Criticality safety control method for dissolvers

Abstract

The application discloses a kind of dissolver critical safety control methods, comprising the following steps: neutron absorber particle is added to dissolver, neutron absorber particle is used to absorb neutron, so that neutron absorber particle is suspended in spent fuel dissolving solution in dissolver, by monitoring the volume fraction of suspended neutron absorber particle in spent fuel dissolving solution is preset volume fraction, the critical safety control of dissolver is carried out.The application provides a kind of dissolver critical safety control method, can greatly reduce the nuclear reactivity of the system where dissolver is located on the basis of not increasing the solid component in dissolving tube, improve the cross-sectional area of dissolver, processing quality, the highest enrichment of processing component, while neutron absorber particle can be removed with insoluble residue in the process flow of sedimentation centrifugation, avoid the adverse effects introduced by adding soluble neutron absorbing material to carry out dissolver critical safety control on subsequent process and final product.

Description

Technical Field

[0001] This invention belongs to the field of nuclear fuel reprocessing technology, specifically relating to a critical safety control method for a dissolver. Background Technology

[0002] The dissolver is a key piece of equipment in spent fuel reprocessing facilities. Due to the uneven distribution of solid and liquid phases in the fuel pellets, the reactivity is high, making critical safety control difficult.

[0003] Traditional melter critical safety control relies primarily on geometric control methods. The melter is designed as a slender cylindrical shape and can only handle spent fuel assemblies with low initial enrichment.

[0004] With the increasing design requirements for improving melter capacity and the initial enrichment of processable spent fuel assemblies, critical safety control of melters has expanded to include methods such as solid neutron absorber control, soluble neutron absorber control, quality control, and enrichment-burnup control. Quality control, which limits the quality of spent fuel dissolved in each batch, significantly restricts the facility's processing capacity. The enrichment-burnup combined control method, by applying a burnup credit system, considers the overall decrease in reactivity due to increased core irradiation and cooling time, thus allowing for a certain computational margin and improving the economics of nuclear equipment or facilities designed for nuclear criticality safety. However, because the burnup depth of spent fuel assemblies is controlled by the nuclear power plant's fuel management scheme, critical safety control of the melter remains challenging at its minimum unloading burnup depth, often requiring the use of neutron absorbers to further increase the melter's processing capacity.

[0005] There are generally two ways to use neutron absorbing materials: one is to use solid neutron absorbers, and the other is to use soluble neutron absorbers.

[0006] For critical safety control methods of solid neutron absorbers, a fixed solid neutron absorber approach is generally adopted. Because the short segments of spent fuel sheared and slid down the inclined chute into the container's main support or hopper, this impacts the structure inside the support or hopper. Furthermore, if other components are installed inside the support or hopper, it may cause localized accumulation of the fuel segments. Therefore, solid neutron absorbers generally cannot be placed inside the support or hopper; they can only be placed outside. This approach has limited control over the most concentrated and reactive dissolution areas of easily fissile materials, and the size of the support or hopper remains a significant limitation.

[0007] For critical safety control methods of soluble neutron absorbers, the soluble gadolinium method is generally used. This involves limiting the gadolinium concentration in the solution within the dissolver to a certain limit to achieve critical safety control. Using soluble gadolinium can effectively reduce the reactivity of the dissolver and improve the equipment's processing capacity. However, soluble gadolinium becomes a difficult component to separate from the solution, requiring separation in subsequent processes. This has a certain adverse impact on the amount of high-level radioactive waste generated and the quality of the final uranium-plutonium product. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to address the above-mentioned deficiencies in the prior art by providing a critical safety control method for a solvent, thereby improving the cross-sectional area of ​​the solvent, the processing quality, and the maximum enrichment of the processing components.

[0009] The technical solution adopted to solve the technical problem of this invention is to provide a critical safety control method for a solvent, comprising the following steps:

[0010] Neutron absorber particles are added to the solvent to absorb neutrons, causing them to suspend in the spent fuel solution within the solvent. By monitoring the volume percentage of the suspended neutron absorber particles in the spent fuel solution to a preset volume percentage, critical safety control of the solvent is achieved.

[0011] Preferably, the neutron absorber particle comprises: a neutron absorber body and pores disposed within the neutron absorber body, the pores being isolated from the outside world. The pores are not in communication with the outside world.

[0012] Preferably, the porosity of the neutron absorber particles is 20% to 70%.

[0013] Preferably, the preset volume percentage is 0.01% to 5%.

[0014] Preferably, the particle size of the neutron absorber particles is 1 μm to 100 μm.

[0015] Preferably, the mass density of the neutron absorber particles is 100 ± 10% of the mass density of the spent fuel solution.

[0016] Preferably, the material of the neutron absorber particles includes one or more of the following: boron carbide, elemental boron, borosilicate, boron titanate, gadolinium oxide, samarium oxide, hafnium oxide, europium oxide, hafnium carbide, samarium hafnium oxide, europium hafnium oxide, dysprosium titanate, samarium titanate, hafnium titanate, europium titanate, dysprosium ferrite, terbium titanate, dysprosium aluminate, gadolinium aluminate, and terbium aluminate.

[0017] Preferably, the specific method for suspending the neutron absorber particles in the spent fuel solution in the dissolver is as follows:

[0018] Neutron absorber particles are added to the spent fuel dissolution solution in the dissolver, or neutron absorber particles are added to an acidic solution before adding the spent fuel assembly.

[0019] Preferably, the critical safety control method for the dissolver further includes the following steps:

[0020] The flow of the suspension of neutron absorber particles is controlled in the dissolver.

[0021] Preferably, the dissolver includes: a dissolver body and a filter mechanism disposed within the dissolver body. The filter mechanism is used to filter undissolved solids in the spent fuel assembly. The filter mechanism is provided with filter holes, and the particle size of the neutron absorber particles is smaller than the filter holes.

[0022] Preferably, the filtration mechanism includes: a large hanging planter disposed within the dissolver body and a small hanging planter disposed within the dissolver body. The dissolver body is provided with a dissolver inlet for adding spent fuel components. The large hanging planter is located above the small hanging planter and is provided with a first filter hole for initial filtration of undissolved solids in the spent fuel components entering through the dissolver inlet. The small hanging planter is provided with a second filter hole for further filtration of the filtrate flowing out of the first filter hole. The pore size of the second filter hole is smaller than that of the first filter hole, and the particle size of the neutron absorber particles is smaller than that of the second filter hole.

[0023] The beneficial effects of this invention are as follows: This invention provides a critical safety control method for a dissolver, which can significantly reduce the nuclear reactivity of the system containing the dissolver without increasing the solid components inside the dissolving tube, and improve the cross-sectional area, processing quality, and maximum enrichment of the processing components of the dissolver. At the same time, the neutron absorber particles can be removed along with the insoluble residues in the sedimentation and centrifugation process, avoiding the adverse effects on subsequent processes and the final product introduced by adding soluble neutron absorber materials for critical safety control of the dissolver. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the dissolver in Embodiment 2 of the present invention;

[0025] Figure 2 This is a partial cross-sectional view of the critical safety analysis model of adding suspended neutron absorber particles to the dissolver in Embodiment 2 of the present invention.

[0026] In the diagram: 1. Inclined chute; 2. Dissolver body; 3. Large hanging plant; 4. Small hanging plant; 5. Circulation tank; 6. Lower circulation pipe; 7. Upper circulation pipe; 8. Power unit; 9. Monitoring and analysis device. Detailed Implementation

[0027] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0028] The embodiments of this patent are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this patent, and should not be construed as limiting this patent.

[0029] Example 1

[0030] This embodiment provides a critical safety control method for a solvent, including the following steps:

[0031] Neutron absorber particles are added to the solvent to absorb neutrons, causing them to suspend in the spent fuel solution within the solvent. By monitoring the volume percentage of the suspended neutron absorber particles in the spent fuel solution to a preset volume percentage, critical safety control of the solvent is achieved.

[0032] The beneficial effects of this embodiment are as follows: This embodiment provides a critical safety control method for a dissolver, which can significantly reduce the nuclear reactivity of the system in which the dissolver is located without increasing the solid components inside the dissolving tube, and improve the cross-sectional area, processing quality, and maximum enrichment of the processing components of the dissolver. At the same time, the neutron absorber particles can be removed along with the insoluble residue in the sedimentation and centrifugation process, avoiding the adverse effects on subsequent processes and the final product introduced by adding soluble neutron absorber materials for critical safety control of the dissolver.

[0033] Example 2

[0034] This embodiment provides a critical safety control method for a solvent, including the following steps:

[0035] Neutron absorber particles are added to the solvent to absorb neutrons, causing them to suspend in the spent fuel solution within the solvent. By monitoring the volume percentage of the suspended neutron absorber particles in the spent fuel solution to a preset volume percentage, critical safety control of the solvent is achieved.

[0036] Specifically, in this embodiment, the neutron absorber particles are insoluble neutron absorber particles, and the neutron absorber particles are in ceramic form.

[0037] Preferably, the neutron absorber particle comprises: a neutron absorber body and pores disposed within the neutron absorber body, the pores being isolated from the outside world. The surface of the neutron absorber body is a sealing layer, which isolates the pores from the outside world, preventing the pores from communicating with the outside world and thus preventing solution from entering, dissolving, or corroding.

[0038] Preferably, the porosity of the neutron absorber particles is 20% to 70%. Specifically, in this embodiment, the porosity of the neutron absorber particles is 50%.

[0039] Preferably, the preset volume percentage is 0.01% to 5%.

[0040] Specifically, in this embodiment, the volume percentage of suspended neutron absorber particles in the spent fuel solution is monitored and analyzed by the monitoring and analysis device 9 to obtain a preset volume percentage.

[0041] Preferably, the particle size of the neutron absorber particles is 1 μm to 100 μm.

[0042] Preferably, the mass density of the neutron absorber particles is 100 ± 10% of the mass density of the spent fuel solution.

[0043] Preferably, the material of the neutron absorber particles includes one or more of the following: boron carbide, elemental boron, borosilicate, boron titanate, gadolinium oxide, samarium oxide, hafnium oxide, europium oxide, hafnium carbide, samarium hafnium oxide, europium hafnium oxide, dysprosium titanate, samarium titanate, hafnium titanate, europium titanate, dysprosium ferrite, terbium titanate, dysprosium aluminate, gadolinium aluminate, and terbium aluminate.

[0044] Preferably, the specific method for suspending the neutron absorber particles in the spent fuel solution in the dissolver is as follows:

[0045] Neutron absorber particles are added to the spent fuel dissolution solution in the dissolver, or neutron absorber particles are added to an acidic solution before adding the spent fuel assembly.

[0046] Preferably, the critical safety control method for the dissolver further includes the following steps:

[0047] The flow of the suspension of neutron absorber particles is controlled in the dissolver.

[0048] Specifically, in this embodiment, the method controls the suspension of neutron absorber particles to circulate in the dissolver through a power device 8, which is a pump.

[0049] Preferably, the dissolver includes: a dissolver body 2 and a filter mechanism disposed within the dissolver body 2. The filter mechanism is used to filter undissolved solids in the spent fuel assembly. The filter mechanism is provided with filter holes, and the particle size of the neutron absorber particles is smaller than the filter holes.

[0050] Preferably, the filtration mechanism includes: a large hanging plant 3 disposed within the dissolver body 2 and a small hanging plant 4 disposed within the dissolver body 2. The dissolver body 2 is provided with a dissolver inlet for adding spent fuel components. The large hanging plant 3 is located above the small hanging plant 4. The large hanging plant 3 is provided with a first filter hole for initial filtration of undissolved solids in the spent fuel components entering through the dissolver inlet. The small hanging plant 4 is provided with a second filter hole for further filtration of the filtrate flowing out of the first filter hole. The pore size of the second filter hole is smaller than that of the first filter hole, and the particle size of the neutron absorber particles is smaller than that of the second filter hole.

[0051] like Figure 1 As shown, specifically, the dissolver in this embodiment is a batch-operated dissolver, dissolving one spent fuel assembly at a time. After dissolution, the dissolving solution and insoluble cladding ends are removed, and the next dissolution operation begins. Specifically, the dissolver in this embodiment includes: an inclined chute 1, a dissolver body 2, a large hanging basket 3, a small hanging basket 4, a circulation tank 5, a lower circulation pipe 6, and an upper circulation pipe 7. The inclined chute 1 is located on the upper part of the dissolver body 2 and is used to add neutron absorber particles or a suspension of acid solution containing neutron absorber particles into the dissolver body 2. The upper circulation pipe 7 is located on the upper part of the dissolver body 2 and is also connected to the circulation tank 5. The lower circulation pipe 6 is located on the lower part of the dissolver body 2 and is also connected to the circulation tank 5. Furthermore, the dissolver also includes a solution circulation power unit 8, which provides power for solution circulation during the spent fuel dissolution process. Specifically, the dissolver body 2 in this embodiment is a dissolution pipe.

[0052] During the dissolution process, the sheared spent fuel segments fall into the large hanging planter 3 via the inclined chute 1, where they dissolve. The wall of the large hanging planter 3 is equipped with a first filter hole. The spent fuel segments dissolve in the large hanging planter 3, while the insoluble shells, ends, etc., remain in the large hanging planter 3. After dissolution is complete, the large hanging planter 3 is removed and poured out. The first filter hole of the large hanging planter 3 is to allow the dissolved liquid inside and outside the large hanging planter 3 to circulate.

[0053] The first filter hole allows the solution to flow. Fuel particles or various residue particles that pass through the first filter hole on the wall of the large spider plant 3 are collected by the small spider plant 4. The small spider plant 4 is used to collect insoluble residues that leak out of the large spider plant 3. The second filter hole is also to allow the solution inside and outside the large spider plant 3 to circulate, but the second filter hole is smaller. During dissolution, the solution circulation power device 8 provides the power for solution circulation. The solution enters from the lower circulation pipe 6 at the bottom of the dissolver body 2, flows upward, and flows through the small spider plant 4, the large spider plant 3, the dissolver body 2, and the upper circulation pipe 7 into the circulation tank 5, and then from the circulation tank 5 into the lower circulation pipe 6, forming a closed loop.

[0054] Applying the critical safety control method for the dissolver in this embodiment, before the dissolution begins, fine particles of insoluble ceramic neutron absorbers with a particle size of 1μm to 100μm are added to the dissolver at a certain percentage, or fine particles of insoluble ceramic neutron absorbers are added to an acid solution, specifically a nitric acid solution, in an acid conditioning device. The nitric acid solution is then used to dissolve spent fuel and is transferred to the dissolver together.

[0055] Because the density of the insoluble ceramic neutron absorber particles is comparable to the maximum mass density of the solution after dissolution in the dissolver, and the density of spent fuel dissolution solution varies within a range—as the uranium-plutonium concentration increases during dissolution, its density also gradually increases—it is qualitatively required that the mass density of the fine particles of the insoluble ceramic neutron absorber be comparable to the maximum mass density after dissolution. The neutron absorber particles have a tight, sealed surface layer, preventing solution entry, dissolution, or corrosion. Therefore, the insoluble ceramic neutron absorber particles form a dispersed suspension distribution in the circulating solution. The monitoring and analysis device 9, located at the upper circulation pipe 7, monitors and verifies the volume percentage of the fine neutron absorber particles. Ensuring that the volume percentage of the fine neutron absorber particles in the solution meets certain limits allows dissolution operations to begin, thus achieving critical safety control of the dissolver. After the spent fuel is sheared, the short segment of the spent fuel enters the large hanging planter 3, where the fuel pellets dissolve. The insoluble shell, end caps, etc. remain in the large hanging planter 3. After dissolution is completed, the fuel is removed from the large hanging planter 3 and poured out for processing. The dissolved liquid is then transferred to the dissolved liquid receiving equipment.

[0056] After dissolution, the solution undergoes sedimentation centrifugation to remove insoluble residues. During this process, the fine particles of the insoluble ceramic neutron absorber are removed along with the residue, avoiding the adverse effects on subsequent processes and the final product that would have been introduced by adding soluble neutron absorbers for critical safety control of the dissolver. The insoluble ceramic particles are then sent to the solid waste disposal process along with the residue.

[0057] Specifically, in this embodiment, the material for the insoluble ceramic neutron absorber particles is boron carbide ceramic particles, which have good corrosion resistance and neutron absorption performance. The processing technology is also relatively mature, the particle surface can be tightly sealed, and the internal density is adjustable. Other neutron absorbing materials are also optional, such as elemental boron, borosilicates, boron titanates, gadolinium oxide, samarium oxide, hafnium oxide, europium oxide, hafnium carbide, samarium hafnium oxide, europium hafnium oxide, dysprosium titanate, samarium titanate, hafnium titanate, europium titanate, dysprosium ferrite, terbium titanate, dysprosium aluminate, gadolinium aluminate, terbium aluminate, etc. When selecting materials, corrosion resistance, neutron absorption performance, surface tightness and sealing performance, and adjustable internal density should be comprehensively considered.

[0058] The critical safety control effect of this embodiment is analyzed. Without using a fixed solid neutron absorber or a soluble neutron absorber, the effective neutron multiplication factor k corresponding to the maximum reactivity of the dissolver is... eff Approximately 1.05.

[0059] Boron carbide ceramic particles with an average particle size of 50 μm were randomly dispersed in the solution of the dissolver. The cross-section at point 3 of the large hanging orchid in the critical safety analysis model considered the optimal slowing distribution during fuel particle dissolution, corresponding to the interphase grid distribution of fuel particles and solution shown in the diagram. The cross-section at the dissolution tube in the critical safety analysis model only considered the single-phase state of the solution. Whether considering the optimal slowing distribution during fuel particle dissolution or the single-phase state of the solution, the presence of insoluble ceramic particles dispersed and suspended in the solution, such as... Figure 2 As shown in the partial cross-sectional view of the critical safety analysis model, neutron absorber particles are distributed in the spent fuel solution.

[0060] Through simulation analysis using a three-dimensional Monte Carlo program and calculations using the three-dimensional Monte Carlo method, it was found that only 1‰ of the volume of insoluble ceramic neutron absorber particles is required to achieve the effective neutron multiplication factor k corresponding to the maximum reactivity of the dissolver. eff The concentration was reduced to below 0.93, meeting the critical safety limit requirements. Considering the total solution volume within the dissolver, less than 2 kg of boron carbide neutron absorber particles are needed per dissolution to meet the critical safety control requirements. Compared to the method of arranging discrete solid neutron poison rods on the outside of the large planter 3, the volume ratio of the neutron absorber material in this embodiment is reduced by 97%. Furthermore, due to the diffuse distribution of the neutron absorber material, the size of the large planter 3 and the dissolution tube can be further increased as needed, and only a small increase in the volume ratio of the insoluble ceramic neutron absorber particles is required.

[0061] Therefore, the critical safety control method for a solvent proposed in this embodiment is a highly efficient and feasible critical safety control method.

[0062] This embodiment relates to a critical safety control method for a dissolver. It employs fine particles of neutron-absorbing material in the form of insoluble ceramic. These particles absorb neutrons by circulating within the solution in the dissolver, relying on a mass density similar to that of the solution. The insoluble ceramic particles are dispersed and suspended within the dissolver. By monitoring and analyzing the volume ratio of the neutron-absorbing particles, the method ensures that the volume ratio of the neutron-absorbing particles in the solution within the dissolver is a preset ratio, meeting certain limit requirements, thereby achieving critical safety control of the dissolver.

[0063] The beneficial effects of this embodiment are as follows: This embodiment provides a critical safety control method for a dissolver, which can significantly reduce the nuclear reactivity of the system containing the dissolver without increasing the number of solid components inside the dissolver tube, thereby increasing the cross-sectional area, processing quality, and maximum enrichment of the processing components. Reactivity refers to an indicator characterizing the possibility of a chain reaction of easily fissile materials. Reducing system reactivity means reducing the possibility of a chain reaction of easily fissile materials in the system, thus making the equipment less prone to critical accidents and safer. The dissolver is a slender cylindrical shape, and its cross-sectional area cannot be too large due to critical safety control, which determines the amount of spent fuel the equipment can process. In addition, under the same cross-sectional area, the enrichment of spent fuel that the equipment can process is also limited due to critical safety control; it cannot be too high. The method of this embodiment can improve the enrichment limit.

[0064] Meanwhile, the neutron absorber particles can be removed along with the insoluble residue during the sedimentation and centrifugation process, avoiding the adverse effects on subsequent processes and the final product introduced by adding soluble neutron absorber materials for critical safety control of the dissolver.

[0065] Example 3

[0066] This embodiment provides a critical safety control method for a solvent, which differs from the critical safety control method for a solvent in Embodiment 2 in that:

[0067] The porosity of the neutron absorber particles in this embodiment is 20%.

[0068] In this embodiment, the preset volume percentage is 0.01%.

[0069] The neutron absorber particles in this embodiment have a particle size of 1 μm.

[0070] In this embodiment, the mass density of the neutron absorber particles is 110% of the mass density of the spent fuel solution.

[0071] The neutron absorber particles in this embodiment are made of elemental boron and borosilicate in a mass ratio of 2:1.

[0072] In this embodiment, the specific method for suspending the neutron absorber particles in the spent fuel solution in the dissolver is as follows:

[0073] Neutron absorber particles are added to an acidic solution, followed by the addition of spent fuel assemblies.

[0074] The beneficial effects of this embodiment are as follows: This embodiment provides a critical safety control method for a dissolver, which can significantly reduce the nuclear reactivity of the system containing the dissolver without increasing the number of solid components inside the dissolver tube, thereby increasing the cross-sectional area, processing quality, and maximum enrichment of the processing components. Reactivity refers to an indicator characterizing the possibility of a chain reaction of easily fissile materials. Reducing system reactivity means reducing the possibility of a chain reaction of easily fissile materials in the system, thus making the equipment less prone to critical accidents and safer. The dissolver is a slender cylindrical shape, and its cross-sectional area cannot be too large due to critical safety control, which determines the amount of spent fuel the equipment can process. In addition, under the same cross-sectional area, the enrichment of spent fuel that the equipment can process is also limited due to critical safety control; it cannot be too high. The method of this embodiment can improve the enrichment limit.

[0075] Meanwhile, the neutron absorber particles can be removed along with the insoluble residue during the sedimentation and centrifugation process, avoiding the adverse effects on subsequent processes and the final product introduced by adding soluble neutron absorber materials for critical safety control of the dissolver.

[0076] Example 4

[0077] This embodiment provides a critical safety control method for a solvent, which differs from the critical safety control method for a solvent in Embodiment 2 in that:

[0078] The porosity of the neutron absorber particles in this embodiment is 70%.

[0079] In this embodiment, the preset volume percentage is 5%.

[0080] The neutron absorber particles in this embodiment have a particle size of 100 μm.

[0081] In this embodiment, the mass density of the neutron absorber particles is 90% of the mass density of the spent fuel solution.

[0082] The material of the neutron absorber particles in this embodiment includes borosilicate.

[0083] The beneficial effects of this embodiment are as follows: This embodiment provides a critical safety control method for a dissolver, which can significantly reduce the nuclear reactivity of the system containing the dissolver without increasing the number of solid components inside the dissolver tube, thereby increasing the cross-sectional area, processing quality, and maximum enrichment of the processing components. Reactivity refers to an indicator characterizing the possibility of a chain reaction of easily fissile materials. Reducing system reactivity means reducing the possibility of a chain reaction of easily fissile materials in the system, thus making the equipment less prone to critical accidents and safer. The dissolver is a slender cylindrical shape, and its cross-sectional area cannot be too large due to critical safety control, which determines the amount of spent fuel the equipment can process. In addition, under the same cross-sectional area, the enrichment of spent fuel that the equipment can process is also limited due to critical safety control; it cannot be too high. The method of this embodiment can improve the enrichment limit.

[0084] Meanwhile, the neutron absorber particles can be removed along with the insoluble residue during the sedimentation and centrifugation process, avoiding the adverse effects on subsequent processes and the final product introduced by adding soluble neutron absorber materials for critical safety control of the dissolver.

[0085] Example 5

[0086] This embodiment provides a critical safety control method for a solvent, which differs from the critical safety control method for a solvent in Embodiment 2 in that:

[0087] The material of the neutron absorber particles in this embodiment includes gadolinium oxide.

[0088] In this embodiment, the preset volume percentage is 2.5%.

[0089] The beneficial effects of this embodiment are as follows: This embodiment provides a critical safety control method for a dissolver, which can significantly reduce the nuclear reactivity of the system containing the dissolver without increasing the number of solid components inside the dissolver tube, thereby increasing the cross-sectional area, processing quality, and maximum enrichment of the processing components. Reactivity refers to an indicator characterizing the possibility of a chain reaction of easily fissile materials. Reducing system reactivity means reducing the possibility of a chain reaction of easily fissile materials in the system, thus making the equipment less prone to critical accidents and safer. The dissolver is a slender cylindrical shape, and its cross-sectional area cannot be too large due to critical safety control, which determines the amount of spent fuel the equipment can process. In addition, under the same cross-sectional area, the enrichment of spent fuel that the equipment can process is also limited due to critical safety control; it cannot be too high. The method of this embodiment can improve the enrichment limit.

[0090] Meanwhile, the neutron absorber particles can be removed along with the insoluble residue during the sedimentation and centrifugation process, avoiding the adverse effects on subsequent processes and the final product introduced by adding soluble neutron absorber materials for critical safety control of the dissolver.

[0091] Example 6

[0092] This embodiment provides a critical safety control method for a solvent, which differs from the critical safety control method for a solvent in Embodiment 2 in that:

[0093] The material of the neutron absorber particles in this embodiment includes samarium oxide.

[0094] The beneficial effects of this embodiment are as follows: This embodiment provides a critical safety control method for a dissolver, which can significantly reduce the nuclear reactivity of the system containing the dissolver without increasing the number of solid components inside the dissolver tube, thereby increasing the cross-sectional area, processing quality, and maximum enrichment of the processing components. Reactivity refers to an indicator characterizing the possibility of a chain reaction of easily fissile materials. Reducing system reactivity means reducing the possibility of a chain reaction of easily fissile materials in the system, thus making the equipment less prone to critical accidents and safer. The dissolver is a slender cylindrical shape, and its cross-sectional area cannot be too large due to critical safety control, which determines the amount of spent fuel the equipment can process. In addition, under the same cross-sectional area, the enrichment of spent fuel that the equipment can process is also limited due to critical safety control; it cannot be too high. The method of this embodiment can improve the enrichment limit.

[0095] Meanwhile, the neutron absorber particles can be removed along with the insoluble residue during the sedimentation and centrifugation process, avoiding the adverse effects on subsequent processes and the final product introduced by adding soluble neutron absorber materials for critical safety control of the dissolver.

[0096] Example 7

[0097] This embodiment provides a critical safety control method for a solvent, which differs from the critical safety control method for a solvent in Embodiment 2 in that:

[0098] The material of the neutron absorber particles in this embodiment includes hafnium oxide.

[0099] The beneficial effects of this embodiment are as follows: This embodiment provides a critical safety control method for a dissolver, which can significantly reduce the nuclear reactivity of the system containing the dissolver without increasing the number of solid components inside the dissolver tube, thereby increasing the cross-sectional area, processing quality, and maximum enrichment of the processing components. Reactivity refers to an indicator characterizing the possibility of a chain reaction of easily fissile materials. Reducing system reactivity means reducing the possibility of a chain reaction of easily fissile materials in the system, thus making the equipment less prone to critical accidents and safer. The dissolver is a slender cylindrical shape, and its cross-sectional area cannot be too large due to critical safety control, which determines the amount of spent fuel the equipment can process. In addition, under the same cross-sectional area, the enrichment of spent fuel that the equipment can process is also limited due to critical safety control; it cannot be too high. The method of this embodiment can improve the enrichment limit.

[0100] Meanwhile, the neutron absorber particles can be removed along with the insoluble residue during the sedimentation and centrifugation process, avoiding the adverse effects on subsequent processes and the final product introduced by adding soluble neutron absorber materials for critical safety control of the dissolver.

[0101] Example 8

[0102] This embodiment provides a critical safety control method for a solvent, which differs from the critical safety control method for a solvent in Embodiment 2 in that:

[0103] The material of the neutron absorber particles in this embodiment includes europium oxide.

[0104] The beneficial effects of this embodiment are as follows: This embodiment provides a critical safety control method for a dissolver, which can significantly reduce the nuclear reactivity of the system containing the dissolver without increasing the number of solid components inside the dissolver tube, thereby increasing the cross-sectional area, processing quality, and maximum enrichment of the processing components. Reactivity refers to an indicator characterizing the possibility of a chain reaction of easily fissile materials. Reducing system reactivity means reducing the possibility of a chain reaction of easily fissile materials in the system, thus making the equipment less prone to critical accidents and safer. The dissolver is a slender cylindrical shape, and its cross-sectional area cannot be too large due to critical safety control, which determines the amount of spent fuel the equipment can process. In addition, under the same cross-sectional area, the enrichment of spent fuel that the equipment can process is also limited due to critical safety control; it cannot be too high. The method of this embodiment can improve the enrichment limit.

[0105] Meanwhile, the neutron absorber particles can be removed along with the insoluble residue during the sedimentation and centrifugation process, avoiding the adverse effects on subsequent processes and the final product introduced by adding soluble neutron absorber materials for critical safety control of the dissolver.

[0106] Example 9

[0107] This embodiment provides a critical safety control method for a solvent, which differs from the critical safety control method for a solvent in Embodiment 2 in that:

[0108] The material of the neutron absorber particles in this embodiment includes hafnium carbide.

[0109] The beneficial effects of this embodiment are as follows: This embodiment provides a critical safety control method for a dissolver, which can significantly reduce the nuclear reactivity of the system containing the dissolver without increasing the number of solid components inside the dissolver tube, thereby increasing the cross-sectional area, processing quality, and maximum enrichment of the processing components. Reactivity refers to an indicator characterizing the possibility of a chain reaction of easily fissile materials. Reducing system reactivity means reducing the possibility of a chain reaction of easily fissile materials in the system, thus making the equipment less prone to critical accidents and safer. The dissolver is a slender cylindrical shape, and its cross-sectional area cannot be too large due to critical safety control, which determines the amount of spent fuel the equipment can process. In addition, under the same cross-sectional area, the enrichment of spent fuel that the equipment can process is also limited due to critical safety control; it cannot be too high. The method of this embodiment can improve the enrichment limit.

[0110] Meanwhile, the neutron absorber particles can be removed along with the insoluble residue during the sedimentation and centrifugation process, avoiding the adverse effects on subsequent processes and the final product introduced by adding soluble neutron absorber materials for critical safety control of the dissolver.

[0111] Example 10

[0112] This embodiment provides a critical safety control method for a solvent, which differs from the critical safety control method for a solvent in Embodiment 2 in that:

[0113] The materials of the neutron absorber particles in this embodiment include samarium hafnium and europium hafnium, with a mass ratio of 1:2.

[0114] The beneficial effects of this embodiment are as follows: This embodiment provides a critical safety control method for a dissolver, which can significantly reduce the nuclear reactivity of the system containing the dissolver without increasing the number of solid components inside the dissolver tube, thereby increasing the cross-sectional area, processing quality, and maximum enrichment of the processing components. Reactivity refers to an indicator characterizing the possibility of a chain reaction of easily fissile materials. Reducing system reactivity means reducing the possibility of a chain reaction of easily fissile materials in the system, thus making the equipment less prone to critical accidents and safer. The dissolver is a slender cylindrical shape, and its cross-sectional area cannot be too large due to critical safety control, which determines the amount of spent fuel the equipment can process. In addition, under the same cross-sectional area, the enrichment of spent fuel that the equipment can process is also limited due to critical safety control; it cannot be too high. The method of this embodiment can improve the enrichment limit.

[0115] Meanwhile, the neutron absorber particles can be removed along with the insoluble residue during the sedimentation and centrifugation process, avoiding the adverse effects on subsequent processes and the final product introduced by adding soluble neutron absorber materials for critical safety control of the dissolver.

[0116] Example 11

[0117] This embodiment provides a critical safety control method for a solvent, which differs from the critical safety control method for a solvent in Embodiment 2 in that:

[0118] The materials of the neutron absorber particles in this embodiment include: dysprosium titanate, samarium titanate, hafnium titanate, and europium titanate, with a mass ratio of 1:2:3:4.

[0119] The beneficial effects of this embodiment are as follows: This embodiment provides a critical safety control method for a dissolver, which can significantly reduce the nuclear reactivity of the system containing the dissolver without increasing the number of solid components inside the dissolver tube, thereby increasing the cross-sectional area, processing quality, and maximum enrichment of the processing components. Reactivity refers to an indicator characterizing the possibility of a chain reaction of easily fissile materials. Reducing system reactivity means reducing the possibility of a chain reaction of easily fissile materials in the system, thus making the equipment less prone to critical accidents and safer. The dissolver is a slender cylindrical shape, and its cross-sectional area cannot be too large due to critical safety control, which determines the amount of spent fuel the equipment can process. In addition, under the same cross-sectional area, the enrichment of spent fuel that the equipment can process is also limited due to critical safety control; it cannot be too high. The method of this embodiment can improve the enrichment limit.

[0120] Meanwhile, the neutron absorber particles can be removed along with the insoluble residue during the sedimentation and centrifugation process, avoiding the adverse effects on subsequent processes and the final product introduced by adding soluble neutron absorber materials for critical safety control of the dissolver.

[0121] Example 12

[0122] This embodiment provides a critical safety control method for a solvent, which differs from the critical safety control method for a solvent in Embodiment 2 in that:

[0123] The material of the neutron absorber particles in this embodiment includes dysprosium ferrite.

[0124] The beneficial effects of this embodiment are as follows: This embodiment provides a critical safety control method for a dissolver, which can significantly reduce the nuclear reactivity of the system containing the dissolver without increasing the number of solid components inside the dissolver tube, thereby increasing the cross-sectional area, processing quality, and maximum enrichment of the processing components. Reactivity refers to an indicator characterizing the possibility of a chain reaction of easily fissile materials. Reducing system reactivity means reducing the possibility of a chain reaction of easily fissile materials in the system, thus making the equipment less prone to critical accidents and safer. The dissolver is a slender cylindrical shape, and its cross-sectional area cannot be too large due to critical safety control, which determines the amount of spent fuel the equipment can process. In addition, under the same cross-sectional area, the enrichment of spent fuel that the equipment can process is also limited due to critical safety control; it cannot be too high. The method of this embodiment can improve the enrichment limit.

[0125] Meanwhile, the neutron absorber particles can be removed along with the insoluble residue during the sedimentation and centrifugation process, avoiding the adverse effects on subsequent processes and the final product introduced by adding soluble neutron absorber materials for critical safety control of the dissolver.

[0126] Example 13

[0127] This embodiment provides a critical safety control method for a solvent, which differs from the critical safety control method for a solvent in Embodiment 2 in that:

[0128] The material of the neutron absorber particles in this embodiment includes terbium titanate.

[0129] The beneficial effects of this embodiment are as follows: This embodiment provides a critical safety control method for a dissolver, which can significantly reduce the nuclear reactivity of the system containing the dissolver without increasing the number of solid components inside the dissolver tube, thereby increasing the cross-sectional area, processing quality, and maximum enrichment of the processing components. Reactivity refers to an indicator characterizing the possibility of a chain reaction of easily fissile materials. Reducing system reactivity means reducing the possibility of a chain reaction of easily fissile materials in the system, thus making the equipment less prone to critical accidents and safer. The dissolver is a slender cylindrical shape, and its cross-sectional area cannot be too large due to critical safety control, which determines the amount of spent fuel the equipment can process. In addition, under the same cross-sectional area, the enrichment of spent fuel that the equipment can process is also limited due to critical safety control; it cannot be too high. The method of this embodiment can improve the enrichment limit.

[0130] Meanwhile, the neutron absorber particles can be removed along with the insoluble residue during the sedimentation and centrifugation process, avoiding the adverse effects on subsequent processes and the final product introduced by adding soluble neutron absorber materials for critical safety control of the dissolver.

[0131] Example 14

[0132] This embodiment provides a critical safety control method for a solvent, which differs from the critical safety control method for a solvent in Embodiment 2 in that:

[0133] The material of the neutron absorber particles in this embodiment includes dysprosium aluminate.

[0134] The beneficial effects of this embodiment are as follows: This embodiment provides a critical safety control method for a dissolver, which can significantly reduce the nuclear reactivity of the system containing the dissolver without increasing the number of solid components inside the dissolver tube, thereby increasing the cross-sectional area, processing quality, and maximum enrichment of the processing components. Reactivity refers to an indicator characterizing the possibility of a chain reaction of easily fissile materials. Reducing system reactivity means reducing the possibility of a chain reaction of easily fissile materials in the system, thus making the equipment less prone to critical accidents and safer. The dissolver is a slender cylindrical shape, and its cross-sectional area cannot be too large due to critical safety control, which determines the amount of spent fuel the equipment can process. In addition, under the same cross-sectional area, the enrichment of spent fuel that the equipment can process is also limited due to critical safety control; it cannot be too high. The method of this embodiment can improve the enrichment limit.

[0135] Meanwhile, the neutron absorber particles can be removed along with the insoluble residue during the sedimentation and centrifugation process, avoiding the adverse effects on subsequent processes and the final product introduced by adding soluble neutron absorber materials for critical safety control of the dissolver.

[0136] Example 15

[0137] This embodiment provides a critical safety control method for a solvent, which differs from the critical safety control method for a solvent in Embodiment 2 in that:

[0138] The materials of the neutron absorber particles in this embodiment include gadolinium aluminate and terbium aluminate, with a mass ratio of 2:3.

[0139] The beneficial effects of this embodiment are as follows: This embodiment provides a critical safety control method for a dissolver, which can significantly reduce the nuclear reactivity of the system containing the dissolver without increasing the number of solid components inside the dissolver tube, thereby increasing the cross-sectional area, processing quality, and maximum enrichment of the processing components. Reactivity refers to an indicator characterizing the possibility of a chain reaction of easily fissile materials. Reducing system reactivity means reducing the possibility of a chain reaction of easily fissile materials in the system, thus making the equipment less prone to critical accidents and safer. The dissolver is a slender cylindrical shape, and its cross-sectional area cannot be too large due to critical safety control, which determines the amount of spent fuel the equipment can process. In addition, under the same cross-sectional area, the enrichment of spent fuel that the equipment can process is also limited due to critical safety control; it cannot be too high. The method of this embodiment can improve the enrichment limit.

[0140] Meanwhile, the neutron absorber particles can be removed along with the insoluble residue during the sedimentation and centrifugation process, avoiding the adverse effects on subsequent processes and the final product introduced by adding soluble neutron absorber materials for critical safety control of the dissolver.

[0141] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A critical safety control method for a dissolver, characterized in that, Includes the following steps: Neutron absorber particles are added to the dissolver. The materials of the neutron absorber particles include one or more of the following: boron carbide, elemental boron, borosilicates, boron titanates, gadolinium oxide, samarium oxide, hafnium oxide, europium oxide, hafnium carbide, samarium hafnium oxide, europium hafnium oxide, dysprosium titanate, samarium titanate, hafnium titanate, europium titanate, dysprosium ferrite, terbium titanate, dysprosium aluminate, gadolinium aluminate, and terbium aluminate. The neutron absorber particles are used to absorb neutrons, causing them to suspend in the spent fuel dissolution liquid within the dissolver. The dissolver includes: a dissolver body and a filtration mechanism disposed within the dissolver body. The filtration mechanism includes: a large sieve and a small sieve disposed within the dissolver body. The filtration mechanism is used to filter undissolved solids from the spent fuel assembly. The filtration mechanism is equipped with filter holes, and the particle size of the neutron absorber particles is smaller than the filter holes. The dissolver body is equipped with a dissolver inlet for adding spent fuel assemblies. The large hanging planter is located above the small hanging planter and is equipped with a first filter hole for initial filtration of undissolved solids in the spent fuel assembly that enters through the dissolver inlet. The small hanging planter is equipped with a second filter hole for further filtration of the filtrate flowing out of the first filter hole. The pore size of the second filter hole is smaller than that of the first filter hole, and the particle size of the neutron absorber particles is smaller than that of the second filter hole. By monitoring the volume percentage of suspended neutron absorber particles in the spent fuel dissolution liquid to a preset volume percentage, the dissolver is subjected to critical safety control.

2. The critical safety control method for a dissolver according to claim 1, characterized in that, The neutron absorber particle includes: a neutron absorber body and pores disposed within the neutron absorber body, the pores being isolated from the outside world.

3. The critical safety control method for a dissolver according to claim 2, characterized in that, The porosity of neutron absorber particles is 20%–70%.

4. The critical safety control method for a dissolver according to claim 1, characterized in that, The preset volume percentage is 0.01% to 5%.

5. The critical safety control method for a dissolver according to claim 1, characterized in that, The particle size of the neutron absorber is 1 μm to 100 μm.

6. The critical safety control method for a dissolver according to claim 1, characterized in that, The mass density of the neutron absorber particles is 100 ± 10% of the mass density of the spent fuel solution.

7. The critical safety control method for a dissolver according to claim 1, characterized in that, The specific method for suspending neutron absorber particles in the spent fuel solution in the dissolver is as follows: Neutron absorber particles are added to the spent fuel dissolution solution in the dissolver, or neutron absorber particles are added to an acidic solution before adding the spent fuel assembly.

8. The critical safety control method for a dissolver according to claim 1, characterized in that, It also includes the following steps: The flow of the suspension of neutron absorber particles is controlled in the dissolver.

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