Device for use in a fuel assembly of a nuclear power plant, method for manufacturing a device and method for activating material in a nuclear power plant

Abstract

The invention relates to a device (20) for use in a fuel assembly (1) of a nuclear power plant, the device comprising at least one rod (30), each rod comprising a plurality of containers (32, 32b, 32c) having a space filled with a material to be activated, characterized in that the device further comprises a flow restrictor (24, 26) for a fuel assembly (1) of a nuclear power plant, the flow restrictor comprising a plurality of fingers (28) adapted to extend into a control rod guide tube (9) of the fuel assembly (1), respectively, when the flow restrictor is inserted into the fuel assembly (1), wherein the at least one rod (30) is connected to the fingers of the flow restrictor, wherein the containers (32) are subsequently arranged in the direction of the longitudinal axis of the respective rod (30).

Description

TECHNICAL FIELD

[0001] The invention relates to a device for use in a fuel assembly of a nuclear power plant, the device comprising at least one rod, each rod comprising a plurality of containers filled with a material to be activated.

[0002] Further, the invention relates to a method for manufacturing such a device, the method comprising the steps of providing a plurality of containers to be filled with a material to be activated, filling the material to be activated into the containers, and sealingly closing the containers.

[0003] According to another aspect, the invention relates to a method for activating a material in a nuclear power plant. BACKGROUND

[0004] Generally, technical and medical applications require radioisotopes.

[0005] EP 3091539 B1 discloses a system for generating isotopes such as cobalt-60 in a nuclear reactor startup source holder. The disclosure describes an irradiation target holder configured to fit in an open location inside a running commercial nuclear core including fuel assemblies. The invention relates to a boiling water reactor.

[0006] EP 2120241 B1 discloses a fuel rod assembly comprising at least one irradiation target holding device adapted to fit into a nuclear fuel rod. The irradiation target holding system comprises at least two holes for irradiation targets.

[0007] EP 2073214 B1 discloses a fuel rod with an irradiation target end piece. The irradiation target end piece has a connection element, e.g. in the form of a thread, configured to engage the end piece to an axial end of a nuclear fuel rod.

[0008] EP 1667166 B1 relates to a method for producing isotopes in a nuclear reactor. For example, a housing structure accommodating one or more targets can be placed in a control blade which is not used for reactor control but is moved or moved into a water rod or water channel during a cycle, in particular its end plug. The water rod serves to divert a moderator fluid from a lower region of a nuclear fuel bundle to an upper region. The described scheme is applicable to a boiling water reactor. SUMMARY

[0009] It is an object of the invention to provide an alternative device for irradiation targets in a pressurized water reactor.

[0010] According to one aspect, a device for use in a fuel assembly of a nuclear power plant, the device comprising at least one rod, each rod comprising a plurality of containers having a space to be filled with a material to be activated, characterized in that the device further comprises a flow restrictor for a fuel assembly of a nuclear power plant, the flow restrictor comprising a plurality of fingers adapted to extend into control rod guide tubes of the fuel assembly when the flow restrictor is inserted into the fuel assembly, wherein the at least one rod is connected with the fingers of the flow restrictor, wherein the containers are subsequently arranged in the direction of the longitudinal axis of the respective rod.

[0011] Further embodiments can relate to one or more of the following features, which can be combined in any technically feasible combination:

[0012] • the containers are connected to each other at the connection portion by one or more threaded connections or welds;

[0013] • the at least one rod further comprises a hollow tube extending from the fingers, wherein the containers are arranged within the hollow tube;

[0014] • each rod comprises a plurality of markings on the outer surface, wherein the markings are arranged in the direction of the longitudinal axis of the rod to identify the end of the space and / or the end of the containers, wherein the markings are in particular notches and / or indentations;

[0015] • the connection portion, in particular one or more threaded connections of the connection portion, is marked on the outer side of the rod, in particular with notches and / or indentations;

[0016] • the outer diameter of the containers or at least one hollow tube corresponds to the inner diameter of the control rod guide tubes, wherein in particular the outer diameter of the containers or at least one hollow tube is about 100 pm smaller than the inner diameter of the control rod guide tubes of the fuel assembly;

[0017] • the threaded connections are pressed or extruded after their assembly, in particular to form the markings of the connection portion and / or to prevent loosening of the threaded connections;

[0018] • the containers are made of stainless steel, Al or Zr alloy

[0019] • the material to be activated is a radioisotope Co, Mo, Sr, Y or a combination thereof;

[0020] • the rod is connected to the flow restrictor using one or more threaded connections or welds;

[0021] • the flow restrictor has the shape of a control rod assembly upper part;

[0022] • the fingers have a length adapted to extend about 15 cm into the control rod guide tubes when the device is inserted into the fuel assembly; and / or

[0023] • the flow restrictor is made of zirconium.

[0024] According to another aspect, a method for manufacturing such a device is provided, comprising the steps of:

[0025] - providing a plurality of containers, the containers having a space to be filled with material to be activated;

[0026] - filling the containers with material to be activated;

[0027] - sealingly closing the containers;

[0028] - connecting a predetermined number of containers to each other by at least one threaded connection to form at least one rod; and

[0029] - connecting the at least one rod to a finger of a flow restrictor of a fuel assembly for a nuclear power plant, the flow restrictor comprising a plurality of fingers.

[0030] Further embodiments can relate to one or more of the following features which can be combined in any technically feasible combination:

[0031] • forming the at least one rod by the predetermined number of containers comprises connecting the containers to each other by at least one threaded connection or welding to form the at least one rod, respectively;

[0032] • marking on the outer surface, wherein the marking is arranged in the direction of the longitudinal axis of the rod to identify an end of the space and / or an end of the container, wherein, in particular, the marking is arranged in the direction of the longitudinal axis at a predetermined distance from the end of the container and / or the space; and / or

[0033] • the marking is made by providing notches and / or indentations.

[0034] According to another aspect, a method for activating material in a nuclear power plant, in particular a pressurized water nuclear power plant, is provided, the method comprising the steps of:

[0035] - providing a device according to the embodiments disclosed herein;

[0036] - inserting the device into a fuel assembly and providing the fuel assembly into a nuclear core of the nuclear power plant during a shutdown of the nuclear power plant, or

[0037] inserting the device into a fuel assembly of a nuclear core during a shutdown of the nuclear power plant;

[0038] - operating the nuclear power plant;

[0039] - removing the fuel assembly from the nuclear core of the nuclear power plant during a shutdown of the nuclear power plant.

[0040] Further embodiments can relate to one or more of the following features which can be combined in any technically feasible combination:

[0041] determining the activation of the material to be activated, and in case the material is sufficiently activated: removing at least one rod from the fuel assembly, in particular cutting at least one rod into segments or opening at least one rod at the mark. BRIEF DESCRIPTION OF DRAWINGS

[0042] Further advantages, features, aspects and details are apparent from the dependent claims, the description and the drawings.

[0043] In order that the above mentioned and other features and advantages of the application can be understood in detail, a more particular description will be rendered by reference to example embodiments thereof which are illustrated in the appended drawings. For the purpose of the present description, like numbers refer to like objects. It will be understood that the drawings are not to scale, but are intended as illustrative only.

[0044] The appended drawings pertain to embodiments of the application and are described in the following:

[0045] Figure 1 a perspective view of a fuel assembly for a nuclear power plant is schematically shown;

[0046] Figure 2 a cross section of a device according to the application is schematically shown;

[0047] Figure 3 a top view of a device of Figure 2

[0048] Figure 4 a schematic cross-sectional side view of an embodiment of a device according to the application is shown;

[0049] Figure 5 a cross-sectional top view of a reactor pressure vessel comprising fuel assemblies of a core and their typical loading pattern is shown;

[0050] Figure 6 a cross-sectional top view of a reactor pressure vessel comprising the position of control rods and the position of instrumentation is shown;

[0051] Figure 7 a flow chart of a method according to an embodiment of the application is shown;

[0052] Figure 8 another flow chart of a method according to an embodiment is shown;

[0053] Figure 9 a cross section of a device according to the application is schematically shown; and

[0054] Figure 10 a cross section of a device according to the application is schematically shown.​ DETAILED DESCRIPTION

[0055] Figure 1 A perspective view of a fuel assembly 1 for a nuclear power plant is schematically shown. The nuclear power plant is used for power generation, wherein a nuclear reactor is used as a heat source. The nuclear power plant comprises a reactor vessel in which a plurality of fuel assemblies 1 are arranged. The plurality of fuel assemblies represents the reactor core of the nuclear power plant. With regard to Figure 4 and Figure 5 The arrangement of the fuel assemblies within the reactor core will be explained. Furthermore, a primary cooling, for example by a water circuit, is connected to the reactor vessel, which transports the heat generated by the fuel assemblies 1 during operation to a heat exchanger and / or a turbine. There are several types of nuclear power plants, in particular pressurized water reactors and boiling water reactors.

[0056] The fuel assembly 1 has a longitudinal axis X, along which the fuel assembly 1 extends.

[0057] Figure 1 The shown fuel assembly 1 is used to combine a plurality of fuel rods together. The fuel assembly 1 has a generally rectangular shape in a plane orthogonal to the longitudinal axis X. According to embodiments, the fuel assembly 1 has a typical length between 2m and 6m. In other embodiments, the fuel assembly can also have other shapes of the plane orthogonal to the longitudinal axis X, for example a hexagonal shape.

[0058] In some embodiments, the fuel assembly 1 comprises a bottom end piece 3. For example, the bottom end piece forms a plurality of nozzles. The nozzles are arranged to distribute a fluid flow in a regular manner.

[0059] Furthermore, the fuel assembly 1 comprises a top end piece 5. The top end piece 5 is arranged to carry the fuel assembly 1. Furthermore, the top end piece 5 can act as a plurality of nozzles for a cooling fluid of a primary cooling water circuit.

[0060] For example, the fuel assembly 1 comprises a plurality of fuel rods 7 extending parallel to the longitudinal axis. The fuel rods 7 are spaced apart in a regular pattern. In Figure 1 In the shown embodiment, the fuel rods 7 are arranged in a 17x17 pattern. In other embodiments, the fuel assembly 1 can comprise fuel rods 7 in a 14x14 pattern.

[0061] The fuel assembly 1 further comprises one or more control rod guide tubes 9 for control rods. The control rod guide tubes 9 for control rods are arranged at a specific position within the fuel assembly 1. The control rod guide tubes 9 extend parallel to the longitudinal axis X.

[0062] The control rod guide tubes 9 are fixed on the bottom end piece 3 and the top end piece 5.

[0063] The control rod guide tubes 9 together with the top end piece 5 and the bottom end piece 3 and some spacers form the skeleton of the fuel assembly 1. The fuel rods 7 are held by the spacers. For example, the spacers can comprise some spring elements for holding the fuel rods 7. Furthermore, the top end piece can also comprise springs to press against the fuel assembly due to the rather strong water flow in upward direction during operation of the nuclear power plant.

[0064] If control rods are inserted into the control rod guide tubes of the fuel assembly 1, these control rods move together. Therefore, these control rods are arranged in a rod cluster control assembly (RCCA).

[0065] As already mentioned above with respect to Figure 5 It is seen that not all fuel assemblies have a RCCA. Some fuel assemblies have a rod cluster control assembly (RCCA) and some do not. In the following, the rod cluster control assembly is also referred to as control rod assembly.

[0066] All fuel assemblies in a nuclear core should have similar thermal hydraulic characteristics. For the control rod guide tubes 9 which are not used for control rods, the control rod guide tubes 9 will be temporarily blocked by so-called flow restrictors which will be explained in the following. Thereby, the thermal hydraulic characteristics in all guide tubes are similar.

[0067] Figure 2 An embodiment of the device 20 for a fuel assembly 1 of a nuclear power plant is shown in a cross-sectional side view. Figure 3 A top view of the device 20 is shown. The device 20 comprises a coupling piece 22 at its upper end. The coupling piece 22 is provided in order to move the device 20 into and out of the fuel assembly 1. The device 20 has a longitudinal axis X which is similar to the fuel assembly 1.

[0068] Furthermore, the device 20 comprises a plate 24 which forms a plurality of arms 26. The arms are rigidly connected to the coupling piece 22. One or more fingers 28 extend from each arm 26 parallel to the longitudinal axis X. For example, two fingers 28 extend from each arm 26 parallel to the longitudinal axis X. The number of fingers depends on the design of the fuel assembly 1. For example, the device 20 can comprise 15-30 fingers. The lower side of the plate 24 is arranged to be placed onto the top end piece 5 of the fuel assembly 1. The fingers extend through the top end piece 5 into the control rod guide tubes 9. In other words, the length of the fingers 28 depends on the size of the fuel assembly 1.

[0069] For example, in one embodiment, the fingers have a length of at least 20 cm.

[0070] According to one embodiment, the fingers 28 have a length adapted to extend at least 15 cm into the control rod guide tube 9 when the device 20 is fully inserted into the fuel assembly 1. In one example, the fingers have a length adapted to extend 25 cm into the control rod guide tube 9 when the device 20 is fully inserted into the fuel assembly 1. Fully inserted means that the plate 24 is positioned on the top end piece 5 of the fuel assembly. In this case, the device 20 cannot be moved further down. According to the embodiment, the device is pressed by a spring 9 to ensure that it does not move during operation of the nuclear reactor. Thereby, it blocks the coolant flow and maintains the activated material at a constant height within the active zone.

[0071] The plurality of arms 26, in particular the link 22 and / or the fingers 28 form a flow restrictor in order to (hydraulically) simulate the missing RCCA. According to the embodiment, the flow restrictor has the shape of the control rod assembly upper part. The flow restrictor, in particular the link 22, the fingers 28 and / or the arms 26 are made of zirconium.

[0072] In one embodiment, the link 22 comprises a spring 29. The spring 29 is provided to fix the device 20 within the fuel assembly 1.

[0073] One rod 30 extends from one or more fingers 28 in the direction parallel to the longitudinal axis X. For example, the rod 30 forms a longitudinal extension of the finger 28. In other words, the outer diameter of the rod corresponds to the maximum diameter of the finger 28. In some embodiments, the finger 28 can have a local reduction at its upper end. For example, the reduction can have a length between 5 cm and 10 cm. The reduction is rotationally symmetrical. The rod 30 has a diameter, for example, such that it fits into the control rod guide tube 9. In other words, the outer diameter of the rod 30 corresponds to the inner diameter of the control rod guide tube 9. Thus, at least 10, in particular more than 15 rods 30 can be attached to the finger 28.

[0074] The rod 30 is connected to the finger 28, for example, using one or more threaded connections 34a. In other words, each rod is connected to the flow restrictor using a threaded connection 34a. For this purpose, the lower end of the finger 28 is provided with an external or internal thread. In other embodiments, the rod 30 can be welded or crimped to the finger 28.

[0075] For example, the outer diameter of the rod 30 can be between 7 mm and 15 mm, in particular between 9 mm and 11 mm, for example 10.4 mm. In some embodiments, the length l of the rod can be between 2 m and 4.80 m. The total length of the finger 28 and the rod 30 is between 3 m and 5 m. The maximum length, the maximum diameter and the maximum number of fingers are given by the reactor design. For example, the maximum length depends on the effective length of the nuclear core.

[0076] In the following, with respect to Figure 2 andFigure 3 The rods 30 are described in more detail. Each rod 30 comprises a plurality of containers 32. The containers 32b have a cylindrical shape with a circular cross-section. The containers 32 are connected to each other in a rigid manner at the connection portions 34b. The containers 32 are connected to each other in a rigid manner at the connection portions 34b by one or more threaded connections 35. For example, the containers have threaded ends in the direction of the longitudinal axis. For example, a first end in the axial direction can have an outer thread and a second end in the axial direction can have a corresponding inner thread, or vice versa. The inner thread cooperates with the outer thread. The length of the containers 32 in the direction of the longitudinal axis depends on the amount of material to be activated.

[0077] In some embodiments, an intermediate piece can be provided between two subsequent containers 32. The intermediate piece forms a connection portion 34b and comprises one inner thread or one outer thread at its ends in the longitudinal direction, respectively, which inner thread or outer thread together with the outer thread or inner thread forms a threaded connection 35. The intermediate piece can be made of stainless steel.

[0078] In embodiments, the containers 32 are arranged in order parallel to the longitudinal axis X, in particular the direction of the longitudinal axis of the respective rod 30.

[0079] In some embodiments, the fingers 28 and / or the connection portions 34b comprise expansion joints. The expansion joints can compensate for a thermal and irradiation-induced elongation of the respective rod 30 or parts thereof.

[0080] According to examples, the device 20 comprises no movable parts other than the spring 29 and / or the expansion joint(s). In other words, the rods 30, the fingers 28, the arms 26 and the coupling 22 are essentially immovable relative to each other.

[0081] Furthermore, the containers 32 can be filled with the material to be activated 36. For this purpose, the containers comprise a closed space. The length of the closed space within the container 32 for the material to be activated in the direction of the longitudinal axis X can be between 10 cm and 1 m. In some embodiments, the closed space inside the container has a cylindrical shape. The diameter of the closed space inside the container can be about 0.4 cm smaller than the outer diameter of the container 32. In some embodiments, the radius of the closed space inside the container can be between 3.5 and 4 micrometers, in particular between 3.8 and 4.2 micrometers, for example 4.1 micrometers. The diameter depends on the reactor design, in particular on the fuel assembly design.

[0082] According to embodiments, the plurality of containers 32 represents at least 70% of the length of each rod 30 in the direction of the longitudinal axis X, in particular up to 98% of this length.

[0083] In some embodiments, each rod 30 comprises a tip 38 at its distal end. The tip 38 is connected to the container 32 at the connection portion 34 by a threaded connection 34c. In embodiments, the length of the tip 38 in the direction of the longitudinal axis X is between 5 and 30 cm, in particular between 5 and 15 cm.

[0084] According to embodiments, the material to be activated material to be achieved is the radioisotope Co, Mo, Sr, Y or a combination thereof. In some embodiments, the material to be activated can be in liquid, solid or gaseous form. The achieved isotope is for example Co-60, Mo-99, Sr-90, Y-90. In other embodiments, the material to be activated is provided as a pellet or as a rod. For example, Co-59 can be provided in the form of a rod, for example a cylinder, with a radius of 4 microns and a length of 30 cm. Each container can comprise a different material.

[0085] Due to the possible dimensions of the closed space inside the container 32, more than 1 Kg of material to be activated can be inserted into a single rod 30.

[0086] In some embodiments, the container 32 is made of Zr or a Zr alloy, for example ZrY-4. In other embodiments, the container is made of stainless steel.

[0087] According to embodiments, the outer diameter of the container 32 corresponds to the outer diameter of the rod 30. In other words, the outer diameter of the container 32 corresponds to the inner diameter of the control rod guide tube 9.

[0088] In some embodiments, which can be combined with other embodiments disclosed herein, each rod 30 comprises markings on the outer surface, which are arranged in the longitudinal direction of the rod or in the direction of the longitudinal axis X, to identify the end of the container 32 and / or the space filled with the material to be activated. The markings are in particular notches and / or indentations. In some examples, the markings are arranged at approximately the same position in the direction of the longitudinal axis X at the end of the container 32 in the longitudinal direction, in particular slightly outside the closed space in the proximal and distal direction of the rod 30.

[0089] In one embodiment, the connection portion 34b, in particular the threaded connections 34a, 34c, 35, is provided with markings on the outer side of the rod, in particular with notches and / or indentations. The markings can be arranged in the direction of the longitudinal axis X at a predetermined distance from the end of the container 32 and / or the closed space, for example.

[0090] The threaded connections 34a, 34c, 35 are then pressed or squeezed to form a mark of the connection. By "then" is meant that the threaded connections 34a, 34c, 35 are pressed or squeezed after the individual components (e.g. the container 32, the tip 38 and the fingers 28) have been screwed together, respectively. Furthermore, the pressing or squeezing of the threaded connections 34a, 34c, 35 prevents loosening of the respective connection during operation of the nuclear power plant.

[0091] Figure 5 and Figure 6 shows a cross-sectional top view of the reactor vessel 50. These figures show a cross-section of the nuclear core 52. Within the nuclear core, a plurality of fuel assemblies 1 is arranged. The fuel assemblies 1 are shown in Figure 5 and Figure 6 are shown as squares. Their position within the nuclear core 52 of the fuel assemblies 1 depends on the cycle number. Older fuel assemblies are usually more peripheral compared to new fuel assemblies. The reactor pressure vessel 50 is filled with water of the first cooling circuit. For example, in the nuclear core of a nuclear reactor, there can be 193 fuel assemblies (KWU Vor / Konvoi type) or 241 fuel assemblies for an enhanced pressurized reactor (EPR).

[0092] Figure 6 shows the position of the fuel assemblies 1 provided with a control rod assembly 56. In other words, each of these fuel assemblies 1 is provided with a control rod assembly 56. Reference 58 denotes the position of the reactor pressure vessel instrument nozzle with instrument lance. Reference 60 denotes the power density detector and thermocouple. Reference 62 denotes the position of the air ball probe. About half of the fuel assemblies in the nuclear core 52 are provided with a rod cluster control assembly to control the power generated by the nuclear reactor.

[0093] According to the embodiment, the device 20 can be arranged at positions where no control rod assembly or RCCA is provided. For example, the device 20 can be positioned at about 90 to 180 positions in the nuclear core 52. For example, in a Konvoi type nuclear reactor, the device 20 can be positioned at 132 positions, while in an EPR it can be positioned at 152 positions.

[0094] The positioning can be chosen according to the desired activation. A higher activation is provided in the central region of the nuclear core 52 and a lower activation is provided in the peripheral region of the nuclear core 52.

[0095] In particular, when the assembly 20 is arranged at the periphery of the nuclear core 52, for example at the outermost positions, the assembly 20 can have a shielding effect so that the reactor pressure vessel 50 is less exposed to radiation. This can prolong the lifetime of the nuclear reactor. This can also avoid the use of specific shielded fuel assemblies.

[0096] Furthermore, the material to be activated and the amount of material can also have an influence on the core and shielding effects.

[0097] The assembly 20 prevents the cooling fluid or water of the primary circuit from flowing through the control rod guide tubes 9. The assembly 20 can be a hot-thermal hydraulic simulation of the missing RCCA.

[0098] Figure 7 A flow chart of a method according to an embodiment of the application is shown.

[0099] In step 1000, a plurality of containers 32 is provided to be filled with material to be activated. As mentioned above, the material to be activated can be the radioisotopes Co, Mo, Sr, Y or a combination thereof. In other embodiments, other materials to be activated can also be used.

[0100] Then, in step 1010, the material to be activated is filled into the containers 32. Subsequently, in step 1020, the containers 32 are sealingly closed, in particular under inert gas. For example, a lid can be provided and welded to the remaining part of the body of the container 32. The ends of the containers 32 in the axial direction are threaded, respectively, in order to form a threaded connection with another container 32 or with the finger 28 of the flow restrictor. For example, the upper end in the axial direction has an external thread and the lower end in the axial direction has an internal thread.

[0101] In step 1030, the containers 32 are connected to each other using the threaded connections to form at least one rod 30. For example, a predetermined number of containers 32 are rigidly connected to each other by the threaded connections. In some embodiments, the tip 38 is also fixed at one end of the rod 30. For example, the rigid connection is a connection, for example, in which the different containers cannot move relative to each other after being connected to each other.

[0102] In step 1040, the one or more rods 30 are connected to one finger 28 of a flow restrictor for a fuel assembly, respectively. As mentioned above, the flow restrictor comprises a plurality of fingers 28.

[0103] In step 1050, the ends of the containers can be marked on the rod. For example, the threaded connections 34a, 34b, 35 are squeezed or pressed. For example, the marking can be provided at a predetermined distance from the end of the container 32. For example, the marking can be provided at a predetermined distance from the end of the container 32. According to an embodiment, the marking is made by providing notches and / or indentations.

[0104] Figure 8 Another flow chart of a method according to an embodiment is shown, in particular a flow chart of a method for activating material in a nuclear power plant.

[0105] In step 1100, the device 20 is provided. For example, according to Figure 7The method production device 20 is shown.

[0106] In step 1110, the device 20 is inserted into the fuel assembly 1. For example, the rod 30 is inserted into the control rod guide tube 9 of the fuel assembly 1. In other words, the device 20 can be inserted only into those fuel assemblies 1, in which no control rod shall be inserted into the control rod guide tube 9. The position can be optimized depending on the position of the nuclear fuel assembly 1 within the nuclear core 52. For example, the device 20 can additionally or alternatively be rotated. Then, during the outage of the nuclear power plant, the fuel assembly 1 is inserted into the nuclear core 52 of the nuclear power plant.

[0107] In other embodiments, the device 20 is inserted into a fuel assembly already present in the nuclear core 52.

[0108] In step 1120, the device 20 is irradiated during operation of the nuclear power plant.

[0109] In step 1130, the operation of the nuclear power plant is stopped, i.e. the next outage of the nuclear power plant, the fuel assembly 1 is removed from the core of the nuclear power plant. For example, the fuel assembly 1 is moved into a fuel pool. In some embodiments, the device 20 is inspected and the activity of the material to be activated is determined. The device 20 can be separated from the respective fuel assembly 1.

[0110] In step 1140, it is determined whether the material is sufficiently activated.

[0111] In case the material is not sufficiently activated, it is again processed to step 1110 and the device 20 is again irradiated in the next cycle. For example, the position of the device 20 can be optimized or modified within the nuclear core 52 in order to obtain an optimal radiation distribution or activation. Additionally or alternatively, the device 20 is rotated by a certain angle, for example 90 degrees, 180 degrees or 270 degrees.

[0112] If the material is sufficiently activated, the rod 30 is removed from the fuel assembly 1 in step 1030 and opened or cut into segments, preferably at or according to the provided markings. The markings enable the cutting of the rod 30 without destroying the container, in particular the closed space of the container 32. Then, the material to be activated is removed and further processed, for example physically or chemically. In other embodiments, the nuclides can be separated. The activated material can be used for industrial or medical applications.

[0113] Figure 9 Further embodiments of the device 20 according to the present application are shown. Identical features are denoted with the same reference signs as in the preceding embodiments.

[0114] In this embodiment, the fingers 28 extend parallel to the direction of the longitudinal axis X with the hollow tubes 28b. The outer diameter of the hollow tubes 28b is about 100 pm smaller than the inner diameter of the control rod guide tubes 9 of the fuel assembly 1. In one example, the hollow tubes 28b are closed at the lower end in Figure 9 In a particular embodiment, the hollow tubes 28b are provided with a tip 38.

[0115] A plurality of containers 32b is arranged within the hollow tubes 28b. The containers 32b are connected to each other at the connection portions 34b, for example by a threaded connection or a weld. This is done in the same way as in the embodiments described with respect to Figure 2 and Figure 4 The length of the containers 32b in the direction of the longitudinal axis X depends on the material and the amount of material to be activated. The containers 32b have a cylindrical shape with a circular cross-section. The containers comprise an inner closed space for the material to be activated. According to some embodiments, the outer diameter of each container 32b is at least 100 pm smaller than the inner diameter of the hollow tubes 28b.

[0116] In one embodiment, Figure 9 The uppermost container in is connected to the finger 28 by a connection portion 34a. The connection portion 34a can be a threaded connection or a weld. In the embodiment of Figure 9 The containers 32b form the rod 30 together with the hollow tubes 28b.

[0117] Each hollow tube 28b is connected to the respective finger 28 by a threaded connection or a weld, in particular after the plurality of containers 32b has been connected to the finger 28.

[0118] Figure 10 A further embodiment of the device 20 according to the application is shown. Identical features are denoted by identical reference signs.

[0119] In this embodiment, the fingers 28 extend parallel to the direction of the longitudinal axis X with the hollow tubes 28b. The outer diameter of the hollow tubes 28b is about 100 pm smaller than the inner diameter of the control rod guide tubes 9 of the fuel assembly 1. In one example, the hollow tubes 28b are closed at the lower end in Figure 9 In a particular embodiment, the hollow tubes 28b are provided with a tip 38.

[0120] A plurality of containers 32c is arranged within the hollow tubes 28b. The containers 32c are not connected to each other. The length of the containers in the direction of the longitudinal axis X depends on the material and the amount of material to be activated. The containers 32c have a cylindrical shape with a circular cross-section. The containers comprise an inner closed space for the material to be activated. According to some embodiments, the outer diameter of each container 32c is at least 100 pm smaller than the inner diameter of the hollow tubes 28b. In Figure 9In an embodiment of the container 32b forms a rod 30 together with the hollow tube 28b.

[0121] Each hollow tube 28b is connected to the respective finger 28 by a threaded connection or a welded connection, in particular after a plurality of containers 32c have been introduced into the hollow tube 28b.

[0122] Figure 9 and Figure 10 The embodiment shown in Fig. 6 benefits from a higher protection of the containers, in particular considering the debris and contamination in the coolant. In the embodiment shown in Fig. 7, the containers can be replaced quickly. Figure 10

[0123] Figure 2 The embodiment shown in Fig. 5 provides a maximum space for the material to be activated as well as the highest conversion rate. Furthermore, the embodiment shown in Fig. 6 provides the fastest access to the material to be activated after irradiation. Figure 2

[0124] Embodiments of the present application allow the cultivation of desired isotopes. Furthermore, if the assembly is arranged at a peripheral position of the reactor core, the assembly can reduce the neutron flux and prolong the life of the nuclear power plant.​​

Claims

1. A device (20) for use in a fuel assembly (1) of a nuclear power plant, the device comprising at least one rod (30), each rod comprising a plurality of containers (32, 32b, 32c), the containers having spaces to be filled with a material to be activated, characterized in that, The device also includes flow restrictors (24, 26) for a fuel assembly (1) in a nuclear power plant, the flow restrictors including a plurality of fingers (28) adapted to extend into a control rod guide tube (9) of the fuel assembly (1) when the flow restrictor is inserted into the fuel assembly (1), wherein at least one rod (30) is connected to the fingers of the flow restrictor, wherein a container (32) is subsequently arranged in the direction of the longitudinal axis of the respective rod (30), wherein the device includes a coupling (22) at its upper end, wherein the coupling includes a device (20) for connecting the device (20). A spring (29) is fixed within the fuel assembly, wherein the containers (32, 32b) are connected to each other at the connection portion by one or more threaded connectors (34a, 34c, 35), wherein the threaded connectors (34a, 34c, 35) are pressed or squeezed after their assembly to form a mark on the connection portion (34b) and to prevent the threaded connectors (34a, 34c, 35) from loosening, wherein the mark is set in the direction of the longitudinal axis of the rod (30) to identify the end of the space and / or the end of the container (32, 32b).

2. The apparatus according to claim 1, wherein, The at least one rod (30) also includes a hollow tube (28b) extending from the finger (28), wherein the containers (32b, 32c) are arranged inside the hollow tube (28b).

3. The apparatus according to claim 1, wherein, Each bar (30) includes multiple markings on its outer surface.

4. The apparatus according to claim 1, wherein, The connecting portion (34b) is marked on the outer surface of the rod (30).

5. The apparatus according to claim 1, wherein, The outer diameter of the container (32) or the at least one hollow tube (28b) corresponds to the inner diameter of the control rod guide tube (9).

6. The apparatus according to claim 5, wherein, The outer diameter of the container (32) or the at least one hollow tube is approximately 100 μm smaller than the inner diameter of the control rod guide tube (9) of the fuel assembly (1).

7. The apparatus according to claim 1, wherein, The container (32) is made of stainless steel, Al or Zr alloy.

8. The apparatus according to claim 1, wherein the material to be activated is a radioactive isotope Co, Mo, Sr, Y, or a combination thereof.

9. The apparatus according to claim 1, wherein, The rod (30) is connected to the current limiter (24, 26) using one or more threaded connectors (34a) or welds.

10. The apparatus according to claim 1, wherein, The current limiters (24, 26) have the shape of the upper part of the control rod assembly.

11. The apparatus according to claim 1, wherein, The finger (28) has a length suitable for extending at least 15 cm into the control rod guide tube (9) when the device is inserted into the fuel assembly (1).

12. The apparatus according to claim 1, wherein, The current limiters (24, 26) are made of zirconium.

13. A method for manufacturing the apparatus according to claim 1, comprising the following steps: - Provide multiple containers (32) having spaces to be filled with the material to be activated; - The material to be activated is filled into the container (32); - The container (32) is sealed in a tight seal; - At least one rod is formed by a predetermined number of containers (32, 32b, 32c), said predetermined number of containers being arranged in the direction of the longitudinal axis of the respective rod; and - Connecting the at least one rod (30) to fingers (28) of flow restrictors (24, 26) for fuel assemblies (1) in a nuclear power plant, the flow restrictors (24, 26) comprising a plurality of fingers (28), wherein forming at least one rod by a predetermined number of containers comprises connecting the containers (32, 32b) to each other by at least one threaded connector (35) to form at least one rod (30), the method further comprising marking the connection portion on the outer surface, wherein the marking is provided in the direction of the longitudinal axis of the rod (30) to identify the end of the space and / or the end of the container (32), wherein the marking is formed by pressing or squeezing the threaded connector after assembly of the threaded connector to prevent loosening of the threaded connector (34a, 34c, 35).

14. The method according to claim 13, wherein, The mark is positioned at a predetermined distance from the end of the container and / or the space in the direction of the longitudinal axis (X).

15. The method according to claim 13, wherein, The markings are made by setting notches and / or indentations.

16. A method for activating materials in a nuclear power plant, the method comprising the following steps: - Provide the apparatus (20) according to claim 1; - Insert the device (20) into the fuel assembly (1) and, during a nuclear power plant shutdown, supply the fuel assembly (1) to the nuclear reactor core (52) of the nuclear power plant, or During the shutdown of the nuclear power plant, the device (20) is inserted into the fuel assembly (1) of the nuclear reactor core (52); - Operate the nuclear power plant; - During the shutdown of the nuclear power plant, the fuel assembly (1) is removed from the nuclear reactor core (52) of the nuclear power plant.

17. The method of claim 16, further comprising determining the activation of the material to be activated, and, if the material is sufficiently activated: removing at least one rod (30) from the fuel assembly (1) and cutting the at least one rod (30) into segments.

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