Manufacturing System and Manufacturing Method of Nuclear Fuel Component with Controlled Number of Nuclear Particles

Abstract

The optical counter of the present invention is used in a method and system for manufacturing a nuclear fuel component containing a uniformly distributed nuclear material in a known volume, and includes the following steps. Supply nuclear fuel particles along a channel provided with a conveyor configured to transport the nuclear fuel particles towards an outlet. Drive the conveyor until a target number of nuclear fuel particles pass through the outlet of the channel, and count the number of nuclear fuel particles passing through the outlet of the channel with an optical counter. After a target number of nuclear fuel particles have passed through the outlet of the channel, stop the conveyor. Supply the target number of nuclear fuel particles to a mold for shaping the nuclear fuel component, fill the remaining voids in the mold with a granular matrix material, uniformly distribute the target number of nuclear fuel particles within the granular matrix material, and convert the granular matrix material into a solid matrix material. By this method, a nuclear fuel component containing a uniformly distributed nuclear material can be manufactured in an accurate volume.

Description

Technical Field

[0001] Various embodiments disclosed herein generally relate to the preparation of nuclear fuel components consisting of particles of nuclear material uniformly distributed within a matrix.

Background Art

[0002] Generally, nuclear fuel components are composed of particles of nuclear material distributed within a matrix. The nuclear fuel particles may contain compounds of uranium, plutonium, or thorium. In various embodiments, the kernel of the nuclear fuel particle may include a ceramic kernel of nuclear metal. In the case of uranium, such ceramic kernels may include uranium oxides (UO2), uranium oxycarbides (UCO), uranium carbides (UC2 or UC), or uranium nitrides (UN). The nuclear fuel particles may include a kernel coated with a protective carbon or ceramic layer, or may include an uncoated kernel. In various embodiments, the nuclear fuel particles may include a kernel of a uranium ceramic compound coated with a protective ceramic or carbon layer.

[0003] The nuclear fuel component may be a tri-structural isotropic (TRISO) fuel particle. The TRISO particles include multiple layers of various thicknesses and different chemical compositions (carbon, SiC, or ZrC). To manufacture the TRISO particles, the ceramic nuclear fuel kernel is sequentially coated as follows.

[0004] Porous carbon layer Inner pyrolytic carbon layer Ceramic layer (e.g., silicon carbide, tungsten carbide, zirconium carbide, or zirconium nitride layer) Outer pyrolytic carbon layer

[0005] The nuclear fuel composition is composed of a matrix in which particles of coated or uncoated nuclear fuel kernels are uniformly distributed. The matrix surrounding the fuel may be a ceramic such as graphite, SiC or ZrC, or a resin such as a phenolic resin. The fuel composition may be shaped into spheres, cubes, or cylinders, and the fuel composition is classified as follows.

[0006] Generally homogeneous ones with uniformly distributed nuclear fuel particles Heterogeneous ones in which the inner core contains fuel particles dispersed in a matrix material and the outer layer consists of a matrix material without nuclear fuel Heterogeneous ones in which the inner core and the outer layer consist of a matrix material without nuclear fuel and there is a layer containing fuel in between Multilayer heterogeneous ones in which each layer contains different types or sizes of fuel particles

[0007] The fuel composition may contain a burnable poison within the matrix material or as individual particles embedded within the matrix material. Such burnable poisons prevent criticality due to excess nuclear fuel at the initial stage of the life of the fuel composition and are consumed by neutron absorption as the nuclear fuel is consumed.

[0008] A nuclear fuel composition containing TRISO particles may be used to produce a nuclear chain reaction in which one nuclear reaction causes one or more subsequent nuclear reactions. The neutron multiplication factor k represents the average number of neutrons from one nuclear fission reaction that cause another nuclear fission and is defined as follows.

[0009] k = (number of neutrons in one generation) / (number of neutrons in the previous generation)

[0010] Generally, the value of k determines the progress of the nuclear reaction. Specifically, When k is greater than 1, the chain reaction is supercritical and the number of neutrons increases exponentially. When k is less than 1, the chain reaction is subcritical and the number of neutrons decreases exponentially. When k is 1, the chain reaction is critical and the number of neutrons is kept constant.

Summary of the Invention

Problems to be Solved by the Invention

[0011] Since the total amount of fissile material present in the matrix material of the nuclear fuel component affects the value of the multiplication factor k, a system for manufacturing fuel components with a predictable mass load is desired. The fuel kernels are supposed to be uniformly distributed within the radioactive fuel component.

Means for Solving the Problems

[0012] In view of the current need for an improved method for providing a nuclear fuel component having a controlled distribution of nuclear fuel kernels, an overview of various embodiments is presented. The following overview may contain some simplifications and omissions, which are intended to highlight and introduce some aspects of various embodiments, but do not limit the scope of the invention.

[0013] In various embodiments disclosed herein, a method for manufacturing a nuclear fuel component having a uniformly distributed nuclear material of a known volume, comprising supplying nuclear fuel particles having a predetermined particle size along a channel having an outlet, the channel comprising a conveyor configured to convey the nuclear fuel particles through the outlet, driving the conveyor and continuing until a target number of the nuclear fuel particles pass through the channel and reach the outlet, counting the number of the nuclear fuel particles passing through the outlet of the channel with an optical counter, stopping the conveyor after the target number of the nuclear fuel particles have passed through the channel, supplying the target number of the nuclear fuel particles to a mold for forming a nuclear fuel component, filling the target number of the nuclear fuel particles in the mold with a granular matrix material, uniformly distributing the nuclear fuel particles within the granular matrix material, converting the granular matrix material into a solid matrix material, the volume of the nuclear material within the target number of nuclear fuel particles being known, and the nuclear fuel particles having a predetermined particle size comprising nuclear fuel kernels having an average kernel size of 200 to 800 microns and optionally having a coating.

[0014] According to various embodiments disclosed herein, it is required that the volume of the granular matrix material be sufficient to fill the voids in the mold after supplying the target number of nuclear fuel particles to the mold, and it is characterized in that the ratio of the volume of the nuclear material in the nuclear fuel particles to the volume of the solid matrix material in the lattice fuel material is determined to be known.

[0015] In various embodiments, the conveyor is a vibrating conveyor having a conveyor surface that travels along the length direction of the channel, and the motor is configured to vibrate the conveyor surface.

[0016] In various embodiments, the channel has a tubular or semi-cylindrical surface, the conveyor includes a rotating auger, the rotating auger is configured to drive the nuclear fuel particles along the tubular or semi-cylindrical surface, and the motor is configured to rotate the rotating auger.

[0017] In various embodiments, the conveyor is an inclined metal conveyor, and the conveyor may be driven by gravity supply, a motor configured to vibrate the conveyor surface, or a combination thereof. When the conveyor is driven by gravity supply, closing the gate at the outlet of the channel is included to stop the conveyor. When the conveyor is driven by vibration, stopping the motor is included to stop the conveyor.

[0018] In various embodiments, the conveyor has at least two rollers and an endless belt supported by the at least two rollers, the endless belt travels to the outlet along the length direction of the channel, and the motor is configured to rotate the at least two rollers.

[0019] In the disclosed method, the optical counter includes a laser disposed at the outlet of the channel, a sensor configured to receive the beam from the laser, and a control circuit. The laser is configured to transmit a beam, and the beam is interrupted each time the nuclear fuel particles pass through the channel. The sensor is configured to transmit a first signal each time the beam is interrupted. The control circuit receives the first signal from the sensor each time the beam is interrupted, calculates the number of nuclear fuel particles passing through the channel, and transmits a second signal to the motor driving the conveyor when the target number of nuclear fuel particles has passed through the channel. The second signal may stop the motor.

[0020] In the disclosed method, the optical counter includes a camera disposed at the outlet of the conveyor and a control circuit. The camera is configured to transmit a first signal for each of the nuclear fuel particles passing through the channel. The control circuit receives the first signal from the camera for each of the nuclear fuel particles passing through the channel, counts the nuclear fuel particles passing through the channel, and transmits a second signal to the motor driving the conveyor when the target number of nuclear fuel particles has passed through the channel. The second signal may stop the motor.

[0021] In the disclosed method, the optical counter includes a high-power LED disposed at the outlet of the channel, a digital camera, and a control circuit. The LED is configured to irradiate light onto the path of the particles passing through the channel. The digital camera is configured to receive the light from the LED and record a sequence of images. The control circuit analyzes each image in the sequence of images, confirms that each dark spot corresponds to a particle, records the total number of particles in the sequence of images until the target number of particles is achieved, transmits a signal to the motor driving the conveyor when the target number of particles is achieved, and preferably, the step of stopping the conveyor includes stopping the motor driving the conveyor after the motor receives the signal.

[0022] In various embodiments disclosed herein, the step of converting the granular matrix material into a solid matrix material preferably involves subjecting the nuclear fuel particles and the granular matrix material within the mold to hot isostatic pressing, cold isostatic pressing, spark plasma sintering, or uniaxial pressing. Further, the granular matrix material may include graphite, phenolic resin, or a metal carbide (e.g., SiC or ZrC), and the granular matrix material preferably further includes a binder. Additionally, the granular matrix material within the mold may include a polymer binder and / or a burnable poison, and suitable burnable poisons preferably include gadolinium, boron, hafnium, and / or their compounds.

[0023] In various embodiments disclosed herein, a system for manufacturing a nuclear fuel component having a known amount of nuclear material uniformly distributed, comprising a channel having an outlet, the channel being configured to receive nuclear fuel particles, the nuclear fuel particles including nuclear fuel kernels having an average kernel size of 200 to 800 microns and having any coating, a conveyor configured to convey the nuclear fuel particles along the channel and through the outlet, an optical counter configured to count the number of nuclear fuel particles passing through the outlet of the channel and transmit a first signal when a target number of the nuclear fuel particles have passed through the channel, and a motor configured to drive the conveyor and continue until the target number of nuclear fuel particles pass through the channel and reach the outlet, and to stop the conveyor after receiving the first signal from the optical counter.

[0024] The system further includes a mold that receives the target number of nuclear fuel particles and the particulate matrix material and uniformly distributes the target number of nuclear fuel particles within the particulate matrix material, and the mold is preferably a graphite mold, a metal mold, or a polymer or elastomer mold. Also, in various embodiments, the uniform distribution of the target number of nuclear fuel particles is achieved by vibrating the mold while filling the mold with the nuclear fuel particles and the particulate matrix material.

[0025] In various embodiments of the system, the conveyor is a vibrating conveyor having a conveyor surface that travels along the length of the channel, and the motor is configured to vibrate the conveyor surface. Also, in various embodiments of the system, the conveyor has at least two rollers and an endless belt supported by the at least two rollers, the endless belt travels to the outlet along the length of the channel, and the motor may be configured to rotate the at least two rollers.

[0026] The optical counter of the disclosed system includes a laser disposed at the outlet of the conveyor, a sensor configured to receive a beam from the laser, and a control circuit, the laser is configured to transmit the beam, the beam is interrupted each time a nuclear fuel particle passes through the channel, the sensor is configured to transmit a second signal each time the beam is interrupted, the control circuit receives the second signal from the sensor each time the beam is interrupted, counts the nuclear fuel particles passing through the channel, and may transmit the first signal to the motor when the target number of nuclear fuel particles has passed through the channel.

[0027] In the disclosed system, the optical counter includes a camera disposed at the outlet of the conveyor and a control circuit. The camera is configured to transmit the second signal for each nuclear fuel particle passing through the channel, and the control circuit receives the second signal from the camera for each nuclear fuel particle passing through the channel, counts the nuclear fuel particles passing through the channel, and may include transmitting the first signal to the motor when the target number of nuclear fuel particles has passed through the channel.

[0028] Various embodiments disclosed herein are methods of manufacturing nuclear fuel components having a predictable multiplication factor k, comprising supplying nuclear fuel particles along a channel having an outlet, the channel comprising a conveyor configured to convey the nuclear fuel particles through the outlet, driving the conveyor and continuing until a target number of the nuclear fuel particles have passed through the channel and reached the outlet, counting the number of nuclear fuel particles passing through the outlet of the channel with an optical counter, and after the target number of nuclear fuel particles have passed through the channel, stopping the conveyor, filling a mold with the target number of nuclear fuel particles and a granular matrix material, vibrating the mold to uniformly distribute the nuclear fuel particles within the granular matrix material, converting the granular matrix material into a solid matrix material, the nuclear fuel particles comprising nuclear fuel kernels having an average kernel size of 200 to 800 microns and having any coating.

Brief Description of the Drawings

[0029]

Figure 1

Figure 2A

Figure 2B

Figure 3

Figure 4

Figure 5

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Figure 8

Figure 9

Figure 10

DETAILED DESCRIPTION OF THE INVENTION

[0030] Referring to the drawings, like numbers refer to like parts or steps, and broad aspects of various embodiments are disclosed.

[0031] As used herein, the term "about" encompasses "plus or minus 10%" of the stated value. The term "substantially" may allow for up to a 15% variation from the value.

[0032] As used herein, the term "uniform distribution" means that the particles within the matrix are evenly distributed, indicating that any two sections of the same volume through the matrix material have substantially the same number of particles.

[0033] When discussing nuclear fuel particles, the term "kernel" refers to a radioactive ceramic particle. The term "particle" refers to a particle formed by coating a kernel with a carbon layer, a ceramic layer, or a combination thereof. The term "TRISO particle" refers to a specific class of kernels sequentially coated with a porous carbon layer, an inner pyrolytic carbon layer, a ceramic layer (e.g., a metal carbide, oxide, or nitride layer), and an outer pyrolytic carbon layer.

[0034] In various embodiments, the present disclosure describes systems and methods for producing a plurality of nuclear fuel components that each contain a precisely determined amount of uranium in each fuel component. Each fuel component contains approximately the same number of nuclear fuel kernels as the other fuel components. Each nuclear fuel kernel has approximately the same volume and mass as the other nuclear fuel kernels. The mass of each nuclear fuel kernel is within ±10% of the target mass M. The number of nuclear fuel kernels contained in each fuel component is counted by an optical counter. By counting each kernel as a nuclear fuel kernel with a mass of M±10% and counting until the target number N is reached, and then preparing a fuel component containing N kernels, a fuel component containing a predictable amount of nuclear material can be obtained. The fuel components are manufactured to contain kernels that are uniformly distributed within each fuel component. Each fuel component contains the same number of kernels within a matrix in which substantially identical kernels are uniformly distributed. The kernels can include ceramic and / or carbon coatings, but the mass of each kernel is substantially the same.

[0035] In conventional processes, nuclear fuel particles with a defined total mass are used rather than a defined number or volume of particles. In such a system, the number of particles cannot be easily predicted because the particles can include a mixture of small and large particles. Additionally, the particles are often kernels coated with a carbon layer, a ceramic layer, or a combination of a carbon layer and a ceramic layer. The mass of each particle includes contributions from the kernel and the coating layer, each with uncertainties. As a result, the error in determining the amount of nuclear material by measuring mass is greater than the error by counting a predefined number of particles.

[0036] As described above, measuring the amount of nuclear material based on mass can result in fuel components with kernels of variable size. If the kernels have different surface areas, i.e., a mixture of small and large kernels, the total kernel surface area decreases. Under this condition, k-infinity increases. The present disclosure describes a system that counts nuclear fuel kernels having substantially the same size and mass to produce a fuel component with a uniform kernel size and a low k-infinity. The various counting processes disclosed herein can be performed very rapidly, and measuring the amount of nuclear material based on the number of particles can be performed with improved accuracy compared to measuring based on particle mass without significantly sacrificing productivity.

[0037] Figure 1 shows a system for filling a mold 7 using nuclear fuel pellets or particles 2 and a granular matrix material 9. The first hopper 1 contains nuclear fuel pellets 2 (e.g., uranium oxide particles, uranium carbide particles, uranium oxycarbide particles, or TRISO particles). The nuclear fuel pellets 2 enter the channel 3 in the direction of arrow A and are supplied to the channel 3 including the vibrating conveyor 4. A motor 16 connected to the conveyor 4 by an actuator 15 vibrates the conveyor 4 and moves the particles 2 along the conveyor 4 towards the output opening 3a of the channel 3. When the particles 2 leave the channel 3 from the opening 3a, they enter the passage 8 and supply the particles 2 to the mold 7 through the output 8a. At the same time, the second hopper 10 contains the granular matrix material 9, and the granular matrix material 9 is supplied to the second passage 11 and then to the mold 7. After the mold 7 is filled with the granular matrix material 9 and the particles 2, a mass flow controller (e.g., valve 12) can be used to stop the flow of the matrix material 9 into the mold 7. The mold 7 is used to prepare a nuclear fuel component.

[0038] In various embodiments, the nuclear fuel pellets or particles 2 have a defined average particle size and / or a defined particle size range. Based on the information regarding the size of such particles 2, it is possible to well estimate the amount of nuclear material present in the nuclear fuel component prepared in the mold 7 by knowing the number of nuclear fuel pellets or particles 2 contained in the nuclear fuel component. Further, by using a known number of nuclear fuel pellets or particles 2 having a controlled average particle size or particle size range, a nuclear fuel component with a controlled surface area is provided. If all the particles have a similar surface area, the total kernel surface area is maximized. Under this condition, k-infinity, i.e., the ratio of neutrons from the current generation of nuclear fissions in a system of infinite size, is minimized.

[0039] To solve this, the system of FIG. 1 uses an optical sensor to count the number of particles entering the mold 7. As the particle 2 moves from the opening 3a of the channel into the passage 8 in the direction of arrow B, it passes through the optical sensor. The optical sensor includes a light source 5 and a sensor 6. In various embodiments, the light source 5 is a laser, which transmits a beam in the direction of arrow C to the sensor 6 and records the intensity of the beam from the light source 5. The sensor 6 is configured to communicate with a control circuit 6a.

[0040] As used herein, the term "control circuit" represents any type of information processing unit. The control circuit may be a central processing unit (CPU) external to the optical sensor that can communicate with the optical sensor through a wired or wireless communication network. The control circuit may be a microprocessor included within the optical sensor, particularly within the sensor 6. The control circuit may be a logic circuit or logic gate included within an integrated circuit within the sensor 6. The control circuit may be a combination of a logic gate included within an integrated circuit within the sensor 6 and a CPU or microprocessor.

[0041] Each time the particle 2 passes through the beam of the laser 5, the intensity of the beam decreases, and the sensor 6 sends a signal to the control circuit 6a. The control circuit 6a records the number of signals received from the sensor 6 and counts the number of particles passing through the sensor 6. When the target number of particles has passed through the sensor 6, the control circuit 6a sends a signal to the motor 16 to stop the motor 16 and thereby stop the vibrating conveyor 4. This ensures that the correct number of nuclear fuel pellets or particles 2 enters the mold 7. The control circuit can be implemented using logic gates implemented in an integrated circuit or using a CPU or microprocessor.

[0042] The control circuit 6a may be a sequential logic circuit implemented on an integrated circuit that counts the particles leaving the channel 3 until the target number is reached and then sends a signal to stop the motor 16. The logic circuit may be designed to reset the particle count to 0 after sending a signal to the motor 16.

[0043] The control circuit 6a may include a logic circuit implemented on an integrated circuit and a CPU or microprocessor. The logic circuit sends a signal to the CPU or microprocessor each time a particle leaves the channel 3, and the CPU or microprocessor counts the number of particles until the target number is reached and then sends a signal to stop the motor 16. In various embodiments, the logic circuit may be a NOT gate that sends a signal each time the particle 2 passes through the beam of the laser 5. In various embodiments, the logic circuit may be a two-input logic gate. For example, the sensor 6 may be configured to detect both a decrease in the laser intensity when the particle 2 passes through the beam of the laser 5 and the time T until the laser returns to its original intensity. This can exclude false signals due to temporary fluctuations in the laser intensity. The two-input logic gate may be, for example, an AND gate that sends a signal each time the particle 2 passes through the beam of the laser 5 when the following conditions are met: When the laser intensity falls below a reference intensity, and When the time until the laser intensity returns to its original intensity exceeds a minimum time T. The two-input logic gate may be an OR gate that sends a signal each time the particle 2 passes through the beam of the laser 5 when any of the following conditions are met: When the laser intensity decreases to a target value, or When the laser intensity decreases for more than a target time. The one-input or two-input logic gate can be assembled from a network of connected NAND gates.

[0044] The control circuit 6a may include a CPU or microprocessor configured to record the output from the sensor 6, count the particles leaving the channel 3 based on this output, and send a signal to stop the motor 16 when the target number is reached.

[0045] In various embodiments, the optical sensor includes a light source 5 and a sensor 6, where the sensor 6 may be a camera disposed at the outlet of the conveyor. The camera is configured to transmit a first signal each time a nuclear fuel particle exits the channel. The optical sensor includes a control circuit configured to receive the first signal from the camera each time a nuclear fuel particle exits the channel and calculate the number of nuclear fuel particles exiting the channel. The control circuit transmits a second signal to the motor driving the conveyor when the target number of nuclear fuel particles exiting the channel is reached, and that second signal stops the motor.

[0046] In various embodiments, the optical sensor includes an LED as the light source 5 and a camera as the sensor 6. The camera is disposed at the outlet of the conveyor and is configured to record a series of images of the particle flow exiting the conveyor. The camera is configured to sequentially transmit each image in the series of images to the control circuit. The control circuit is configured to sequentially analyze each image and detect dark spots, i.e., spots where the brightness of the image is below a threshold. Each dark spot corresponds to a particle. The control circuit counts the number of particles in each image and calculates the total number of nuclear fuel particles exiting the channel within the series of images. When the total number of nuclear fuel particles exiting the channel reaches the target value, the control circuit transmits a signal to the motor driving the conveyor, and upon receiving that signal, the motor stops the conveyor.

[0047] In various embodiments, the control circuit is configured to analyze the diameter or area of each dark spot, generally the particle size. The control circuit may transmit a warning signal if a threshold number or percentage of the particles are outside the target size range. Since the number of nuclear fuel pellets or particles 2 entering the mold 7 is known and the average particle size or particle size range of the nuclear fuel pellets or particles 2 is known, the number of pellets 2 and the total volume of the nuclear fuel material can be well estimated.

[0048] Finally, returning to FIG. 1, the mold 7 may be placed on a vibrating table 41 that vibrates by a motor 42 during the filling process. The vibration evenly distributes the nuclear fuel pellets or particles 2 within the matrix material 9. Thus, after the filling of the mold 7 is complete, a known number of nuclear fuel pellets or particles 2 having a known particle size are evenly distributed within a known amount of matrix material 9. The matrix material 9 within the mold is solidified by sintering and / or compression to produce a nuclear fuel component in which a known amount of uranium particles or pellets are evenly distributed within a known amount of matrix material.

[0049] In various embodiments, the mold includes a core element that is free of nuclear fuel kernels before being filled with nuclear fuel particles and matrix material. The nuclear fuel particles and matrix material are added to the mold so as to surround the core element, and the final fuel component includes a zone free of nuclear fuel particles and a zone including nuclear fuel particles uniformly distributed within the matrix material. The core element may be cylindrical, spherical, or cubic. The core element has a hollow hole, and a first zone including nuclear fuel particles uniformly distributed within the hollow hole of the core element exists, and a second zone surrounding the outer surface of the core element has nuclear fuel particles uniformly distributed therein.

[0050] An efficient distribution of fuel particles within the matrix is important, and k-infinity increases when: The distance between kernels decreases The average distance between the kernel and the end of the fuel component decreases When fuel kernels are very close to each other, they act as a single large kernel. When a kernel is close to the end of the fuel component and far from other kernels, k-infinity also increases. Uniformly distributed kernels of approximately the same size produce a more controllable nuclear chain reaction with reduced k-infinity.

[0051] In the prior art procedure, rather than a known number of particles with known particle sizes, uranium particles of known mass are used to fill the mold for the nuclear fuel component. Such a system may include a small number of large particles and a large number of small particles that contribute unevenly to the total mass. Even when vibrating during mold filling, in such a system, due to the non-uniform particle size distribution, uranium particles or pellets may not be uniformly distributed within the matrix material.

[0052] Furthermore, the method disclosed herein counts nuclear fuel kernels or coated nuclear fuel particles having a narrow kernel size distribution. By counting such particles, an accurate total mass of fissile material can be obtained. Simply weighing the particles as in the prior art is less accurate than counting the particles because the particle size distribution is not well controlled. Further, in the case of coated particles, determining the target amount of fissile material by weighing the mass of the coated particles is inaccurate due to the uncertainty in the kernel mass and the coating mass of each particle. TRISO particles and other coated particle fuels contain a significant amount of non-fissile material. Even when the total mass of the particles is known, due to the uncertainty in the combination of kernel mass and coating mass, a large uncertainty remains in the kernel mass of each coated fuel particle.

[0053] In various embodiments disclosed herein, the average fissile mass per kernel and the particle size are known before the addition of the non-fissile mass (e.g., the coating layer). The kernel size and / or the distribution of kernel mass is very narrow (e.g., ±10%), and the average value of the kernel mass is very representative. In various embodiments, the number of fuel particles within each fuel component is determined by dividing the target fissile mass of each fuel component by the fissile mass per known particle. This provides a more accurate result than simply measuring the total mass of the fuel particles. Since the mass of fissile material per kernel is accurately known, a wider range of coated fuel particle sizes can be accepted while maintaining the accuracy and precision of the fissile mass of the fuel component.

[0054] When measuring the coated particles by total mass, the number of kernels and the mass of the fissionable material per kernel are not known precisely, and the acceptable particle size range becomes narrow. For example, large particles may be rejected because they may have oversized kernels. Some of these particles may simply have a thick coating.

[0055] The particulate matrix material 9 is supplied from the hopper 10 to the mold 7 and is supplied until the mold is filled. Since the total volume of the nuclear fuel material in the mold is known, the volume of the matrix material in the mold 7 is also known. Thereby, the ratio of the volume of the nuclear fuel material to the volume of the matrix material can be determined.

[0056] In various embodiments, the nuclear fuel pellets or particles 2 should have a substantially uniform size. In the case of TRISO particles, the average size of the kernels is about 200 - 800 microns, 300 - 700 microns, or 350 - 500 microns in diameter, and the size of the average multi-layer coated TRISO particles is about 500 - 1500 microns, 600 - 1200 microns, or 800 - 1000 microns in diameter. If a set of particles is determined to have an unacceptable wide particle size range, for example, as shown in Figure 2A, if it contains unacceptable large particles 2a and unacceptable small particles 2b, the particles may be processed to remove particles outside the optimal size range. As shown in Figure 2A, the particle size range can be narrowed by sieving. The nuclear fuel pellets or particles pass through a high-mesh screen 39 that retains the large particles 2a, and then through a low-mesh screen 40 that retains the particles of the desired size and allows the small particles 2b to pass through. Thereby, the average size of the uranium kernels can be estimated. As described above, the optical counter of the apparatus of Figure 1 can directly measure the number of particles added to the mold 7.

[0057] In various embodiments, the particle size range can be narrowed with a roller classifier as shown in Figure 2B. The nuclear fuel pellets or particles 2 are supplied to hopper 43 and then to chute 44 and directed towards a pair of classification rolls 45 whose axes diverge and have a gap therebetween. At the beginning of the classification rolls 45, the small particles 2b pass through the gap and the large particles 2 and 2a are retained by the classification rolls. The small particles 2b are conveyed by the first classification chute 47 to the first container 48b. At the end of the classification rolls, the largest particles 2a are conveyed by chute 49 to the container 48a for oversize particles. The particles 2 of the target diameter pass through the gap at the point where the width of the gap corresponds to the target diameter and are supplied to the container 48 for receiving particles having the target diameter through the classification chute 47. One or more containers 48n may be arranged at different positions of the rolls 45 and configured to receive particles having different target diameters from different classification chutes 47. The intermediate-sized particles pass through the gap at an intermediate position along the classification rolls and are conveyed to the appropriate containers by the appropriate classification chutes respectively. This enables the collection of particles having a very narrow size range.

[0058] In various embodiments, the nuclear fuel kernels are classified with a roller classifier or a screen classifier to produce kernels having a narrow size distribution. As a result, the mass of the nuclear material contained in each particle is known. The kernels may then be coated with a ceramic layer, a carbon layer, or a mixture thereof. The coating may introduce some variation in the overall size of the particles, but each particle has substantially the same kernel size. Optionally, after coating the kernels, the coated particles are classified with a screen classifier or a roller classifier to produce particles having a narrow size distribution and provide nuclear fuel particles having the following characteristics: Substantially constant kernel size Substantially constant total coating thickness This enables the production of substantially homogeneous nuclear fuel particles.

[0059] If the average diameter of the spherical uranium oxide kernel is known to be about 500 microns, the volume of uranium oxide contained in each kernel is about 0.52 mm 3 3. Based on the exact number of nuclear fuel pellets or particles 2, the volume of uranium oxide within the mold 7 for the nuclear fuel component can be known. Further, if the volume of uranium oxide within the mold, or the volume of the coated uranium oxide particles, such as the volume of TRISO particles, is known, the amount of granular matrix material 9 added to the mold 7 can be determined, and the ratio of nuclear material to matrix material can be accurately determined. Specifically, an amount of granular matrix material equal to the void volume remaining within the mold after the nuclear fuel pellets or particles 2 are added to the mold 7 can be added to the mold 7.

[0060] Figure 3 shows the conversion of a defined number of nuclear fuel pellets or particles 2 and a defined amount of granular matrix material 9 into a nuclear fuel component. The mold 7 containing the particles 2 and the granular matrix material 9 is sealed with a closure element 7a and heated and / or pressurized to fuse the granular matrix material 9 into a solid matrix 13, such as a solid mass of sintered particles. The mold 7 and the closure element 7a are removed, leaving a nuclear fuel component containing the nuclear fuel pellets or particles 2 and the solid matrix 13. The nuclear fuel pellets or particles 2 may be bare kernels, ceramic-coated kernels, carbon-coated kernels, or kernels coated with carbon and ceramic layers (e.g., TRISO particles). Various materials that may be used as the inert matrix material for nuclear fuel include the following: Ceramics (e.g., MgO, ZrO2, CeO2, or SiC) Refractory materials (e.g., graphite) Ceramic-metal composites (cermets) Composites consisting of two or more ceramics (cerasors) Metals (e.g., stainless steel, zirconium, molybdenum, or tungsten)

[0061] In various embodiments, the granular matrix material 9 may contain a small amount of combustible poison. Combustible poisons have a high neutron absorption cross-section but are converted to substances with a relatively low absorption cross-section by combustion in the reactor. The negative reactivity of the combustible poison decreases over time. Suitable combustible poisons include gadolinium, boron, hafnium, or their compounds.

[0062] FIG. 4A shows an apparatus including a first embodiment of a vibrating conveyor. The tongue 4a on the conveyor 4 has holes, the first end of the cable or rope 20 is fixed to a solid surface (e.g., the floor), and the second end is fixed to the end of the first wheel 18. The cable or rope 20 passes through the holes in the tongue 4a, and a spring 21 may be incorporated into the cable or rope. The motor 16 rotates the second wheel 17, and the belt 19 driven by the wheel 17 rotates the wheel 18. When the wheel 18 rotates, the spring 21 alternately stretches and contracts, vibrating the conveyor 4 vertically.

[0063] FIG. 4B shows an apparatus including a second embodiment of a vibrating conveyor. The conveyor 4 is attached to a spring 23. The motor 16 is connected to an actuator 22, and the actuator 22 transmits the vibrating motion from the motor 16 to the conveyor 4. Due to the spring 23, the conveyor 4 can vibrate up and down.

[0064] In various embodiments, the system of FIG. 1 may be modified by replacing the vibrating conveyor with a rotating auger. The channel has a tubular or semi-cylindrical conveyor surface 50 that runs along the length of the channel to the outlet, as shown in FIG. 5A, and a screw auger 51 is installed therein. The conveyor is driven by rotating the screw auger 51 to carry the particles 2 in the helical screw 52 of the auger 51 along the conveyor surface 50 to the outlet. The motor 53 is configured to rotate the screw auger 51.

[0065] In various embodiments, the system of FIG. 1 may be modified by replacing the vibrating conveyor with an inclined metal conveyor surface. The channel has an inclined metal conveyor surface 54 that runs along the length of the channel to the outlet as shown in FIG. 5B. The conveyor may be driven by gravity feed, a motor 55 configured to vibrate the conveyor surface, or a combination thereof. When the conveyor is driven by gravity feed, closing the gate 56 at the channel outlet is included in stopping the conveyor. When the conveyor is driven by vibration, stopping the motor is included in stopping the conveyor.

[0066] FIG. 6 shows an apparatus including an endless belt conveyor. The conveyor 4b is a flexible belt carried by rollers 25 and 25a. The conveyor 4b is driven by a motor 16, and the motor 16 includes an actuator 24 that rotates the roller 25. The roller 25a may rotate as the conveyor 4b moves around the roller 25. Alternatively, the roller 25a may rotate by a second motor. As the rollers 25 and 25a carry the flexible belt of the conveyor 4b, the particles 2 are carried along the channel 3 and reach the outlet 3a. When the particles fall from the outlet 3a, they pass through the light source 5 and the sensor 6, and a signal is sent to the control circuit 6a each time a particle passes through the sensor 6. When a predetermined number of particles are detected, the control circuit 6a sends a signal to the motor 16, and the motor 16 stops the rotation of the roller 25, stopping the movement of the endless belt conveyor.

[0067] When the mold 7 is filled with nuclear fuel pellets or particles 2 and a defined amount of granular matrix material 9, the contents are heated and / or pressurized, and the granular matrix material 9 is converted to a solid matrix material 13 (see FIG. 3). This can be done by several techniques.

[0068] Figure 7 shows the preparation of nuclear fuel components by cold isostatic pressing, and Figure 7 shows the wet bag technique. A mold 7 containing nuclear fuel pellets or particles 2 and granular matrix material 9 is placed in a container 27. The mold 7 is a flexible mold and may be made of an elastomeric material (e.g., rubber). The opening of the mold is closed by a closure element 7a. In some embodiments, the mold 7 is a disposable mold, and the closure element 7a may have a diameter smaller than the inside of the mold 7. In some embodiments, the mold 7 is a reusable mold, and the closure element 7a has the same diameter as the inside of the mold 7, allowing the nuclear fuel components to be recovered without damaging the mold.

[0069] After the mold 7 is placed in the container 27, the container 27 is filled with a liquid material 26 (e.g., water) through a pipe 28 under high pressure. When the desired pressure is reached, the valve 29 of the pipe 28 is closed, and the pressure from the high-pressure liquid 26 is applied to the contents of the elastomeric mold 7 and applied until the granular matrix material 9 sinters into a solid mass of solid matrix material 13. In some embodiments, the liquid material 26 can be heated and both heat and pressure can be applied to the mold 7. The use of pressurized heated liquid may enhance the sintering process. The dry bag isostatic pressing method is known in the art and may be used to form nuclear fuel components.

[0070] Figure 8 shows the preparation of nuclear fuel components by hot isostatic pressing. A flexible elastomeric mold 7 containing nuclear fuel pellets or particles 2 and granular matrix material 9 is placed in a container 27. The opening of the mold is closed by a closure element 7a. In some embodiments, the mold 7 is a disposable mold, and the closure element 7a may have a diameter smaller than the inside of the mold 7. In some embodiments, the mold 7 is a reusable mold, and the closure element 7a has the same diameter as the inside of the mold 7, allowing the nuclear fuel components to be recovered without damaging the mold.

[0071] After the mold 7 is placed in the container 27, the container 27 is filled with a gas 30 (e.g., air, nitrogen, argon, or other inert gas) under high pressure through the pipe 28. When the desired pressure is reached, the valve 29 of the pipe 28 is closed, and the pressure of the pressurized gas 30 is applied to the contents of the elastomeric mold 7. Also, the gas 30 is heated to the sintering temperature. The heated pressurized gas 30 applies both heat and pressure to the mold 7, and is applied until the particulate matrix material 9 is sintered to the solid mass of the solid matrix material 13.

[0072] Figure 9 shows the preparation of nuclear fuel components by spark plasma sintering. A mold 33 having a hollow body is filled with nuclear fuel pellets or particles 2 and particulate matrix material 9. A lid 32 is placed on the mold 33 and pressed against the contents of the mold. The mold 33 and the lid 32 are made of a resistive material such as graphite. An electrical circuit 35 is connected to the mold 33 and the lid 32. A power source 34 and a switch 36 may be included in the circuit 35. When the switch 36 is closed, an electric current flows through the mold 33 and the lid 32 in the direction of arrow F. The mold 33 and the lid 32 are resistively heated, heating the matrix material 9 and sintering it to the solid matrix material 13. When the sintering process is complete, the switch 36 is opened to stop the current to the mold. When the mold and its contents are cooled, the lid 32 can be removed from the mold 33, and the completed fuel component containing the nuclear fuel particles 2 in the sintered solid matrix 13 can be removed from the mold.

[0073] Figure 10 shows the preparation of nuclear fuel components by uniaxial compression. The mold 38 with a hollow body is filled with nuclear fuel pellets or particles 2 and granular matrix material 9. A lid 37 is placed on the mold 38 and pressed against the contents of the mold in the direction of arrow G by a piston or other device 37a. Thereby, pressure is applied to the particles 2 and the granular matrix material 9, and it is compressed until the granular matrix material 9 is converted into a solid matrix material 13. In various embodiments, the mold may be heated to assist in the solidification or sintering of the granular matrix material 9. Although Figure 10 shows compression from one direction, the contents of the mold may be compressed by a piston driven in the opposite direction.

[0074] In the processes of forming nuclear fuel components by hot or cold isostatic pressing, spark plasma sintering, and uniaxial compression, the mold may be of any shape such as spherical, cylindrical, or cubic.

[0075] Although various embodiments have been described in detail with particular reference to certain aspects, it should be understood that the present invention is capable of other embodiments and that details thereof are capable of variation in various obvious respects. As will be apparent to those skilled in the art, modifications and variations can be made within the spirit and scope of the invention. Accordingly, the foregoing disclosure, description, and figures are for illustrative purposes only and do not limit the invention, which is defined only by the claims.

Explanation of Reference Numerals

[0076] 1... First hopper, 2... Nuclear fuel pellet (particle), 2a... Large particle, 2b... Small particle, 3... Channel, 3a... Output opening, 4... Conveyor, 5... Light source, 6... Sensor, 6a... Control circuit, 7... Mold, 8... Passage, 8a... Output, 9... Granular matrix material, 13... Solid matrix, 10... Hopper, 11... Second passage, 12... Valve, 15... Actuator, 16... Motor, 39... High mesh screen, 40... Low mesh screen, 41... Vibration table, 42... Motor

Claims

1. A method for manufacturing a nuclear fuel component having a nuclear material of a known volume uniformly distributed therein, comprising: Supplying nuclear fuel particles having a predetermined particle size along a channel having an outlet, the channel comprising a conveyor configured to convey the nuclear fuel particles through the outlet; Driving the conveyor and continuing until a target number of the nuclear fuel particles pass through the channel and reach the outlet; Counting the number of the nuclear fuel particles passing through the outlet of the channel with an optical counter; After a target number of the nuclear fuel particles have passed through the channel, stopping the conveyor; Supplying a target number of the nuclear fuel particles to a mold for forming a nuclear fuel component; Filling the target number of the nuclear fuel particles in the mold with a granular matrix material and uniformly distributing the nuclear fuel particles in the granular matrix material; Converting the granular matrix material into a solid matrix material; The volume of the nuclear material in the target number of nuclear fuel particles being known; The nuclear fuel particles having the predetermined particle size comprising nuclear fuel kernels having an average kernel size of 200 to 800 microns and having an optional coating, a method for manufacturing a nuclear fuel component.

2. The method according to claim 1, comprising: Requiring that the volume of the granular matrix material is sufficient to fill the voids in the mold after supplying the target number of nuclear fuel particles to the mold, and determining that the ratio of the volume of the nuclear material in the nuclear fuel particles to the volume of the solid matrix material in the nuclear fuel material is known, a method for manufacturing a nuclear fuel component.

3. The method according to claim 1, a method comprising: The conveyor is a vibrating conveyor having a conveyor surface running along the length direction of the channel; A method for manufacturing nuclear fuel components, characterized in that the motor is configured to vibrate the conveyor surface.

4. The method according to claim 1, wherein the channel has a tubular or semi-cylindrical surface, the conveyor includes a rotating auger, and the rotating auger is configured to drive the nuclear fuel particles along the tubular or semi-cylindrical surface, A method for manufacturing nuclear fuel components, characterized in that the motor is configured to rotate the rotating auger.

5. The method according to claim 1, characterized in that the conveyor is an inclined metal conveyor.

6. The method according to claim 1, wherein the optical counter includes a laser disposed at the outlet of the channel, a sensor configured to receive the beam from the laser, and a control circuit, the laser is configured to transmit a beam, the beam is interrupted each time the nuclear fuel particles pass through the channel, the sensor is configured to transmit a first signal each time the beam is interrupted, the control circuit receives a first signal from the sensor each time the beam is interrupted, calculates the number of nuclear fuel particles passing through the channel, and when the target number of nuclear fuel particles has passed through the channel, transmits a second signal to the motor driving the conveyor, and the second signal stops the motor. A method for manufacturing nuclear fuel components, characterized by the above.

7. The method according to claim 1, wherein the optical counter includes a camera disposed at the outlet of the conveyor and a control circuit, the camera is configured to transmit a first signal for each of the nuclear fuel particles passing through the channel, The control circuit receives a first signal from the camera for each of the nuclear fuel particles passing through the channel, counts the nuclear fuel particles passing through the channel, and when the target number of nuclear fuel particles has passed through the channel, transmits a second signal to a motor that drives the conveyor, and the second signal stops the motor. A method for manufacturing a nuclear fuel component, characterized in that.

8. The method according to claim 1, wherein the step of converting the granular matrix material into a solid matrix material includes subjecting the nuclear fuel particles and the granular matrix material in the mold to hot isostatic pressing, cold isostatic pressing, spark plasma sintering, or uniaxial pressing. A method for manufacturing a nuclear fuel component, characterized in that.

9. The method according to claim 1, wherein the granular matrix material includes graphite, phenolic resin, or metal carbide. A method for manufacturing a nuclear fuel component, characterized in that.

10. The method according to claim 9, wherein the metal carbide includes SiC or ZrC. A method for manufacturing a nuclear fuel component

11. The method according to claim 9, wherein the granular matrix material further includes a binder. A method for manufacturing a nuclear fuel component, characterized in that.

12. The method according to claim 1, wherein the granular matrix material further includes a burnable poison selected from gadolinium, boron, hafnium, and their compounds. A method for manufacturing a nuclear fuel component, characterized in that.

13. A system for manufacturing a nuclear fuel component having a known amount of nuclear material uniformly distributed, comprising a channel having an outlet, the channel being configured to receive nuclear fuel particles, The nuclear fuel particles include nuclear fuel kernels having an average kernel size of 200 to 800 microns and having any coating, A conveyor configured to convey the nuclear fuel particles along the channel and through the outlet; An optical counter configured to count the number of nuclear fuel particles passing through the outlet of the channel and transmit a first signal when the target number of nuclear fuel particles has passed through the channel; A motor configured to drive the conveyor and continue until the target number of nuclear fuel particles passes through the channel and reaches the outlet, and stop the conveyor after receiving the first signal from the optical counter. A manufacturing system for nuclear fuel components, characterized by comprising: A manufacturing system for nuclear fuel components, characterized in that:

14. The system according to claim 13, wherein: The system for manufacturing nuclear fuel components, characterized by having a mold that receives the target number of nuclear fuel particles and a granular matrix material, and uniformly distributes the target number of nuclear fuel particles within the granular matrix material.

15. The system according to claim 13, wherein: The conveyor is a vibrating conveyor having a conveyor surface that travels along the length direction of the channel, The motor is configured to vibrate the conveyor surface. A manufacturing system for nuclear fuel components, characterized in that:

16. The system according to claim 13, wherein the conveyor has at least two rollers and an endless belt supported by the at least two rollers, and the endless belt travels along the length direction of the channel to the outlet, The motor is configured to rotate at least two of the rollers. A manufacturing system for nuclear fuel components, characterized in that:

17. The system according to claim 13, wherein the optical counter includes a laser disposed at the outlet of the conveyor, a sensor configured to receive a beam from the laser, and a control circuit. The laser is configured to transmit the beam, and the beam is interrupted each time the nuclear fuel particles pass through the channel. The sensor is configured to transmit a second signal each time the beam is interrupted. The control circuit receives the second signal from the sensor each time the beam is interrupted, counts the nuclear fuel particles passing through the channel, and transmits the first signal to the motor when the target number of nuclear fuel particles has passed through the channel. A manufacturing system for nuclear fuel components is characterized by this.

18. The system according to claim 13, wherein the optical counter includes a camera disposed at the outlet of the conveyor and a control circuit. The camera is configured to transmit a second signal for each nuclear fuel particle passing through the channel. The control circuit receives the second signal from the camera for each nuclear fuel particle passing through the channel, counts the nuclear fuel particles passing through the channel, and includes transmitting the first signal to the motor when the target number of nuclear fuel particles has passed through the channel. A manufacturing system for nuclear fuel components is characterized by this.

19. The system according to claim 13, wherein the mold is a metal mold, a graphite mold, or a rubber mold. A manufacturing system for nuclear fuel components is characterized by this.

20. A method for manufacturing a nuclear fuel component having a predictable magnification factor k, Supply nuclear fuel particles along a channel having an outlet, the channel comprising a conveyor configured to convey the nuclear fuel particles through the outlet. Drive the conveyor and continue until a target number of the nuclear fuel particles pass through the channel and reach the outlet. Count the number of nuclear fuel particles passing through the outlet of the channel with an optical counter After the target number of nuclear fuel particles has passed through the channel, stop the conveyor. Fill the mold with the target number of nuclear fuel particles and the particulate matrix material, and by vibrating the mold, uniformly distribute the nuclear fuel particles within the particulate matrix material. Convert the particulate matrix material into a solid matrix material, wherein the nuclear fuel particles comprise nuclear fuel kernels having an average kernel size of from 200 to 800 microns and having any coating, a method for manufacturing a nuclear fuel component. The address registered for the applicant's identification number and the address described in the international publication are different in terms of the presence or absence of "Suite 300", but are substantially the same address.

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