Micron-sized monodisperse uranium-thorium mixed particle and preparation method and preparation system thereof
阅读说明：本技术 一种微米级单分散铀钍混合微粒及其制备方法及制备系统 (Micron-sized monodisperse uranium-thorium mixed particle and preparation method and preparation system thereof ) 是由 王凡 胡睿轩 陈彦 沈彦 姜小燕 李力力 赵永刚 于 2021-09-02 设计创作，主要内容包括：本公开涉及一种微米级单分散铀钍混合微粒及其制备方法及制备系统。包括以下步骤：将含铀化合物和含钍化合物与溶剂混合获得铀钍混合溶液；在气溶胶发生条件下,使所述铀钍混合溶液在气溶胶发生装置中形成铀钍混合液滴,并在载气作用下沿所述溶胶发生器的第一垂直气路向下沉降,进入热分解装置；使所述铀钍混合液滴在载气作用下沿所述热分解装置的第二垂直气路向下沉降,在沉降过程中进行热分解,得到铀钍混合微粒。本公开制备得到的铀钍混合微粒可以达到微米级别且具有显著的单分散性,该铀钍混合微粒还具有规则的球形微粒形貌、较窄的粒度分布、更均一的铀钍元素组成；并且本公开还可以大幅提升混合微粒的制备回收效率。(The invention relates to a micron-sized monodisperse uranium-thorium mixed particle, and a preparation method and a preparation system thereof. The method comprises the following steps: mixing a uranium-containing compound and a thorium-containing compound with a solvent to obtain a uranium-thorium mixed solution; under the condition of aerosol generation, enabling the uranium-thorium mixed solution to form uranium-thorium mixed liquid drops in an aerosol generation device, and enabling the uranium-thorium mixed liquid drops to settle downwards along a first vertical gas path of the sol generator under the action of carrier gas to enter a thermal decomposition device; and enabling the uranium-thorium mixed liquid drop to settle downwards along a second vertical gas path of the thermal decomposition device under the action of carrier gas, and carrying out thermal decomposition in the settling process to obtain the uranium-thorium mixed particle. The uranium-thorium mixed particle prepared by the method can reach a micron level and has remarkable monodispersity, and the uranium-thorium mixed particle also has a regular spherical particle shape, narrower particle size distribution and more uniform uranium-thorium element composition; and the preparation recovery efficiency of the mixed particles can be greatly improved.)
1. The method for preparing micron-sized monodisperse uranium-thorium mixed particles is characterized by comprising the following steps of:
mixing a uranium-containing compound and a thorium-containing compound with a solvent to obtain a uranium-thorium mixed solution;
under the condition of aerosol generation, enabling the uranium-thorium mixed solution to form uranium-thorium mixed liquid drops in an aerosol generation device, and enabling the uranium-thorium mixed liquid drops to settle downwards along a first vertical gas path of the sol generator under the action of carrier gas to enter a thermal decomposition device;
and enabling the uranium-thorium mixed liquid drops to settle downwards along a second vertical gas path of the thermal decomposition device under the action of carrier gas, and performing thermal decomposition in the settling process to obtain the uranium-thorium mixed particles.
2. The method according to claim 1, wherein the uranium-containing compound is one or two of uranyl nitrate and uranyl sulfate, preferably uranyl nitrate; the thorium-containing compound is one or two of thorium nitrate and thorium sulfate, preferably thorium nitrate; the solvent is one or more of isopropanol, ethanol, acetone and water, and is preferably isopropanol.
3. The method according to claim 1 or 2, wherein the uranium-thorium mixed solution has a uranium content of 1 x 10-6～1×10-4g/ml, preferably 5X 10-6～5×10-5g/ml; thorium content of 1X 10-6～1×10-4g/ml, preferably 5X 10-6～5×10-5g/ml。
4. The method of claim 1, wherein the aerosol-generating conditions comprise: in the vibrating hole aerosol generating device, the flow rate of carrier gas is 40-50L/min, and the carrier gas is compressed air; the vibration frequency is 40-60 kHz; the sample introduction rate is 1.0-4.0 x 10-3cm/s; the stable pressure is 275 to 345 KPa.
5. The method of claim 1, wherein the conditions of thermal decomposition comprise: the thermal decomposition temperature is 800-900 ℃, and the thermal decomposition is carried out in a muffle furnace.
6. The method of claim 1, further comprising:
cooling the mixed particles obtained by thermal decomposition in a third vertical gas path of a cooler at the temperature of 5-25 ℃, wherein optionally, the cooler adopts cooling water as a cooling medium;
and collecting and filtering the cooled mixed particles to obtain the micron-sized monodisperse uranium-thorium mixed particles.
7. Micron-sized monodisperse uranium-thorium mixed particles, which are prepared by the method according to any one of claims 1 to 6.
8. The uranium-thorium mixed particulate according to claim 7, wherein a content ratio of the uranium-containing oxide to the thorium-containing oxide in the uranium-thorium mixed particulate is in a range of (100:1) to (1: 1); the particle size of the uranium-thorium mixed particle is 0.1-3 mu m.
9. A system for preparing micron-sized monodisperse uranium-thorium mixed particles is characterized by comprising an aerosol generating device (1) and a thermal decomposition device (2);
the aerosol generating device (1) is provided with a uranium-thorium mixed solution inlet, a carrier gas inlet and a mixed liquid drop outlet; along the height direction of the aerosol generating device (1), the uranium-thorium mixed solution inlet is arranged at the top of the aerosol generating device (1), and the mixed liquid drop outlet is arranged at the bottom of the aerosol generating device (1), so that a first vertical gas path is formed between the uranium-thorium mixed solution inlet and the mixed liquid drop outlet for mixed liquid drop sedimentation; the carrier gas inlet is arranged on the side wall of the aerosol generating device and used for providing carrier gas for the system;
the thermal decomposition device (2) is provided with a mixed liquid drop inlet and a mixed particle outlet, and the mixed liquid drop inlet is communicated with the mixed liquid drop outlet of the aerosol generating device (1) through a first vertical pipeline (9); the thermal decomposition device (2) is arranged below the aerosol generating device (1) along the material flowing direction; the mixed liquid drop inlet and the mixed particle outlet are respectively arranged at the top and the bottom of the thermal decomposition device (2) to form a second vertical gas path in the thermal decomposition device (2) for enabling the mixed liquid drops from the aerosol generating device (1) to continue to settle and to be thermally decomposed in the settling process.
10. A system according to claim 9, further comprising an air compressor (6), a compressed air outlet of the air compressor (6) being in communication with a carrier gas inlet of the aerosol generating device (1);
the mixed particle outlet of the thermal decomposition device (2) is communicated with a post-treatment device;
optionally, in the vertical direction, the post-treatment device comprises a cooling device (3), a collecting membrane (4) and a filter (5) which are sequentially communicated from top to bottom; the top of the cooling device (3) is provided with a mixed particle cooling inlet which is communicated with a mixed particle outlet of the thermal decomposition device (2) through a second vertical pipeline (10); a mixed particle cooling outlet is formed in the bottom of the cooling device (3), and a third vertical gas path is formed between the mixed particle cooling inlet and the mixed particle cooling outlet and is used for cooling the mixed particles from the thermal decomposition device (2) in the sedimentation process of the third vertical gas path;
optionally, the system further comprises a cooling water circulation device (7) for circulating cooling to the cooling device (3);
optionally, the first vertical pipe and the second vertical pipe are quartz pipes;
optionally, the aerosol generating device is a vibrating-orifice aerosol generating device and the thermal decomposition device is a split muffle.
Technical Field
The disclosure relates to the field of micron-sized particle preparation, in particular to micron-sized monodisperse uranium-thorium mixed particles and a preparation method and a preparation system thereof.
Background
Monodisperse, also called monodispersed systems or monodispersed systems, generally refer to dispersions in which the disperse phase has a single component and a narrow particle size distribution.
When nuclear material diffusion or nuclear events occur, it is desirable to track the source and history of the nuclear material, where the production time (age) of the material is an important analytical test. The age determination technology of nuclear materials is an important technical means for nuclear guarantee and nuclear evidence collection. The nuclear security environment sampling analysis technology is an effective means for detecting nuclear materials or nuclear activities. In the uranium conversion, uranium enrichment and element manufacturing processes, micron (mum) and submicron uranium-containing particles are released inside and outside a facility, an environment wiping sample is collected inside or around the nuclear facility, the uranium-containing particles are subjected to age detection, the ratio of Th-230 to U-234 in the uranium-containing particles is measured, the relevant information of the production time can be obtained, and whether illegal uranium enrichment activities exist is judged. In order to accurately measure the thorium-uranium ratio of uranium particles in an environmental sample, standard particles which are consistent with the properties of chemical components, physical forms, geometric dimensions and the like of an actual sample as far as possible are adopted to correct a measurement result. In addition, through the introduction of the standard particles, the traceability of the measurement can be established, and conditions are provided for effective international comparison of the measurement results.
Although a large number of researchers have studied the method for preparing microparticles in China, the preparation of monodisperse mixed microparticles is rarely involved at present, and no relevant literature is reported. Only the chinese atomic energy science institute (CIAE) successfully produced micron-sized monodisperse uranium oxide particles in a close field.
Abroad, n.erdmann et al, the joint research center for the european union (JRC) transuranics Institute (ITU), has internationally succeeded for the first time in producing monodisperse uranium oxide particles (monodisperse uranium oxide particles) having a particle size of 1 μm by the aerosol spray pyrolysis method, which is mature in producing uranium oxide particles, and research groups have turned to the production of plutonium particles and mixed particles, as described below. In 2003, Zitouni Ould-Dada et al also used a sol spray pyrolysis method to prepare quasi-monodisperse uranium oxide particles, which have particle size distribution in the range of 0.13-1.37 μm and cannot meet the requirement of monodispersion. By 2005, y.j.park et al produced microparticles using an aerosol generating device: after obtaining the aerosol, SiO with the grain diameter of 5, 10, 15 and 20 mu m is formed by gravity sedimentation and ignition2The particles, wherein U-235 with the abundance of 5% is adsorbed, are used as standard substances for fission track analysis, and although the particles prepared by the method have better dispersity, the particle size is larger than that of an environmental sample. In 2010, ITU continued to develop monodisperse particles of uranium oxide and mixed particles of uranium and plutonium for the purpose of determining the uranium and plutonium ion yields of SIMS, in addition to the previously developed monodisperse particles of uranium oxide.
The related art disclosed so far includes a technique for producing monodisperse uranium plutonium mixed particles established by ITU and a technique for producing monodisperse uranium oxide particles developed by CIAE. The preparation technology of the monodisperse uranium plutonium mixed particles established by ITU adopts a device framework of 'preheating, neutralizer, double gas paths (variable flow rate) and three muffle furnaces'; preheating is added on a dilution gas path; reducing particle agglomeration by adopting an electrostatic neutralizer; the flow rate of the carrier gas is changed from high to low (the flow rate of the carrier gas is 55L/min during preheating and 8L/min during thermal decomposition); besides the preparation gas path, an auxiliary gas path is added for cleaning; three muffle furnaces are connected in series for gradual temperature rise to promote thermal decomposition of particles. The whole equipment architecture of the scheme is complex (13 pieces of various equipment are needed to work cooperatively), the preparation process is complicated (the steps of aerosol preparation, desolvation, static electricity removal, gradual heating thermal decomposition, cooling, collection, tail gas treatment and the like are covered), the difficulty in controlling and optimizing the preparation parameters is high, the loss of prepared samples is high, and the recovery rate is low. The technology for preparing the monodisperse uranium oxide particles developed by CIAE adopts an equipment framework of 'preheating, neutralizer, single gas path (constant flow) and single muffle furnace'; reducing particle agglomeration by adopting an electrostatic neutralizer; preheating is added at the rear end of the device; the carrier gas flow is constant (35-45L/min); carrying out thermal decomposition by adopting a single muffle furnace; the technology optimizes the gas path of the carrier gas and the heating process, and 9 devices work cooperatively. Although the preparation technology of the monodisperse uranium oxide particles developed by CIAE simplifies the equipment architecture, the recovery rate of the prepared particles is still low, and is only about 1.2%.
Disclosure of Invention
The purpose of the disclosure is to provide micron-sized monodisperse uranium-thorium mixed particles, a preparation method and a preparation system thereof, which are used for preparing micron-sized monodisperse uranium-thorium mixed particles with regular appearance, narrow particle size distribution and consistent ratio of uranium to thorium, and obviously improve the preparation recovery rate of the particles.
In order to achieve the above object, a first aspect of the present disclosure provides a method for preparing micron-sized monodisperse uranium-thorium mixed particles, including the following steps: mixing a uranium-containing compound and a thorium-containing compound with a solvent to obtain a uranium-thorium mixed solution; under the condition of aerosol generation, enabling the uranium-thorium mixed solution to form uranium-thorium mixed liquid drops in an aerosol generation device, and enabling the uranium-thorium mixed liquid drops to settle downwards along a first vertical gas path of the sol generator under the action of carrier gas to enter a thermal decomposition device; and enabling the uranium-thorium mixed liquid drops to settle downwards along a second vertical gas path of the thermal decomposition device under the action of carrier gas, and performing thermal decomposition in the settling process to obtain the uranium-thorium mixed particles.
Optionally, the uranium-containing compound is one or two of uranyl nitrate and uranyl sulfate, and is preferably uranyl nitrate; the thorium-containing compound is one or two of thorium nitrate and thorium sulfate, preferably thorium nitrate; the solvent is one or more of isopropanol, ethanol, acetone and water, and is preferably isopropanol.
Optionally, in the uranium-thorium mixed solution, the uranium content is 1 × 10-6～1×10-4g/ml, preferably 5X 10-6～×10-5g/ml; thorium (Th)The content is 1 × 10-6～1×10-4g/ml, preferably 5X 10-6～5×10-5g/ml。
Optionally, the aerosol generating conditions comprise: in the vibrating hole aerosol generating device, the flow rate of carrier gas is 40-50L/min, and the carrier gas is compressed air; the vibration frequency is 40-60 kHz; the sample introduction rate is 1.0-4.0 x 10-3cm/s; the stable pressure is 275 to 345 KPa.
Optionally, the conditions of thermal decomposition include: the thermal decomposition temperature is 800-900 ℃, and the thermal decomposition is carried out in a muffle furnace.
Optionally, the method further comprises: cooling the mixed particles obtained by thermal decomposition in a third vertical gas path of a cooler at the temperature of 5-25 ℃, wherein optionally, the cooler adopts cooling water as a cooling medium; and collecting and filtering the cooled mixed particles to obtain the micron-sized monodisperse uranium-thorium mixed particles.
In a second aspect of the present disclosure, micron-sized monodisperse uranium-thorium mixed particles are provided, which are prepared according to the method of the first aspect of the present disclosure.
Optionally, the content ratio of the uranium-containing oxide to the thorium-containing oxide in the uranium-thorium mixed particles ranges from (100:1) to (1: 1); the particle size of the uranium-thorium mixed particle is 0.1-3 mu m.
The third aspect of the disclosure provides a system for preparing micron-sized monodisperse uranium-thorium mixed particles, which comprises an aerosol generating device and a thermal decomposition device; the aerosol generating device is provided with a uranium-thorium mixed solution inlet, a carrier gas inlet and a mixed liquid drop outlet; along the height direction of the aerosol generating device, the uranium-thorium mixed solution inlet is arranged at the top of the aerosol generating device, and the mixed liquid drop outlet is arranged at the bottom of the aerosol generating device, so that a first vertical gas path is formed between the uranium-thorium mixed solution inlet and the mixed liquid drop outlet and is used for mixed liquid drop sedimentation; the carrier gas inlet is arranged on the side wall of the aerosol generating device and used for providing carrier gas for the system; the thermal decomposition device is provided with a mixed liquid drop inlet and a mixed particle outlet, and the mixed liquid drop inlet is communicated with the mixed liquid drop outlet of the aerosol generating device through a first vertical pipeline; the thermal decomposition device is arranged below the aerosol generating device along the material flowing direction; the mixed liquid drop inlet and the mixed particle outlet are respectively arranged at the top and the bottom of the thermal decomposition device so as to form a second vertical gas path in the thermal decomposition device for enabling the mixed liquid drops from the aerosol generating device to continue to settle and to be thermally decomposed in the settling process.
Optionally, the system further comprises an air compressor, wherein a compressed air outlet of the air compressor is communicated with a carrier gas inlet of the aerosol generating device; the mixed particle outlet of the thermal decomposition device is communicated with the post-treatment device; optionally, in the vertical direction, the post-treatment device comprises a cooling device, a collecting membrane and a filter which are sequentially communicated from top to bottom; the top of the cooling device is provided with a mixed particle cooling inlet which is communicated with a mixed particle outlet of the thermal decomposition device through a second vertical pipeline; a mixed particle cooling outlet is formed at the bottom of the cooling device, and a third vertical gas path is formed between the mixed particle cooling inlet and the mixed particle cooling outlet and is used for cooling the mixed particles from the thermal decomposition device in the sedimentation process of the third vertical gas path; optionally, the system further comprises a cooling water circulation device for circularly cooling the cooling device; optionally, the first vertical pipe and the second vertical pipe are quartz pipes; optionally, the aerosol generating device is a vibrating-orifice aerosol generating device and the thermal decomposition device is a split muffle.
Through the technical scheme, the disclosure provides micron-sized monodisperse uranium-thorium mixed particles and a preparation method and a preparation system thereof. The uranium-thorium mixed particle prepared by the method can reach a micron level and has remarkable monodispersity, and the uranium-thorium mixed particle also has a regular spherical particle shape, narrower particle size distribution and more uniform uranium-thorium element composition; and the preparation recovery efficiency of the mixed particles can be greatly improved. On the preparation system. The method improves the framework of the instrument and equipment, changes the original horizontal preparation pipeline into a vertical preparation pipeline, effectively reduces the loss of particles and improves the yield of the particles; in addition, the vertical pipeline can reduce the stress of liquid drops and particles in different directions in the preparation process, and is beneficial to preparing mixed particles. The preparation process is greatly simplified, the core link of the preparation of the monodisperse uranium-thorium mixed particles is defined, the non-core link is simplified, the preparation processes of aerosol preparation, thermal decomposition, cooling and collection are finally formed, and the influence of the non-essential link is reduced; through simplifying the flow, the auxiliary equipment framework is adjusted, the equipment is simplified, the pipeline is shortened, the particle loss is reduced, and the particle recovery rate is improved.
Additional features and advantages of the disclosure will be set forth in the detailed description which follows.
Drawings
The accompanying drawings, which are included to provide a further understanding of the disclosure and are incorporated in and constitute a part of this specification, illustrate embodiments of the disclosure and together with the description serve to explain the disclosure without limiting the disclosure. In the drawings:
fig. 1 is a schematic diagram of an apparatus of a system for preparing micron-sized monodisperse uranium-thorium mixed particles provided by the present disclosure;
FIG. 2 is a scanning electron microscope image of uranium-thorium mixed particles prepared in example 1;
FIG. 3 is a particle size distribution diagram of uranium-thorium mixed particles prepared in example 1;
FIG. 4 is a scanning electron microscope image of uranium-thorium mixed particles prepared in example 2;
FIG. 5 is a particle size distribution diagram of uranium-thorium mixed particles prepared in example 2;
FIG. 6 is a scanning electron micrograph of uranium-thorium mixed particles prepared in example 3;
FIG. 7 is a particle size distribution diagram of uranium-thorium mixed particles prepared in example 3;
FIG. 8 is a scanning electron micrograph of uranium-thorium mixed particles prepared in example 4;
fig. 9 is a particle size distribution diagram of uranium-thorium bulk microparticles produced in example 4;
fig. 10 is a scanning electron microscope image of the uranium-thorium mixed microparticle prepared in comparative example 1.
Description of the reference numerals
1-aerosol generating device, 2-thermal decomposition device, 3-cooling device, 4-collecting membrane, 5-filter, 6-air compressor, 7-cooling water circulating device, 8-vacuum pump, 9-first vertical pipeline, 10-second vertical pipeline
Detailed Description
The following detailed description of specific embodiments of the present disclosure is provided in connection with the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating the present disclosure, are given by way of illustration and explanation only, not limitation.
In the present disclosure, unless otherwise specified, the terms "first", "second", and the like are used only for distinguishing different members and do not have actual meanings such as the order of connection before and after the present disclosure. In the present disclosure, the use of directional words such as "upper" and "lower" are upper and lower in the normal use state of the device, and "inner" and "outer" are in terms of the device profile.
The first aspect of the disclosure provides a method for preparing micron-sized monodisperse uranium-thorium mixed particles, which comprises the following steps:
mixing a uranium-containing compound and a thorium-containing compound with a solvent to obtain a uranium-thorium mixed solution;
under the condition of aerosol generation, enabling the uranium-thorium mixed solution to form uranium-thorium mixed liquid drops in an aerosol generation device, and enabling the uranium-thorium mixed liquid drops to settle downwards along a first vertical gas path of the sol generator under the action of carrier gas to enter a thermal decomposition device;
and enabling the uranium-thorium mixed liquid drops to settle downwards along a second vertical gas path of the thermal decomposition device under the action of carrier gas, and performing thermal decomposition in the settling process to obtain the uranium-thorium mixed particles.
The uranium-thorium mixed particle prepared by the method can reach a micron level and has remarkable monodispersity, and the uranium-thorium mixed particle also has a regular spherical particle shape, narrower particle size distribution and more uniform uranium-thorium element composition; and the preparation recovery efficiency of the mixed particles can be greatly improved. The method changes the original horizontal preparation pipeline into the vertical preparation pipeline, effectively reduces the particle loss and improves the particle yield; in addition, the vertical pipeline can reduce the stress of liquid drops and particles in different directions in the preparation process, and is beneficial to preparing mixed particles. The method greatly simplifies the preparation process, defines the core link of the preparation of the monodisperse uranium-thorium mixed particles, simplifies the non-core link, finally forms the preparation processes of aerosol preparation, thermal decomposition, cooling and collection, reduces the influence of the non-essential link, and simplifies the process, the auxiliary equipment framework adjustment, simplifies the equipment, shortens the pipeline, reduces the particle loss and improves the particle recovery rate.
In one embodiment, the uranium-containing compound is one or two of uranyl nitrate and uranyl sulfate, preferably uranyl nitrate; the thorium-containing compound is one or two of thorium nitrate and thorium sulfate, preferably thorium nitrate; the solvent is one or more of isopropanol, ethanol, acetone and water, and is preferably isopropanol.
According to the method, a commonly used hydroalcoholic mixed solvent is changed into a single isopropanol as a solvent, so that the surface tension of prepared droplets is increased, uranium-thorium segregation is effectively inhibited, and the preparation of mixed particles is facilitated. In addition, the volatility of the isopropanol solvent is superior to that of the original water-alcohol mixed solvent, and the simplification and optimization of an instrument framework are facilitated. And the improvement of the volatility of the solvent provides feasibility for the optimization of the processes of heating, preheating, desolvation and the like in the preparation process, and provides a prerequisite for the preparation of the monodisperse uranium-thorium mixed particles.
In one embodiment, the uranium-thorium mixed solution has a uranium content of 1 × 10-6～1×10-4g/ml, preferably 5X 10-6～5×10-5g/ml; thorium content of 1X 10-6～1×10-4g/ml, preferably 5X 10-6～5×10-5g/ml。
In one embodiment, the aerosol generating conditions comprise: in the vibrating hole aerosol generating device, the flow rate of carrier gas is 40-50L/min, and the carrier gas is compressed air; the vibration frequency is 40-60 kHz; the sample introduction rate is 1.0-4.0 x 10-3cm/s; the stable pressure is 275-345KPa。
In one embodiment, the conditions of the thermal decomposition include: the thermal decomposition temperature is 800-900 ℃, and the thermal decomposition is carried out in a muffle furnace.
Preparation parameters are optimized in the preparation process, parameters closely related to the preparation of the uranium-thorium mixed particles are refined and defined, and the parameters comprise carrier gas flow, heating temperature, vibration frequency, sampling speed, stable pressure and the like, wherein the effect of preparing the uranium-thorium mixed particles is directly influenced by the change of any parameter, and the recovery rate of micron-sized monodisperse uranium-thorium mixed particles and the performance of the uranium-thorium mixed particles can be further improved.
In one embodiment, the method further comprises: cooling the mixed particles obtained by thermal decomposition in a third vertical gas path of a cooler at the temperature of 5-25 ℃, wherein optionally, the cooler adopts cooling water as a cooling medium;
and collecting and filtering the cooled mixed particles to obtain the micron-sized monodisperse uranium-thorium mixed particles.
The sedimentation cooling is carried out in the third vertical gas path of the cooling device, so that the loss rate of mixed particles is further reduced.
In a second aspect of the present disclosure, micron-sized monodisperse uranium-thorium mixed particles are provided, which are prepared according to the method of the first aspect of the present disclosure.
In one embodiment, the weight content ratio of the uranium-containing oxide to the thorium-containing oxide in the uranium-thorium mixed fine particles is constant, and the ratio ranges from (100:1) to (1: 1); the particle sizes of the uranium-thorium mixed particles are basically consistent, and the particle size range is 0.1-3 mu m. The uranium-thorium mixed particles prepared by the method are regular spherical particles; the ratio of uranium to thorium in the pre-preparation uranium-thorium mixed solution is consistent with that in the prepared uranium-thorium mixed particle, so that the segregation phenomenon is avoided; and the particle size distribution is narrow, and the obvious monodispersity is presented.
The micron-sized monodisperse uranium-thorium mixed particle provided by the disclosure can be applied to the fields of nuclear guarantee and nuclear law evidence.
In a third aspect of the present disclosure, a system for preparing micron-sized monodisperse uranium-thorium mixed particles is provided, as shown in fig. 1, the system includes an aerosol generating device 1 and a thermal decomposition device 2;
the aerosol generating device 1 is provided with a uranium-thorium mixed solution inlet, a carrier gas inlet and a mixed liquid drop outlet; along the height direction of the aerosol generating device 1, a uranium-thorium mixed solution inlet is arranged at the top of the aerosol generating device 1, and a mixed liquid drop outlet is arranged at the bottom of the aerosol generating device 1, so that a first vertical gas path is formed between the uranium-thorium mixed solution inlet and the mixed liquid drop outlet and is used for mixed liquid drop sedimentation; the carrier gas inlet is arranged on the side wall of the aerosol generating device and is used for providing carrier gas for the system;
the thermal decomposition device 2 is provided with a mixed liquid drop inlet and a mixed particle outlet, and the mixed liquid drop inlet is communicated with the mixed liquid drop outlet of the aerosol generating device 1 through a first vertical pipeline 9; the thermal decomposition device 2 is arranged below the aerosol generating device 1 along the material flowing direction; the mixed liquid drop inlet and the mixed particle outlet are respectively arranged at the top and the bottom of the thermal decomposition device 2 so as to form a second vertical gas path in the thermal decomposition device 2 for enabling the mixed liquid drops from the aerosol generating device 1 to continue to settle and to be thermally decomposed in the process of settling.
In one embodiment, the aerosol generating device 1 is a vibrating-hole aerosol generating device and the thermal decomposition device 2 is a split muffle.
In one embodiment, the first vertical pipe and the second vertical pipe are quartz pipes.
In one embodiment, as shown in fig. 1, the system further comprises an air compressor 6, wherein a compressed air outlet of the air compressor 6 is communicated with a carrier gas inlet of the aerosol generating device 1;
the mixed fine particle outlet of the thermal decomposition device 2 is communicated with a post-treatment device.
In one embodiment, as shown in fig. 1, the post-treatment device comprises a cooling device 3, a collecting membrane 4 and a filter 5 which are arranged in communication from top to bottom in the vertical direction; the top of the cooling device 3 is provided with a mixed particle cooling inlet which is communicated with a mixed particle outlet of the thermal decomposition device 2 through a second vertical pipeline 10; the bottom of the cooling device 3 is provided with a mixed particle cooling outlet, and a third vertical gas path is formed between the mixed particle cooling inlet and the mixed particle cooling outlet and used for cooling the mixed particles from the thermal decomposition device 2 in the sedimentation process of the third vertical gas path.
In one embodiment, as shown in fig. 1, the system further comprises a cooling water circulation device 7 for circulating cooling water to the cooling device 3. Specifically, the cooling device 3 comprises a cooling pipe and a cooling water circulation layer, the cooling water circulation layer is coated on the outer side wall of the cooling pipe, and the third vertical gas path is arranged in the cooling pipe; the cooling water circulation layer is provided with a cooling water inlet and a warm water outlet, the cooling water circulation device 7 is provided with a cooling water outlet and a warm water inlet, the cooling water outlet of the cooling water circulation device 7 is communicated with the cooling water inlet of the cooling device 3, and the warm water outlet of the cooling device 3 is communicated with the warm water inlet of the cooling water circulation device 7.
In one embodiment, the present disclosure provides a system in which the passage from the aerosol generating device 1 to the thermal decomposition device 2 to the cooling device 3 to the collecting membrane 4 to the filter 5 is vertical in the vertical direction, thereby reducing the loss of particles and improving the recovery rate of particles.
In one embodiment, the system provided by the present disclosure does not use an electrostatic neutralizer, simplifies equipment, shortens piping, reduces particle loss, and improves particle recovery.
In one embodiment, the system further comprises a vacuum pump 8, and the input port of the vacuum pump 8 is communicated with the filter 5 for pumping air to provide a negative pressure environment.
The specific process for preparing the micron-sized monodisperse uranium-thorium mixed particles by adopting the system shown in the figure 1 of the disclosure comprises the following steps: introducing the uranium-thorium mixed solution above a first vertical gas path of the aerosol generating device 1 through a uranium-thorium mixed solution inlet, introducing carrier gas into the first vertical gas path of the aerosol generating device 1 through a carrier gas inlet, and settling the uranium-thorium mixed solution in the first vertical gas path under the action of the carrier gas and the self gravity to form uranium-thorium mixed liquid drops in the settling process; the mixed liquid drops enter the first vertical pipeline 9 to continue to settle; enabling the uranium-thorium mixed liquid drops to enter the position above a second vertical gas path of the thermal decomposition device through the mixed liquid drop inlet, continuously settling under the action of carrier gas, and thermally decomposing at high temperature to form uranium-thorium mixed particles; the uranium-thorium mixed particles enter a second vertical pipeline 10 through a mixed particle outlet, then enter a third vertical gas path of the cooling device 3 through a mixed particle cooling inlet, continue to settle under the action of the mixed particle cooling inlet, and simultaneously exchange heat with circulating cooling water for cooling; the cooled mixed fine particles are deposited on the collecting membrane 4 through the mixed fine particle cooling outlet, collected, and filtered by the filter 5.
The present disclosure is further illustrated by the following examples.
The preparation apparatus and reaction reagents used in the following examples include:
medical pure oil-free air compressor (WSC22140B Shanghai Huaichi electromechanical Co., Ltd.), precision pressure reducing valve (IR2020-02 Japan SMC Co., Ltd.), vibrating hole aerosol generator (VOAG-3450 American TSI Co., Ltd.), quartz pipe (Beijing Kott quartz glass works), split tube muffle and its temperature control box (Beijing century metalworking electric furnace Co., Ltd.), cooling water circulation device (CFT300 American Thermo Electron Corporation), vacuum pump (V600 German WIGGENS Labortechnik GmbH), ten thousandth electronic balance (Germany Saedodes GmbH), collecting film (Chinese atomic energy science institute physical institute), and filter (German FestoAG & Co.
Isopropanol, analytical pure AR, chemical reagents ltd of the national drug group;
uranyl nitrate, analytically pure, chinese pharmaceutical company;
thorium nitrate, analytically pure, kralmar.
In the following examples and comparative examples, tests were carried out including:
and (3) analyzing the appearance and the appearance of the particles by adopting a Scanning Electron Microscope (SEM): the instrument is JSM-6360LV, JEOL company of Japan; the detection conditions include: amplification factor 5000, vacuum 30Pa, voltage 25 kV.
The average particle size detection method comprises the following steps: single measurement statistics.
Particle size distribution of the particles: single measurement statistics.
The particle preparation recovery rate detection method comprises the following steps: and (5) theoretically calculating statistics.
The thorium-uranium ratio of the original solution and the dissolved particles in the solution is tested by ICP-MS: the instrument is an Isoprobe type multi-receiving inductively coupled plasma mass spectrometer MC-ICP-MS (GV company, UK), and the detection conditions comprise: working voltage 6000V, RF power 1100W, atomizer flow 0.85L/m.
The uniformity of uranium-thorium composition of the mixed particles is tested by SEM-EDX and SIMS: the instrument comprises the following steps: double focusing secondary ion mass spectrometry IMS-6f (CAMECA, France); the detection conditions include: the primary beam energy is 12.5KV, the sample high voltage is 5000V, and the field diaphragm is 1800 μm. The instrument comprises the following steps: high and low vacuum scanning electron microscope JSM-6360LV (JEOL corporation, Japan), spectrometer AZtec (Oxford Instruments, UK); the detection conditions include: amplification factor 5000, vacuum 30Pa, voltage 25 kV.
Example 1
This example was used to prepare monodisperse uranium-thorium hybrid microparticles.
Respectively weighing 0.89g of uranyl nitrate powder and 0.91g of thorium nitrate powder according to a nearly equal ratio (equal weight ratio);
dissolving the two powders in isopropanol, diluting to constant volume via volumetric flask, and gradually diluting to concentration of 4 × 10-5And (3) using a mixed solution of uranium and thorium in g/ml as an aerosol generating solution. Uranium-thorium bulk pellets were prepared using the system shown in fig. 1, according to the parameters in table 1 below.
TABLE 1
Condition parameter
Parameter selection
Frequency of vibration of vibrating orifice
52.5kHz
The sample introduction rate is
1.5×10-3cm/s
Stabilized pressure
310KPa
Carrier gas flow rate
50L/min
Heating temperature of muffle furnace
900℃
The preparation method comprises the following specific steps: (1) and (3) loading the uranium-thorium mixed solution into a sample injection injector of an aerosol generator, and forming monodisperse aerosol through the generator.
(2) And (3) carrying out high-temperature thermal decomposition on the monodisperse aerosol through 1 muffle furnace to form uranium-thorium mixed particles.
(3) The temperature of cooling water is set to be 15 ℃, the high-temperature uranium-thorium mixed particles after thermal decomposition are collected on a nuclear pore membrane after being cooled, and the collection time is about 30 minutes.
The morphology image of the particle prepared in this example observed by SEM is shown in fig. 2. From the particle topography, the prepared particles are spherical, and have smooth surfaces and clear boundaries. The particle size distribution of the prepared particles is shown in figure 3. From the particle size distribution, it can be found that the prepared particles are relatively concentrated in particle size, wherein the number of the uranium-thorium mixed particles with the particle size of 2-3 mu m is 70% of the total number of all the uranium-thorium mixed particles, and the particles have monodispersity. The ratio (atomic number ratio) of thorium to uranium in the original solution and the solution after the particles were dissolved (the solvent for dissolving the particles was nitric acid) was 0.87 by ICP-MS, and it was confirmed by SEM-EDX and SIMS analysis that the composition of uranium and thorium in the mixed particles was uniform, i.e., the ratio of thorium to uranium in the single mixed particle was 0.87. The microparticle preparation recovery of this example was 5.1%.
Example 2
The same preparation method as that of example 1 was adopted, differing from example 1 only in that: according to a near-equal ratioWeighing appropriate amount of uranyl nitrate and thorium nitrate powder, dissolving in isopropanol, fixing volume by volumetric flask, and gradually diluting to 5 × 10-6And (3) using a mixed solution of uranium and thorium in g/ml as an aerosol generating solution.
The morphology image of the prepared particles observed by SEM is shown in FIG. 4. From the particle topography, the prepared particles are spherical, and have smooth surfaces and clear boundaries. The particle size distribution of the prepared particles is shown in figure 5. From the particle size distribution, it can be found that the prepared uranium-thorium mixed particles with the particle size of 1-1.2 mu m are relatively concentrated in particle size, the number of the prepared uranium-thorium mixed particles is 84% of the total number of all the uranium-thorium mixed particles, and the prepared uranium-thorium mixed particles have monodispersity. The thorium-uranium ratio of the original solution and the solution after the particles are dissolved is 0.87 measured by ICP-MS, and SEM-EDX and SIMS analysis proves that the mixed particles have uniform uranium-thorium composition, namely the ratio of thorium to uranium in the single mixed particle is 0.87. The recovery rate of fine particles in this example was 4.7%.
Example 3
The same preparation method as that of example 2 was used, except that: uranium thorium blended microparticles were prepared according to the parameters in table 2 below.
TABLE 2
Condition parameter
Parameter selection
Frequency of vibration of vibrating orifice
47.7kHz
The sample introduction rate is
1.2×10-3cm/s
Stabilized pressure
320KPa
Carrier gas flow rate
40L/min
Heating temperature of muffle furnace
850℃
The morphology image of the prepared particles observed by SEM is shown in FIG. 6. From the particle topography, the prepared particles are spherical, and have smooth surfaces and clear boundaries. The particle size distribution of the prepared particles is shown in figure 7. From the particle size distribution, it can be found that the prepared uranium-thorium mixed particles with the particle size of 1.2-1.4 mu m are relatively concentrated in particle size, the number of the prepared uranium-thorium mixed particles is 83% of the total number of all the uranium-thorium mixed particles, and the prepared uranium-thorium mixed particles have monodispersity. The thorium-uranium ratio of the original solution and the solution after the particles are dissolved is 0.87 measured by ICP-MS, and SEM-EDX and SIMS analysis proves that the mixed particles have uniform uranium-thorium composition, namely the ratio of thorium to uranium in the single mixed particle is 0.87. The recovery rate of fine particles in this example was 5.2%.
Example 4
The same preparation method as that of example 1 was used, except that: respectively weighing 9.74g of uranyl nitrate powder and 0.91g of thorium nitrate powder; dissolving the two powders in isopropanol, diluting to constant volume by volumetric flask, and gradually diluting until the uranyl nitrate concentration is 5 × 10-6g/ml, thorium nitrate concentration of 5X 10-7And (3) using a mixed solution of uranium and thorium in g/ml as an aerosol generating solution.
The morphology image of the particles prepared in this example observed by SEM is shown in fig. 8. From the particle topography, the prepared particles are spherical, and have smooth surfaces and clear boundaries. The particle size distribution of the prepared particles is shown in figure 9. From the particle size distribution, it can be found that the prepared uranium-thorium mixed particles with the particle size of 1-1.2 mu m are relatively concentrated in particle size, the number of the prepared uranium-thorium mixed particles is 78% of the total number of all the uranium-thorium mixed particles, and the prepared uranium-thorium mixed particles have monodispersity. The ratio (atomic ratio) of thorium to uranium in the original solution and the solution after the particles were dissolved (the solvent for dissolving the particles was nitric acid) was 0.09 by ICP-MS, and it was confirmed by SEM-EDX and SIMS analysis that the composition of uranium and thorium in the mixed particles was uniform, i.e., the ratio of thorium to uranium in the single mixed particle was 0.09. The microparticle preparation recovery of this example was 5.3%.
Comparative example 1
Weighing appropriate amount of uranyl nitrate powder and thorium nitrate respectively as powder according to nearly equal ratio (equal weight ratio), dissolving the two powders in isopropanol, fixing volume by volumetric flask, and diluting step by step to concentration of 5 × 10-6And (3) using a mixed solution of uranium and thorium in g/ml as an aerosol generating solution.
Uranium-thorium mixed particles were then prepared using the method disclosed in patent application CN 101891253B. The preparation method comprises the following specific steps: (1) setting the vibration frequency of the vibrating hole aerosol generator to be 55.8kHz, setting the carrier gas flow to be 40L/min, filling the uranium-thorium mixed solution into a sample injection injector of the aerosol generator, and forming monodisperse aerosol through the generator.
(2) The monodisperse aerosol passes through a neutralizer to remove the charges on the surfaces of the aerosol droplets. And then preheating the carrier gas at the rear end of the neutralizer, setting the temperature of a heating belt to be 120 ℃, and heating the carrier gas to be about 79-80 ℃ to evaporate the solvent in the aerosol droplets to form solid particles.
(3) And carrying out high-temperature thermal decomposition on the obtained solid particles in 1 muffle furnace, wherein the heating temperature of the muffle furnace is 690-710 ℃, and finally forming the uranium-thorium mixed particles.
(4) And setting the temperature of cooling water to be 15 ℃, cooling the uranium-thorium mixed particles subjected to thermal decomposition, collecting the particles on a nuclear pore membrane for about 30 minutes, and filtering the collected uranium-thorium mixed particles to obtain the final uranium-thorium mixed particles.
The shape image of the prepared mixed particle observed by SEM is shown in FIG. 10. From the particle morphology graph, the prepared particles are nonspherical, irregular and loose in morphology; the uranium-thorium content in the mixed particles prepared in the comparative example is greatly different from that in the original solution, specifically, the uranium content in the original solution is 43.0 wt%, and the thorium content in the original solution is 57 wt%; the uranium content in the prepared particles was 67.9 wt%, and the thorium content was 32.1 wt%, indicating that there was significant segregation of the uranium-thorium element. The particulate recovery of this comparative example was 1.2%.
As can be seen from the comparison between the above examples 1 to 4 and the comparative example 1, the preparation recovery rate of the uranium-thorium mixed particles prepared by the method and the system provided by the application is higher, the particle shape of the uranium-thorium mixed particles is more regular, the particle size distribution is narrower, the monodispersity is better, the composition of uranium and thorium in the uranium-thorium mixed particles is uniform, and the segregation phenomenon of uranium-thorium elements does not exist.
The preferred embodiments of the present disclosure are described in detail with reference to the accompanying drawings, however, the present disclosure is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solution of the present disclosure within the technical idea of the present disclosure, and these simple modifications all belong to the protection scope of the present disclosure.
It should be noted that the various features described in the above embodiments may be combined in any suitable manner without departing from the scope of the invention. In order to avoid unnecessary repetition, various possible combinations will not be separately described in this disclosure.
In addition, any combination of various embodiments of the present disclosure may be made, and the same should be considered as the disclosure of the present disclosure, as long as it does not depart from the spirit of the present disclosure.