CN106653102B - Thorium-containing fluoride fused salt and/or uranium-containing fluoride fused salt and preparation method thereof - Google Patents
Thorium-containing fluoride fused salt and/or uranium-containing fluoride fused salt and preparation method thereof Download PDFInfo
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- CN106653102B CN106653102B CN201510740787.XA CN201510740787A CN106653102B CN 106653102 B CN106653102 B CN 106653102B CN 201510740787 A CN201510740787 A CN 201510740787A CN 106653102 B CN106653102 B CN 106653102B
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- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21C—NUCLEAR REACTORS
- G21C3/00—Reactor fuel elements and their assemblies; Selection of substances for use as reactor fuel elements
- G21C3/42—Selection of substances for use as reactor fuel
- G21C3/44—Fluid or fluent reactor fuel
- G21C3/54—Fused salt, oxide or hydroxide compositions
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- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21C—NUCLEAR REACTORS
- G21C17/00—Monitoring; Testing ; Maintaining
- G21C17/10—Structural combination of fuel element, control rod, reactor core, or moderator structure with sensitive instruments, e.g. for measuring radioactivity, strain
- G21C17/104—Measuring reactivity
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E30/00—Energy generation of nuclear origin
- Y02E30/30—Nuclear fission reactors
Abstract
The invention discloses thorium-containing fluoride molten salt and/or uranium-containing fluoride molten salt and a preparation method thereof. Of thorium-containing and/or uranium-containing molten fluoridesThe preparation method comprises the following steps: heating the mixture of the substance A and the substance B to a molten state in an inert atmosphere or a vacuum atmosphere; wherein the substance A is thorium tetrafluoride and/or uranium tetrafluoride, the dosage of the substance A is 0.1-80%, and the percentage is that the substance A accounts for the mass percentage of the substance B; the material B has a density of 1-4 g/cm3The fluoride molten salt of (1); in the mixture, the particle sizes of the substance A and the substance B are respectively 0.2 mu m-2 mm. The preparation method is simple and easy to operate, and is suitable for large-scale production; the prepared thorium-containing fluoride molten salt and/or uranium-containing fluoride molten salt has no layering and segregation phenomena; the thorium-containing fluoride molten salt and/or uranium-containing fluoride molten salt after rapid cooling is a homogeneous system, and can be used as a molten salt standard sample in quantitative analysis.
Description
Technical Field
The invention particularly relates to thorium-containing fluoride molten salt and/or uranium-containing fluoride molten salt and a preparation method thereof.
Background
The molten salt refers to a molten mass formed after the salt is melted or a solid formed after the molten mass is cooled. In general, in a high temperature state, a molten salt is called a melt, and in a low temperature solidification state, it is called a solid solution.
For element quantitative analysis, the prior art mainly measures the element content of an aqueous solution, a sample to be measured needs to be diluted by dozens of times or even thousands of times, then measures the element content, a standard sample is needed to make a standard working curve, and the advantage of water phase quantification is that the distribution uniformity of elements in the sample is good. When the quantitative analysis is carried out on the elements in the solid phase of the molten salt, a solid standard sample with good element uniformity is also prepared, and as with the water phase quantification, the solid phase quantification also needs to establish a standard working curve, so that a standard sample which is matched with a matrix and has proper and uniform content needs to be searched, and the difficulty in the element quantification of the molten salt sample is caused. For the standard-free analysis method, the obtained magnitude is a semi-quantitative value rather than an absolute magnitude.
Thorium has long been recognized as a potential nuclear energy resource. Thorium exists as a thorium-232 (Th-232) single isotope in nature, is not a fissile material, but can become a good fissile material when absorbing neutrons and converting the uranium-233 (U-233) which does not exist in nature (the fission performance of U-233 is equivalent to that of U-235), can be fissured by thermal neutrons, and outputs energy, namely thorium-uranium fuel circulation.
The thorium-uranium fuel cycle has good adaptability to various reactor types, and thorium-based fuel experimental research is conducted internationally in various reactor types such as a high-temperature gas cooled reactor, a light water reactor, a molten salt reactor and a heavy water reactor since the last 60 th century. Among them, the Molten Salt Reactor (MSR) is the only liquid fuel reactor among six candidate fourth generation reactor types, and is favored by the international nuclear power community due to its inherent characteristics, and is considered to be an ideal reactor type for realizing U-233 proliferation by using thorium-uranium fuel circulation.
The fuel salt in the molten salt reactor is F L iBeThU, and in order to establish a method for quickly and conveniently and quantitatively analyzing thorium and uranium elements in the fuel salt, a group of molten salt standard samples must be prepared.
Disclosure of Invention
The invention aims to solve the technical problem of overcoming the defect that thorium and/or uranium elements cannot be uniformly distributed in fluoride fused salt in the prior art, and provides thorium-containing fluoride fused salt and/or uranium-containing fluoride fused salt and a preparation method thereof. The preparation method is simple and easy to operate, and is suitable for large-scale production; the prepared thorium-containing fluoride molten salt and/or uranium-containing fluoride molten salt has no layering and segregation phenomena; the thorium-containing fluoride molten salt and/or uranium-containing fluoride molten salt after rapid cooling is a homogeneous system, and can be used as a molten salt standard sample in quantitative analysis.
ThF due to the high density and high melting point of thorium fluoride or uranium fluoride4The density was 6.19g/cm3Melting point of 1103 ℃ and UF4The density was 6.70g/cm3The melting point is 1036 ℃, and the data far exceed the density and the melting point of the fluoride molten salt or the raw material of the fluoride molten salt (L iF density is 2.635 g/cm)3The melting point is 848 ℃; BeF2The density is 1.986g/cm3Melting point 552 ℃). Through a large number of experimental researches, the inventor of the invention finds that particles are easy to generate among materials in the process of preparing thorium-containing and/or uranium fluoride molten saltAgglomeration, and due to the overlarge difference between the material density and the melting point, the phenomena of serious component layering, component segregation, difficult control of products and the like of the molten salt are easily caused, so that thorium and/or uranium cannot be uniformly dispersed in the fluoride molten salt to form a homogeneous system. If the particle size is outside the range defined in the present invention, homogeneous melting cannot be achieved. Moreover, in the fluoride fused salt, if the content of thorium tetrafluoride and/or uranium tetrafluoride is too high, the melting point is increased, and the melting temperature needs to be increased to melt the thorium tetrafluoride and/or uranium tetrafluoride.
The invention solves the technical problems through the following technical scheme.
The invention provides a preparation method of thorium-containing fluoride molten salt and/or uranium-containing fluoride molten salt, which comprises the following steps: heating the mixture of the substance A and the substance B to a molten state in an inert atmosphere or a vacuum atmosphere;
the substance A is thorium tetrafluoride and/or uranium tetrafluoride, the using amount of the substance A is 0.1-80%, and the percentage is the mass percentage of the substance A in the substance B; the substance B has a density of 1-4 g/cm3The fluoride molten salt of (1); in the mixture, the particle sizes of the substance A and the substance B are respectively 0.2 mu m-2 mm.
In the present invention, the molten salt obtained by the above preparation method is a molten salt in a high temperature state, and is generally called a melt.
In the present invention, the substance B is preferably selected from one or more of lithium fluoride, sodium fluoride, potassium fluoride, rubidium fluoride, cesium fluoride, ferrous fluoride, ferric fluoride, beryllium fluoride, magnesium fluoride, calcium fluoride, and barium fluoride, and more preferably from one or more of lithium fluoride, beryllium fluoride, sodium fluoride, and potassium fluoride.
In the present invention, when the substance B is a mixed molten salt of lithium fluoride and beryllium fluoride, the mass of beryllium fluoride in the mixed molten salt is preferably 16 to 94%.
In the present invention, when the substance B is a mixed molten salt of lithium fluoride, sodium fluoride, and potassium fluoride, the mass ratio of lithium fluoride, sodium fluoride, and potassium fluoride is preferably 29.3: 11.7: 59.
in the present invention, preferably, the substance a or the substance B is a product after oxygen removal. The oxygen removal can be carried out according to methods conventional in the art.
In the present invention, the particle diameters of the substance A and the substance B are preferably 0.2 to 3 μm, more preferably 0.2 to 1 μm, respectively.
In the present invention, the temperature of the molten state is preferably 450 to 850 ℃.
In the present invention, it is preferable to keep the temperature after the temperature is raised to the molten state. The longer the heat preservation time is, the better the heat preservation time is, considering the cost such as time, the preferable time is 1 to 5 hours, and the more preferable time is 3 to 5 hours.
In the present invention, it is preferable that the mixture in a molten state is rapidly cooled at a cooling rate of 50 ℃/min or more.
The inventor of the invention finds that the rapid cooling can ensure that a uniform component and a molecular structure of a high-temperature liquid phase are obtained, and the phenomena of component segregation and phase change caused by slow cooling are avoided. The faster the cooling rate of the rapid cooling is, the more beneficial the homogeneous thorium-containing fluoride molten salt and/or uranium-containing fluoride molten salt can be obtained. The thorium-containing fluoride molten salt and/or uranium-containing fluoride molten salt prepared after rapid cooling is in a low-temperature solidification state and is generally called as solid solution. The solid solution is a homogeneous system and can be used in quantitative analysis for a molten salt standard sample.
In the present invention, the mixture is preferably obtained after crushing and mixing. The method of crushing is conventional in the art, preferably one or more of grinding, impacting and extruding.
The invention also provides thorium-containing fluoride molten salt and/or uranium-containing fluoride molten salt prepared by the preparation method. According to the common knowledge in the field, the thorium-containing fluoride molten salt and/or the uranium-containing fluoride molten salt are molten masses formed after the salts are melted or cooled solids of the molten masses.
On the basis of the common knowledge in the field, the above preferred conditions can be combined randomly to obtain the preferred embodiments of the invention.
The reagents and starting materials used in the present invention are commercially available.
The positive progress effects of the invention are as follows:
the preparation method is simple and easy to operate, is suitable for large-scale production, and the prepared thorium-containing fluoride molten salt and/or uranium-containing fluoride molten salt particles are not easy to agglomerate, and the molten salt components are not layered.
If the molten salt is rapidly cooled, homogeneous thorium-containing fluoride molten salt and/or homogeneous uranium-containing fluoride molten salt can be obtained, the segregation phenomenon is avoided, and the molten salt can be used as a molten salt standard sample in quantitative analysis.
Detailed Description
The invention is further illustrated by the following examples, which are not intended to limit the scope of the invention. The experimental methods without specifying specific conditions in the following examples were selected according to the conventional methods and conditions, or according to the commercial instructions.
Examples 1 to 6
The products prepared in examples 1-6 are all F L iNaKU molten salt, and the difference is only UF4UF in examples 1 to 6 were varied in the addition amount4The amounts added of (A) are shown in Table 1.
TABLE 1
Note: UF4The percentages in the addition amounts of (A) and (B) are mass percentages relative to the total amount of L iF, NaF and KF, and the percentages in the theoretical content of U are mass percentages relative to the total amount of the sample.
The preparation methods of the F L iNaKU molten salt in the embodiments 1 to 6 all comprise the following steps:
adopting a ball mill crushing and mixing method, weighing 15g of three fluorides L iF, NaF and KF according to the mass ratio of 29.3: 11.7: 59, mixing and adding into a ball mill, grinding for 3 hours by a grinding machine until the particle sizes are all 0.2-1 mu m, and UF according to the table 14Respectively placing the raw materials into a ball mill, grinding for 3h to obtain particles with a particle size of about 0.2-1 μm, taking out the materials, placing into a nickel crucible, heating to 650-850 deg.C (UF) under inert atmosphere4Or ThF4The more the addition amount of the (B), the higher the melting point), so that the material is melted, the heat is preserved for 2 hours, and the material is rapidly cooled at the speed of 100 ℃/min to obtain the homogeneous F L iNaKU molten salt of the embodiment 1-6.
Comparative example 1
This comparative example is a blank control with no UF added4Or ThF4The other conditions were the same as in examples 1 to 6.
Examples 7 to 12
The products prepared in examples 7-12 are all F L iNaKTh fused salts, and the difference is only that ThF4In examples 7 to 12, ThF was added in different amounts4The amounts added of (A) are shown in Table 2.
TABLE 2
Note: ThF4The percentage of (B) is the mass percentage of L iF, NaF and KF, and the percentage of Th is the mass percentage of sample.
In examples 7 to 12, the method for preparing F L iNaKTh fused salt was compared with examples 1 to 6 except that UF was removed4Replacement by ThF4Otherwise, the operation or conditions were the same as in examples 1 to 6.
Examples 13 to 16
The products prepared in the examples 13 to 16 are mixed homogeneous molten salts containing Th and U, and the difference is only UF4And ThF4UF in examples 13 to 16 were varied in the amounts added4And ThF4The amounts added are shown in Table 3.
TABLE 3
Note: UF4And ThF4In the amount of (A) is L iF and NMass percent of total amount of aF and KF; the percentages in the theoretical contents of Th and U are both mass percentages relative to the total amount of the sample.
In examples 13 to 16, the method of preparing a molten salt was conducted except that UF was used in comparison with examples 1 to 64Replacement by UF4And ThF4The operation or conditions other than the mixture of (1) are the same as those in examples 1 to 6.
Effects of the embodiment
Since the thorium fluoride-containing molten salt and/or uranium fluoride-containing molten salt is easy to absorb water and damp in the air, and affects the analysis test result of an X-Ray Fluorescence spectrum analyzer (all called X Ray Fluorescence in English, abbreviated as XRF), a standard sample of the mixed molten salt is pressed into a tablet and put into a sample with a diameter of
A circular container having a depth of 5mm was sealed with a plastic film from above.
After the products in examples 1-16 were packaged with plastic films, the content of U and/or Th was tested at multiple points using XRF analysis techniques, respectively, to analyze the uniformity of U and/or Th elements in the fluoride fused salt. All data in tables 4-6 below were measured using a micro-area XRF400 spectrometer produced by the laboratory of Shanghai atomic nucleus research.
Table 4 shows XRF multi-spot test analysis data for U element in F L iNaKU molten salt of examples 1 to 6, Table 5 shows XRF multi-spot test analysis data for Th element in F L iNaKTh molten salt of examples 7 to 12, Table 6 shows XRF multi-spot test analysis data for Th and U elements in F L iNaKU and F L iNaKTh of examples 13 to 16, and tables 4 to 6 show that three sampling points are randomly selected to test the uniformity of the samples in the longitudinal directions 1 to 3.
The data in tables 4 to 6 are the mass percentages of the respective elements relative to the total amount of the respective samples.
TABLE 4
TABLE 5
TABLE 6
Claims (11)
1. A method for preparing thorium-containing fluoride molten salt and/or uranium-containing fluoride molten salt is characterized by comprising the following steps: heating the mixture of the substance A and the substance B to a molten state in an inert atmosphere or a vacuum atmosphere;
the substance A is thorium tetrafluoride and/or uranium tetrafluoride, the using amount of the substance A is 0.1-80%, and the percentage is the mass percentage of the substance A in the substance B; the substance B has a density of 1-4 g/cm3The fluoride molten salt of (1); in the mixture, the particle sizes of the substance A and the substance B are respectively 0.2-3 μm; rapidly cooling the mixture in the molten state at a cooling rate of 50 ℃/min or more.
2. The method according to claim 1, wherein the substance B is one or more selected from the group consisting of lithium fluoride, sodium fluoride, potassium fluoride, rubidium fluoride, cesium fluoride, ferrous fluoride, ferric fluoride, beryllium fluoride, magnesium fluoride, calcium fluoride, and barium fluoride.
3. The method according to claim 2, wherein the substance B is one or more selected from the group consisting of lithium fluoride, beryllium fluoride, sodium fluoride, and potassium fluoride.
4. The preparation method according to claim 1, wherein the substance B is a mixed molten salt of lithium fluoride and beryllium fluoride, and the mass ratio of the beryllium fluoride in the mixed molten salt is 16-94%;
or the substance B is a mixed molten salt of lithium fluoride, sodium fluoride and potassium fluoride, and the mass ratio of the lithium fluoride to the sodium fluoride to the potassium fluoride is 29.3: 11.7: 59;
and/or the substance A or the substance B is a product after oxygen removal.
5. The method according to claim 1, wherein the particle diameters of the substance a and the substance B are 0.2 μm to 1 μm, respectively.
6. The method of claim 1, wherein the temperature of the molten state is 450 to 850 ℃;
and/or heating to a molten state and then carrying out heat preservation.
7. The method according to claim 6, wherein the holding time is 1 to 5 hours.
8. The method according to claim 7, wherein the holding time is 3 to 5 hours.
9. The method of claim 1, wherein the mixture is obtained by crushing and mixing.
10. The method of claim 9, wherein the crushing is one or more of a grinding process, an impact process, and an extrusion process.
11. Thorium-containing fluoride molten salt and/or uranium-containing fluoride molten salt prepared by the method for preparing thorium-containing fluoride molten salt and/or uranium-containing fluoride molten salt according to any one of claims 1 to 10.
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| CN108511088B (en) * | 2018-06-13 | 2023-07-28 | 中国科学院上海应用物理研究所 | Heavy water moderated molten salt reactor core and heavy water moderated molten salt reactor system |
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| CN103219052B (en) * | 2013-04-25 | 2016-04-13 | 中国科学院上海有机化学研究所 | A kind of highly purified fluoride molten salt and preparation method thereof |
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