A method for solidifying chlorine and / or fluorine-containing radioactive waste by glass ceramics and a glass ceramic solidified body obtained thereby

Abstract

The present invention relates to a method for solidifying chlorine and / or fluorine-containing radioactive waste by glass ceramics, which comprises: adding radioactive waste according to the ratio of chlorine and / or fluorine in the radioactive waste to P in Ca3(PO4)2, P (mol) :F(Cl) (mol) =3-5, dry and exhaust after mixing evenly, grind the obtained material into powder; introduce the powder into a graphite mold; place the graphite mold in a sintering furnace; evacuate the sintering furnace, set the pressurization pressure to 0.3t-1.5t, set the heating program to 50-100℃ / min and heat to 350-550℃, and perform spark plasma sintering for 1-3mins; use a demoulding machine to remove the glass ceramic solidified body from the graphite mold. The present invention also provides a glass ceramic solidified body obtained according to the above method. According to the method of the present invention, the material is converted into a solidified body form in one step, which simplifies the preparation process, has a simple process, and is short in time.

Description

Technical Field

[0001] The invention relates to the field of radioactive waste solidification treatment and environmental protection, and more specifically to a method for solidifying chlorine- and / or fluorine-containing radioactive wastes through glass ceramics and a glass ceramic solidified body obtained thereby. Background Art

[0002] Dry reprocessing is a spent fuel reprocessing technology applicable to advanced nuclear fuel cycle technology and one of the key technologies for the sustainable development of nuclear energy. Its main high-level radioactive waste is solid waste salt containing halogen compounds produced during electrolytic reduction and electrolytic refining, referred to as "molten salt waste". Molten salt waste is a solid salt containing halogen (Cl, F) compounds, and carries a small amount of actinides and unseparated fission products (FP). It has the characteristics of strong radioactivity, corrosiveness, poor chemical stability, easy deliquesce, and low melting point. High radioactivity may also cause radiolysis of waste salt to generate halogen-containing gases. Some wastes may contain toxic components (such as beryllium fluoride). It is a complex system with strong radioactivity, chemical corrosiveness, and chemical toxicity, which is difficult to handle and dispose of. Therefore, the research on the treatment technology of high-level radioactive molten salt waste generated by dry reprocessing of spent fuel is of great significance to the development of spent fuel reprocessing and nuclear fuel cycle technology. Extensive research has been carried out on the treatment of molten salt waste internationally. Researchers from the United States, France, Australia and other countries have conducted research on the solidification treatment of high-level radioactive waste containing halogen compound waste and molten salt waste from dry reprocessing. Compared with the traditional vitrification, it is necessary to melt the waste, which makes the process complicated and needs to consider the release of molten fluoride and volatile nuclides and tail gas treatment (Molten Salt Panel of the Committee on Remediation of Buried and Tank Wastes NRC, Evaluation of the USDepartment of Energy's Alternatives for the Removal and Disposition of Molten Salt Reactor Experiment Fluoride Salts. Technical Report 1997; Siemer DD Improving the integral fast reactor's proposed salt waste management system. Nucl. Technol., 2011, 178: 341-352; Siemer DD Molten Salt Breeder Reactor Waste Management. Nucl. Technol., 2012, 185: 100-108; Donze S., Montagne L., Palavit G. Thermal conversion of heavy metal chlorides (PbCl2, CdCl2) and alkalinechlorides(NaCl,KCl) into phosphate glasses.Chemistry of materials,2000,12(7):1921-1925;Lavrinovich YG,Kormilitsyn M.,Konovalov V.,et al fuel.At.Energ,2003,95(5):781-785;Mesko M.,Day D.,BunkerB.Immobilization of CsCl and SrF2 in iron phosphate glass al.Properties ofPhosphate-Glass Waste Forms Containing Fluorides from Molten SaltReactor.Nuclear Science and Techniques,2016,27(3):96-102;Yaping Sun,XiaobinXia,Yanbo Qiao,et al Materials,2016,59(4):279-286;Xueyang Liu,Yanbo Qiao,Zhenghua Qian,et al 508(2018)286-291), Proceedings of the National Chemical Engineering Society.

[0003] It has been reported in the literature (Riley, BJ, McFarlane, J., DelCul, GD, et al..Molten salt reactor waste and effluent management strategies: A review. Nucl. Eng. Des. 2019, 345, 94-109; Metcalfe B, Donald I. Candidate waste forms for the immobilization of chloride-containing radioactive waste. Journal of non-crystalline solids, 2004, 348: 225-229) that a variety of crystals have been studied for solidifying high-level radioactive waste, among which the three best types of crystals suitable for treating molten salt waste include titanates, sodalites and apatites. At present, the glass-ceramic solidification technologies developed based on the above target crystals include glass-ceramic solid phase sintering technology based on a two-step method, hot isostatic pressing glass-ceramic preparation technology, etc. However, due to the disadvantages of the above technologies such as complex process flow, high process conditions and long preparation time, they have not been promoted for engineering application. Summary of the invention

[0004] In order to solve the problems of complex process flow of the glass ceramic solidification technology in the above-mentioned prior art, the present invention provides a method for solidifying chlorine and / or fluorine-containing radioactive wastes by glass ceramics and a glass ceramic solidified body obtained thereby.

[0005] The present invention provides a method for solidifying chlorine- and / or fluorine-containing radioactive waste by glass ceramics, which comprises: S1, grinding and mixing Fe2O3, (NH4)H2PO4 and H3BO3 to prepare a raw material, adding Ca3(PO4)2 to the raw material after grinding and mixing, adding radioactive waste according to the ratio of chlorine and / or fluorine in the radioactive waste to P in Ca3(PO4)2, P (mol) :F(Cl) (mol) =3-5, after mixing evenly, drying and exhausting, the obtained material is ground into powder; S2, introducing the powder into a graphite mold; S3, placing the graphite mold in a sintering furnace; S4, evacuating the sintering furnace, setting the pressure to 0.3t-1.5t, setting the heating program to 50-100℃ / min and heating to 350-550℃, and performing spark plasma sintering (SPS) for 1-3mins; S5, using a demolding machine to remove the glass ceramic solid body from the graphite mold.

[0006] Preferably, the radioactive waste is radioactive waste containing fluoride and / or chloride. More preferably, the radioactive waste is intermediate- and high-level radioactive waste containing fluoride and / or chloride, wherein the radioactivity level of the intermediate-level waste is greater than 4×10 9 Bq / kg, the radioactivity level of high-level waste is greater than 4×10 11 Bq / kg. In a preferred embodiment, the radioactive waste is radioactive waste containing fluoride. In a preferred embodiment, the molar percentage of each component in the radioactive waste is 63LiF-28MgF2-1.2CsF-1.6SrF2-1.2CeF3-4.96ZrF4-0.04AnFn, An is an actinide element, and n is 2 or 3 or 4 or 5 or 6 or 7. In a preferred embodiment, the radioactive waste is radioactive waste containing chloride. In a preferred embodiment, the molar percentage of each component in the radioactive waste is 63LiCl-28MgCl2-1.2CsCl-1.6SrCl2-1.2CeCl3-4.96ZrCl4-0.04AnCln, An is an actinide element, and n is 2 or 3 or 4 or 5 or 6 or 7.

[0007] Preferably, in step S1, the ratio of Fe2O3, (NH4)H2PO4 and H3BO3 is 36-40wt%: 54-60wt%: 0-10wt%. In a preferred embodiment, the ratio of Fe2O3, (NH4)H2PO4 and H3BO3 is 38wt%-57wt%-5wt%.

[0008] Preferably, in step S1, the mass ratio of the raw material to Ca3(PO4)2 is 1:2. In a preferred embodiment, the mass ratio of the raw material to Ca3(PO4)2 is 1:1.5.

[0009] Preferably, step S2 includes: a first graphite paper is closely attached to the inner wall of the cylinder of the graphite mold, a second graphite paper is laid on the bottom of the cylinder, powder is introduced into the space defined by the first graphite paper and the second graphite paper, a third graphite paper is covered on top of the powder, and a head of the graphite mold is inserted into the cylinder above the third graphite paper and pressed down.

[0010] Preferably, in step S4, a negative pressure of 1000 Pa is maintained after vacuuming.

[0011] Preferably, in step S4, the pressurizing pressure is set to 0.5t-1.2t. In a preferred embodiment, the pressurizing pressure is set to 0.8t.

[0012] Preferably, in step S4, the heating program is set to heat to 350°C at 50°C / min and heat to 450-550°C at 100°C / min.

[0013] Preferably, in step S4, after spark plasma sintering, the temperature is lowered to below 50°C at a rate of 50°C / min, the heating program is turned off, and the vacuum pump is turned off.

[0014] The present invention also provides a glass ceramic solidified body obtained according to the above method.

[0015] Preferably, the glass-ceramic solidified body comprises a ceramic mixture bonded by ferrophosphate glass, and the ceramic mixture is a mixture of fluoro(chloro)apatite, fluoro(chloro)apatite and monazite.

[0016] Preferably, the chemical structural formulas of the fluoro(chloro)apatite, fluoro(chloro)apatite and monazite are M5(PO4)3F, M5(PO4)3Cl and NPO4, respectively, wherein M is a metal cation of Li, Ca, Ba, Sr, Cs, La, U, Zr, and N is a cation of Ce, Th, U, or Pu. In a preferred embodiment, M is Ca, Sr, or Mg, and N is Ce.

[0017] According to the method for curing chlorine- and / or fluorine-containing radioactive wastes by glass ceramics of the present invention, after all materials are mixed, the materials are converted into a solidified body form by utilizing the heating characteristics of discharge plasma in one step, which simplifies the preparation process, has a simple process, a short time, and is synthesized in one step. The glass ceramic solidified body thus obtained can cure and treat radioactive molten salt wastes containing fluoride and / or chloride, obtain a stable solidified body, and can solve the problems of complicated process, high condition requirements, long preparation cycle, and high preparation temperature in the prior art. The present invention uses solid powder (Fe2O3, (NH4)H2PO4, H3BO3, and Ca3(PO4)2) as raw materials, which can be directly mixed with fluoride and / or chloride to prepare a solidified body, reducing the risk of reaction and corrosion of fluoride and / or chloride; because there is no liquid, the evaporation amount and the generation of secondary radioactive waste liquid in the preparation process are reduced. The present invention can quickly (1 to 3 minutes) convert powder into a solid glass ceramic solid body at a relatively low temperature (350°C-550°C), effectively reducing the volatilization of volatile elements such as fluorine, chlorine, and cesium, and reducing the process of tail gas treatment at the rear end and the generation of secondary waste. The crystal particles in the solid body prepared by the present invention are more uniform and have a smaller particle size, so that the solid body reaches 98.5-99.8% of the theoretical density and has higher strength. The generated solid body is composed of target crystals and glass, has good water erosion resistance, and exhibits good chemical stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a structural schematic diagram of an SPS graphite mold according to a preferred embodiment of the present invention;

[0019] Figure 2 Shows Figure 1The first and third graphite papers of SPS graphite mold;

[0020] Figure 3 Shows Figure 1 The second graphite paper of SPS graphite mold;

[0021] Figure 4 is a structural schematic diagram of an SPS sintering furnace according to a preferred embodiment of the present invention;

[0022] Figure 5 is a SEM image of a glass ceramic solidified body obtained according to Example 5 of the present invention;

[0023] Figure 6 It is a SEM picture of the glass ceramic solidified body obtained according to Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0024] The preferred embodiments of the present invention are given below in conjunction with the accompanying drawings and described in detail.

[0025] The raw materials in the following examples are all commercially available products.

[0026] The particle size of the fluoride molten salt waste in the following examples is ≤1 mm.

[0027] The purity of the glass raw materials and Ca3(PO4)2 in the following examples is ≥99wt%, and the particle size is ≤0.35um.

[0028] The radioactive waste in the following embodiments is medium- and high-level radioactive waste containing fluoride and / or chloride. For example, the radioactive waste is radioactive waste A containing fluoride. In a preferred embodiment, the molar percentage of each component in the radioactive waste is 63LiF-28MgF2-1.2CsF-1.6SrF2-1.2CeF3-4.96ZrF4-0.04AnFn, An is an actinide element, and n is 2 or 3 or 4 or 5 or 6 or 7. For another example, the radioactive waste is radioactive waste B containing chloride. In a preferred embodiment, the molar percentage of each component in the radioactive waste is 63LiCl-28MgCl2-1.2CsCl-1.6SrCl2-1.2CeCl3-4.96ZrCl4-0.04AnCln, An is an actinide element, and n is 2 or 3 or 4 or 5 or 6 or 7.

[0029] The SPS graphite mold used in the following examples is as follows: Figure 1As shown, it includes a cylinder 1, a first graphite paper 2, a second graphite paper 3, a third graphite paper 4 and a sealing head 5, wherein the cylinder 1 is open upward, the first graphite paper 2 is close to the inner wall of the cylinder 1, the second graphite paper 3 is laid on the bottom wall of the cylinder 1, the material 6 is placed in the space defined by the first graphite paper 2 and the second graphite paper 3, the third graphite paper 4 is laid on the top of the material 6, and the sealing head 5 is inserted into the cylinder 1 above the third graphite paper 4 to seal the material 6. Preferably, the cylinder 1 is cylindrical, the first graphite paper 2 is made of Figure 2 The square graphite paper shown is folded to form a second graphite paper 3 and a third graphite paper 4. Figure 3 The circle shown.

[0030] The SPS sintering furnace used in the following examples is as follows: Figure 4 As shown, it includes the above-mentioned mold, a pressure head 7, a temperature detector 8 and a heating element 9, wherein the pressure head 7 is configured to act on the mold head 5 to pressurize the mold, the temperature detector 8 is arranged in the mold to detect the temperature of the mold, and the heating element 9 is arranged at both ends of the mold to heat the mold. Specifically, a pulse current is directly passed between the powder particles of the material 6 in the mold for heating and sintering. During the SPS sintering process, the discharge plasma generated instantly when the DC pulse current is passed through the electrode causes each particle inside the sintered body to evenly generate Joule heat and activate the particle surface.

[0031] Example 1

[0032] Fe2O3, (NH4)H2PO4 and H3BO3 were ground and mixed in a ratio of 36wt%-54wt%-10wt% to prepare a raw material, and then Ca3(PO4)2 was added to the raw material in a mass ratio of 1:1 and ground and mixed. Radioactive waste was added according to the ratio of fluorine and chlorine in the simulated waste to P in the Ca3(PO4)2 raw material. (mol) :F(Cl) (mol) =3, after mixing evenly, dry and exhaust at 400℃, grind the obtained material into powder with a powder size of ≤0.35um.

[0033] Take out the cleaned SPS graphite mold, and cut a square graphite paper and two round graphite papers with the same inner diameter as the mold according to the size of the mold. First, roll the square graphite paper into a cylindrical shape and put it into the cylinder 1 so that it is close to the inner wall to provide the first graphite paper 2. Then take a round graphite paper and place it on the bottom of the cylinder 1 to make it flat to provide the second graphite paper 3. Introduce the powder into the space defined by the first graphite paper 2 and the second graphite paper 3. After adding about 95% of the volume of the cylinder 1, cover the powder with another layer of round graphite paper to provide the third graphite paper 4, and then insert the head 5 into the cylinder 1 until it cannot be pressed down further by hand.

[0034] Place the mold filled with materials in the SPS sintering furnace, place it stably, manually lower the pressure head 7 until the pressure value starts to be displayed on the pressure gauge, then stop lowering, insert the temperature probe 8 into the monitoring hole in the middle of the mold, and place the mold again to ensure that the upper and lower pressure heads and the mold as a whole are in a vertical line, and close the furnace door after adjustment.

[0035] After closing the furnace door, turn on the vacuum pump to exhaust the gas in the furnace and maintain a negative pressure of 1000 Pa. Set the pressurization pressure to 0.3t, turn on the heating element 9, set the heating program to heat to 350℃ at 50℃ / min, maintain this temperature for 3mins, then cool down to below 50℃ at 50℃ / min, turn off the heating program, turn off the vacuum pump, and release the negative pressure.

[0036] Open the furnace door, slowly lift the pressure head 7, take out the mold, remove the head 5, use a demoulding machine to take out the internal solidified body, remove the graphite paper, and obtain the final glass ceramic solidified body.

[0037] Example 2

[0038] The ratio of fluorine in the simulated waste and P in the Ca3(PO4)2 raw material P in component A of this embodiment (mol) :F (mol) =4, and the rest is the same as in Example 1.

[0039] Example 3

[0040] The ratio of chlorine in the simulated waste and P in the Ca3(PO4)2 raw material in component B of this embodiment is P (mol) :Cl (mol) =3, and the rest is the same as in Example 1.

[0041] Example 4

[0042] The ratio of chlorine in the simulated waste and P in the Ca3(PO4)2 raw material in component B of this embodiment is P (mol) :Cl (mol) =5, and the rest is the same as in Example 1.

[0043] Example 5

[0044] Fe2O3, (NH4)H2PO4 and H3BO3 are ground and mixed in a ratio of 36wt%-54wt%-10wt% to prepare a raw material, and then Ca3(PO4)2 is added to the raw material in a mass ratio of 1:1 and ground and mixed, and radioactive waste is added according to the ratio of fluorine in the simulated waste of component A to P in the Ca3(PO4)2 raw material, P (mol) :F (mol) =3, after mixing evenly, dry and exhaust at 400℃, grind the obtained material into powder with a powder size of ≤0.35um.

[0045] Take out the cleaned SPS graphite mold, and cut a square graphite paper and two round graphite papers with the same inner diameter as the mold according to the size of the mold. First, roll the square graphite paper into a cylindrical shape and put it into the cylinder 1 so that it is close to the inner wall to provide the first graphite paper 2. Then take a round graphite paper and place it on the bottom of the cylinder 1 to make it flat to provide the second graphite paper 3. Introduce the powder into the space defined by the first graphite paper 2 and the second graphite paper 3. After adding about 95% of the volume of the cylinder 1, cover the powder with another layer of round graphite paper to provide the third graphite paper 4, and then insert the head 5 into the cylinder 1 until it cannot be pressed down further by hand.

[0046] Place the mold filled with materials in the SPS sintering furnace, place it stably, manually lower the pressure head 7 until the pressure value starts to be displayed on the pressure gauge, then stop lowering, insert the temperature probe 8 into the monitoring hole in the middle of the mold, and place the mold again to ensure that the upper and lower pressure heads and the mold as a whole are in a vertical line, and close the furnace door after adjustment.

[0047] After closing the furnace door, turn on the vacuum pump to exhaust the gas in the furnace and maintain a negative pressure of 1000 Pa. Set the pressurization pressure to 0.5t, turn on the heating element 9, set the heating program to heat to 350℃ at 50℃ / min, heat to 450℃ at 100℃ / min, maintain this temperature for 3mins, then cool down to below 50℃ at 50℃ / min, turn off the heating program, turn off the vacuum pump, and release the negative pressure.

[0048] Open the furnace door, slowly lift the pressure head 7, take out the mold, remove the head 5, use the demoulding machine to take out the internal solidified body, remove the graphite paper, and obtain the final glass ceramic solidified body, the SEM image of which is as follows: Figure 5 As shown, it can be observed from the surface morphology of the sample that the sample is relatively dense as a whole and the particles are uniform, indicating that the components have reacted with each other and are evenly mixed with each other, and it is speculated that it has good stability.

[0049] Example 6

[0050] Fe2O3, (NH4)H2PO4 and H3BO3 were ground and mixed in a ratio of 38wt%-57wt%-5wt% to prepare a raw material, and then Ca3(PO4)2 was added to the raw material in a mass ratio of 1:1.5, and then radioactive waste was added according to the ratio of fluorine and chlorine in the simulated waste to P in the Ca3(PO4)2 raw material. (mol) :F(Cl) (mol) =3, after mixing evenly, dry and exhaust at 400℃, grind the obtained material into powder with a powder size of ≤0.35um.

[0051] Take out the cleaned SPS graphite mold, and cut a square graphite paper and two round graphite papers with the same inner diameter as the mold according to the size of the mold. First, roll the square graphite paper into a cylindrical shape and put it into the cylinder 1 so that it is close to the inner wall to provide the first graphite paper 2. Then take a round graphite paper and place it on the bottom of the cylinder 1 to make it flat to provide the second graphite paper 3. Introduce the powder into the space defined by the first graphite paper 2 and the second graphite paper 3. After adding about 95% of the volume of the cylinder 1, cover the powder with another layer of round graphite paper to provide the third graphite paper 4, and then insert the head 5 into the cylinder 1 until it cannot be pressed down further by hand.

[0052] Place the mold filled with materials in the SPS sintering furnace, place it stably, manually lower the pressure head 7 until the pressure value starts to be displayed on the pressure gauge, then stop lowering, insert the temperature probe 8 into the monitoring hole in the middle of the mold, and place the mold again to ensure that the upper and lower pressure heads and the mold as a whole are in a vertical line, and close the furnace door after adjustment.

[0053] After closing the furnace door, turn on the vacuum pump to exhaust the gas in the furnace and maintain a negative pressure of 1000 Pa. Set the pressurization pressure to 0.5t, turn on the heating element 9, set the heating program to heat to 350℃ at 50℃ / min, heat to 450℃ at 100℃ / min, maintain this temperature for 3mins, then cool down to below 50℃ at 50℃ / min, turn off the heating program, turn off the vacuum pump, and release the negative pressure.

[0054] Open the furnace door, slowly lift the pressure head 7, take out the mold, remove the head 5, use a demoulding machine to take out the internal solidified body, remove the graphite paper, and obtain the final glass ceramic solidified body.

[0055] Example 7

[0056] The pressurizing pressure in this embodiment is set to 0.8t, and the rest is the same as in Embodiment 6.

[0057] Example 8

[0058] The pressurization pressure in this embodiment is set to 1.2t, and the rest is the same as in Embodiment 6.

[0059] Example 9

[0060] The pressurizing pressure in this embodiment is set to 1.5t, and the rest is the same as in Embodiment 6.

[0061] Example 10

[0062] Fe2O3, (NH4)H2PO4 and H3BO3 were ground and mixed in a ratio of 40wt%-60wt%-0wt% to prepare a raw material, and then Ca3(PO4)2 was added to the raw material in a mass ratio of 1:2 and ground and mixed. Radioactive waste was added according to the ratio of fluorine and chlorine in the simulated waste to P in the Ca3(PO4)2 raw material. (mol) :F(Cl) (mol) =3, after mixing evenly, dry and exhaust at 400℃, grind the obtained material into powder with a powder size of ≤0.35um.

[0063] Take out the cleaned SPS graphite mold, and cut a square graphite paper and two round graphite papers with the same inner diameter as the mold according to the size of the mold. First, roll the square graphite paper into a cylindrical shape and put it into the cylinder 1 so that it is close to the inner wall to provide the first graphite paper 2. Then take a round graphite paper and place it on the bottom of the cylinder 1 to make it flat to provide the second graphite paper 3. Introduce the powder into the space defined by the first graphite paper 2 and the second graphite paper 3. After adding about 95% of the volume of the cylinder 1, cover the powder with another layer of round graphite paper to provide the third graphite paper 4, and then insert the head 5 into the cylinder 1 until it cannot be pressed down further by hand.

[0064] Place the mold filled with materials in the SPS sintering furnace, place it stably, manually lower the pressure head 7 until the pressure value starts to be displayed on the pressure gauge, then stop lowering, insert the temperature probe 8 into the monitoring hole in the middle of the mold, and place the mold again to ensure that the upper and lower pressure heads and the mold as a whole are in a vertical line, and close the furnace door after adjustment.

[0065] After closing the furnace door, turn on the vacuum pump to exhaust the gas in the furnace and maintain a negative pressure of 1000 Pa. Set the pressurization pressure to 0.3t, turn on the heating element 9, set the heating program to heat to 350℃ at 50℃ / min, heat to 550℃ at 100℃ / min, maintain this temperature for 3mins, then cool down to below 50℃ at 50℃ / min, turn off the heating program, turn off the vacuum pump, and release the negative pressure.

[0066] Open the furnace door, slowly lift the pressure head 7, take out the mold, remove the head 5, use a demoulding machine to take out the internal solidified body, remove the graphite paper, and obtain the final glass ceramic solidified body.

[0067] Embodiment 11

[0068] Fe2O3, (NH4)H2PO4 and H3BO3 were ground and mixed in a ratio of 36wt%-54wt%-10wt% to prepare a raw material, and then Ca3(PO4)2 was added to the raw material in a mass ratio of 1:1 and ground and mixed. Radioactive waste was added according to the ratio of fluorine and chlorine in the simulated waste to P in the Ca3(PO4)2 raw material. (mol):F(Cl) (mol) =3, after mixing evenly, dry and exhaust at 400℃, grind the obtained material into powder with a powder size of ≤0.35um.

[0069] Take out the cleaned SPS graphite mold, and cut a square graphite paper and two round graphite papers with the same inner diameter as the mold according to the size of the mold. First, roll the square graphite paper into a cylindrical shape and put it into the cylinder 1 so that it is close to the inner wall to provide the first graphite paper 2. Then take a round graphite paper and place it on the bottom of the cylinder 1 to make it flat to provide the second graphite paper 3. Introduce the powder into the space defined by the first graphite paper 2 and the second graphite paper 3. After adding about 95% of the volume of the cylinder 1, cover the powder with another layer of round graphite paper to provide the third graphite paper 4, and then insert the head 5 into the cylinder 1 until it cannot be pressed down further by hand.

[0070] Place the mold filled with materials in the SPS sintering furnace, place it stably, manually lower the pressure head 7 until the pressure value starts to be displayed on the pressure gauge, then stop lowering, insert the temperature probe 8 into the monitoring hole in the middle of the mold, and place the mold again to ensure that the upper and lower pressure heads and the mold as a whole are in a vertical line, and close the furnace door after adjustment.

[0071] After closing the furnace door, turn on the vacuum pump to exhaust the gas in the furnace and maintain a negative pressure of 1000 Pa. Set the pressurization pressure to 0.3t, turn on the heating element 9, set the heating program to heat to 350℃ at 50℃ / min, heat to 450℃ at 100℃ / min, maintain this temperature for 2mins, then cool down to below 50℃ at 50℃ / min, turn off the heating program, turn off the vacuum pump, and release the negative pressure.

[0072] Open the furnace door, slowly lift the pressure head 7, take out the mold, remove the head 5, use a demoulding machine to take out the internal solidified body, remove the graphite paper, and obtain the final glass ceramic solidified body.

[0073] Example 12

[0074] In this embodiment, the holding time at the highest temperature is 1 min, and the rest is the same as in Example 11.

[0075] Comparative Example 1

[0076] Fe2O3, (NH4)H2PO4 and H3BO3 are ground and mixed in a ratio of 36wt%-54wt%-10wt% to prepare a raw material, and then Ca3(PO4)2 is added to the raw material in a mass ratio of 1:1 and ground and mixed, and radioactive waste is added according to the ratio of fluorine in the simulated waste of component A to P in the Ca3(PO4)2 raw material, P (mol) :F (mol)=3, after mixing evenly, dry and exhaust at 400℃, grind the obtained material into powder with a powder size of ≤0.35um.

[0077] Take out the clean 316 stainless steel mold, and cut a square reagent paper and two round reagent papers with the same inner diameter as the mold according to the size of the mold. First, roll the square reagent paper into a cylindrical shape and put it into the cylinder so that it fits tightly against the inner wall. Then take a round reagent paper and place it on the bottom of the cylinder to make it flat. Introduce the powder. After adding it to about 95% of the volume of the cylinder, cover the powder with another layer of round reagent paper, and then insert the head into the cylinder until it cannot be pressed down any further by hand.

[0078] Place the mold filled with materials on the press, and after it is placed stably, manually lower the pressure head until the pressure value starts to be displayed on the pressure gauge, then stop lowering it, and place the mold again to ensure that the upper and lower pressure heads and the mold as a whole are in a vertical line. After adjustment, start the automatic pressurization program, set the end pressure to 40MPa, and maintain this pressure for 1 minute before releasing the pressure, withdrawing the mold, and removing the pressed sample from the mold.

[0079] After removing the reagent paper from the surface of the pressed sample, place it in a drying oven for 24 hours. Then place it in a resistance heating furnace for heating. Set the heating program to heat to 450°C at 10°C / min, keep it at 450°C for 1 hour, then heat it to 850°C at 10°C / min, maintain this temperature for 3 hours, then turn off the heating program until the temperature in the furnace drops below 60°C, take out the sample, and obtain the final glass ceramic solidified body sample. Its SEM image is shown below. Figure 6 As shown, it can be clearly seen that there are obvious depressions and protrusions on the surface of the solidified body, and the crystals on the entire plane are very uneven, failing to show good morphological characteristics, which affects the performance of the solidified body.

[0080] The solidified body prepared in the comparative example can obtain the target crystals, but due to the different heating methods and the lack of pressure during the heating process, the solidified body has very tiny pores on its surface and is not dense enough, which is not conducive to the solidification of fluoride salt waste.

[0081] Comparative Example 2

[0082] Fe2O3, (NH4)H2PO4 and H3BO3 are ground and mixed in a ratio of 36wt%-54wt%-10wt% to prepare a raw material, and then Ca3(PO4)2 is added to the raw material in a mass ratio of 1:1 and ground and mixed, and radioactive waste is added according to the ratio of fluorine in the simulated waste of component A to P in the Ca3(PO4)2 raw material, P (mol) :F (mol) =3, after mixing evenly, dry and exhaust at 400℃, grind the obtained material into powder with a powder size of ≤0.35um.

[0083] Take out the cleaned SPS graphite mold, and cut a square graphite paper and two round graphite papers with the same inner diameter as the mold according to the size of the mold. First, roll the square graphite paper into a cylindrical shape and put it into the cylinder 1 so that it is close to the inner wall to provide the first graphite paper 2. Then take a round graphite paper and place it on the bottom of the cylinder 1 to make it flat to provide the second graphite paper 3. Introduce the powder into the space defined by the first graphite paper 2 and the second graphite paper 3. After adding about 95% of the volume of the cylinder 1, cover the powder with another layer of round graphite paper to provide the third graphite paper 4, and then insert the head 5 into the cylinder 1 until it cannot be pressed down further by hand.

[0084] Place the mold filled with materials in the SPS sintering furnace, place it stably, manually lower the pressure head 7 until the pressure value starts to be displayed on the pressure gauge, then stop lowering, insert the temperature probe 8 into the monitoring hole in the middle of the mold, and place the mold again to ensure that the upper and lower pressure heads and the mold as a whole are in a vertical line, and close the furnace door after adjustment.

[0085] After closing the furnace door, turn on the vacuum pump to exhaust the gas in the furnace and maintain a negative pressure of 1000 Pa. Set the pressurization pressure to 0.3t, turn on the heating element 9, set the heating program to heat to 350℃ at 50℃ / min, heat to 850℃ at 100℃ / min, maintain this temperature for 3mins, then cool down to below 50℃ at 50℃ / min, turn off the heating program, turn off the vacuum pump, and release the negative pressure.

[0086] The furnace door was opened, the pressure head 7 was slowly lifted, the mold was taken out, and after removing the sealing head 5, the internal solidified body was taken out using a demoulding machine. It was found that the added materials were completely melted at 850°C, and the final glass ceramic solidified body could not be obtained.

[0087] In Comparative Example 1, the simulated waste of component A was subjected to cold pressing and sintering at 850°C for 3 hours to obtain a solidified body, but in Comparative Example 2, under the same conditions, the added material had melted and could not be formed under pressure. In Example 5, the same component only needed to be formed at 450°C for 3 minutes.

[0088] The above is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. The above embodiment of the present invention can also be modified in various ways. That is, all simple, equivalent changes and modifications made according to the claims and the description of the present invention fall within the scope of protection of the claims of the present invention. The contents not described in detail in the present invention are all conventional technical contents.

Claims

1. A method for solidifying chlorine and / or fluorine-containing radioactive waste by glass ceramics, characterized in that: The method includes: S1, grinding and mixing Fe2O3, (NH4)H2PO4 and H3BO3 to prepare raw materials, adding Ca3(PO4)2 to the raw materials after grinding and mixing, adding radioactive waste according to the ratio of chlorine and / or fluorine in the radioactive waste to P in Ca3(PO4)2, wherein the molar ratio of P to F or the molar ratio of P to Cl is between 3-5, mixing evenly, drying and exhausting, and grinding the obtained material into powder; S2, introducing the powder into the graphite mold; S3, placing the graphite mold in a sintering furnace; S4, evacuate the sintering furnace, set the pressure to 0.3t-1.5t, set the heating program to 50-100℃ / min and heat to 350-550℃, and perform spark plasma sintering for 1-3mins; S5, use a demolding machine to remove the glass-ceramic solid body from the graphite mold, the glass-ceramic solid body includes a ceramic mixture bonded by iron phosphate glass, the ceramic mixture is a mixture of fluorine / chlorapatite, fluorine / chlorapatite and monazite, the chemical structural formulas of the fluorine / chlorapatite, fluorine / chlorapatite and monazite are M5(PO4)3F, M5(PO4)3Cl and NPO4, respectively, wherein M is a metal cation of Li, Ca, Ba, Sr, Cs, La, U, Zr, and N is a cation of Ce, Th, U, Pu.

2. The method according to claim 1, characterized in that In step S1, the ratio of Fe2O3, (NH4)H2PO4 and H3BO3 is 36-40wt%:54-60wt%:0-10wt%.

3. The method according to claim 1, characterized in that In step S1, the mass ratio of the raw material to Ca3(PO4)2 is 1:

2.

4. The method according to claim 1, characterized in that: Step S2 includes: the first graphite paper is close to the inner wall of the cylinder of the graphite mold, the second graphite paper is laid on the bottom of the cylinder, the powder is introduced into the space defined by the first graphite paper and the second graphite paper, the third graphite paper is covered on the top of the powder, and the head of the graphite mold is inserted into the cylinder above the third graphite paper and pressed down.

5. The method according to claim 1, characterized in that In step S4, after evacuation, a negative pressure of 1000 Pa is maintained.

6. The method according to claim 1, characterized in that In step S4, the pressurizing pressure is set to 0.5t-1.2t.

7. The method according to claim 1, characterized in that In step S4, the heating program is set to heat to 350°C at 50°C / min and heat to 450-550°C at 100°C / min.

8. The method according to claim 1, characterized in that: In step S4, after spark plasma sintering, the temperature is lowered to below 50°C at a rate of 50°C / min, the heating program is turned off, and the vacuum pump is turned off.

9. A glass ceramic solidified body obtained by the method according to any one of claims 1 to 8.

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