Pumped subcritical apparatus

Description

[0001] Subsequent registration evo-partners GmbH, E32277WO

[0002] Pumped subcritical device

[0003] The invention relates to a subcritical device using nuclear fuel. In a subcritical device, such as a subcritical nuclear reactor, a chain reaction with a constant reaction rate can be achieved by supplying free neutrons from one or more independent neutron sources. If the neutron source is based on a particle accelerator, and thus can be switched off at any time, a subcritical nuclear reactor offers improved safety against reactivity-related accidents. Such driven reactors, which operate with a particle accelerator as the neutron source, have occasionally been built and operated for experimental purposes.

[0004] The object of the invention is to provide an improved, preferably subcritical, device which avoids the disadvantages of a very complex neutron source based on a particle accelerator and can therefore be provided and operated with increased safety and modularity while simultaneously reducing costs, material and time expenditure.

[0005] The problem is solved by a device having the features according to claim 1. Embodiments of the invention are specified in the dependent claims.

[0006] The device according to the invention is configured to hold a nuclear fuel and comprises one or more neutron sources configured to emit free neutrons which can interact with isotopes of the nuclear fuel and cause nuclear fission of the isotopes. The one or more neutron sources are configured such that the neutron flux intensity of the generated neutrons is at least 10 10 neutrons per second and preferably more than 10 12 The number of neutrons per second (n / s) is given. The one or more neutron sources have at least one power supply by which the neutron flux strength of the neutron sources can be controlled. The one or more neutron sources can have a common power supply or separate power supplies.

[0007] One or more neutron sources are set up, with a neutron flux strength of more than 10 12They can generate n / s, but can also produce a neutron flux strength of more than 10 13 n / s or more than 10 14 n / s can be generated. With such neutron flux intensities, a high number of free neutrons can be achieved with a small number of neutron sources used in the device, thereby increasing the power delivered by the device or the subcritical arrangement. When using 1 to 50 neutron sources, particularly 1 to 15 or 15 to 30 neutron sources in the device, power outputs of more than 10 kW to more than 100 MW can be achieved. The device's power is preferably and primarily generated in the form of thermal power.

[0008] The use of one or more neutron sources whose neutron flux intensity can be electrically controlled by means of a power supply or operating voltage makes it possible, in the device according to the invention, to avoid the disadvantages of a complex spallation neutron source based on a particle accelerator. This reduces the costs as well as the material and time required to set up and operate the device. In addition, the device can be switched off at any time, thus ensuring increased operational reliability.

[0009] According to one embodiment, the device according to the invention comprises one or more neutron sources configured to produce neutrons with a kinetic energy of 1 MeV (megaelectronvolt) or more, in particular with a kinetic energy between 1 MeV and 10 MeV, or with a kinetic energy of more than 10 MeV, preferably 14.1 MeV. The one or more neutron sources can be configured to operate in such a way as to emit fusion neutrons based on deuterium-tritium reactions with an energy of 14.1 MeV.

[0010] The device according to the invention is preferably operated with a multiplication factor of less than 1, so that a self-sustaining chain reaction cannot occur. With a multiplication factor of less than 1, a smaller number of neutrons are produced in each subsequent generation of nuclear fissions in the nuclear fuel than were present in the previous generation. This means that the number of neutrons produced by the nuclear fuel decreases over time, and the chain reaction eventually ceases. However, the one or more neutron sources of the device according to the invention provide a sufficient number of free neutrons in addition to those produced by nuclear fissions in the nuclear fuel, so that a sufficient number of nuclear fissions and neutron emissions occur in subsequent generations of nuclear fissions, and energy can be generated with the device.By injecting free neutrons from one or more neutron sources, a constant fission rate or thermal power of the subcritical assembly can be achieved. The device can be described as a pumped reactor. The principle of subcritical operation of the device also provides inherent safety against reactivity-related accidents. A medium suitable for the respective neutron spectrum, such as a noble gas, lead, sodium, or water, can be used for cooling. According to one embodiment, the device has one or more neutron sources for generating neutrons, in which the generation of neutrons occurs through plasma-induced fusion processes in a material surface of the neutron source that is in contact with a plasma.The material surface can be part of a neutron source housing, the surface of an anode or cathode, or a flat area inside the neutron source. The anode, cathode, or flat area inside the neutron source is connected to the power supply.

[0011] According to one embodiment, the device has one or more neutron sources for generating neutrons that operate according to the lattice confinement fusion (LCF) principle. Neutron flux strengths of more than 1000 can be achieved with LCF-operated neutron sources. 12 n / s, of more than 10 13 n / s or more than 10 14 n / s can be achieved, so that with a number of 1 to 50 neutron sources arranged in the device, a power output of more than 10kW, more than 100kW, more than 200kW or more than 300kW can be achieved.

[0012] According to one embodiment, the neutron source or the multiple neutron sources for generating neutrons have an anode and cathode structure, of which at least either the anode or the cathode structure is configured to be used as a source for neutrons.

[0013] According to one embodiment, the neutron source or the multiple neutron sources each have an anode, a cathode and a first enriched surface, wherein the first enriched surface is enriched with isotopes and the first enriched surface comprises at least a part of a surface of the anode or a surface of the cathode.

[0014] The enriched surface can be further enriched with deuterium and / or tritium through suitable processes, such as electrolysis with a deuterated and / or tritiated heavy water solution containing conductive salts for electrolysis. This allows for sufficient deuterium enrichment of the surface to induce lattice confinement fusion with a substantial free neutron production rate.

[0015] The anode or cathode, or both, can have a cylindrical shape. This allows for the provision of cylindrical neutron sources with substantially axially symmetrical emission of free neutrons, which can be arranged near preferably also cylindrical containers containing a nuclear fuel or radioisotope suitable for interacting with the free neutrons emitted by the neutron source(s). According to one embodiment, the device comprises one or more first containers arranged next to the one or more neutron sources, the one or more containers being configured to hold a nuclear fuel.

[0016] Mixed oxide fuel (MOX) can be used as nuclear fuel, for example, a mixture of 80% uranium oxide (UO2) and 20% plutonium oxide (PUO2). Other mixtures are also conceivable, such as using only uranium oxide or using other nuclear fuels, such as thorium, uranium-molybdenum, or isotopes from spent fuel elements. The nuclear fuel can be in solid or liquid form. Liquefaction is achieved through suitable processes, such as melting or conversion to a molten salt.

[0017] According to one embodiment, the device has one or more second containers arranged next to or inside the one or more neutron sources.

[0018] According to one embodiment, the one or more second containers comprise a nuclear fuel comprising minor actinides (MA), which decay into lighter isotopes by interacting with free neutrons from the one or more neutron sources and with free neutrons from the nuclear fuel contained in the one or more first containers. Preferably, for the fission of the MA, the one or more neutron sources are operated such that the neutrons emitted from them have a fast spectrum, in particular a kinetic energy of 1 MeV (megaelectronvolt) or more, especially between 1 MeV and 10 MeV or more than 10 MeV, preferably 14.1 MeV.

[0019] According to one embodiment, the MA containing spent nuclear fuel consists of spent nuclear fuel from nuclear reactors, particularly from critically operated nuclear reactors. Spent nuclear fuel from such reactors, which cannot be further processed, is currently stored, but its long half-life causes problems. With the device according to the invention, a reduction in volume and a reduction in the half-life of spent nuclear fuel can be achieved by transmutation and conditioning the MA fed into one or more secondary containers (see Fig. 1). As shown in Fig. 1, the relative radiotoxicity can be reduced more quickly to the level of natural uranium ore by using conditioning and transmutation processes.

[0020] According to one embodiment, one or more secondary containers contain isotopes, e.g., Yb-176, which transmute into other isotopes, e.g., Lu-177, upon neutron bombardment. These other isotopes can then be used for specific further processes. According to this embodiment, the device can, for example, be used to produce radioisotopes that can be used for medical applications, e.g., in radiomolecular precision oncology. Depending on the isotope, different neutron energies are required, e.g., thermal energies for the production of Lu-177.

[0021] According to another application, the device according to the invention can be used to produce isotopes suitable for the operation of fusion power plants by introducing suitable radioisotopes into one or more second containers. Such materials include, for example, tritium.

[0022] According to one embodiment, the device comprises several containers, particularly hexagonal ones, arranged in a bundle and at least partially surrounding one or more neutron sources. Containers with a hexagonal cross-sectional shape allow for a higher packing density for the nuclear fuel within the device. This shape also permits the use of both fuel pins and plate-shaped fuels. A higher packing density results in a higher neutron flux or, more generally, higher device performance. The containers can also have a cylindrical or circularly symmetrical shape. The containers can comprise the first or second containers, or both, as well as the containers for holding the nuclear fuel and the neutron sources, or combinations thereof.

[0023] According to one embodiment, the device includes a feed device for nuclear fuel, such as MA, or isotopes into one or more first or second containers. The feed device can be configured to continuously supply the nuclear fuel or radioisotopes into the first or second containers at a specific flow rate.

[0024] According to one embodiment, the device includes a means of removing the nuclear fuel from one or more first or second containers. Removing the nuclear fuel ensures, in particular, that the decay products formed from the one or more neutron sources after interaction with free neutrons do not act as neutron absorbers near the reactor, thereby impairing or disabling its function through unwanted absorption of free neutrons.

[0025] According to one embodiment, the device for supplying the nuclear fuel, the device for removing the nuclear fuel, or both each have a pump with which nuclear fuel can be pumped through one or more of the first and second containers.

[0026] According to one embodiment, the reactor device includes a device for separating fission products from the nuclear fuel. The fission product separation device can be located in a closed circuit downstream of the zone of interaction between neutrons and the nuclear fuel or radioisotopes, so that fission products resulting from this interaction are present. In a device for the continuous feed of nuclear fuel into the container(s), the fission product separation device is preferably also located downstream of a zone of interaction between neutrons and the nuclear fuel.

[0027] According to the invention, a system is further provided comprising the device according to the invention and a closed circuit into which the device is integrated. The closed circuit is configured to supply nuclear fuel to a container in the device or to the reactor and, after the interaction between the neutrons and the nuclear fuel, to discharge it from the container. The device for supplying the nuclear fuel, the device for transporting the nuclear fuel, one or more pumps, or the device for separating fission products, or combinations thereof, can be arranged together with one or more first or second containers in the closed circuit.

[0028] Further features, properties and advantages of the device according to the invention will become apparent from the description of an embodiment with reference to the accompanying drawing, in which

[0029] Fig. 1 shows the relative radiotoxicity of nuclear fuel elements and natural sources.

[0030] Uranium as a function of time;

[0031] Fig. 2 shows a schematic cross-sectional view of the device according to a first embodiment;

[0032] Fig. 3 shows a schematic cross-sectional view of the device according to a second embodiment; and

[0033] Fig. 4 shows a schematic representation of a device for transmutation of isotopes according to one embodiment.

[0034] The device is described below with reference to the drawing, according to its embodiments. The devices shown in Figures 2 and 3 represent nuclear reactors, which are preferably operated in a subcritical range with a multiplication factor less than 1.

[0035] The hexagonal reactor shown in cross-section in Fig. 2 has an inner structure consisting of a first outer ring with neutron sources 1 arranged at the corners of a hexagon and a second inner ring with twelve further neutron sources 1. The neutron sources 1 are cylindrical, and neutrons are emitted from the neutron sources 1 in a substantially radially symmetrical manner. Cylindrical containers 3, designed to hold nuclear fuel, are arranged symmetrically to the reactor axis between and parallel to the neutron sources 1. The nuclear fuel can be, for example, mixed oxide fuel (MOX), consisting of a mixture of 80% uranium oxide (UO₂) and 20% plutonium oxide (PuO₂). Other mixtures or the use of uranium oxide alone are also conceivable.The neutron sources 1 can be formed by LCF systems whose neutron emission can be controlled by the supplied current. The neutron sources 1 shown, for example, have a total emission power of 43*io. 13 n / s. Neutrons with an energy of 14.1 MeV can be generated using the neutron sources 1. The neutrons emitted from the neutron sources 1 collide with the nuclear fuel located in the containers 3 and cause a fission reaction of the isotopes in the nuclear fuel. The neutron sources 1 and the containers 3 are surrounded by a reflector 5 made of or containing graphite. Helium is used as the coolant. The total power generated during reactor operation is, for example, approximately 66 kW. The number and arrangement of the neutron sources 1, as well as the number and arrangement of the containers 3, can vary.

[0036] The reactor shown in Fig. 3 is similar to the reactor shown in Fig. 2 and has 12 neutron sources 1 surrounding several containers 3, with additional containers 3 arranged between the neutron sources 1. Unlike the reactor according to Fig. 2, some of the containers 7 arranged inside are intended for other materials that are meant to interact with the neutrons emitted by the neutron sources 1 and the nuclear fuels present in the containers 3, such as minor actinides (MA), which originate, for example, from spent fuel elements in nuclear reactors and can no longer be used as fuel in them.By introducing these MA-containing nuclear fuels into containers 7, the volume of the nuclear fuel can be reduced by generating lighter isotopes through fission via interaction with free neutrons. These lighter isotopes have a significantly shorter half-life (< 1000 years) than the original long-lived radioisotopes in the spent fuel elements. To treat the MA with free neutrons in the reactor, these are extracted from unusable nuclear fuel elements in a process and preferably introduced into containers 7 in liquid form. This introduction into containers 7 can also be carried out as part of a closed loop. To implement a closed loop, one or more pumping devices, as well as one or more feed and separation devices, can be integrated into the loop.Furthermore, the pumped subcritical assembly includes additional containers 9 intended for holding isotopes, Yb-176, which, during reactor operation, interact with free neutrons from the fuel-filled containers 3 and from the neutron sources 1 and can be transmuted into desired isotopes, e.g., Lu-177, through decay reactions. The produced isotopes can be used for specific applications, such as medical applications.

[0037] The number and arrangement of containers 3 for nuclear fuel, containers for isotopes, and containers 9 for transmutation processes, and their placement within the arrangement, can vary, or only one type of container may be present. Containers 3 and 9 may also be of the same design, differing only in the material used for filling. Containers 3 or 9 may be configured to hold isotopes in solid or liquid form. Furthermore, containers 3 or 9, or both types of containers, may be configured for the flow of isotopes in liquid form and connected, for example, to a fixed circuit or one or more pumping devices (not shown in the figure).

[0038] The transmutation device shown in Fig. 4 comprises a circuit including a transmutation device 10 and a conditioning device 12. The transmutation device 10 includes a neutron source, such as a reactor previously described with reference to Fig. 2 or Fig. 3, or another type of reactor, such as those used for power generation. The arrangement should be configured to emit a fast neutron field with neutrons in the range of more than 1 MeV or more than 10 MeV, preferably 14.1 MeV. This allows isotopes, such as minor actinides, to be transmuted into lighter isotopes. The circuit includes a conditioning device 12, which is configured to feed isotopes, such as minor actinides, into the circuit and to remove fission products resulting from the interaction with the fast neutron field from the circuit.The fission products in the reactor can have the effect of absorbing a number of neutrons, which are then no longer available for fission of isotopes in the nuclear fuel or for transmutation. This can cause the reactor to stop running, as the number of neutrons produced is insufficient to sustain a chain reaction. Furthermore, a liquefaction device 18 for transmutation material is provided, with which transmutation material in solid form, such as MA, derived from spent nuclear fuel rods, can be liquefied in order to circulate it through the cycle. For this purpose, one or more pumps (not shown) are used. Numerous modifications can be made to the invention without altering its scope.

[0039] Reference symbol list:

[0040] 1 neutron source

[0041] 3 containers for nuclear fuel

[0042] 5 Reflector

[0043] 7 containers for transmutation material

[0044] 9 containers for radioisotopes

[0045] 10 Transmutation device

[0046] 12 Conditioning device

[0047] 14 Device for separating fission products

[0048] 16 Device for supplying transmutation material

[0049] 18 Liquefaction unit for transmutation material

Claims

Subsequent registration evo-partners GmbH, E32277WO Claims 1. Device which is configured to receive a nuclear fuel and has several neutron sources (i) which are configured to emit free neutrons which can interact with isotopes of the nuclear fuel, wherein the generation of neutrons in the neutron sources (1) is carried out by the lattice confinement fusion (LCF) principle and the neutron sources (i) are each configured such that the neutron flux strength of the generated neutrons is at least 10 10 neutrons per second and preferably more than 10 12neutrons per second and the neutron sources (i) have a power supply by means of which the neutron flux strength can be controlled, and wherein the device has several first containers (3) arranged next to the neutron sources (1), wherein the several first containers (3) are each configured to hold a nuclear fuel, and the device has one or more second containers (7, 9) arranged next to at least one of the neutron sources (1), wherein the one or the several second containers are configured to hold a nuclear fuel comprising minor actinides or is configured to hold isotopes that transmute into other isotopes under neutron bombardment, and wherein the device has several containers (3, 7, 9) with a hexagonal cross-section arranged in a bundle below the first containers and at least partially surrounding at least one of the several neutron sources (1).

2. Device according to claim 1, wherein the one or more neutron sources (1) are configured to produce neutrons with a kinetic energy of 1 MeV or more, with a kinetic energy between 1 MeV and 10 MeV or with a kinetic energy of more than 10 MeV.

3. Device according to claim 1 or 2, wherein the device comprises one or more neutron sources (1) in which the generation of neutrons takes place by plasma-induced fusion processes in a material surface of the neutron source (1) that is in contact with a plasma.

4. Device according to one of the preceding claims, wherein the one neutron source or the several neutron sources (1) each comprise an anode, a cathode and a first enriched surface, wherein the first enriched surface is enriched with isotopes and the first enriched The surface comprises at least a part of a surface of the anode or a surface of the cathode.

5. Device according to one of the preceding claims, wherein the device comprises a feed device (16) for nuclear fuel or isotopes into one or more first or second containers (3, 7, 9).

6. Device according to one of the preceding claims, wherein the device comprises a device for removing the nuclear fuel or isotopes from one or from the several first or second containers.

7. Device according to one of the preceding claims, wherein the device comprises a device (14) for separating fission products from the nuclear fuel.

8. Device according to one of the preceding claims, wherein the neutron sources are configured to emit neutrons with a kinetic energy of 14.1 MeV, preferably by deuterium-tritium fusion.

9. Device according to one of the preceding claims, wherein the generation of neutrons is carried out by plasma-induced fusion processes on a material surface in contact with a plasma.

10. Device according to one of the preceding claims, wherein the anode or cathode surfaces of the neutron sources are enriched with deuterium and / or tritium by electrolysis.

11. Device according to one of the preceding claims, wherein the neutron sources and / or containers have a cylindrical or hexagonal cross-sectional shape to increase the packing density.

12. Device according to one of the preceding claims, wherein the nuclear fuel consists of mixed oxide fuel (MOX), thorium, uranium-molybdenum or isotopes from spent fuel elements and is in solid or liquid form.

13. Device according to any of the preceding claims, wherein the containers are configured for the transmutation of minor actinides (MA) to reduce the volume and half-life of spent nuclear fuel. 14- Device according to one of the preceding claims, wherein the device is configured for the production of medical isotopes, such as Lu-177, by neutron irradiation of Yb-176.

15. Device according to one of the preceding claims, further comprising a closed circulating system for the continuous supply and removal of nuclear fuel or isotopes, including pumps for circulation.

16. Device according to one of the preceding claims, wherein a graphite reflector surrounds the neutron sources and containers and helium is used as a coolant.

17. Device according to one of the preceding claims, further comprising a liquefaction device for transmutation material.

18. System for the transmutation of radioisotopes, comprising a device according to one of the preceding claims and a closed circuit in which the device is integrated, wherein the closed circuit is configured to supply a nuclear fuel to a container (3, 7, 9) and to discharge it from the container (3, 7, 9) after the interaction between the neutrons and the nuclear fuel.

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