CN101789272A - Neutron absorption ball preparation method - Google Patents
Neutron absorption ball preparation method Download PDFInfo
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- CN101789272A CN101789272A CN201010101755A CN201010101755A CN101789272A CN 101789272 A CN101789272 A CN 101789272A CN 201010101755 A CN201010101755 A CN 201010101755A CN 201010101755 A CN201010101755 A CN 201010101755A CN 101789272 A CN101789272 A CN 101789272A
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Abstract
The invention relates to a neutron absorption ball preparation method which includes the following steps: the carbon material and neutron absorption material are mixed to form powder material, the powder material is added to the mixed water solution of PVA and PEG under stirring state, boric acid is added to the solution during kneading process to prepare the thickener; the neutron absorption ball is prepared after pre-pressing, extrusion forming, carbonization, cutting, grinding, high temperature treatment and surface packaging treatment. The invention adopts PVA as bonding agent, is environment-friendly and has low price. The extrusion forming technique has high efficiency, low equipment investment and meets the large-scale industrial production requirement.
Description
Technical field
The invention belongs to nuclear reactor field, particularly relate to a kind of preparation method by extrusion molding thereof of neutron absorption ball.
Background technology
As energy cleaning, safety, environmental protection, nuclear energy power generation is all significant for alleviating the world and various countries' energy security and Global climate change problem.Though passed through three miles islands of the U.S. and USSR (Union of Soviet Socialist Republics) Chernobyl Plant accident setback, people are still safer at active development, the better nuclear energy power generation technology of economy.At present, third generation nuclear power technology is mature on the whole.
In the 4th generation of technology such as nuclear energy system of researching and developing, high temperature gas cooled reactor can realize very high outlet temperature, has the hot deliverability of high generating efficiency and high-grade, causes people's extensive concern.
High temperature gas cooled reactor adopts ceramic mould coated particle fuel element, and helium is as cooling medium, and graphite is made moderator, and core exit temperature can reach 700 ℃, until 950～1000 ℃.High temperature gas cooled reactor is the good heap type of a kind of security performance, this be because: 1) You Yi fuel element performance; 2) thermal capacity of graphite core is big; 3) FR negative reactivity temperature coefficient; 4) helium coolant is an inert gas, and chemical stability is good, can not undergo phase transition.
KLAK system is second reactor shut-off system of high temperature gas cooled reactor, cooperates with the control rod system in the high temperature gas cooled reactor operational process, plays shutdown and the effect of regulating operate power.Its principle of work is that when normal shutdown or emergency shut-down, the absorption ball falls into the absorption ball duct of reactor, utilizes in the boron carbide
10The intercept neutrons characteristic of B, the chain reaction of intercept neutrons and then prevention reactor, the shutdown of realization response heap; When reactor need start, absorb ball and deliver in the ball-storing tank of reactor roof by gas delivery, make it to be in stand-by state.
According to the applying working condition that absorbs ball, requiring to absorb ball has good abrasion resistance properties and thermal shock resistance, simultaneously and between the graphite duct good matching is arranged.Pure boron carbide ball
10B content height, the neutron absorptive character are good, but easily wearing and tearing caused in the graphite duct.The graphite nodule that contains boron carbide can possess neutron absorption, and improves the wearing and tearing that absorb between ball and duct, owing to adopt graphite as matrix material, makes it have good thermal shock resistance simultaneously.
On the conventional graphite forming method, what generally adopt is isostatic compaction or compression molding, and these two kinds of forming methods also can be made the graphite nodule that contains boron carbide, but make efficiency is relatively low, needs to drop into a large amount of manpowers.Extrusion molding is used in a large number at plastic industry, this forming method efficient height, can produce continuously.Traditional extrusion molding generally adopts pitch as adjuvant, because the impurity content of pitch is higher, can not satisfy the production requirement of high-purity goods.
Summary of the invention
The purpose of this invention is to provide a kind of new neutron absorption ball preparation method,, solve the technical matters of globular graphite goods large-scale industrial production to solve the problems referred to above that prior art exists.
The invention provides a kind of neutron absorption ball preparation method, comprise the steps: carbon raw materials and neutron absorbing material mixed in the mixed aqueous solution that the powder that obtains joins PVA and PEG and stir, add boric acid in the kneading process, make thickener; Coat processing through precompressed, extrusion molding, charing, cutting, mill processing, pyroprocessing and surface.
Wherein said powder comprises graphite 35%～75%, boron carbide 5%～35% and optional, carbon black 0～30% by mass percentage; Used boron carbide is the pure level of nuclear, and other material purity is greater than 99.5%; Graphite can be native graphite or Delanium.
In the mixed aqueous solution of described PVA and PEG, the mass percent concentration of PVA and PEG is 5%～20%, and PVA and PEG mass ratio are (1～5): 1; PVA and PEG both can be dissolved fully under the aforementioned proportion.
The mass ratio of the mixed aqueous solution of described powder and PVA and PEG is 1: (1～4).
Add boric acid in the kneading process, addition is 0.1%～2.0% of a powder general assembly (TW), and the temperature of kneading process is 10～100 ℃, is preferably 20～100 ℃, and mixing the time of pinching is 0.5～6 hour, and making can be for the thickener of extrusion molding.Its mesoboric acid and PVA can interact and play plasticization, and PEG can play peptizaiton as coupling agent, also will be as the release agent effect when extrusion molding.
The pressure of described precompressed is 200～400MPa, pressurize 1～10 minute; The pressure that described extrusion molding is adopted is 150～400Mpa, obtains the bar that diameter is 5～15mm; The pressure of wherein said precompressed is greater than forming pressure.The gained thickener is to pack into to carry out precompressed in the extrusion shaping machine; The pressure of precompressed is greater than forming pressure, but pressing time is shorter, mainly is for getting rid of the gas in thickener, obtaining higher powder density.
The pressure that described extrusion molding is adopted is 150～400Mpa, obtains the bar that diameter is 5～15mm.
The charing under nitrogen or inert gas shielding of described bar is warmed up to 700～1600 ℃ with 1～5 ℃ of per minute, is incubated 1～10 hour.
The bar that obtains after the charing is cut into pillar, and its length and diameter are basic identical; Then the gained pillar is ground processing and handle, obtain the spheroid that diameter is 5～15mm.
In the described high-temperature process, be raised to 1600～2300 ℃, be incubated 1～24 hour with the speed of 1～20 ℃ of per minute.
Adopt CVI (chemical vapor infiltration) technology to carry out the surface and coat processing, form the surface and coat charcoal, improve wearing quality; The CVI treatment temperature is 800～1300 ℃.Promptly obtain neutron absorption ball after coating processing.
The present invention also provides according to the neutron absorption ball that adopts method for preparing to obtain.
Neutron absorption ball preparation method of the present invention has following beneficial effect:
1) the present invention as adjuvant, reaches plasticization effect with acid reaction with PVA (polyvinyl alcohol (PVA)), is coupling agent with PEG (polyglycol) simultaneously, and graphite can be dispersed in the aqueous solution of PVA;
2) make cementing agent with PVA, PVA purity height does not have influence substantially to goods purity, and PVA is nontoxic simultaneously, and easily cracking is discharged, and is environmentally friendly, cheap;
3) extrusion forming process efficient height, equipment drops into low, can satisfy large-scale industrial production.
Description of drawings
Fig. 1 is this preparation method's a process chart;
Fig. 2 is for adopting the prepared absorption ball of this technology.
Embodiment
Following examples are used to illustrate the present invention, but are not used for limiting the scope of the invention.
Its raw material source is commercially available acquisition among the embodiment.
Embodiment 1
Take by weighing native graphite 55Kg, carbon black 20Kg, boron carbide 25Kg.Preparation PVA and PEG mixed aqueous solution, mixed aqueous solution concentration is 10wt%, wherein PVA: the PEG mass ratio is 4: 1.The powder that takes by weighing is joined in the mixed aqueous solution, and mass ratio is 2: 3, mixes in kneading machine and pinches 1 hour, and kneading temperature is 80 ℃, adds boric acid 2Kg then, continues to mix and pinches 3 hours, and making can be for the thickener of extrusion molding.With the precompressed in the SL65B type extrusion shaping machine of packing into of gained thickener, pressurization 350MPa, pressurize 5min.After the precompressed, extrude the bar that diameter is 10.5mm on extruder, extrusion pressure is 300MPa.With bar charing under nitrogen protection, be warmed up to 800 ℃ with 4 ℃ of per minutes, be incubated 4 hours, naturally cooling.Bar is cut into pillar, and its length and diameter are basic identical.Gained moulding pillar is ground processing handle, obtain the spheroid that diameter is 10mm.Graphite nodule after the processing carries out pyroprocessing, 10 ℃ of programming rate per minutes, and the pyroprocessing temperature is 2300 ℃, is incubated 2 hours, naturally cooling.The boron carbide graphite nodule that contains after the pyroprocessing is carried out surface coating processing with CVI technology, and 1100 ℃ of CVI treatment temperatures form the surface and coat charcoal.Promptly obtain the neutron absorption ball that diameter is about 10mm after coating processing.With the absorption ball of above-mentioned technology preparation, the crushing force testing mean is 1322N.
Embodiment 2
Take by weighing native graphite 55Kg, carbon black 30Kg, boron carbide 15Kg.Preparation PVA and PEG mixed aqueous solution, mixed aqueous solution concentration is 10wt%, wherein PVA: the PEG mass ratio is 4: 1.The powder that takes by weighing is joined in the mixed aqueous solution, and mass ratio is 2: 3, mixes in kneading machine and pinches 1 hour, and kneading temperature is 60 ℃, adds boric acid 2Kg then, continues to mix and pinches 2 hours, and making can be for the thickener of extrusion molding.With the precompressed in the SL65B type extrusion shaping machine of packing into of gained thickener, pressurization 350MPa, pressurize 5min.After the precompressed, extrude the bar that diameter is 10.5mm on extruder, extrusion pressure is 300MPa.With bar charing under argon shield, be warmed up to 1000 ℃ with 3 ℃ of per minutes, be incubated 3.5 hours, naturally cooling.Bar is cut into pillar, and its length and diameter are basic identical.Gained moulding pillar is ground processing handle, obtain the spheroid that diameter is 10mm.Graphite nodule after the processing carries out pyroprocessing, 10 ℃ of programming rate per minutes, and the pyroprocessing temperature is 2200 ℃, is incubated 2 hours, naturally cooling.The boron carbide graphite nodule that contains after the pyroprocessing is carried out surface coating processing with CVI technology, and 1100 ℃ of CVI treatment temperatures form the surface and coat charcoal.Promptly obtain the neutron absorption ball that diameter is about 10mm after coating processing.With the absorption ball of above-mentioned technology preparation, the crushing force testing mean is 1435N.
Embodiment 3
Take by weighing native graphite 50Kg, carbon black 25Kg, boron carbide 25Kg.Preparation PVA and PEG mixed aqueous solution, mixed aqueous solution concentration is 8wt%, wherein PVA: the PEG mass ratio is 4: 1.The powder that takes by weighing is joined in the mixed aqueous solution, and mass ratio is 1: 1, mixes in kneading machine and pinches 1 hour, and kneading temperature is 20 ℃, adds boric acid 1.5Kg then, continues to mix and pinches 2 hours, and making can be for the thickener of extrusion molding.With the precompressed in the SL65B type extrusion shaping machine of packing into of gained thickener, pressurization 300MPa, pressurize 8min.After the precompressed, extrude the bar that diameter is 6.5mm on extruder, extrusion pressure is 250MPa.With bar charing under nitrogen protection, be warmed up to 900 ℃ with 3 ℃ of per minutes, be incubated 3 hours, naturally cooling.Bar is cut into pillar, and its length and diameter are basic identical.Gained moulding pillar is ground processing handle, obtain the spheroid that diameter is 6mm.Graphite nodule after the processing carries out pyroprocessing, 12 ℃ of programming rate per minutes, and the pyroprocessing temperature is 2100 ℃, is incubated 2 hours, naturally cooling.The boron carbide graphite nodule that contains after the pyroprocessing is carried out surface coating processing with CVI technology, and 1150 ℃ of CVI treatment temperatures form the surface and coat charcoal.Promptly obtain the neutron absorption ball that diameter is about 10mm after coating processing.With the absorption ball of above-mentioned technology preparation, the crushing force testing mean is 516N.
Embodiment 4
Take by weighing Delanium 75Kg, carbon black 5Kg, boron carbide 20Kg.Preparation PVA and PEG mixed aqueous solution, mixed aqueous solution concentration is 20wt%, wherein PVA: the PEG mass ratio is 1: 1.The powder that takes by weighing is joined in the mixed aqueous solution, and mass ratio is 1: 3, mixes in kneading machine and pinches 1 hour, and kneading temperature is 100 ℃, adds boric acid 0.5Kg then, continues to mix and pinches 2 hours, and making can be for the thickener of extrusion molding.With the precompressed in the SL65B type extrusion shaping machine of packing into of gained thickener, pressurization 200MPa, pressurize 10min.After the precompressed, extrude the bar that diameter is 12.5mm on extruder, extrusion pressure is 150MPa.With bar charing under nitrogen protection, be warmed up to 700 ℃ with 20 ℃ of per minutes, be incubated 3 hours, naturally cooling.Bar is cut into pillar, and its length and diameter are basic identical.Gained moulding pillar is ground processing handle, obtain the spheroid that diameter is 6mm.Graphite nodule after the processing carries out pyroprocessing, 1 ℃ of programming rate per minute, and the pyroprocessing temperature is 1600 ℃, is incubated 20 hours, naturally cooling.The boron carbide graphite nodule that contains after the pyroprocessing is carried out surface coating processing with CVI technology, and 850 ℃ of CVI treatment temperatures form the surface and coat charcoal.Promptly obtain the neutron absorption ball that diameter is about 10mm after coating processing.With the absorption ball of above-mentioned technology preparation, the crushing force testing mean is 500N.
Embodiment 5
Take by weighing Delanium 35Kg, carbon black 35Kg, boron carbide 30Kg.Preparation PVA and PEG mixed aqueous solution, mixed aqueous solution concentration is 20wt%, wherein PVA: the PEG mass ratio is 5: 1.The powder that takes by weighing is joined in the mixed aqueous solution, and mass ratio is 1: 4, mixes in kneading machine and pinches 6 hours, and kneading temperature is 20 ℃, adds boric acid 2.0Kg then, continues to mix and pinches 3 hours, and making can be for the thickener of extrusion molding.With the precompressed in the SL65B type extrusion shaping machine of packing into of gained thickener, pressurization 400MPa, pressurize 8min.After the precompressed, extrude the bar that diameter is 5.5mm on extruder, extrusion pressure is 200MPa.With bar charing under nitrogen protection, be warmed up to 700 ℃ with 5 ℃ of per minutes, be incubated 9 hours, naturally cooling.Bar is cut into pillar, and its length and diameter are basic identical.Gained moulding pillar is ground processing handle, obtain the spheroid that diameter is 6mm.Graphite nodule after the processing carries out pyroprocessing, 2 ℃ of programming rate per minutes, and the pyroprocessing temperature is 1600 ℃, is incubated 18 hours, naturally cooling.The boron carbide graphite nodule that contains after the pyroprocessing is carried out surface coating processing with CVI technology, and 1250 ℃ of CVI treatment temperatures form the surface and coat charcoal.Promptly obtain the neutron absorption ball that diameter is about 10mm after coating processing.With the absorption ball of above-mentioned technology preparation, the crushing force testing mean is 512N.
Experiment effect:
1) neutron absorption ball of embodiment 1～4 gained employing native graphite is a primary raw material, and PVA (polyvinyl alcohol (PVA)) is as adjuvant, and PEG (polyglycol) is a coupling agent, boric acid is as plastifier, introducing impurity is few, and the purity height of gained sample satisfies the request for utilization of neutron absorption ball.
2) make cementing agent, PEG with PVA and make the sample of coupling agent and all increasing aspect blank strength and the physical strength, PVA, PEG are nontoxic, environmentally friendly simultaneously, and easily cracking is discharged, cheap, can be applied to extruding-out process, satisfy large-scale industrial production.
3) compared with prior art, the neutron absorption ball of embodiment 1～4 gained has higher crushing force index, and anti-wear performance is good, can satisfy the application requirements of high temperature gas cooled reactor.
Claims (10)
1. neutron absorption ball preparation method comprises the steps: carbon raw materials and neutron absorbing material mixed in the mixed aqueous solution that the powder that obtains joins PVA and PEG and stirs, and adds boric acid in the kneading process, makes thickener; Coat through precompressed, extrusion molding, charing, cutting, mill processing, pyroprocessing and surface then and handle.
2. preparation method according to claim 1 is characterized in that, described powder comprises graphite 35%～75%, boron carbide 5%～35% and optional, carbon black 0～30% by mass percentage.
3. preparation method according to claim 1 is characterized in that, in the mixed aqueous solution of described PVA and PEG, the mass percent concentration of PVA and PEG is 5%～20%, and PVA and PEG mass ratio are (1～5): 1.
4. neutron absorption ball according to claim 1 is characterized in that, the mass ratio of the mixed aqueous solution of described powder and PVA and PEG is 1: (1～4).
5. preparation method according to claim 1 is characterized in that, adds boric acid in the kneading process, and addition is 0.1%～2.0% of a powder general assembly (TW), and the temperature of kneading process is 10～100 ℃, and mixing the time of pinching is 0.5～6 hour.
6. preparation method according to claim 1 is characterized in that, the pressure of described precompressed is 200～400MPa, pressurize 1～10 minute; The pressure that described extrusion molding is adopted is 150～400Mpa, obtains the bar that diameter is 5～15mm; The pressure of wherein said precompressed is greater than forming pressure.
7. preparation method according to claim 6 is characterized in that, the charing under nitrogen or inert gas shielding of described bar is warmed up to 700～1600 ℃ with 1～5 ℃ of per minute, is incubated 1～10 hour.
8. preparation method according to claim 1 is characterized in that, in the described high-temperature process, is raised to 1600～2300 ℃ with the speed of 1～20 ℃ of per minute, is incubated 1～24 hour.
9. preparation method according to claim 1 is characterized in that, adopts CVI technology to carry out the surface and coats processing, and treatment temperature is 800～1300 ℃.
10. the neutron absorption ball that adopts each described method of claim 1～9 to prepare.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102432295A (en) * | 2011-08-12 | 2012-05-02 | 清华大学 | Ceramic substrate neutron absorption ball and preparation method thereof |
| CN115536394A (en) * | 2022-09-23 | 2022-12-30 | 华能核能技术研究院有限公司 | Preparation method of high-temperature gas cooled reactor absorption ball with silicon nitride coating |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN101290814B (en) * | 2008-06-18 | 2011-06-29 | 清华大学 | Method of preparing carbon absorption spherical containing boron carbide |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102432295A (en) * | 2011-08-12 | 2012-05-02 | 清华大学 | Ceramic substrate neutron absorption ball and preparation method thereof |
| CN115536394A (en) * | 2022-09-23 | 2022-12-30 | 华能核能技术研究院有限公司 | Preparation method of high-temperature gas cooled reactor absorption ball with silicon nitride coating |
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