CN111383787B - Preparation method of spherical fuel element ball blank - Google Patents
Preparation method of spherical fuel element ball blank Download PDFInfo
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- CN111383787B CN111383787B CN201811619914.0A CN201811619914A CN111383787B CN 111383787 B CN111383787 B CN 111383787B CN 201811619914 A CN201811619914 A CN 201811619914A CN 111383787 B CN111383787 B CN 111383787B
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- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21C—NUCLEAR REACTORS
- G21C21/00—Apparatus or processes specially adapted to the manufacture of reactors or parts thereof
- G21C21/02—Manufacture of fuel elements or breeder elements contained in non-active casings
- G21C21/10—Manufacture of fuel elements or breeder elements contained in non-active casings by extrusion, drawing, or stretching by rolling, e.g. "picture frame" technique
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- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21C—NUCLEAR REACTORS
- G21C21/00—Apparatus or processes specially adapted to the manufacture of reactors or parts thereof
- G21C21/02—Manufacture of fuel elements or breeder elements contained in non-active casings
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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
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Abstract
The embodiment of the invention relates to a preparation method of a spherical fuel element ball blank, which comprises the following steps: placing a rubber mold in a mold cavity of pressing equipment, filling matrix graphite powder and dressing particles positioned in the center of the matrix graphite powder in the rubber mold, and prepressing in the pressing equipment to obtain a prepressed body; vacuum sealing and packaging the prepressing body taken out of the rubber mold to obtain a vacuum-packaged single prepressing body; and (4) putting the single prepressing body after vacuum packaging into a hydraulic cylinder of an isostatic pressing machine, and performing isostatic pressing. The preparation method adopts an isostatic pressing mode, is simple and convenient, can prepare a plurality of ball blanks by one-time pressing, and has uniform stress on the ball blanks and uniform product performance in the pressing process.
Description
Technical Field
The invention relates to the field of nuclear energy material preparation, in particular to a preparation method of a spherical fuel element sphere blank.
Background
The pebble-bed high temperature gas cooled reactor is recognized as one of the most advanced nuclear reactors due to its inherent safety and economical efficiency. The fuel used by the pile is a spherical fuel element, the ball blank forming method is a quasi-isostatic pressing process at present, the process utilizes the characteristic that rubber materials have approximate fluid under high pressure to carry out pressing, the process is to put a rubber mould filled with dressing particles and matrix graphite powder into a mould cavity of a quasi-isostatic pressing machine, and the one-step pressing forming is carried out according to the set program and process parameters. However, the process adopts a quasi-isostatic pressing mode, so that different positions of the ball blank in the die are stressed unevenly; in addition, in order to prevent the spherical blank from cracking in the pressing process, the mould filled with the dressing particles and the matrix graphite powder needs to be vacuumized, namely, the gas around the matrix graphite powder and the dressing particles in the mould is vacuumized in a quasi-isostatic pressing machine, which is difficult to complete; moreover, in the production process, only one mold can be placed in one press, only one ball blank can be pressed in one cycle, and the production efficiency cannot meet the requirement of large-scale production of spherical fuel elements.
The information disclosed in this background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.
Disclosure of Invention
Object of the Invention
In order to further improve the performance of the spherical fuel element, adapt to the requirements of scale production of the spherical fuel element and improvement of the production efficiency of the element, the invention aims to provide the preparation method of the spherical blank of the spherical fuel element, the preparation method adopts an isostatic pressing mode, and the spherical blank is uniformly stressed in the pressing process, so that the performance of the spherical fuel element is improved; the preparation method is simple and convenient, the step of vacuumizing gas around matrix graphite powder and dressing particles in the die in a quasi-isostatic pressing machine is avoided, a plurality of spherical blanks can be prepared by one-time pressing, and the rest steps can be produced in batch.
Solution scheme
In order to achieve the purpose of the invention, the embodiment of the invention provides the following technical scheme:
a preparation method of a spherical fuel element ball blank comprises the following steps:
placing a rubber mold in a mold cavity of pressing equipment, filling matrix graphite powder and dressing particles positioned in the center of the matrix graphite powder in the rubber mold, and prepressing in the pressing equipment to obtain a prepressed body;
vacuum sealing and packaging the prepressing body taken out of the rubber mold to obtain a vacuum-packaged single prepressing body;
and (4) putting the single prepressing body after vacuum packaging into a hydraulic cylinder of an isostatic pressing machine, and performing isostatic pressing.
In a possible implementation manner, when isostatic pressing is performed, an isostatic press is firstly boosted to a set pressure, and pressing is performed through the steps of pressure maintaining and pressure relief to a normal pressure, wherein: the set pressure during isostatic pressing is 150MPa-300MPa, preferably 160MPa-280MPa, and further preferably 220MPa-260 MPa.
In one possible implementation mode of the preparation method, the time for increasing the pressure to the set pressure in isostatic pressing is 1-20 min; optionally 1min-10 min; further optionally 1min-5 min.
In one possible implementation of the above preparation method, the dwell time during isostatic pressing is 5s-10min, optionally 5s-6min, further optionally 1min-5 min.
In a possible implementation manner of the preparation method, the pressure relief during isostatic pressing is slow pressure relief firstly and then fast pressure relief; wherein: the slow pressure relief time is 1min-10min, and the fast pressure relief time is 2s-100 s; optionally, the slow pressure relief time is 1-7 min, and the fast pressure relief time is 10-100 s.
In one possible implementation of the above preparation method, the isostatic pressing is performed at a temperature of from ambient temperature to 100 ℃.
In a possible implementation manner, the preparation method comprises the steps of boosting the pressure of the pressing equipment to a set pressure during prepressing, and maintaining the pressure and relieving the pressure to normal pressure to prepare the prepressing, wherein: the set pressure of the pre-press forming is 13kg/cm3-300kg/cm3Optionally 15kg/cm3-250kg/cm3。
In a possible implementation mode of the preparation method, the time for increasing the pressure to the set pressure in the pre-pressing forming process is less than or equal to 5 s.
In one possible implementation manner of the preparation method, the pressing manner of the pre-pressing forming includes any one of unidirectional pressing, bidirectional pressing or isostatic pressing. The pre-pressing is carried out by setting the pressure to be lower, so that the adopted pressing modes are various, unidirectional pressing, bidirectional pressing or isostatic pressing can be carried out, and the pressing equipment adopted during pre-pressing forming can be selected from the existing equipment according to the pressing mode.
In one possible implementation mode of the preparation method, the pressure maintaining time in the pre-pressing forming process is 1s-20s, and 5s-10s can be selected.
In a possible implementation manner of the preparation method, the pressure relief during the pre-pressing molding is slow pressure relief firstly and then fast pressure relief; wherein: the slow pressure relief time is 5s-30s, optionally 5s-15 s; the quick-release time is 1s-20s, and optionally 1s-5 s.
In a possible implementation mode of the preparation method, the vacuum degree in vacuum sealing is more than or equal to 600 Pa; and optionally more than or equal to 300 Pa.
In one possible implementation of the preparation method, the spherical fuel element comprises a spherical fuel element suitable for a high-temperature gas-cooled reactor.
In one possible implementation mode of the preparation method, the prepressed body after vacuum packaging is placed in a hydraulic cylinder of an isostatic pressing machine in a layered mode, and the layered layers are 1-3.
In one possible implementation of the above-described preparation method, the drying of the surface moisture of the packaging and the removal of the packaging are carried out after isostatic pressing.
In one possible implementation manner of the preparation method, the drying of the moisture on the surface of the packing material comprises the following steps: drying with strong air at 0-75 deg.C, optionally room temperature, by four-stage three-turn process; the flow of the fan is not less than 1200m3The air pressure is 400-700 Pa, the rotating speed of a fan is not less than 1450r/min, and the drying is finished within 5 minutes.
In one possible implementation manner of the preparation method, the removal of the packaging material comprises the following steps: the dried packing materials are arranged on a material conveying belt of automatic dismounting equipment in a single layer mode, after each product is automatically positioned, the sealing parts are cut off from the periphery, and the cut-off packing materials are automatically collected.
In one possible implementation mode of the preparation method, the heat sealing temperature is 80-200 ℃; the heat sealing time is 0.5-2s, optionally not more than 1.5 s; the heat sealing pressure is 0.05-0.7 MPa.
Advantageous effects
1. In the preparation method of the spherical fuel element ball blank provided by the embodiment of the invention, the independent prepresses subjected to vacuum packaging exist in isostatic pressing equipment independently and are directly and uniformly subjected to pressure from all directions, so that the ball blank is uniformly stressed, and the product performance is better and more uniform.
2. In the preparation method of the spherical fuel element spherical blank provided by the embodiment of the invention, the step of vacuumizing gas around matrix graphite powder and dressing particles in a mold in a quasi-isostatic pressing device is eliminated, and the method of prepressing the matrix graphite powder (namely a fuel-free area) and the dressing particles positioned at the central part of the matrix graphite powder (namely a fuel area), carrying out vacuum sealing packaging and then carrying out isostatic pressing is adopted. In the method of the embodiment of the invention, on one hand, the vacuumized object is changed from vacuumizing the gas around the matrix graphite powder and the dressing particles in the mould in the pressing equipment to vacuumizing the gas around the prepressing body in the packaging bag at the outside, and the vacuumized object is changed, so that the vacuumizing difficulty is greatly reduced, the time is greatly reduced, the batch operation can be carried out, and the production efficiency is greatly improved; on the other hand, the purpose of vacuum pumping is changed, and the vacuum pumping in the prior quasi-isostatic pressing process is performed in a die cavity of a press in order to prevent uneven deformation of a pressed body during forming and crack of a ball caused by pressure relief due to structural defects formed in the ball during pressing; the isostatic pressing vacuum pumping is carried out in a vacuum heat sealing area of vacuum packaging equipment, the equipment is simple and easy to operate, and the aim is to eliminate the ball cracking caused by formed air flow in the forming process.
In addition, the prepressing, the vacuumizing and the unsealing of the packaging bags can be operated in batch, so that the production efficiency is greatly improved.
3. In the preparation method of the spherical fuel element ball blank provided by the embodiment of the invention, the following parameters are selected, so that higher production efficiency is obtained, and a product with better and more uniform performance is obtained:
(1) the pressing pressure during isostatic pressing can influence the product performances such as density, strength, heat conduction and the like, the pressing pressure is too small, the product has low density, low strength and poor heat conduction performance, and the technical requirements of spherical fuel elements cannot be met; the selection of the pressure rising time, the pressure maintaining time and the pressure relief time during isostatic pressing influences the production efficiency and the yield of products, and if the pressure rising time, the pressure maintaining time and the pressure relief time are short, cracks can be generated on the ball blank, and the yield is reduced.
(2) When the pre-pressing is carried out, the set pressure is low, the matrix graphite powder and the dressing particles positioned at the central part of the matrix graphite powder are basically pressed and formed without loosening, but the set pressure for the pre-pressing is important, the isostatic pressing is difficult when the set pressure is too high, and the pre-pressing body cracks when the pre-pressing body is too low; the pressure maintaining time and the pressure releasing time of the pressure during the pre-pressing forming can influence the production efficiency and are also key factors influencing the yield, and if the pressure maintaining time and the pressure releasing time are short, cracks can be generated on the pre-pressing body, and the yield is reduced.
(3) If the vacuum degree is lower than a certain standard, the packaging bag and the ball body can crack during isostatic pressing;
drawings
One or more embodiments are illustrated by the corresponding figures in the drawings, which are not meant to be limiting. The word "exemplary" is used exclusively herein to mean "serving as an example, embodiment, or illustration. Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments.
FIG. 1 is a schematic flow chart of examples 1 to 4 of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are a part of the embodiments of the present invention, but not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention. Throughout the specification and claims, unless explicitly stated otherwise, the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element or component but not the exclusion of any other element or component.
Furthermore, in the following detailed description, numerous specific details are set forth in order to provide a better understanding of the present invention. It will be understood by those skilled in the art that the present invention may be practiced without some of these specific details. In some embodiments, materials, elements, methods, means, and the like that are well known to those skilled in the art are not described in detail in order to not unnecessarily obscure the present invention.
FIG. 1 is a schematic flow chart of examples 1 to 4 of the present invention. In the following examples, the yield of the green pellets after isostatic pressing and the average crush strength and bulk density of the matrix graphite spheres were used as the main parameters to be examined.
Example 1
(1) Preparation of prepressed body
Placing a rubber mould in a mould cavity of a quasi-isostatic pressing device, and pressurizing the pressing device to 17kg/cm by matrix graphite powder and dressing particles positioned in the central part of the matrix graphite powder in the rubber mould3And performing prepressing molding, keeping the pressure for 10s, slowly releasing the pressure for 10s, and then quickly releasing the pressure for 5s to normal pressure to prepare a prepressing body.
(2) Vacuum package of pre-pressed body
And (3) carrying out vacuum sealing packaging on the prepressed body, vacuumizing the packaging bag to the vacuum degree of 500Pa, carrying out heat sealing for 2s at the temperature of 100 ℃ and under the pressure of 0.5MPa, and cutting a plurality of connected vacuum packaging bodies into single vacuum packaging bodies.
(3) Isostatic pressing of pre-pressed bodies
And (3) layering the prepressed body after vacuum packaging (no more than three layers, and more than three layers can crush the prepressed body), placing the prepressed body in a container capable of being hoisted, placing the container in a hydraulic cylinder of an isostatic pressing machine, boosting the pressure to 220MPa at 180s according to a set program at room temperature, and pressing the prepressed body through steps of pressure maintaining for 300s, slow pressure relief for 60s and fast pressure relief for 16s to normal pressure.
(4) Drying of surface moisture of packages
Adopting strong air drying equipment and adopting a four-section three-turning process, wherein the drying temperature is 70 ℃; the flow rate of the fan is 1300m3The drying is finished within 5 minutes at the wind pressure of 500Pa and the fan speed of 1500 r/min.
(5) Removal of the wrapper
The dried packing materials are arranged on a material conveying belt of automatic dismounting equipment in a single layer mode, after each product is automatically positioned, the sealing parts are cut off from the periphery, and the cut-off packing materials are automatically collected.
The yield of the ball blank is 100%; the average crushing strength of the matrix graphite nodule sample is 22.52 KN; the average bulk density was 1.71g/cm3. Since the strength and density tests of nuclear fuel elements cannot be determined using true spheres with nuclear fuel inside, the strength and density tests were performed using matrix graphite spheres without nuclear fuel but produced using the same materials under the same process conditions, instead of using nuclear fuel elements. The method is equivalent to that only the matrix graphite powder is used for replacing nuclear fuel, other materials and steps for preparing the spherical blank are completely the same as those of the embodiment of the invention, and the obtained spherical blank is used for preparing the matrix graphite spheres according to the preparation process of the existing nuclear fuel element (see the research on the spherical fuel element in the demonstration engineering of the pebble-bed high-temperature gas cooled reactor, Vol.48, No.7 and 2014 7 months), so that the strength and density test is carried out instead of the nuclear fuel element.
Note: the above-mentioned isostatic pressing manner means that the ball blank is prepared in the manner of example 1, including quasi-isostatic pre-pressing and isostatic final-pressing; the above table shows the way of quasi-isostatic pressing, which means one-step forming in a quasi-isostatic press by using a quasi-isostatic pressing process. The molding direction is as follows: the samples were subjected to the crush strength test in 2 directions perpendicular or parallel to the pressure direction in the quasi-isostatic pressing or quasi-isostatic pressing one-shot forming process, respectively, so that there were two test results of the crush strength perpendicular to the pressure direction (t) and parallel to the pressure direction (/). As can be seen from the above table, the samples obtained by the preparation method of the present application have a smaller difference between the average values of the crush strengths in the direction perpendicular to the pressure direction (. quadrature.) and in the direction parallel to the pressure direction/, indicating a more uniform overall distribution of the product.
In the table above, a universal material testing machine is adopted for detecting the crushing strength, the base graphite nodule is positioned by using a clamp, an upper pressing plate of the press slowly moves downwards to press the base graphite nodule, the clamp is removed, and the upper pressing plate continues to move downwards at the speed of 1 mm/min until the graphite nodule is crushed, so that the crushing strength is obtained.
Example 2
(1) Preparation of prepressed body
Placing a rubber mold in a mold cavity of a quasi-isostatic pressing device, filling the rubber mold with powder and dressing particles positioned in the center of the powder, and pressurizing the pressing device to 150kg/cm3And performing prepressing molding, keeping the pressure for 5s, slowly releasing the pressure for 8s, and then quickly releasing the pressure for 3s to normal pressure to prepare a prepressing body.
(2) Vacuum package of pre-pressed body
And (3) carrying out vacuum sealing packaging on the prepressed body, vacuumizing to the vacuum degree of 300Pa, carrying out heat sealing for 1.5s under the conditions of 100 ℃ and 0.6MPa, and cutting a plurality of connected vacuum packaging bodies into single vacuum packaging bodies.
(3) Isostatic pressing of pre-pressed bodies
And (3) layering (no more than three layers) the prepressed body after vacuum packaging in a container capable of being hoisted, putting the container into a hydraulic cylinder of an isostatic pressing machine, boosting the pressure to 230MPa at 180s at room temperature according to a set program, and pressing the container through the steps of maintaining the pressure for 60s, slowly releasing the pressure for 500s and quickly releasing the pressure for 100s to the normal pressure.
(4) Drying of surface moisture of packages
Adopting strong air drying equipment and adopting a four-section three-turning process, wherein the drying temperature is 70 ℃; the flow rate of the fan is 1400m3The drying is finished within 5 minutes at the wind pressure of 450Pa and the fan speed of 1400 r/min.
(5) Removal of the wrapper
The dried packing materials are arranged on a material conveying belt of automatic dismounting equipment in a single layer mode, after each product is automatically positioned, the sealing parts are cut off from the periphery, and the cut-off packing materials are automatically collected.
The yield of the ball blank is 100%; the average crushing strength of the matrix graphite nodule sample is 22.6 KN; the average bulk density was 1.72g/cm3。
Example 3
(1) Preparation of prepressed body
Placing a rubber mold in a mold cavity of a quasi-isostatic pressing device, filling the rubber mold with powder and dressing particles positioned in the center of the powder, and pressurizing the pressing device to 150kg/cm3And performing prepressing molding, keeping the pressure for 15s, slowly releasing the pressure for 15s, and then quickly releasing the pressure for 5s to normal pressure to prepare a prepressing body.
(2) Vacuum package of pre-pressed body
And (3) carrying out vacuum sealing packaging on the prepressed body, vacuumizing to the vacuum degree of 200Pa, carrying out heat sealing for 1.5s under the conditions of 100 ℃ and 0.08MPa, and cutting a plurality of connected vacuum packaging bodies into single vacuum packaging bodies.
(3) Isostatic pressing of pre-pressed bodies
And (3) layering (no more than three layers) the prepressed body after vacuum packaging in a container capable of being hoisted, putting the container into a hydraulic cylinder of an isostatic pressing machine, boosting the pressure to 260MPa at 180s at room temperature according to a set program, and pressing the container through steps of pressure maintaining for 300s, slow pressure relief for 300s and fast pressure relief for 60s to normal pressure.
(4) Drying of surface moisture of packages
Adopting strong current air drying equipment and adopting a four-section three-turning process, wherein the drying temperature is room temperature; the flow of the fan is 1600m3The drying is finished within 5 minutes at the wind pressure of 550Pa and the fan speed of 1560 r/min.
(5) Removal of the wrapper
The dried packing materials are arranged on a material conveying belt of automatic dismounting equipment in a single layer mode, after each product is automatically positioned, the sealing parts are cut off from the periphery, and the cut-off packing materials are automatically collected.
The yield of the ball blank is 100%; the average crushing strength of the matrix graphite nodule sample is 22.2 KN; the average bulk density was 1.74g/cm3。
Example 4
(1) Preparation of prepressed body
Placing a rubber mold in a mold cavity of a quasi-isostatic pressing device, filling the rubber mold with powder and dressing particles positioned in the center of the powder, and pressurizing the pressing device to 240kg/cm3And performing prepressing molding, keeping the pressure for 10s, slowly releasing the pressure for 10s, and then quickly releasing the pressure for 5s to normal pressure to prepare a prepressing body.
(2) Vacuum package of pre-pressed body
And (3) carrying out vacuum sealing packaging on the prepressed body, vacuumizing to the vacuum degree of 200Pa, carrying out heat sealing for 1.5s under the conditions of 100 ℃ and 0.08MPa, and cutting a plurality of connected vacuum packaging bodies into single vacuum packaging bodies.
(3) Isostatic pressing of pre-pressed bodies
And (3) layering (no more than three layers) the prepressed body after vacuum packaging in a container capable of being hoisted, putting the container into a hydraulic cylinder of an isostatic pressing machine, boosting the pressure to 180MPa at 180s at room temperature according to a set program, and pressing the container through steps of pressure maintaining for 300s, slow pressure relief for 270s and fast pressure relief for 10s to normal pressure.
(4) Drying of surface moisture of packages
Adopting strong current air drying equipment and adopting a four-section three-turning process, wherein the drying temperature is room temperature; the flow of the fan is 1600m3The drying is finished within 5 minutes at the wind pressure of 550Pa and the fan speed of 1560 r/min.
(5) Removal of the wrapper
The dried packing materials are arranged on a material conveying belt of automatic dismounting equipment in a single layer mode, after each product is automatically positioned, the sealing parts are cut off from the periphery, and the cut-off packing materials are automatically collected.
The yield of the ball blank is 100%; the average value of the crushing strength of the matrix graphite nodule sample is 23 KN; the average bulk density was 1.71g/cm3。
Examples 2-4 also achieve the advantage of a more uniform overall product distribution.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (13)
1. A preparation method of a spherical fuel element ball blank is characterized by comprising the following steps:
placing a rubber mold in a mold cavity of pressing equipment, filling matrix graphite powder and dressing particles positioned in the center of the matrix graphite powder in the rubber mold, and prepressing in the pressing equipment to obtain a prepressed body;
vacuum sealing and packaging the prepressing body taken out of the rubber mold to obtain a vacuum-packaged single prepressing body;
putting the vacuum packed single prepressing body into a hydraulic cylinder of an isostatic pressing machine for isostatic pressing,
wherein, will step up the pressing equipment to the set pressure when carrying out the pre-compaction, prepare the pre-compaction through the step of pressurize, pressure release to ordinary pressure, wherein: the set pressure of the pre-press forming is 13kg/cm3-300kg/cm3，
Wherein, the time for boosting to the set pressure in the pre-pressing forming is less than or equal to 5 s;
and/or the pressure maintaining time during the pre-pressing forming is 1s-20 s;
and/or the pressure relief during the pre-pressing molding is slow pressure relief firstly and then fast pressure relief; wherein: the slow pressure relief time is 5-30 s; the quick pressure relief time is 1-20 s,
wherein, when carrying out isostatic pressing, the isostatic pressing machine is firstly boosted to the set pressure, and the pressing is carried out through the steps of pressure maintaining and pressure releasing to the normal pressure, wherein the set pressure during the isostatic pressing is 150MPa-300MPa,
wherein the time for increasing the pressure to the set pressure in the isostatic pressing is 1-20 min,
and/or the pressure maintaining time is 5s-10min during isostatic pressing,
and/or the pressure relief during isostatic pressing is slow pressure relief firstly and then fast pressure relief; wherein: the slow pressure relief time is 1-10 min, and the fast pressure relief time is 2-100 s.
2. The method of claim 1, wherein: the set pressure during isostatic pressing is 160MPa-280 MPa.
3. The method of claim 2, wherein: the set pressure during isostatic pressing is 220MPa-260 MPa.
4. The method of claim 1, wherein: the time for increasing the pressure to the set pressure in isostatic pressing is 1-10 min;
and/or the pressure maintaining time is 5s-6min during isostatic pressing;
and/or the slow pressure relief time is 1-7 min, and the fast pressure relief time is 10-100 s.
5. The method of claim 4, wherein: the time for increasing the pressure to the set pressure in isostatic pressing is 1-5 min;
and/or the pressure maintaining time is 1min-5min during isostatic pressing.
6. The method of claim 1, wherein: the isostatic pressing is carried out at normal temperature-100 ℃.
7. The method of claim 1, wherein: the set pressure of the pre-pressing forming is 15kg/cm3-250kg/cm3。
8. The method of claim 1, wherein:
the pressure maintaining time during the pre-pressing forming is 5s-10 s;
and/or the slow pressure relief time is 5-15 s; the quick-release time is 1s-5 s.
9. The method of claim 1, wherein: the pre-press forming includes any one of unidirectional pressing, bidirectional pressing, or isostatic pressing.
10. The method of claim 1, wherein: the vacuum degree in vacuum sealing is more than or equal to 600 Pa.
11. The method of manufacturing according to claim 10, wherein: the vacuum degree in vacuum sealing is more than or equal to 300 Pa.
12. The method of claim 1, wherein: the spherical fuel element comprises a spherical fuel element suitable for a high-temperature gas cooled reactor.
13. The method of claim 1, wherein: after the isostatic pressing, drying of the surface moisture of the packages and removal of the packages are carried out.
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