EA043120B1 - LIQUID SALT NUCLEAR REACTOR WITH MODULAR CORE - Google Patents

Description

The invention relates to a circuit of a modular nuclear reactor, in particular, to a circuit of a modular molten-salt nuclear reactor. The present invention also relates to a modular nuclear reactor, in particular, to a modular liquid-salt nuclear reactor, consisting of nuclear reactor circuits. The invention further relates to a method for operating a modular nuclear reactor circuit. The invention further relates to a method for operating a modular nuclear reactor and a method for testing/determining compliance with the specified requirements of a nuclear reactor. The invention also relates to a method for replacing part of a nuclear reactor circuit.

As global energy demand grows, there is a continued need for nuclear power, despite the disadvantages associated with early generation nuclear power plants. New generations of nuclear power plants (4th and 5th generation) are being developed, which are specifically aimed at supplying large quantities of safe and clean energy, while at the same time deliberately approaching standards for the proliferation of nuclear materials and the generation of nuclear waste.

One of them is the so-called molten-salt reactors.

A molten salt reactor (MSR) is a type of nuclear reactor where the primary coolant, or even the fuel itself, is a molten salt mixture. Many designs have been proposed for this type of reactor and many prototypes have been built. Early and many modern concepts are based on nuclear fuel dissolved in a fluoride salt melt. The fluid may reach criticality by flowing into the core, where a moderator such as graphite may be present. Many well-known concepts are based on the flow of fuel through channels in a graphite matrix with molten salt, providing cooling at low pressure and high temperature. Some recently developed concepts exclude the use of a moderator to create a system with a characteristic fast neutron spectrum, or use special moderation to locally generate neutron spectra specifically designed for specific purposes, such as burning long-lived actinides from nuclear waste streams.

Although molten salt reactors have been successfully designed, built and operated in the past, the knowledge and experience required to modernize this type of reactor is limited. The key benefits of molten salt reactor plants regarding safety, minimum waste streams and maximum resource efficiency have been developed in many cases, and with increasing frequency in the last 5-10 years. Without a doubt, one can consider broad prospects for molten-salt reactor plants, especially with thorium fuel, to provide safe energy for millennia, with a minimal burden of radioactive waste. However, technical and economic viability as well as long time to market are the main obstacles to modern implementation, and hence to investment, despite the fact that proof of the principle of operation of molten salt reactors was successfully demonstrated by studies of molten salt reactors in the 50s and 60s. e gg. in USA.

Molten-salt reactors typically provide optimum neutron economy by allowing frequent cleaning of the salt from neutron-absorbing fission and activation products, thereby minimizing neutron losses, by providing the ability to close nuclear fuel cycles in which fission fuel is generated from excess neutrons produced in fission reaction, allowing the transmutation of fertile elements such as ²³² Th or ²³⁸ U into fissile elements such as ²³³ U and ²³⁹ Pu.

The prospect of closing nuclear fuel cycles, creating very high resource efficiency combined with very high levels of (passive) safety and minimizing the generation of long lived waste, especially in the case of a closed thorium fuel cycle, makes molten salt reactors very promising for future energy sources.

When combining fuel and coolant in the LSR system, the technology has one key difficulty: in the primary system, all physical and engineering disciplines converge, and they significantly influence each other. Chemistry, neutron physics, materials science, thermohydraulics, thermomechanics, etc. converge in the components of a liquid-salt primary system. Therefore, the installation of a molten salt reactor requires an interdisciplinary approach with interdisciplinary analysis and design, as well as interdisciplinary experimental verification.

A significant amount of effort is needed to develop and validate interdisciplinary design tools, codes, and licensing systems for molten salt containment. Given the interdisciplinary complexity, even direct in-reactor experiments or small-scale demonstrations will be difficult to fully predict and justify from a safety point of view in the absence of adequate and proven interdisciplinary knowledge and experience.

The present invention develops an approach to minimizing the time-to-market for NSR nuclear power plants, proposing an efficient nuclear equipment qualification approach covering all interdisciplinary complexity, and proposing principles for the design of NSR nuclear power plants that best utilize the nuclear equipment qualification strategy. This can virtually eliminate the complicated intermediate steps that are

- 1 043120 both costly and time consuming. This combination of an efficient nuclear qualification path and a design that closely matches such qualification could result in liquid-salt nuclear power plants being mass-produced within a 15-year time period, much shorter than the 20-30 years that are currently available. considered realistic. This assessment implies the viability of the ZhSR technology, which can be considered proven through successful operation in the 50s and 60s. in USA.

Liquid-salt nuclear reactors have previously been described, for example, in US 2015/0243376, US 2017/0117065, WO 2017/098228, GB 2508537, WO 2017/070791.

In molten-salt reactors, the composition of the coolant fuel can be adjusted and, consequently, conditioned during operation. This does not apply to structural materials and structural components in the primary system of the known LSRs. The interaction between the heat transfer fuel and the components and materials of the primary systems, as well as the intense irradiation fields to which the primary materials and components will be exposed, are major concerns. Materials are needed or must be tested that can withstand these harsh conditions for the 4,060 years normally envisaged for nuclear power plants. Many of the GSR's preliminary concept designs either neglect this aspect or include some form of radiation shielding barrier or sacrificial material layer to protect the primary material from radiation-induced degradation and chemical interaction with salts.

One of these HSR designs is described in US 2999057. In US 2999057 a loop design is used for a complete nuclear reactor in which several separate fluid streams are fed into and out of the reaction core, circulated and fed back into the core or moderator. The design is such that the moderator contains a number of channels, and fluid flows are fed into the lower part of the moderator and output in its upper part in the form of a single stream. The entire installation is a completely fixed (unchangeable) structure.

US 2009/0279658 also discloses a molten salt reactor with a two-fluid reactor design. This design, as a rule, is a container filled with molten salt, in which there are separate tubes in an unchanged configuration, through which liquid salt fuel is also pumped. The tube sizes and fissile content are such that each tube is subcritical, and criticality is only achieved when the tubes are close together. The structure is a fixed (unchangeable) structure consisting of one large vessel/containment in which the circulating salt tubes are located in a fixed configuration, without the possibility of removal and replacement of components located in the core. The tank has a single inlet and outlet of the molten salt.

US 3,403,076 describes a fixed molten salt fuel breeder which provides graphite fuel cells with vertically arranged channels through which molten salt fuel can be pumped, enclosed in a molten salt blanket as a heat exchanger. This system has one single large pressurized reactor vessel, and the graphite fuel cells are supplied with molten salt through a single inlet and outlet.

GB 2073938 shows a single reactor vessel filled with molten salt and a containment through which a molten salt fuel pipe system passes. This single containment is supplied with salt through a single inlet and outlet.

All of these configurations are similar in that the entire installation is immutable (fixed). Tubes or fuel elements transporting liquid salt fuel are placed in a critical configuration and placed in an enclosing large reactor vessel / containment with a single salt inlet and outlet, with primary or blanket salt circulating in the volume of the reactor vessel or in tubes or fuel elements in the center.

In general, reactor concepts adopting state of the art coolant fuels use and recommend a relatively large and undivided (solid) volume of salt filling the system core and auxiliary piping and equipment. This creates a number of problems related to the feasibility of these types of systems. A large containment vessel is required to maintain the containment of nuclear material. These large containers are difficult to manufacture and handle, are expensive, are not (easily) replaceable, and are not (easily) unloaded after use. The concept of defense in depth is the cornerstone of the philosophy of nuclear safety and emphasizes the need to use multiple barriers to prevent the release of the stored nuclear source. One container containing all of the fuel maximizes the supply of the source in one containment and forms one single first line of defense against release. After use, a large container becomes contaminated and can be activated by neutrons, which in itself is a serious problem in terms of waste. Especially if the tank and the components connected to it are still filled with highly active and toxic waste heat transfer fuel. Transportation, storage and disposal of this volume is difficult due to the size and potential danger of radioactive impact.

- 2 043120 Viya. The large container forming the containment complicates the replacement of the core components, since the container must be able to open and enter, as well as extract and insert components. Core components and materials in coolant fuel systems typically suffer severe radiation damage under extreme temperature and chemical (corrosive) conditions. The convenient exchange of materials and core components will greatly accelerate the implementation of these systems, since materials that can withstand the harsh conditions in the critical zone of coolant fuel systems for an extended period of time have not yet been found or developed.

The present inventors have now essentially found an improved design for the molten salt nuclear reactor loop. The advanced design provides more flexibility, for example, in that a single circuit can be built and tested before being assembled into a complete nuclear reactor. The circuit is designed so that it can be placed in and removed from the reactor or moderator without dismantling the entire reactor or without affecting (disassembling, removing) other circuits in the reactor.

The fundamental choice made by the inventors is to partition the molten salt coolant fuel into separate, individual and independent modules placed in such an assembly that it is possible to maintain a stable nuclear fission reaction in the core region, consisting of core parts from modules. Each module has independent functionality and has its own pump, heat exchanger and processing units. Each module is a self-contained system with its own (double) containment. The modules may only be connected via secondary non-nuclear coolant system(s) or other secondary systems. This means that the modules do not have a common molten salt or nuclear material, and each module is provided with its own individual amount of molten salt and nuclear material. Each module is a separate nuclear reactor in itself, but can only reach criticality when two or more modules are placed in close proximity to each other.

The modules are placed close to each other so that they can be easily removed. Each module or circuit is independently extractable from the nuclear reactor. An example is shown in FIG. 6 and 7. The design (approximately cylindrical) of the module allows them to be placed side by side, while the removal of one module from the array can be done, for example, by raising or lowering the corresponding module.

In general, the invention relates to a nuclear reactor comprising nuclear reactor circuits, a nuclear reactor circuit, and methods for operating a nuclear reactor and a nuclear reactor circuit.

The nuclear reactor loop of the invention is not a traditional salt-filled reactor vessel, but a configuration of pipes, tube bundles, or channeled blocks/cylinders through which the salt is circulated in individual and independent circuits. The individual circuits of a nuclear reactor and the salt melt circuits in it are not connected to each other or are not connected to each other by a blanket salt circuit.

The individual circuits of a nuclear reactor are independent of each other and can be operated independently.

This is in contrast to prior art installations in which the molten salt circuits are one system, where they are connected to each other by a central primary or blanket salt circulation system. The slurry plant of the prior art is usually undivided. Thus, the concept of a nuclear reactor according to the invention is a modular concept. Individualized (isolated) circuits or modules of a nuclear reactor, which are designed separately, and modular salt loops placed in their vicinity, still do not have a common system of pipes, molten salt or fuel. Each module contains its own molten salt, fuel and piping system. Each module is a separate compartment of a nuclear reactor.

In US 2999057, for example, in FIG. 6 shows an installation in which the pipelines converge close together to form a core and then diverge. However, the entire installation remains fixed (unchangeable) and cannot be removed from the reactor without complete dismantling of the reactor.

The modular core approach of the present invention offers the following advantages:

Each module retains at least two containment shells (i.e. two lines of defense), and the integrity of both of them can be continuously monitored by measuring the content of fission product in the gas flowing in the gap between the first and second containment shells, and in the coolant outside of the second protective shell.

Containment monitoring allows the use of detachable primary containment components. Typically, the integrity of the primary boundary is ensured by welding or soldering, turning the primary boundary into a single piece, leaving no doubt that the containment is closed. When monitoring containment integrity, components can be allowed to become detached.

Each module contains a part of the total coolant fuel volume, i.e. the stock of fission source per containment decreases.

Each module contains a subcritical amount of coolant fuel that cannot introduce criticality at the module level. The fission reaction can only be initiated and sustained by placing the modules in a particular configuration, with the fuel-coolant of multiple combined modules.

When a module fails, the coolant fuel in that module can be passively diverted from the critical core area, and criticality in the entire core is reduced or terminated, while the functionality of the remaining modules is not affected.

Large components are eliminated, which reduces cost, facilitates handling, transportation (with reasonable container sizes) and replacement. For example, large parts or entire modules can be removed and replaced, not only allowing the life of the system to be extended by replacement, but also allowing for the introduction of new, improved modules or other coolant fuel.

Since the total supply of coolant fuel is subdivided into modules, the amount of waste coolant fuel is dealt with at the module level, i. controllable volumes are transported, which can be further processed at a separate location.

The modules in the reactor can be placed in and removed from the reactor without complex disassembly of the entire reactor. Module replacement can be achieved by raising or lowering modules from the array of modules that make up the reactor and only requires disconnecting secondary connections such as instrumentation, power, secondary heat exchangers, etc.

The modular core approach results in a core configuration that is close to optimal from a neutron physics point of view, since the configuration is determined by practical design considerations at the module level, such as interchangeability and the possibility of inserting containments on the module in the critical core. The inventors have prioritized nuclear safety as it is a necessary condition for fuel coolant systems to become practicable. Although this approach limits the scope for optimizing the core configuration for maximum neutron savings, the use of a coolant fuel offers advantages in offsetting the shortcomings in neutron savings of the chosen modular approach. The use of a coolant fuel offers the potential for higher neutron efficiency than in solid fuel reactors, especially in the case of undesired neutron absorption, fission products in the coolant fuel can be efficiently and quickly removed. Heat transfer fuel systems are low pressure, which means containments can be left relatively thin as they primarily serve as a barrier to low pressure liquid and gas. Therefore, the negative impact on core performance caused by neutron absorption by containment materials in the reactor core area can be minimized by optimizing safety and relatively fast development, licensing, approval, and implementation times.

The installation of a nuclear reactor loop of the invention (whether single piping, multiple piping, tube bundles or channeled blocks/cylinders) allows nuclear testing and loop system qualification in a single loop system on suitable nuclear reactor test equipment.

In one aspect, the nuclear reactor loop of the invention comprises a loop that is capable of containing and/or circulating nuclear fuel. The loop contains a channel, optionally substantially straight, in a substantially vertical arrangement. The channel provides an up and down passage for fluid in the loop.

An individual molten salt nuclear loop, or an appropriate variation thereof, may be placed in the irradiation field of an existing reactor (e.g., a suitable material testing reactor) and thus may be used to design, develop, test, and certify materials and components for a molten salt nuclear reactor loop.

An individual molten salt nuclear loop can be used as a component of a molten salt nuclear reactor, which in turn is composed of a plurality of such individual loops.

In another aspect, the invention relates to a nuclear reactor, which contains one or more circuits according to the invention. A nuclear reactor containing a single loop can be used to test and test the loop. A plurality of loops can be combined to form a molten salt nuclear reactor based on individual molten salt loops.

A nuclear reactor contains a core area and a cladding area. The core area is surrounded by the shell area. In a nuclear reactor, a plurality of nuclear reactor circuits are provided. Each nuclear reactor circuit in a nuclear reactor contains a loop that contains one or more channels.

The loop is capable of containing a fluid containing fertile and/or fissile materials. One or more fluid reservoirs are located, optionally releasably, in connection with the loop

- 4 043120 and are capable of containing a liquid containing fertile and/or fissile materials. The channels of the said plurality of circuits are located in the region of the active zone. The location of the channels in the core forms the critical zone of a nuclear reactor that supports the nuclear fission reaction.

Channels of multiple individual loops can be placed in a critical configuration, in an inherently safe and efficient configuration for the development and operation of a molten salt nuclear reactor. Each of the individual circuits contains a subcritical amount of nuclear fuel. The channels of each individual loop configuration may contain a subcritical amount of nuclear fuel.

A nuclear reactor built from individual circuits provides fuel cycle flexibility (the circuits may contain different combinations of fuels/salts, or combinations of fuels/salts can be changed), and the primary components of the circuits, and hence the nuclear reactor, are replaceable (replaceable). By having a circuit and reactors in which the primary components are replaceable (replaceable), the lifetime of the reactor can be extended and it can be reliably controlled. Nuclear reactor loops and reactors built from them also allow for further optimization as system components can be replaced with new and improved components. The design of the circuits is such that the elements of the circuits can be individually tested and certified. The design of the nuclear reactor circuit (or loop), and the nuclear reactor that is built from these loops, exhibits an improved safety profile, since such a configuration provides a design in which the nuclear reactor ceases operation when one or more molten nuclear nuclear circuits deviate from its desired function. .

Essentially, the reactor is made up of multiple individual loops that can be placed in a circular arrangement, with one part of each loop located at small radii (channel or hot leg), creating a critical configuration supporting a nuclear reaction (critical zone), and the rest part of the circuit is located at large radii, to a large extent outside the irradiation field of the critical zone, in a non-critical configuration. The channels or piping of the circuit are in direct contact with the salt. The channels contain salt and form the critical zone of the reactor by providing appropriate amounts of fissile material in the critical configuration formed by the combined channels and by using moderating materials in case the target is a reactor with a (supra-)thermal neutron spectrum. The channels are exposed to intense radiation fluxes. The use of pipes allows for replacement once the materials reach their limits in terms of exposure to radiation and/or exposure to salt, and are relatively easy to replace. The channels may be single tubes or bundles of tubes or ducted units, deteriorating relatively quickly due to the intense radiation fluxes in the critical zone of the reactor combined with contact with (corrosive) salt and fission products, and are relatively small components that also can be replaced, increasing the lifetime of the reactor. Although the replacement of primary piping and ducting requires significant development of remote manipulation, it is considered more feasible than trying to find and qualify materials that can withstand the conditions of the JSR for decades.

Alternatively, the loop can be made in a vertical arrangement with channels in the top half of the loop and other components in the bottom half, for example as explained in FIG. 6 and 7. When stacked vertically, the channels are in close proximity to each other, facilitating the exchange of neutrons between modules, establishing a critical core configuration in which a nuclear fission reaction can be maintained. The removal of one loop or the deactivation of the loop due to the draining of the salt melt from the channels into the tank in the lower half violates the criticality of the reactor.

A nuclear reactor comprises a plurality of separate and individual nuclear reactor circuits or modules, each module containing a molten salt liquid and fertile or fissile materials as nuclear fuel in a non-critical amount as a primary system, each module being connected to a secondary reactor system, each module located in the reactor in a certain configuration with other modules, each module is placed in the neutron flux of one or more other modules, and the said plurality of modules contain a critical amount of fertile and/or fissile materials when combined and placed in said configuration and in the neutron flux of said one or more other modules, each module being individually removable from the reactor plant by disconnecting (parts of) the module from the secondary system while maintaining the configuration of the other modules in the reactor, the module's primary system comprising a pump, a primary heat exchanger, and a primary treatment means such as a drain tank , either separate or built into the loop, the secondary system comprising a secondary control and non-nuclear secondary heat exchangers capable of exchanging heat with the primary heat exchangers of the modules.

In embodiments, modules may have a vertically elongated polygonal or cylindrical shape. In embodiments, the primary system is a (closed) loop in a vertical configuration in a module. In embodiments, modules containing molten salt loops are located predominantly in the upper half of the vertically elongated polygonal or cylindrical shape, and an additional element of the primary system, such as a pump, a primary heat exchanger, and a primary treatment means, such as a drain tank, are located in the lower half. When modules are placed in a configuration, the configuration allows the molten salt loop of one module to be placed in the neutron flux from other modules to achieve a critical configuration to sustain the nuclear reaction and generate power.

In a further aspect, the invention relates to a method of operating a nuclear reactor loop by placing a nuclear reactor loop duct, or a representative variation of a nuclear reactor loop, near the core of another nuclear reactor such that the loop duct is exposed to the reactor's neutron flux. This allows the simulation of the operation of a loop in a nuclear reactor composed of multiple reactor loops to test, characterize, and qualify loop materials, loop fluids, and loop components, in a representative test environment, including the interdisciplinary complexity of the LSR.

In a further aspect, the invention relates to a method for operating a nuclear reactor which includes the steps of providing a nuclear reactor comprising the nuclear reactor circuits of the invention and possibly a moderator (neutrons). The method further includes providing a plurality of nuclear fuels containing fertile and/or fissile materials and supplying said plurality of nuclear fuels to said plurality of circuits. The nuclear fuel in some or all of the channels and the material configuration of the moderator and/or channels create a critical zone in which a nuclear fission reaction can be sustained. The method of the invention makes it possible that the circuits of the present invention can be used in a nuclear reactor for a variety of applications, some of which are power generation, use as a means of reproduction by using neutrons/neutron absorption to convert fertile elements to fissile elements, with thereby generating nuclear fuel, and/or generating isotopes and materials for other uses and combinations thereof. The modular design of a nuclear reactor with nuclear loops according to the invention provides that the operation of a nuclear reactor can be used to meet different needs at the same or consecutive times without major changes in the configuration of the reactor, but by changing the individual loops and/or changing the liquids contained in the loops. , and/or changes in retarding materials.

Brief description of the figures

Fig. 1 shows a schematic top view of a nuclear reactor in which channels are placed in the reactor core.

Fig. 1A shows a top view schematic representation of four individual contours (separated by schematic dotted lines) with channels located at the points of the pie-like representation. Being located in the reactor, the channel (4) is a section of the nuclear reactor circuit, located in close proximity to other individual nuclear reactor circuits, which together form the nuclear reactor core, generating a combined critical balance of neutrons due to their individual (subcritical) neutron contributions.

Fig. 2 shows a schematic representation of the circuit of a nuclear reactor.

Fig. 3A-C show a schematic representation of the circuit of a nuclear reactor (side view), in which the channel is located at a distance from the return line and in a substantially vertical position. The channel contains bi-directional flow established in a U-shaped curved tube or U-shaped curved tubes in a pipe-in-pipe or channeled block configuration.

Fig. 4 shows a schematic representation of the components and input-output streams of a nuclear reactor loop.

Fig. 5 shows a schematic side view of one circuit of a nuclear reactor.

Fig. 6 shows a schematic representation in side view (left) and top view (right) of the outline of a nuclear reactor in a cylindrical arrangement. In the upper part, the channels are arranged in a circle with vertical channels with a passage up and down. Pumps, heat exchangers, expansion tanks and units for extraction and storage of fission products, as well as instrumentation are located in the lower part, under the channels, outside the neutron flux field. The top view shows the preferred up and down channel arrangement.

Fig. 7A shows an individual arrangement of nuclear reactor loops (here 7 loops arranged in a circular configuration) in one embodiment of the invention. When placing individual circuits close to each other, the channels of each individual circuit are also located close to each other, and criticality can be achieved by selecting the appropriate amount and concentration of fuel in the channels. Outlines are removable from the configuration.

Fig. 7B shows the arrangement of loops in a square lattice reactor.

Fig. 7C shows an embodiment in which a number of alternating loops are located around the circular region of the reactor core, which can either contribute to the fission reaction in the core region or perform another function such as fuel generation by breeding or neutron activation using neutrons, emerging from the active zone radially. In the case when neutrons are mainly absorbed and not generated by peripheral circuits, they form the so-called shell (or blanket) region of the reactor.

Detailed description

The present invention relates in one aspect to a nuclear reactor circuit comprising:

loop (3), wherein the loop (3) is capable of containing a liquid containing fertile and/or fissile materials as nuclear fuel and optionally circulating, wherein the loop (3) contains a channel (4), preferably substantially straight, which is part of the loop and which is located in a substantially vertical arrangement, the channel (4) providing an up and down passage (4a,4b) for the liquid in the loop.

The nuclear reactor circuit according to the invention may comprise a loop (3) which contains a channel (4) and may be connected to a reservoir (5) for liquid. The loop may contain a supply line (6), a channel (4), a return line (7), a return line (8). In a loop, a supply line, a conduit, a return line, and a return line are connected and arranged to form a loop that is capable of containing liquid. The liquid may contain fertile and/or fissile materials. The liquid reservoir is connected to the loop and is positioned and configured to contain the liquid. The channel of each loop can be independently placed in a nearly vertical arrangement.

An advantageous feature of the present invention is the arrangement of upflow, reverse flow and downflow in an individual circuit in the channel when it is mounted in a substantially vertical position. This configuration allows the conduit to be surrounded by protective sheaths, which may be closed at one end, preferably the top, and connected to the loop at the location where the conduit is also connected. This allows convenient detachment, removal and replacement of the containment and the channel vertically, through the top baffle and/or radiation shield of the reactor containment. For LSR systems with core components exposed to a combination of high temperatures, intense radiation fluxes, and potentially detrimental chemical interactions with the molten salt and its components, convenient regular replacement of core materials and components is an important consideration for reactor life and economy.

The channel may be releasably connected (ie connected so that it can be detached, optionally together with the protective sheath (29)). When providing a channel as an up-down passage, the supply and output are placed on the same side (top or bottom) of the loop. This allows the loop (and/or channel) to be removed from its surroundings, either from the nearby reactor core where the loop was placed so that it is exposed to or interacts with radiation from the nuclear reactor, or from the moderator if the loop channel was located in the reactor moderator. In such a case, removal can be achieved by raising or lowering the (released) channel and/or the entire circuit from the reactor without the need to dismantle the reactor. This provides a huge advantage over conventional (liquid-salt) reactors as it allows parts of the reactor to be replaced, repaired or otherwise treated without the need to dismantle (a large part of) the reactor.

The channel may be surrounded or enclosed in a protective sheath, which is also removable and/or replaceable. An inert gas may be present between the containment and the duct, which may act as thermal insulation, which may be monitored (operationally) to detect salt leakage and may be used to heat (warm up) the primary components.

The remainder of the circuit also conforms to defense in depth designs by means of suitable containment layers to prevent the release of radioactive material from containments or containment areas. Similar to the function of the conduit containment, the gas gaps may have the functions of detecting/monitoring leaks and/or heating the loop system.

Between the individual (contained) channels, moderator material can be installed or omitted to adjust and optimize the neutron spectrum adapted to the fuel cycle envisaged by the system (for example, a simple uranium burn cycle, or a thorium-uranium or uranium-plutonium breeding cycle). For the design of a thermal reactor, the use of individual reactor circuits provides for the separation of the moderator from contact with the salt. The functionality of the moderator and containment for the molten salt, or the functionality of directing the flow of the molten salt, is separated, unlike other known or in-development thermal LSR system designs.

Thus, in another aspect of the invention, a method is provided in which components of the reactor loop are removed by detaching the conduit, conduit containment and/or liquid reservoir.

- 7 043120 from the loop and removing the channel, the containment of the channel and/or the liquid reservoir from the loop or by removing the entire loop from the reactor. In the case where the loop is located in a reactor configuration, the replaceable connected conduit, conduit containment, and fluid reservoirs can be removed and/or replaced from the containment or region of the reactor core. In some embodiments, removing the conduit, conduit containment, and/or fluid reservoir from the loop includes removing the entire nuclear reactor loop from the reactor prior to removing the conduit, conduit containment, and/or fluid reservoir from the loop. In other embodiments, the duct, duct containment, and/or liquid reservoir may be removed from the nuclear reactor loop while the rest of the nuclear reactor loop remains in the nuclear reactor.

The supply line for the channel is located at one end of the channel. The branch line is located at the other end of the channel. The channel has a supply end (inlet line) and an outlet end (outlet line), both of which are part of and / or connected to the loop so that the supply of liquid to the channel and its discharge from the channel occur on the same side of the channel.

The circuit may contain liquid and circulate it. The contour contains a loop that contains a channel (4).

The channel (sometimes identified as the hot leg) as used herein is the part of the circuit most exposed to neutron radiation caused by nuclear fission reactions inside the channel and/or outside the channels (when exposed to external neutron radiation), and where the channel and fluid in the channel are heated by nuclear fission reactions and/or nuclear heating (the energy released in the materials of the channel and the fluid upon absorption of radiation). The loop fluid flows through the channel in a bi-directional manner (up-down or down-up). The channel may be selected from a single up and down passage pipe, a bundle of pipes, a pipe-in-pipe design, or a channeled block/cylinder. The channel can provide one-way or two-way salt flow. The channel can be connected to a supply line (6) and a return line (8) supplying liquid to the channel and removing liquid from the channel. Preference is given to a conduit that provides two-way flow, such as a tube bundle, a pipe in a pipe, or a channeled block/cylinder.

The substantially straight channel position preferably applies to the outer channel position of the loop. In an alternative embodiment, the conduit may have an up and down passage spiraling up (or down) around the outer perimeter of the conduit and through the spiral loops down (or up) until completion of the passage.

The channel can be connected at one end to the supply line. At the other end, the channel is connected to the outlet line (7). The branch line at one end is connected to the channel. The return line at the other end is connected to the return line. The return line is connected at one end to the return line. The return line at the other end is connected to the supply line. This arrangement of supply line, channel, return line and return line provides a closed loop or loop as used in the invention.

Typically, a conduit is connected at the two ends (inlet and outlet) of the conduit such that the conduit is part of a closed loop that is capable of containing and circulating fluid. At one of these ends, an inlet line may be present upstream of the channel, and a return line may be provided downstream of the channel. The return line may be located downstream of the return line and upstream of the supply line, whereby a loop containing a channel can be provided.

One or more liquid tanks (5) can be connected to the circuit. The circuit is capable of containing liquid. The liquid may contain fertile and/or fissile materials. The nuclear circuit of the present invention forms a loop in which the conduit can be placed and spaced apart from the rest of the circuit so that in operation the conduit can be placed in the radiation flux of an existing nuclear reactor (i.e. a suitable materials testing reactor). ). The channel itself and the contents of the channel can be exposed to radiation from an existing (tested) nuclear reactor. Other elements of the nuclear reactor loop can be placed additionally outside the radiation flux of the existing reactor.

This provides a facility in which the materials and configuration of the nuclear reactor circuit itself can be tested and qualified. Thus, the loop of a nuclear reactor can be used for general testing, model validation, and validation of a new reactor concept by placing it in the radiation flux of the nuclear reactor under test. One or more liquid reservoirs connected to the loop may be used to fill the nuclear reactor loop and may also be used to store the contents of the liquid.

In one embodiment, preferably, the channel does not contain a critical amount of nuclear material, ie. the channel is subcritical.

In some embodiments, the loop may contain liquid. The liquid may contain fertile and/or fissile elements. The liquid may be a molten salt. The liquid may be circulated through the loop, for example by convection and/or by means of a pump built into the loop.

- 8 043120

Typically, molten salt has a high coefficient of thermal expansion. Thus, when molten salt is used, natural circulation can occur in the loop. The salt in the channel, which is heated by the fission reaction, rises to the top of the channel or is squeezed out further where the heat can be removed from the molten salt, for example by means of an optional heat exchanger. The molten salt having a high coefficient of thermal expansion becomes denser and moves in a reverse trend through the output line and return line of the loop and is replaced by the salt that has been heated within the active region. As the chilled salt moves through the circuit, it passes through the critical zone in the channel, i.e. where it can be exposed to external radiation. Passing through the critical zone generates heat in the molten salt, causing it to become less dense and circulate to the top of the vessel channel, repeating the process. Thus, natural flow causes the hot salt to circulate through the loop and optional heat exchanger where heat can be removed, and brings the colder salt back through the critical zone region where it is heated. This natural circulation may form the primary flow drive within the loop.

The natural circulation effect in the loop can reduce the need to operate a loop pump or loop to circulate material through the core reaction vessel. Pumps may be provided to supplement this natural circulation effect and/or may be required as a primary circulation force. For example, when a large amount of energy is generated in a loop, it is preferable that the pump actively move heat from the duct to the part of the loop where the heat is removed.

In some embodiments, the channel is placed in a substantially vertical arrangement. Nearly vertical in this context means that the fluid in the channel can move through the channel due to convection and/or gravity. The channel may be at an angle to the vertical of at most about 45 degrees, preferably no more than about 20, 15, or 10 degrees. More preferably, this angle is less than about 5 degrees. It is preferred that the loop and loop elements are designed and positioned such that the loop either allows or facilitates the passive flow of fluid into the fluid reservoir under the action of gravity.

In an embodiment where the nuclear reactor loop is a molten salt reactor that may contain fertile and/or fissile materials, the liquid reservoir may be connected to the loop through an actively or passively actuated valve or through passage.

An example of a passively activated through passage is a salt plug (or solidified plug) (11) in the connection between the loop and the liquid reservoir, which is usually achieved by actively cooling the area so that the salt melt solidifies. This area is usually located between the loop and the tank. Immediately after deactivation or elimination of cooling or temperature increase, the plug will melt and the contents of the circuit will drain into the reservoir. A salt plug is typically used in the event of an overheated nuclear reactor loop, and by passively draining through the salt plug, fissile material is removed from the core, effectively reducing or stopping the nuclear fission reaction. The liquid reservoir is preferably located near the lowest point of the nuclear reactor loop. The combination of a substantially vertical arrangement of at least the channel and the placement of a salt plug and a liquid reservoir near the lowest point of the loop allows, in case of emergency (i.e. accidents or overheating), to empty the contents of the loop into the reservoir, thereby removing fissile material from the loop and from the area the critical core of the reactor, with the termination or weakening of the nuclear fission reaction in the circuit so that the reactor plant is no longer critical. Preferably, the reservoir is located outside the reactor radiation flow, or at least in a position where the reactor radiation is not capable of supporting a nuclear reaction in the loop. The liquid reservoir can be used to drain liquid from the loop (shutdown scenario) and/or fill the loop with liquid (startup scenario). The liquid tank can be adapted to store liquid and is temperature controlled for salt conditioning purposes. The fluid reservoir can be removed and replaced. The presence of removable and replaceable fluid reservoirs allows for the introduction of new molten salt compositions into the circuit or for controlling the cleaning or alteration of the molten salt elsewhere. Alternatively, the individual tanks can be emptied into a portable tank or container that can be removed and replaced.

In some embodiments, the circuit may further comprise other components, such as an expansion tank, to cope with pressure fluctuations and volume changes of the molten salt, for example due to thermal expansion. The loop may further comprise pumps for transporting fluid in the loop, a heat exchanger for heating the fluid in the loop, or for removing heat from the fluid in the loop to a secondary medium used to transfer heat to the power generation unit. The circuit may additionally contain or be connected to means for chemical treatment, for example, to remove impurities, unwanted by-products, neutron-absorbing activation or fission products, or formed in a salt melt

- 9 043120 elements that enhance the degradation of the system due to corrosion or deposition. Potential non-proliferation issues in material recovery should and can be addressed by design. The loop may further comprise or may be connected to means for adding and/or removing one or more of fertile material, fissile material, fission products, neutron activation source materials and neutron activated materials, as well as liquids such as molten salts.

In one embodiment, the fluid reservoir is a plurality of fluid reservoirs. The amount of nuclear material in the loop and/or in the channel may be less than the critical amount (ie, the channel of the loop contains a subcritical amount of nuclear material). In this embodiment, preferably, the channel does not contain a critical amount of nuclear material, i. e. the channel was subcritical. Thus, in some embodiments, multiple fluid reservoirs may be provided such that a single fluid reservoir may contain a portion of the fluid contained in the loop, and thus only a subcritical amount of nuclear fuel.

The liquid reservoirs may be removed from the structure and placed in shipping containers to remove the liquid at a salt refining site, a salt composition optimization site, or for other salt treatment purposes, including conditioning for waste storage and disposal.

The liquid in the nuclear reactor loop (and thus in the reactor) according to the invention may contain fertile materials, preferably selected from one or more of ²³² Th, ²³⁸ Pu, ²³⁸ U, ²⁴⁰ Pu, ²⁴² Pu and other actinide isotopes.

The liquid in the nuclear reactor loop (and thus in the reactor) according to the invention may contain fissile materials, preferably selected from one or more of ^233U , ^235U , ^239Pu , ^241Pu and other actinide isotopes.

In this respect, the term fertile material means material that can be converted into fissile material by neutron transmutation and subsequent nuclear decay. In this respect, the term fissile material means material that can be made to undergo nuclear fission by neutron irradiation (i.e., is fissile) and also to produce neutrons from such fission that can sustain a nuclear reaction under appropriate conditions. The process of transmuting fertile materials into fissile materials by absorbing neutrons is called fuel breeding.

The liquid in the nuclear reactor loop (and thus in the reactor) according to the invention may contain fissile materials, preferably selected from one or more of ^233U , ^235U , ^239Pu , ^241Pu and other actinide isotopes.

The liquid in the nuclear reactor loop (and thus in the reactor) according to the invention may contain long-lived isotopes recovered from nuclear waste, such as isotopes of neptunium, plutonium, americium, curium and other actinides, for example, in order to reduce the shelf life of nuclear waste.

The liquid in the nuclear reactor loop (and thus in the reactor) according to the invention may contain isotopes specifically designed to generate fission or activation products that have medical or industrial uses, ranging from enriched stable isotopes such as ¹⁷⁶ Yb (to generate ¹⁷⁷ Lu ), ¹⁶⁰ Gd (to generate ¹⁶¹ Tb), to selected semi-stable or unstable isotopes such as ²³⁵ U/ ²³³ U/ ²³⁹ Pu (to generate ⁹⁹ Mo, ⁹⁰ Sr and ¹³¹ I by fission), ²³⁷ Np (to generate ²³⁸ Pu ) and ²²⁶ Ra (for generating ²²⁷ Ac, ²²⁸ Th, ²²⁹ Th, ²²⁵ Ac, etc.), among others.

The liquid in the nuclear reactor loop according to the invention may be a molten salt. In a preferred embodiment, the molten salt is selected from fluorides and/or chlorides, preferably one or more of LiF, NaF, KF, RbF, BeF ₂ , ZrF ₄ , LiCl, NaCl, KCl, RbCl, BeCl ₂ , ZrCU and mixtures thereof.

The conduit of the present invention is made of a material that can adequately withstand molten salt corrosion in the loop, with minimal damage due to neutron flux and radiation, while minimizing neutron absorption, thus optimizing neutron savings. A material that has high resistance to molten salt corrosion can withstand radiation damage relatively well and has low neutron absorption. Suitable material may be molybdenum alloys, graphite, silicon carbides and other carbides.

The channel of the present invention in its simplest form is a single tube (pipe) or channel. In one embodiment, the channel (4) comprises a tube (4a) with an upward passage and a tube (4b) with a passage down, which are connected to each other at the top or bottom. This can also be embodied as a U-tube with a bend at the top or bottom (single tube), preferably at the top.

Thus, preferably, the channel is a U-tube, with each inlet line and outlet line located independently at or near the lower end (lower half) of the channel (FIG. 3A).

- 10 043120

In one embodiment, the channel is a pipe-in-pipe design (FIG. 3B). The pipe-in-pipe design (double pipe, double-sided) contains an inner tube (14) located inside the outer tube (15), the inner tube having a smaller outer diameter than the inner diameter of the outer tube, with one end (preferably the lower end) of the inner tube connected to the supply line, and one end of the outer tube (preferably the lower end) is connected to the outlet line, while the outer tube has a closed end remote from the end connected to the outlet line (preferably at the top), or one end of the inner tube is connected to the outlet line, and one end of the outer tube is connected to the inlet line, and the outer tube has a closed end remote from the end connected to the inlet line, and the other end of the inner tube has an opening and is located near the closed top of the outer tube, and the length of the inner tube in the outer tube is shorter than that of the outer tube. This creates a section in which the fluid flow reverses in direction.

In additional embodiments of the channel, the inner or ascending tube is placed coaxially with respect to the return or outer tube, and vice versa.

In another embodiment, the channel may include one tube in which fluid flows up (or down) and a plurality of tubes in which fluid flows down (or up). To ensure this, the tubes can have different diameters. See in this regard FIG. 3C.

In yet another embodiment, the conduit may be provided as a solid block or cylinder in which passages are provided through the block or cylinder to accommodate upflow, reverse flow, and downflow together (FIG. 3C). The block design may be optimized for optimum fuel distribution, and may also contain retarding elements, and/or itself be composed of retarder material.

It is preferred that the conduit accommodate upflow and downflow, and the reversal section is important because it can allow the entire conduit to be disconnected at the end location where it is connected to the rest of the loop, preferably at the lower end. The same applies for containment jackets that surround the channel, which can also be connected at the same end, preferably at the lower end, to form a shroud, which can be replaced by detaching the containment and moving the containment vertically from the reactor through the upper neutron reflector and/ or the radiation shield of the reactor containment.

A nuclear reactor circuit containing a loop that contains a channel may contain or may be connected to other elements and/or functionality, such as heat exchangers, pumps, chemical treatment facilities, etc., essentially as explained in this document in other places, to form an individual independent circuit.

The present invention, in another aspect, relates to a nuclear reactor comprising a core region and a cladding region, wherein the reactor is composed of a plurality of separate and individual nuclear reactor circuits or modules, each circuit comprising a loop (3), wherein the loop (3) is capable of containing liquid containing fertile and/or fissile materials as nuclear fuel and optionally circulating, wherein the loop comprises a channel (4), preferably substantially straight, which is part of the loop and which is located in a substantially vertical arrangement, the channel providing passage (4a, 4b) up and down for fluid in the loop, each of the channels of said plurality of loops being located in the core region, and each loop being independently extractable from the nuclear reactor.

Thus, a nuclear reactor contains a core region (1) and a cladding region (2). The core area is surrounded by the shell area. The shell region may have the functionality of a neutron reflector, a radiation shield, or a neutron absorbing blanket for generating materials and isotopes by neutron activation, or a combination of these functionalities. The functionality of the envelope blanket can be achieved with circuits supplying and withdrawing fluid into the envelope containing target materials for neutron activation. In a nuclear reactor, a plurality of nuclear reactor circuits are provided.

The channel is a part of the circuit located in the critical zone of the reactor, i.e. exposed to the neutron flux.

A nuclear reactor is built from a group (multiple) of individual circuits of a nuclear reactor. The circuits are separate circuits or modules and are extractable from the reactor without affecting other modules. The circuit channels are located close to each other. Said plurality of loops may be arranged in a configuration forming the reactor, such as a circular, rectangular, or other configuration. The circular configuration is preferred. Loop channels can be located at smaller distances from each other (ie, closer to each other) than other elements that make up the loop. An effective visualization is that with a reactor shaped like a pie in a top view, the individual contours form a ku

- 11 043120 pie juices, each with a contour channel closer to the center of the pie. This makes it possible to effectively place other elements of the circuit outside or more remotely from the critical zone of the reactor. A loop may contain multiple channels. In a circular configuration, the channel may be at a smaller radius from the center of the reactor than other elements. The channels together form a critical zone, which is the active zone of the reactor. In some embodiments, channels may be placed in multiple circles to form a critical zone. Another circle of channels (9) may surround the critical zone. The critical zone is surrounded by a sheath area that may provide the functionality of a neutron reflector, neutron moderator, radiation shield, or blanket. The functionality of the blanket can be achieved by additional circuits that feed the blanket target material into the channels (9) which are located in the area of the shell surrounding the critical zone. Blanket can be used to generate fissile material (breeding) from fertile material or to produce isotopes for a variety of purposes. The functionality of the blanket can be provided by channels having the same or different geometric shape (in cross section) than the channels (4) used in the core. The loop channels, both in the core (4) and outside the core (9), in the shell, may have geometric shapes (cross-sections) that are circular (as shown in figure 1), but can also independently be oval and /or elliptical. The channels in the cladding region may be designed to absorb neutrons from the critical zone of the reactor and, depending on their purpose, may be configured very differently from the configuration of the channels of the core circuits designed and optimized for their function. Each of the channels may independently contain a liquid, which may contain fertile and/or fissile material or other target material activated by the neutron flux in the shell region.

To properly bring the reactor core to criticality, selected or all of the circuits can individually supply a subcritical amount of nuclear fuel to the critical zone of the reactor. In such a case, the channels combined in the core (and the optional moderating materials in the channels and/or in the spaces between the channels) provide sufficient critical mass and retardation to achieve criticality in the reactor core. Criticality is highly dependent on temperature, resulting in a decrease in the density of fissile material in the channels in the event of an increase in temperature and vice versa, thus passively adding fission safety control. To further control or stop the fission reaction, the control rods may introduce or remove neutron absorbing materials from the core region by moving them in or close to the spaces between the channels, in the moderator materials if they are present in the spaces between the channels, or in the cladding region.

In some embodiments, the core comprises 2 or more, 4 or more, 6 or more, 10 or more, or 25 or more, preferably 6 to 20 channels. In some embodiments, the implementation of the reactor contains 2 or more, 4 or more, 6 or more, 8 or more, or 10 or more circuits.

In a typical embodiment, the reactor is based on multiple individual loops containing loops that can be placed in a circle, with one part of each loop located at small radii (channel or hot leg), creating a critical configuration that supports a nuclear reaction (critical zone), and the rest of the contour (other elements, functionality) is (s) at a greater distance or radius, largely outside the radiation field of the critical zone, in a non-critical configuration.

The channel is a separate and separable component that can be detached, removed and replaced. The protective cover (29) of the channel is a separate component that can be detached, removed and replaced. The channel guard may comprise multiple female guards. An inert gas may be present between the duct containment(s) and the duct, which may provide thermal insulation, which may be monitored for fission products or other salt (volatile) ingredients to detect leakage, and which may be used to heat (warm) the duct by blowing the space between the protective shells of the channel and the channel with hot gas. The conduit and/or containment are separate components that can be detached, removed and replaced individually. The channel may be (partially) enclosed by one or more separate containments. Alternatively, the entire circuit may be removed (pulled out or removed) from the core region for replacement.

Each of the channels, preferably with protective shells, of the said plurality of circuits is located in the region of the active zone. In some embodiments, the implementation of the core area may contain a moderator (10). The moderator (10) may be located in the spaces between the channels or surrounding the channels. Thus, the channels (and the moderator) together form the critical zone of the reactor core. A suitable moderator may be any low atomic mass, low neutron absorption solid material, including carbon-based materials.

In some embodiments, it is possible to provide a nuclear reactor without a moderator, i.e. the so-called fast neutron reactor, providing a spectrum of fast neutrons. Although these types of reactors have certain technical problems, such as the rapid degradation of materials, the concept using the loops of the invention would allow a relatively quick and easy replacement of the primary materials that form the loops, such as channels and channel shrouds from the loops, or the entire circuit.

In a number of applications that require a more suprathermal spectrum (more thermal than fast neutrons, for example in the thorium cycle), or a thermal spectrum, it is preferable to have a reactor containing a moderator.

Deceleration can be further imparted by selecting the material of the channels and channel sheaths and by adding retarding material in the spaces between the channels of the loops, or it can be minimized by using non-retarding materials in the loops and filling the space between the channels of the loops with a non-retarding medium or material.

Criticality in this regard refers to the mode of normal operation of a nuclear reactor, in which the nuclear fuel supports the fission reaction. A reactor reaches criticality (and is considered critical) when each fission event releases enough neutrons to sustain an ongoing sequence of nuclear fission reactions.

The channels of the reactor can be arranged so that each of the channels (and the liquid in them) is exposed to a similar neutron flux and neutron spectrum. Alternatively, the critical zones can be arranged so that each channel in the critical zone can be affected by different fluxes and/or different neutron spectra. This arrangement can be useful when a particular critical zone requires a specific neutron flux, such as a zone in which a channel is located that is part of a circuit designed to generate specific isotopes by neutron activation, or through the use of neutrons/neutron absorption for conversion of reproducing elements into fissile elements.

In contrast to conventional nuclear reactors, criticality, and thus the fission chain reaction, can already be properly stopped or downgraded by intervention in one or more circuits, instead of the required intervention in all circuits in the reactor to bring the entire core to a non-critical state. Thus, not all circuits have to be switched to off mode or adjusted down. This can be very convenient in terms of maintenance and safety. To illustrate, consider a reactor containing 10 circuits, each of which contributes 10% of the critical amount of nuclear material to the core, as a result of which the criticality of the core is achieved. In an emergency (accident) only one circuit needs to be shut down (drained into the liquid reservoir(s)), and the entire reactor becomes non-critical, while the other 9 circuits can remain unaffected.

In a further aspect, the invention provides a method for operating a nuclear reactor comprising a plurality of individual nuclear reactor circuits of the present invention. The method makes use of the flexibility that can be provided by a nuclear reactor containing a plurality of nuclear reactor loops.

The method further includes providing a plurality of nuclear fuels or target materials containing fertile materials and/or fissile materials and/or other materials activated by a neutron flux, and supplying a plurality of nuclear fuels and/or target materials to a plurality of circuits. The method further includes supplying a plurality of nuclear fuels containing fertile and/or fissile materials to the loops, preferably each of the loops. Nuclear fuel in the channels of the circuits is brought into a critical configuration.

The critical reactor core may be formed by loop channels introducing fissile material in appropriate amounts and in a suitable configuration into the region of the reactor core.

The reactor spectrum can be controlled by salt, channel materials, containment materials and/or a special moderator in between or around the channels of the loops.

Moderation can be tuned to the desired neutron spectrum, either to the reactor core with the fast neutron spectrum (minimized moderation), or to the reactor core with the (extra)thermal neutron spectrum, or to various special neutron spectra in individual sections in the core area for optimization division, reproduction or activation in different circuits at different locations.

The modular core reactor facility also allows the individual loops to be switched step by step from breeding to breeding-burning and from burning to breeding. In the event that most of the circuits provide adequate criticality to sustain the nuclear fission reaction in the core region, for example by ²³⁵ U fission (burning), one or more circuits may use the excess neutrons produced from the fission reaction in the core, for example, for the conversion/transmutation of fissile ²³³ U from reproducing ²³² Th (reproduction), until the reproduction-burning equilibrium is established in the circuit, and in this case, the same amount of ²³³ U is formed from ²³² Th as is spent on the fission reaction. The economy of neutrons in the reactor and circuit must be sufficiently optimized to avoid too much loss of neutrons. Contours previously used primarily

- 13 043120 for burning, you can then switch from the regular burning function to the reproduction function by replacing the salt or adding thorium to the salt. Over time, this circuit can then be switched from breeding to breeding-burning function, eventually reaching a balance between breeding and burning. Thus, the reactor is being converted in stages towards operation in a closed thorium cycle, in which ²³² Th is converted to ²³³ U fuel, which requires no or minimal addition of fissile material to the reactor loops to maintain the fission reaction.

The present invention can provide a method for closing the uranium-plutonium cycle in which eventually the fission reaction in the critical zone of the reactor can be maintained by fissioning the plutonium and excess neutrons are used to transmute fertile ^238U to fissile ^239Pu in appropriate amounts.

The present invention can provide a method that can be used to burn long lived isotopes that have been recovered from nuclear waste to reduce the shelf life of nuclear waste. In this case, the reactor is critical, but one or more of the circuits either in the critical/core or in the cladding region has a special salt composition in which these long-lived isotopes extracted from nuclear waste can be transmuted and/or fissioned to produce short-lived isotopes. and medium-living isotopes and fission products.

The present invention may provide a method for producing specific isotopes by neutron activation of specific elements. In this case, the reactor is critical, but one or more of the circuits, either in the critical zone/core region or in the cladding region, has a specific salt composition in which these target materials are included, and the desired activation products are removed from the circuit for their use at a given appointment.

The advantage of this approach in terms of the (closed) nuclear fuel cycle of the present invention, both in the loop and in the reactor, is the combination of:

the use of a salt melt, which makes it possible to quickly purify and condition the salt, as well as, by removing neutron-absorbing fission or activation products, to optimize the economy of neutrons by minimizing losses due to neutron absorption. Potential non-proliferation issues in retrieval of material must and can be addressed by design;

the use of an individual channel of circuits, together forming a critical zone, which in principle allows each circuit to contain a different mixture of salts and a different content of fertile fissile material, which can be changed by adjusting or replacing the salt.

Conventional reactor plants, primarily solid fuels, do not have the ability to minimize the neutron absorption of activation and fission products by removing fission products, since they are contained in the fuel and can only be removed by careful processing of solid fuel in a separate location, and not have the flexibility to conveniently (partially) modify, optimize, or customize the contents of the core. The circuit and reactor according to the invention allow the removal of fission products.

Conventional molten salt reactors generally operate with a single volume of salt, which makes it difficult to incrementally adjust the composition of the salt, since such a change affects the entire volume of salt, in which the salt performs a non-optimized and non-localized breeding and burning function. The reactor and circuit of the invention are capable of handling a variety of different salts and allow relatively easy and convenient incremental adjustment of the salt composition.

The aforementioned advantages of a modular core reactor plant over other molten salt reactor designs are in addition to the disadvantages of handling large volumes of salt, such as large components that are difficult to replace and rapidly degrade in the molten salt reactor environment, with limited understanding of where fuel, a problematic qualification and licensing protocol where small-scale testing cannot easily be extrapolated to full-scale operation, and limited flexibility in optimizing reactor performance by replacing optimized components, all of which can be avoided by using the modular core reactor facility of the invention.

It should be clear that in a nuclear reactor that is composed of individual nuclear reactor loops, the elements and embodiments that have been described in relation to the nuclear reactor loop also form elements and embodiments of the nuclear reactor itself, and that the elements and embodiments of the nuclear reactor that are part of or related to the circuit of a nuclear reactor, are also elements and embodiments of the circuit of a nuclear reactor.

The invention further relates to a method for operating a nuclear reactor loop, as described elsewhere herein, by providing a nuclear reactor loop, placing a nuclear reactor loop duct near the core of another (tested) nuclear reactor such that the critical zone of the loop duct is exposed to radiation flux another reactor. The method further comprises supplying a liquid to the loop, circulating the liquid through the loop, and exposing the liquid to the radiation flux of the nuclear device under test.

- 14 043120 reactor in the channel. The method further includes monitoring the characteristics (elements) of the loop and/or fluid (which may be a molten salt and may contain fissile and/or fertile materials or other chemical elements). The method may further include providing nuclear fuel containing fissile and/or fertile materials. Nuclear fuel can be fed into the loop. The nuclear fuel may be circulated in a loop and may be exposed to radiation from another reactor, preferably in the critical zone.

By placing the loop of a nuclear reactor, and in particular the channel of the loop, into the neutron flux of another nuclear reactor, the facility, the materials of which the loop is made and/or the liquid (molten salts) and/or the fertile and fissile material in the nuclear fuel can be tested and attestations, either in combination with each other or separately. For example, in one embodiment, the method may include providing a loop as described elsewhere herein, providing a fluid (preferably a molten salt), and exposing the loop and fluid to an existing nuclear reactor's radiation flux to monitor, test, and experiment on the behavior of the loop material. , fluid and overall circuit performance. The data obtained in this way is useful in improving the circuit itself, the composition of the fluids used in the circuit, and, ultimately, in the further design and optimization of the nuclear reactor according to the invention.

Thus, in some embodiments of the invention, the parameters for the (components) of the loop are, among others, the behavior of materials subject to degradation mechanisms under molten salt reactor conditions, such as contact with molten salt, high temperature and (neutron) radiation, usually these aspects behaviors like corrosion resistance, strength, embrittlement, creep, fracture toughness, thermal expansion, thermal conductivity.

Thus, in some embodiments of the invention, the parameters for liquid characteristics are, among others, chemical composition, dissolution or precipitation of fission products, behavior of activation products, destruction/decomposition by radiation, coagulation of elements in salt, thermal and electrical conductivity, corrosiveness, fluoride/chloride potential, viscosity.

Thus, in some embodiments of the invention, the parameters for nuclear fuel are, among others, dissolution in molten salt, precipitation potential, coagulation with other elements in salt.

Thus, in some embodiments of the invention, the parameters for loop performance are heat dissipation, operational safety, heat dissipation and heat transfer efficiency, testing and qualification of loop components, among others.

By operating the circuit in this manner, it is also possible to use the circuit of the invention for a large number of applications, which will be discussed elsewhere in this document, such as the generation of specific isotopes by neutron activation, fissile material from fertile material, and so on.

In a specific embodiment, the method may further include the step of generating isotopes, for example, for medical, diagnostic or imaging applications. This embodiment may include the step of supplying specific elements to the loop, exposing the elements to the neutron flux from the reactor, and causing the elements to transmute into other elements and isolate the resulting elements from the liquid. The selection can be carried out in-line or offline (ie, the liquid can be removed from the loop and the selection is carried out elsewhere). Similarly, fission products can be recovered from circuits in which fission reactions take place, for example, for medical, diagnostic, or imaging applications.

The design of the circuit according to the invention and a nuclear reactor containing circuits according to the invention have certain advantages, such as, but not limited to:

They enable a replacement strategy and optimization of reactor performance by replacing loops with improved loops and loops with improved channel designs.

The multiple reactor loops together form the critical zone of the reactor. Therefore, the critical mass in the critical zone is divided into separate protective shells. In the event of leakage from the loop, the critical mass in the critical zone is effectively reduced, thereby reducing or stopping the nuclear reaction.

Individual channels (or circuits) may contain different salt formulations with different fertile, fissile or other materials.

The reactor core configuration may be chosen such that individual loop channels are placed at different locations in the critical zone to serve different purposes such as fission, breeding, and neutron activation for optimized performance.

- 15 043120

The core configuration can be chosen such that individual loop channels are placed at different locations in the critical zone to generate a neutron flux spectrum and distribution to optimize the performance of each channel at each location in the reactor.

The salt in the channel can be replaced with another salt composition to change the purpose of the channel in the critical zone of the reactor or the cladding zone.

The production of many relatively small components can be more cost effective than the production of a few very large components. Economies of quantity may outweigh economies of scale.

Relatively small components allow for convenient testing at representative scales, facilitating and reducing costs and time for component and reactor development and qualification.

Unlike other (thermal) molten salt reactor designs, specific moderator materials, such as graphite, can be located outside and in the spaces between the channels, instead of being in direct contact with the nuclear fuel-bearing salts. Thus, the function of the moderator can be separated from the functions of directing or holding the flow of salt melts. This is especially useful for graphite, which is a very suitable moderator but exhibits very complex behavior in a nuclear reactor environment. As a life extension and maintenance measure, a separate moderator around the channels can be subjected to a temperature increase to anneal radiation damage, either during or between service cycles, whereby the original material properties can be restored. For graphite, this can be very effective, providing suitable moderator properties by (repetitive) annealing, to the extent that the moderator material will no longer need to be replaced during the lifetime of the reactor.

The physical separation of the salt in the channels from the moderator in between the channels also allows for thermal optimization of the moderator largely independent of channel and salt temperature. The moderator material, for example, can be brought to and maintained at temperatures other than those of the salt or channel to minimize the effects of radiation damage during operation to maximize service life. For example, the graphite moderator can be maintained at a lower temperature than typical salt temperatures, whereby the effect of radiation damage is reduced and service life is maximized.

Since the modular core reactor is formed by an assembly of separate, individual and independent reactor loops, the system and each individual loop consists of relatively small components that operate at low pressure. The system, built from small components, allows, for example, the channel to be disconnected from the loop and removed from the loop into a shielded container for transport to a conditioning site, disposal, or, if applicable, for recycling. After that, a new channel (or other element) can be introduced. For example, this can happen vertically through a radiation shield at the top of the reactor. The same approach can be applied to other parts and components of the path, or the entire path.

Reference numbers:

- area of the active zone;

- shell area;

- a loop;

- channel;

a - channel with upward passage;

b - channel with a passage down;

- reservoir for liquid;

- supply line;

- branch line;

- return line;

- shell channel;

- moderator or non-retarding medium;

- active or passive valve (frozen plug) to the fluid reservoir;

- a tube with a passage up;

- a tube with a passage down;

- inner tube;

- outer tube;

- expansion tank;

- heat exchanger;

- pump;

- treatment;

- supplied material;

- 16 043120

- secondary heating system;

- fission and activation products;

- fission and activation products;

- reproducing, fissile materials and target materials;

- screen;

- critical zone;

- a single tube with a passage up;

- multiple tubes with a passage down;

- protective shell of the channel;

- connection of the loop-protective shell of the channel;

- passing through a neutron reflector and/or a radiation shield to remove/replace the channel and the containment of the channel;

- passage through the neutron reflector and/or radiation shield to remove/replace the liquid reservoir.

Claims (19)

1. A nuclear reactor containing a core area and a shell area, and moreover, the reactor is composed of a plurality of separate and individual circuits or modules of a nuclear reactor, each circuit contains a loop (3), moreover, the loop (3) is capable of containing a liquid containing reproducing and / or fissile materials as nuclear fuel and optionally circulating, wherein the loop comprises a channel (4), preferably substantially straight, which is part of the loop and which is located in a substantially vertical arrangement, the channel providing an up and down passage (4a, 4b) for liquid in the loop, wherein each of the channels of said plurality of circuits is located in the core area, and each separate and individual circuit of the nuclear reactor is independently extractable from the nuclear reactor. 2. Nuclear reactor according to claim 1, wherein the individual circuit contains a subcritical amount of nuclear fuel in the critical zone of the reactor. 3. The nuclear reactor of claim 1, wherein said plurality of separate and individual nuclear reactor circuits or modules provide a critical amount of fuel to the reactor, preferably in the critical zone, so that nuclear reaction can be maintained. 4. Nuclear reactor according to claim 1, wherein the channel in the loop is a single pipe, a bundle of pipes, a pipe in a pipe, or a (monolithic) channeled body. 5. Nuclear reactor according to any one of the preceding claims, wherein the channel is removable. 6. Nuclear reactor according to any one of the preceding claims, wherein the duct is provided with an optional removable containment (29). 7. Nuclear reactor according to any of the preceding claims, wherein the channel has a supply end and an outlet end, both of which are part of a loop and/or connected to the loop, so that the supply of liquid to the channel and the outlet from the channel occur on the same side of the channel . 8. Nuclear reactor according to claim 5, wherein the arrangement of the channels forms the critical zone of the nuclear reactor. 9. Nuclear reactor according to claim 5 or 6, each channel contains a subcritical amount of nuclear fuel in the critical zone of the reactor. 10. A nuclear reactor according to any one of the preceding claims, wherein the critical zone of the reactor further comprises a moderator. 11. A nuclear reactor according to any one of the preceding claims, wherein the channels are located in the core, preferably in one or more circles, preferably in one concentric circle. 12. A nuclear reactor according to any one of the preceding claims, wherein the channels are arranged in the moderator, preferably in one or more circles, preferably in one concentric circle. 13. A method of operating a nuclear reactor, including the steps: providing a nuclear reactor, described in paragraphs.1-10, containing multiple circuits; provision of nuclear fuel containing fertile and/or fissile materials; supply of nuclear fuel to a plurality of circuits; bringing nuclear fuel in the channels of the circuits to a critical configuration. 14. A method of operating a nuclear reactor loop by locating a nuclear reactor loop duct as defined in any one of claims 1 to 5 near the core of another nuclear reactor such that the loop duct is exposed to the neutron flux of the other reactor. 15. The method according to claim 14, including the steps: - 17 043120 providing the loop of a nuclear reactor, characterized in any one of paragraphs.1-10; provision of nuclear fuel containing fertile and/or fissile materials; supply of nuclear fuel to the circuit; optionally, ensuring the circulation of nuclear fuel in the loop; exposing nuclear fuel in the critical zone of the circuit to the neutron flux of another reactor and monitoring and/or modeling one or more parameters: i) circuit components, ii) fluid, iii) behavior of material sample, iv) nuclear fuel and/or v) loop performance. 16. The method of claim 13, further comprising the steps of operating the reactor in a critical configuration, wherein at least a portion of the loops feed fissile material into the critical zone, with or without delay, to sustain the fission reaction; operation of part of the circuits in breeding mode during combustion in the critical zone, and excess neutrons from the fission reaction make it possible to generate fissile material from fertile materials, for example, ²³³ U from ²³² Th, or ²³⁹ Pu from ²³⁸ U, preferably ²³³ U from ²³² Th, and cause fission at least a portion of the generated fissile materials; establishing a balance between reproduction and combustion in one or more circuits; replacing fluid in one or more other reactor circuits, thereby switching the other circuits from a combustion mode to a breeding mode; enabling the circuits to achieve equilibrium, thereby providing a reactor plant that operates in a closed nuclear fuel cycle of breeding-burning. 17. A method for removing and/or replacing components of a nuclear reactor loop according to any one of claims 1 to 12, comprising the steps of detaching the channel, the channel containment and/or the liquid reservoir from the nuclear reactor loop, removing and/or replacing the channel, the channel containment and/or a reservoir for liquid from the nuclear reactor loop. 18. The method of claim 17, wherein the nuclear reactor loop is placed in a nuclear reactor configuration comprising multiple nuclear reactor loops, wherein from one of the nuclear reactor loops, replaceable connected conduit, conduit containment, and fluid reservoirs are removed and/or replaced from the active region. zones or reactor shells. 19. The method according to claim 17 or 18, wherein the removal or replacement is carried out by substantially vertical movement of the interchangeable connected conduit, conduit containment and/or fluid reservoirs.