, wherein the first spatial grid position is at a greater distance from the center of the spatial grid than the second spatial grid position. (Item 41) The method according to item 35, wherein the third spatial grid position is at a greater distance from the center of the spatial grid than both the first and second spatial grid positions. (Item 42) The method according to item 35, wherein the third spatial grid position is not previously occupied by either a fuel element or a reflector element. (Item 43) The method according to item 35, wherein the third spatial grid position is dedicated to either a fuel element or a reflector element. (Item 44) A method for refueling a reactor core having a plurality of fuel elements arranged in a spatial grid, wherein the method is The first fuel element is moved from a first spatial grid position to a second spatial grid position, wherein the first spatial grid position is a distance from the center of the spatial grid that is different from the second spatial grid position. The second fuel element is introduced into the first spatial grid position. Methods that include... (Item 45) The method according to item 44, wherein the first fuel element is an irradiated fuel element and the second fuel element is an unirradiated fuel element. (Item 46) The method according to item 44, wherein the first fuel element is not removed from the reactor core. (Item 47) The method according to item 44, wherein the second spatial grid position is at a greater distance from the center of the spatial grid than the first spatial grid position. (Item 48) The aforementioned reactor core is A core barrel having at least one side, An active fuel region, which includes the plurality of fuel elements, is located within the core barrel. A reflector region located within the core barrel, comprising the plurality of reflector elements, wherein the reflector region is concentric with the active fuel region and comprises an inner boundary adjacent to the active fuel region and an outer boundary closer to the side surface of the core barrel than the inner boundary, the first spatial grid position is located within the active fuel region, and the second spatial grid position is located at or near the inner boundary of the reflector region. The method described in item 44, which includes the features described. (Item 49) The method according to item 48, wherein the second spatial grid position is not previously occupied by either a fuel element or a reflector element. (Item 50) The method according to item 48, wherein the second spatial grid position is dedicated to either a fuel element or a reflector element. (Item 51) The method of item 48, further comprising moving a reflector element from the second spatial grid position to the third spatial grid position, or outside the core, prior to moving the first fuel element from the first spatial grid position to the second spatial grid position. [Brief explanation of the drawing]

[0098] [Figure 1] Figure 1 shows a cross-sectional view of an exemplary implementation of a reactor vessel system according to this disclosure.

[0099] [Figure 2] Figure 2 shows a cross-sectional view of an exemplary reactor vessel system with a booster pump.

[0100] [Figure 3] Figure 3 shows a cross-sectional view of an exemplary reactor vessel system with a cold trap.

[0101] [Figure 4] Figure 4 shows a cross-sectional view of a cold trap that is cooled by an intermediate heat exchanger.

[0102] [Figure 5]Figure 5 shows a cross-sectional view of an exemplary reactor vessel system with a free upper surface hydraulic connection and a lower hydraulic connection.

[0103] [Figure 6] Figure 6 shows a cross-sectional view of an exemplary reactor vessel system with an enclosed coolant loop.

[0104] [Figure 7] Figure 7 shows a cross-sectional view of an exemplary reactor vessel system with a drain siphon.

[0105] [Figure 8] Figure 8 shows a schematic diagram of an exemplary reactor power system designed to transfer heat directly from the primary system through the heat exchanger of the power conversion system.

[0106] [Figure 9] Figure 9 shows a schematic diagram of an exemplary reactor power system, including an intermediate thermal energy storage system and a PCS heat exchanger.

[0107] [Figure 10] Figure 10 shows a schematic diagram of an exemplary reactor power system with in-vessel thermal energy storage.

[0108] [Figure 11] Figures 11A and 11B show upper cross-sectional views of the reactor core.

[0109] [Figure 12] Figure 12 is a schematic diagram of a computer system implemented according to this disclosure. [Modes for carrying out the invention]

[0110] Detailed explanation Implementations of this disclosure include a reactor and a support system. The reactor may include fuel containing fissile material such as uranium-233, uranium-235, or plutonium-239, a coolant using alkali metals to transport heat away from the fuel, a heat exchanger for transferring heat from the coolant or cooling device to a power conversion system, as well as instrumentation, a support structure, and shielding. The fissile material may be contained within fuel elements, which may be held inside the reactor vessel. A liquid metal transfers heat from the fuel and carries that heat to a heat exchanger, to which the heat is transferred to an intermediate coolant or to a power conversion working fluid. Auxiliary heat exchangers may be used to remove excess heat and stored energy. These heat exchangers use liquid metal, salt, or gas to remove excess heat, which is then released into ambient air or water. External cooling can remove heat from the vessel system via a fluid such as air or liquid. In some embodiments, a decay heat removal auxiliary cooling system is used to passively remove decay heat from the reactor vessel.

[0111] In an exemplary implementation, the reactor operates using a liquid metal such as liquid sodium or liquid lead, which flows by natural circulation, driven by the difference in density between the coolant in the core at its operating temperature and the coolant in the heat exchanger at its operating temperature, in combination with the difference in altitude between the core and the heat exchanger.

[0112] The entire primary system can be enclosed within a container filled with shielding and heat-conducting materials to allow heat to be conducted radially outward, and the volume can accommodate coolant leakage while keeping the fuel covered. An electromagnetic pump can drive the coolant through this system. The reactor package can be containerized and transported together with the power conversion system.

[0113] The fuel may consist of hydride-containing fuel forms such as zirconium uranium hydride (UZrH). The reactor may be cooled by a liquid metal such as sodium. The fuel may be arranged in a hexagonal space grid in a tightly packed manner with a pitch greater than 1.1 or less in diameter ratio. A control drum may be used to control neutron reflection. A stop rod or other absorption mechanism is used for stopping. The coolant transports heat from the reactor to a heat exchanger, where the heat is transferred to an intermediate coolant loop and ultimately to a power conversion system, which may include a turbine such as a small Brayton or Stirling engine.

[0114] The reactor core, including fuel, structures, reflectors, shielding materials, risers, primary heat exchangers, and support components, can be cooled by a liquid metal primary coolant flow loop, which is entirely housed inside the reactor vessel. The primary coolant flow loop is immersed in a pool fluid, which is contained within an immersion pool inside the reactor vessel. The pool fluid can be used to provide cooling to components or systems and can also be used to provide heat storage capacity.

[0115] Figure 1 shows a schematic diagram of an exemplary reactor vessel system 100. The reactor vessel system 100 includes an inner vessel 110, for example, a reactor vessel. The reactor vessel system 100 also includes an outer vessel 120, for example, a protective vessel. The reactor vessel system 100 includes a core 102 within a core barrel 105 (for example, a cylindrical barrel, or a barrel with a cross-section other than circular, such as hexagonal, octagonal, or rectangular). The core 102 has a core inlet 114. The core 102 includes an active fuel region 202 and a shielding and reflector region 103.

[0116] The reactor vessel system 100 includes a riser 104 and a shroud 108. A down tube 112 is located between the riser 104 and the shroud 108. A heat exchanger 106 is located within the down tube 112. The heat exchanger 106 has a heat exchanger outlet 118. A pool area 130, for example, a cold pool, is located inside the inner vessel 110, as well as outside the core barrel 105 and the riser 104.

[0117] In the exemplary configuration shown in Figure 1, the liquid metal coolant 115 flows upward 116 through the core 102, removing heat from the fuel elements in the active fuel region 202. As the liquid metal coolant 115 flows through the core 102, it is heated.

[0118] Low-pressure drop fuel design can be achieved, for example, by using an appropriate pitch for the diameter ratio within the range of 1.1 to 1.25. Wire wraps or spacer grids may be used along the axial length of the core to guide and ensure fuel spacing. Vertical fuel element conduits may have vents or perforations to allow cross-flow in case of flow blockage. Conduits may also have a ribbed pattern or similar internal structure to reduce peripheral flow area.

[0119] The liquid metal coolant 115 exits the core 102 and flows upward through a riser 104, which can be shaped into a cylindrical, square, rectangular, hexagonal, or any number of preferred shapes. The riser 104 functions similarly to a chimney, providing a channel through which the liquid metal coolant 115 can rise.

[0120] The liquid metal coolant then flows downward in direction 122 through the riser 104 and through the heat exchanger 106. The heat exchanger may be, for example, a secondary heat exchanger 106 or a decay heat removal heat exchanger 206. As it passes through the heat exchanger 106, the liquid metal coolant transfers heat to the secondary coolant or power conversion fluid. As the liquid metal coolant transfers heat through the heat exchanger, it is cooled. The heat exchanger is located within the down tube 112, i.e., between the inner riser 104 and the outer shroud 108. The heat exchanger 106 may include, among other design configurations, flow channels, such as conduits, tubes, or rings. A low-pressure-drop heat exchanger may be used to reduce the pressure drop and provide a preferential flow path.

[0121] The cooled liquid metal coolant 115 exits the heat exchanger 106 and flows downward 126 into the pool area 130 within the area outside the riser 104 and core barrel 105. The cooled liquid then flows through the core inlet 114, restarting the circuit.

[0122] The shroud 108 provides a barrier between the flow area of ​​the downpipe 112, including the heat exchanger 106, and the pool area 130. The pool area 130 acts as a reservoir and heat sink for the liquid metal coolant 115.

[0123] In some configurations, the top of the shroud 108 is positioned above the free surface 132 of the liquid metal coolant 115 in the riser 104. When the liquid metal coolant 115 is heated to a sufficient temperature, it may overflow the shroud 108 (124) and expand sufficiently to flow into the pool area 130. For example, at normal operating temperatures, the coolant may not overflow the shroud 108, but at temperatures above normal operating temperatures, the coolant may overflow the shroud 108 (124). Cover gas 111 is positioned above the liquid metal coolant 115.

[0124] Separating the pool area 130 from the heat exchanger 106 can provide enhanced thermal performance while lowering the container temperature. Furthermore, separating the pool area 130 from the heat exchanger 106 can provide an enhanced heat removal path when needed, for example, when the liquid metal coolant 115 reaches a temperature high enough to cause the liquid metal coolant 115 to overflow the shroud 108 (124).

[0125] The liquid metal coolant 115 flows by natural circulation and can transfer heat by natural convection. The liquid metal flows by natural circulation under steady-state conditions within a range of power levels from reactor startup to full power.

[0126] Figure 2 shows a cross-sectional view of an exemplary reactor vessel system 200 with booster pumps 210. One or more booster pumps 210 may be used to facilitate reactor startup by establishing a flow pattern via forced and mixed circulation. The liquid metal coolant 115 can then transition to natural circulation at the desired power level. Depending on the achievement of natural circulation, the booster pumps 210 are shut down.

[0127] The booster pump 210 may be located within the reactor vessel system, for example, at the heat exchanger outlet 118, as shown in Figure 2. In some embodiments, the booster pump 210 may be located at the core inlet 114 instead of, or in addition to, the heat exchanger outlet 118. In some embodiments, the booster pump 210 may be installed in a section of the primary flow loop outside the outer vessel 120. A momentum-based circulator 212, such as a flywheel, may be installed at the booster pump outlet to provide rotational inertia for the liquid metal coolant 115.

[0128] Figure 3 shows a cross-sectional view of an exemplary reactor vessel system 300 with a cold trap 310. Maintaining sufficient control over the chemical properties and purity of the coolant is important to ensure the lifespan of the coolant and its components. The cold trap 310 is used to control the chemical properties and purity of the liquid metal coolant. The cold trap 310 is located within the reactor vessel and in an area where sufficient coolant flow occurs. For example, as shown in Figure 3, the cold trap 310 is located at the outlet of the decay heat removal heat exchanger 206.

[0129] Figure 4 shows a cross-sectional view of the cold trap 310, which is cooled by the intermediate heat exchanger 404. Coolant flows into the heat exchanger 404 through the inlet 412 and out of the heat exchanger 404 through the outlet 414. The cold trap can be cooled by a pre-cooled bypass flow 402 of intermediate coolant, which is cooled by the heat exchanger 404 to the cold trap operating temperature. The coolant returns to the heat exchanger 404 through the cold trap bypass return 402.

[0130] In some embodiments, the cold trap 310 may be cooled by a direct cooling device. The cold trap may also be cooled by a residual heat or decay heat removal system. In some embodiments, the cold trap is cooled by a bypass flow of coolant from a decay heat removal auxiliary cooling system, which has been cooled to the cold trap operating temperature. Thus, the cold trap may be integrated into a passive reactor cooling system and cooled by it.

[0131] In some embodiments, the coolant purification system may utilize a hot trap. The hot trap may include a heater. When electrically powered, the heater heats the liquid metal coolant to a temperature range in which the liquid metal coolant flows in contact with a material that reacts with impurities in the liquid metal coolant. For example, the liquid metal coolant may flow in contact with a material that reacts with oxygen, causing the oxygen to precipitate out of the liquid metal coolant solution.

[0132] Figure 5 shows a cross-sectional view of an exemplary reactor vessel system with an immersion pool 530. The reactor vessel system 500 includes a free upper surface 532 of the immersion pool. The reactor vessel system 500 includes an upper hydraulic connection 510 and a lower hydraulic connection 520 between the coolant 115 in the primary coolant flow loop and the coolant in the immersion pool 530. The coolant 115 in the primary coolant flow loop may be hydraulically connected to the coolant in the immersion pool. These hydraulic connections, for example, the upper connection 510 or the lower connection 520, can be made by flow diodes, pressure gates, permeable membranes, or height differences, designed to allow flow between coolant bodies under certain conditions such as a range of flow rates, coolant levels, pressure differences, and temperatures. Hydraulic connections between the primary coolant and immersion fluid enhance the natural circulation characteristics of the system, increase the thermal mass of the fluid available to the system, and provide thermal coupling to an auxiliary heat removal path for residual heat removal.

[0133] Figure 6 shows a cross-sectional view of an exemplary reactor vessel system 600 with an enclosed coolant loop. In the exemplary reactor vessel system 600, the immersion fluid 632 of the immersion pool 630 and the liquid metal primary coolant 115 are isolated from each other. The immersion fluid 632 is located outside the core barrel 105 and inside the reactor vessel 110. The liquid metal primary coolant 115 flows through the primary coolant loop from the reactor 102 to the riser 104, i.e., to the heat exchanger 106, and returns to the core inlet 114. The immersion fluid 632 does not enter the core inlet. The immersion pool 630 is separated from the primary coolant loop and from the core inlet by a barrier 634.

[0134] Figure 7 shows a cross-sectional view of an exemplary reactor vessel system 700 with a drain siphon. The reactor vessel system 700 includes an internal drain system via a siphon or standpipe to the top of the vessel, allowing for coolant filling, replenishment, inspection, and removal to the outside of the vessel with minimal intrusion into the vessel. As shown in Figure 7, the drain system includes a drain pipe 714, a drain bowl 712, and a drain outlet interface 716.

[0135] In some embodiments, fuel elements and other in-core elements are removed from the reactor via conduits or pipelines that reach the top of the upper pool of each fuel assembly or near the top of its free surface, and the conduits can serve as standpipe-like structures for easier fuel removal. Fuel elements may be handled or removed using temporary fuel handling equipment that is brought into the plant only when handling equipment is required.

[0136] In some embodiments, the fuel element has a unique marker column that extends upward through the riser to or near the surface of the free pool. The marker column is structurally connected to the fuel element and acts as an extended lifting handle, reducing or eliminating the need to handle the fuel element through the deep liquid metal pool.

[0137] Reactor components such as heat exchangers or pumps may be integrated into modular packages to allow for easier inspection, maintenance, and replacement. Pumps may be packaged together with or in close proximity to heat exchangers. In some embodiments, an intermediate coolant flowing into the heat exchanger may be used to cool the pump. In some embodiments, the intermediate coolant may be cooled below the operating temperature of the primary coolant to cool the pump. In some embodiments, the pump is installed in contact with the vessel wall so that it may be cooled by conduction through the vessel wall.

[0138] In some embodiments, the intermediate coolant may be the same coolant as the primary coolant. The coolant may also be a heat transfer fluid with a high specific heat, such as a liquid salt.

[0139] The reactor may use absorption rods to control the reactor's power level, and in some cases, the rods may be used alone to shut down the reactor. These rods may be positioned to be inserted into the core within the active fuel region or the reflector region. The reactor may also use flammable poisons in a manner favorable to the neutron characteristics of the system.

[0140] In some embodiments, passive or intrinsic reactor control devices may be housed in a removable assembly cartridge that allows for testing, replacement, and inspection. Such devices may include, among other things, fluid buoyancy absorbents, fusible latch absorbents, Curie point latch absorbents, expanding liquid absorbents, or expanding gas-driven absorbents.

[0141] The rotating drum can also be used to control neutron leakage and, therefore, the power of the reactor. As shown in Figure 7, the drum 710 may be located outside the active fuel region 202 of the core 102. The drum contains a neutron absorbing material, a neutron leakage enhancer, and / or a neutron reflector.

[0142] The drum 710 may be suspended via its drive line shaft or mounted on a bearing or disc. The bearing or disc may be compatible with the coolant while providing structural support and alignment and sufficient lubrication to enable rotation. The bearing may be made of a metallic material such as a nitride or carbide, or a ceramic material. The drum 710 may also be contained within a cartridge that isolates the drum 710 from the primary coolant.

[0143] Figure 8 shows a schematic diagram of an exemplary reactor power system 800, designed to directly transfer heat from the primary system of the reactor module 820 via a heat exchanger 830 of the power conversion system (PCS). Liquid metal transfers heat from the fuel of the reactor module 820 and transports that heat through a first pipe 802 to a heat exchanger 830, to which the heat is transferred to the power conversion working fluid. The power conversion working fluid flows through a second pipe 804 to the PCS system 840. The PCS system 840 includes a turbine 842, a pump 844, and an auxiliary pump 846.

[0144] The auxiliary heat exchanger 850 is used to remove residual heat and stored energy. The heat exchanger 850 uses liquid metal, salt, or gas to remove residual heat, which is then released into ambient air or water. External cooling can remove heat from the container system via a fluid such as air or liquid.

[0145] Figure 9 shows a schematic diagram of an exemplary reactor power system 900, including an intermediate thermal energy storage system 930 and a PCS heat exchanger 830. The liquid metal transfers heat from the fuel in the reactor module 820 and carries that heat through the first piping 802 to the thermal energy storage system 930 and to the heat exchanger 830, where the heat is transferred to the power conversion working fluid. The heat from the thermal energy storage system 930 heats the power conversion working fluid.

[0146] The power conversion working fluid flows into the PCS system 840 through a second pipe 804. The PCS system 840 includes a turbine 842, a pump 844, and an auxiliary pump 846. The power conversion system 840 may be connected to an intermediate coolant, through a heat exchanger 830, where the working fluid is heated. The working fluid can then be used to drive power conversion turbomachinery, such as the turbine 842, to produce electricity. The power conversion system 840 may use steam, gas, or a supercritical fluid as the working fluid.

[0147] Figure 10 shows a schematic diagram of an exemplary reactor power system 1000 with an in-vessel thermal energy storage system 1010. As described above with reference to Figure 1, the in-vessel thermal energy storage system 1010 may include a pool area 130, for example, a cold pool. The immersed fluid in the pool area 130 can provide heat storage capacity.

[0148] Figures 11A and 11B show upper cross-sectional views of the reactor core. Figure 11A shows upper cross-sectional view 950a of core 102 before the refueling process. Figure 11B shows upper cross-sectional view 950b of core 909 after the refueling process. The reactor core 102 depicted in Figures 11A and 11B may be, for example, the reactor core of Figures 1, 2, 3, 5, 6, or 7. The reactor core 102 includes hexagonal elements arranged in a spatial grid. In some implementations, instead of or in addition to hexagonal elements, the reactor core 102 may include elements having other shapes such as squares and circles. The reactor elements are located within the reactor core barrel 905.

[0149] Reactor elements can be arranged in a manner that facilitates refueling. For example, an unfilled region may be included within the core 102 where fuel elements, control elements, or reflector elements are not located. During refueling, fuel elements from the region near the core center can be moved to a location further away from the core center. Fuel elements from the region near the core center can be at least partially consumed or depleted. In some implementations, fuel elements from the region near the core center can be moved to an unfilled location. In some implementations, fuel elements from the region near the core center can be moved to a location where reflector elements were previously located, and reflector elements can be moved to an unfilled location.

[0150] By moving spent fuel elements outward from the core, the depleted fuel elements can be positioned in a manner that expands the width and volume of the active region of the core. This reduces the surface area, and the volume ratio will decrease, for example, by 10% or more, or 20% or more. This can increase geometric buckling and reduce neutron leakage. In addition, the disclosed technique may, as a result, allow spent or irradiated fuel to remain inside the core barrel after refueling. This can simplify fuel handling operations, reduce radiation exposure to personnel, and reduce the amount of spent fuel stored outside the core. Thus, the amount of spent fuel storage space required can be reduced. For example, the number of spent fuel casks and / or the size of the spent fuel pool required to store spent fuel can be reduced.

[0151] In the embodiments shown in Figures 11A and 11B, the core 102 includes a fuel element 904, a reflector element 906, and a control element 908. The core 102 also includes an unfilled region 902 in which no fuel element, control element, or reflector element is located. The unfilled region 902 may contain primary coolant, and the primary coolant may be conducted through the core 102 during operation. In Figures 11A and 11B, the fuel element 904 is represented by dark gray shading, the control element 908 by light gray shading, the reflector element 906 by a diagonal pattern, and the unfilled region 902 is represented as white without shading or patterning.

[0152] As shown in Figure 11A, prior to refueling, the core 102 includes an unfilled region at element location 910, i.e., at the outer boundary where the reflector element 906 abuts the unfilled region. Prior to refueling, the core 102 includes a reflector element at element location 920, i.e., at the outer boundary where the fuel element 904 abuts the reflector element 906. The innermost fuel element 940 is located near the core center 911 and is indicated by a white outline. The innermost fuel element, for example, the fuel element at element location 940, is exposed to high levels of neutron flux and can therefore be consumed more rapidly than fuel elements located further away from the center 911.

[0153] During the refueling process, fuel elements from locations near the core center 911 are moved to areas further away from the center 911, for example, to replace reflector elements 906. The replaced reflector elements 906 can also be moved further away from the center 911, for example, to an unfilled location 902. For example, a reflector element located at element location 920 can be moved to an unfilled element location 910. A fuel element located at element location 940 can then be moved to element location 920. This pattern can be repeated for multiple fuel elements and reflector elements. In some implementations, new fuel elements can be introduced into the core at the innermost element location, for example, in element location 940. New fuel elements may be, for example, unirradiated fuel elements.

[0154] As shown in Figure 11B, after refueling, core 102 includes a reflector element at element location 910, which has been moved from element location 920. Core 102 also includes a fuel element at element location 920, which has been moved from element location 940. A similar pattern is repeated around the core, with the six innermost fuel elements moving to the outer boundary of the active fuel region and the replaced reflector element moving to the outer boundary of the reflector region. The new fuel element 960, represented by black shading, is introduced into the innermost fuel region.

[0155] While described as moving elements outward from the core center 911, other implementations are also possible. For example, the core can be arranged such that unfilled regions are located throughout the core. In addition, during refueling, fuel elements from any location within the core can be moved to any unfilled region of the core, or to any location not previously occupied by reflector elements. In some embodiments, instead of moving replaced reflector elements to unfilled locations, reflector elements can be removed from the core.

[0156] Figure 12 is a schematic diagram of computer system 1100. System 1100 can be used to perform operations described in relation to any of the computer implementation methods described above, in several implementations. In some implementations, computing systems and devices, as well as the functional operations described herein, can be implemented in a digital electronic network, in tangibly embodied computer software or firmware, in computer hardware (e.g., system 1100), including structures disclosed herein and their structural equivalents, or in one or more combinations thereof. System 1100 is intended to include various forms of digital computers, such as notebook computers, desktop computers, workstations, personal digital assistants, servers, blade servers, mainframes, and other suitable computers, including vehicles that are installed on a base unit or pod unit of a modular vehicle. System 1100 may also include mobile devices such as personal digital assistants, mobile phones, smartphones, and other similar computing devices. In addition, the system may include portable storage media such as Universal Serial Bus (USB) flash drives. For example, a USB flash drive may store an operating system and other applications. A USB flash drive may include input / output components such as a USB connector that can be inserted into a USB port of a wireless transducer or another computing device.

[0157] System 1100 includes a processor 1110, memory 1120, storage device 1130, and input / output device 1140. Each of components 1110, 1120, 1130, and 1140 is interconnected using a system bus 1150. Processor 1110 is capable of processing instructions for execution within system 1100. The processor may be designed using one of several architectures. For example, processor 1110 may be a CISC (Complex Instruction Set Computer) processor, a RISC (Reduced Instruction Set Computer) processor, or a MISC (Minimum Instruction Set Computer) processor.

[0158] In one implementation, the processor 1110 is a single-threaded processor. In another implementation, the processor 1110 is a multi-threaded processor. The processor 1110 is capable of processing instructions stored in memory 1120 or on storage device 1130 in order to display graphical information about the user interface on input / output device 1140.

[0159] Power plants, including nuclear reactors, are controlled using automated control mechanisms that leverage compiler advances, enabling the training of system controllers, such as processor 1110, and allowing for better simulation of all control operations from the same program. Automated differential calculus capabilities for use in machine learning techniques may be used to create differentiable programs in which the derivative can be obtained through complex code involving loops, branches, and other structures. Various tools are connected to the compiler to create compiled differential versions of functions so that the differential f'(x) for any complex number f(x) can be efficiently compiled.

[0160] This can be used to calculate sensitivity studies. It can also be used to find the derivative of an arbitrary complex function with respect to any of its parameters, allowing the trainable model to be used as part of a differentiable program. A function is created whose inputs are the current system state and some desired target state, and the resulting information is provided to the trainable model, which acts as a controller and gives interpretable suggestions for control operations to bring the system to the target state. These suggestions and the current system state are used to solve differential equations and determine the actual results of those control operations. The difference between the results of the differential equation solver and the target state provides a metric for the usefulness of the trainable model of the reactor and power plant.

[0161] Automatic differentiation allows for the direct calculation of the gradient of the loss value with respect to the intrinsic parameters of the controller model. A neural network is an example of this. This function is executed in a loop, updating the controller parameters and thereby minimizing losses and improving the quality of control proposals derived from models for nuclear reactors and power plants.

[0162] The controller can be trained by having it repeatedly attempt to bring the system to a target state, without the need to define a reward function or generate any kind of training data. This reduces reliance on black-box reinforcement learning algorithms by selecting a differentiable control method to achieve faster convergence to a more effective control scheme for nuclear reactors and power plants.

[0163] Memory 1120 stores information within system 1100. In one implementation, memory 1120 is a computer-readable medium. In another implementation, memory 1120 is a volatile memory unit. In yet another implementation, memory 1120 is a non-volatile memory unit.

[0164] The storage device 1130 is capable of providing large-capacity storage for the system 1100. In one implementation, the storage device 1130 is a computer-readable medium. In various different implementations, the storage device 1130 may be a floppy disk device, a hard disk device, an optical disk device, a tape device, or a solid-state device.

[0165] The input / output device 1140 provides input / output operation for the system 1100. In one implementation, the input / output device 1140 includes a keyboard and / or a pointing device. In another implementation, the input / output device 1140 includes a display unit for displaying a graphical user interface.

[0166] The described features can be implemented within a digital electronic network or within computer hardware, firmware, software, or a combination thereof. The device can be implemented within a computer program product, tangibly embodied within an information carrier, for example, within a machine-readable storage device for execution by a programmable processor, and the method steps can be carried out by a programmable processor that executes a program of instructions to perform the function of the described implementation by acting on input data and generating outputs. The described features can be advantageously implemented in one or more computer programs executable on a programmable system, which includes a data storage system, at least one input device, and at least one output device, and at least one programmable processor coupled to receive data and instructions from and transmit data and instructions to them. A computer program is a set of instructions that can be used directly or indirectly within a computer to perform an activity or to produce a result. Computer programs can be written in any form of programming language, including compiled or interpreted languages, and can be deployed in any form, including as standalone programs or as modules, components, subroutines, or other units suitable for use in a computing environment.

[0167] Processors suitable for executing instruction programs include, in examples, both general-purpose and dedicated microprocessors, as well as one of the sole or multiple processors of any type of computer. Generally, a processor will receive instructions and data from read-only memory or random-access memory, or both. An essential element of a computer is a processor for executing instructions, as well as one or more memories for storing instructions and data. Generally, a computer also includes, or is operationally coupled to, one or more mass storage devices for storing data files, and such devices may include magnetic disks such as internal hard disks and removable disks, magneto-optical disks, and optical disks. Storage devices suitable for tangibly embodying computer program instructions and data include, in examples, semiconductor memory devices such as EPROMs, EEPROMs, and flash memory devices, magnetic disks such as internal hard disks and removable disks, magneto-optical disks, and all forms of non-volatile memory, including CD-ROMs and DVD-ROMs. Processors and memory can be complemented by or incorporated into ASICs (Application-Specific Integrated Circuits).

[0168] To provide user interaction, the features can be implemented on a computer having a display device such as a CRT (cathode ray tube) or LCD (liquid crystal display) monitor for displaying information to the user, and a keyboard and pointing device such as a mouse or trackball, thereby allowing the user to provide input to the computer. In addition, such activities can be implemented via a touchscreen flat panel display and other suitable mechanisms.

[0169] The system can be implemented in a computer system that includes backend components such as data servers, middleware components such as application servers or internet servers, or frontend components such as client computers with a graphical user interface or internet browser, or any combination thereof. The components of this system can be connected by digital data communication in any form or medium, such as a communication network. Examples of communication networks include local area networks ("LANs"), wide area networks ("WANs"), peer-to-peer networks (with ad-hoc or static members), grid computing infrastructure, and the internet.

[0170] A computer system can include a client and a server. Clients and servers are generally remote from each other and typically interact through a network, such as the one described. The client-server relationship arises from computer programs running on separate computers that have a client-server relationship with each other.

[0171] This specification contains many specific implementation details, which should be interpreted not as limitations on the scope of any invention or claim, but rather as descriptions of features specific to a particular implementation of a particular invention. Certain features described herein in the context of separate implementations may also be implemented in combination in a single implementation. Conversely, various features described in the context of a single implementation may also be implemented in multiple implementations, separately or in any preferred secondary combination. Furthermore, features are described above as acting in a combination, and may initially be claimed as such, but one or more features from a claimed combination may, in some cases, be removed from the combination, and the claimed combination may also cover secondary combinations or variations of secondary combinations.

[0172] Similarly, while operations are depicted in a specific order in the diagrams, this should not be understood as requiring that such operations be performed in a specific or sequential order to achieve the desired result, or that all illustrated operations be performed. In some situations, multitasking and parallel processing may be advantageous. Furthermore, the separation of various system components in the implementations described above should not be understood as requiring such separation in all implementations, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged in multiple software products.

[0173] Several implementations have been described. Nevertheless, it should be understood that various modifications can be made without departing from the spirit and scope of this disclosure. For example, the exemplary operations, methods, or processes described herein may include more or fewer steps than those described. Furthermore, the steps in such exemplary operations, methods, or processes may be performed in a different arrangement than those described or illustrated in the figures. Thus, other implementations are also within the scope of the following claims.

Claims

1. A reactor vessel system, An inner vessel defining an internal volume sized to at least partially enclose a nuclear reactor, wherein the reactor comprises a plurality of nuclear fuel elements at least partially enclosed within a cladding material, A primary coolant loop is configured to circulate a liquid metal coolant to cool the reactor, An outer container sized to completely or substantially enclose the inner container, The core barrel inside the inner vessel, The riser inside the inner container, A shroud within the inner container, wherein the upper part of the shroud is positioned at a height above the free surface of the liquid metal coolant in the riser, The riser and the shroud are connected by a descending pipe, A heat exchanger configured to transfer heat from the liquid metal coolant to an intermediate coolant or to a power conversion working fluid, wherein the heat exchanger is located within the descending pipe, A pool of immersion fluid occupying a certain volume inside the inner container, wherein the pool of immersion fluid is located inside the inner container and outside the core barrel and riser. A reactor vessel system equipped with the following features.

2. The reactor vessel system according to claim 1, wherein the heat exchanger is a low-pressure drop heat exchanger.

3. The reactor vessel system according to claim 1, comprising a cold trap configured to purify the liquid metal coolant, wherein the cold trap is located within the primary coolant loop at the outlet of the heat exchanger and is cooled by an intermediate coolant flowing from one of an intermediate coolant circuit or a passive reactor cooling system.

4. The reactor vessel system according to claim 1, further comprising a hot trap located within the primary coolant loop and configured to purify the liquid metal coolant.

5. The reactor vessel system according to claim 1, wherein during operation under steady-state conditions at power levels ranging from reactor startup to full power, the liquid metal coolant flows through the primary coolant loop by natural circulation.

6. A booster pump configured to pump the liquid metal coolant through the primary coolant loop, wherein the booster pump is located at one of the following: the outlet of a heat exchanger, the inlet of a reactor, or a section of the primary coolant loop outside the outer vessel. A momentum-based circulation device located at the outlet of the aforementioned booster pump and The reactor vessel system according to claim 1, comprising:

7. The reactor vessel system according to claim 1, wherein the immersion fluid comprises the same fluid as the liquid metal coolant.

8. The reactor vessel system according to claim 7, wherein the pool of immersion fluid is hydraulically isolated from the primary coolant loop.

9. The reactor vessel system according to claim 7, wherein the pool of immersed fluid is hydraulically connected to the primary coolant loop by one of a flow diode, a pressure gate, a permeable membrane, or a height difference.

10. The reactor vessel system according to claim 1, comprising a modular package of reactor vessel components, the modular package being removable from the system, the modular package comprising a heat exchanger and a pump, wherein during operation, an intermediate coolant flowing through the heat exchanger cools the pump to a temperature below the operating temperature of the liquid metal coolant.

11. A method comprising operating a reactor vessel system to produce electricity, wherein the reactor vessel system is An inner vessel defining an internal volume sized to at least partially enclose a nuclear reactor, wherein the reactor comprises a plurality of nuclear fuel elements at least partially enclosed within a cladding material, An outer container sized to completely or substantially enclose the inner container, The core barrel inside the inner vessel, The riser inside the inner container, A shroud within the inner container, wherein the upper part of the shroud is positioned at a height above the free surface of the liquid metal coolant in the riser, The riser and the shroud are connected by a descending pipe, A heat exchanger, wherein the heat exchanger is located within the descending pipe, A pool of immersion fluid occupying a certain volume inside the inner container, wherein the pool of immersion fluid is located inside the inner container and outside the core barrel and riser. Equipped with, The aforementioned method, Cooling the reactor using the liquid metal coolant in the primary coolant loop, The heat exchanger transfers heat from the liquid metal coolant to the intermediate coolant, or to the power conversion working fluid. Methods that include...

12. The method according to claim 11, wherein the heat exchanger is a low-pressure drop heat exchanger.

13. The method according to claim 11, wherein the cold trap includes purifying the liquid metal coolant, the cold trap is located within the primary coolant loop at the outlet of the heat exchanger and is cooled by an intermediate coolant flowing from one of an intermediate coolant circuit or a passive reactor cooling system.

14. The method according to claim 11, wherein a hot trap located within the primary coolant loop purifies the liquid metal coolant.

15. The method according to claim 11, wherein during operation under steady-state conditions at power levels ranging from reactor startup to full power, the liquid metal coolant flows through the primary coolant loop by natural circulation.

16. The method according to claim 11, comprising a booster pump pumping the liquid metal coolant through the primary coolant loop, wherein the booster pump is located at one of the following: a heat exchanger outlet, a reactor inlet, or a section of the primary coolant loop outside the outer vessel, and the reactor vessel system comprises a momentum-based circulator located at the booster pump outlet.

17. The method according to claim 11, wherein the immersion fluid comprises the same fluid as the liquid metal coolant.

18. The method according to claim 17, wherein the pool of immersion fluid is hydraulically isolated from the primary coolant loop.

19. The method according to claim 17, wherein the pool of immersion fluid is hydraulically connected to the primary coolant loop by one of a flow diode, a pressure gate, a permeable membrane, or a height difference.

20. The method according to claim 11, wherein the reactor vessel system comprises a modular package of reactor vessel components, the modular package is removable from the system, the modular package comprises a heat exchanger and a pump, and the method comprises cooling the pump to a temperature below the operating temperature of the liquid metal coolant by an intermediate coolant flowing through the heat exchanger.

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