Method for solidifying electrolytic refining waste salt through glass ceramic with monazite as ceramic phase and application

Abstract

The invention discloses a method for solidifying electrolytic refining waste salt through glass ceramic with monazite as a ceramic phase and application, and belongs to the technical field of radioactive nuclear waste treatment. LiCl-KCl molten salt obtained after electrolytic refining contains chlorides of splitting elements and actinide elements, and K3PO4 and K2CO3 are added into the molten salt so that the splitting elements and the actinide elements can be precipitated in the molten salt. And after cooling, separating the precipitate from the LiCl-KCl fused salt in a washing, filtering and recrystallizing manner. Mixing the precipitate with a curing agent NH4H2PO4, and carrying out pressureless sintering to obtain a monazite single-phase pre-sintered ceramic material; the recrystallized LiCl-KCl uses 4A zeolite to adsorb chloride ions, and salt-loaded zeolite is obtained. And adding the pre-sintered ceramic material and the salt-loaded zeolite into the glass material, blending, and sintering to obtain the glass ceramic solidified body. According to the method, the precipitation product REPO4 of the retrograde element (RE) is used for embedding other retrograde elements (Sr, Ba) and actinide elements, various simulated radioactive elements such as the retrograde elements, the actinide elements and the like and the chlorine element are successfully solidified at the same time, and the method has large inclusion capacity and low leaching rate.

Description

Technical Field

[0001] The present invention belongs to the technical field of radioactive nuclear waste treatment, and particularly relates to a method and application for vitrifying electrolytically refined waste salt with monazite as the ceramic phase in a glass-ceramic. Background Art

[0002] With the development and application of nuclear technology, dry reprocessing technology is more suitable for future treatment of fast reactor spent fuels with high irradiation, high burnup, and high plutonium content. The electrolytic refining technology is one of the dry reprocessing technologies with industrialization prospects. Its advantages are simple process flow, high temperature resistance, small device volume, small waste production, and radiation resistance. It can realize the reprocessing of different types of spent fuels and also the recovery of minor actinides. A representative one is the pyrochemical electrolytic refining process developed by Argonne National Laboratory in the United States, and the molten salt system uses LiCl-KCl. The waste salt unloaded from the electrolytic refining cell contains more fission products and a small amount of actinides, which can be directly disposed of as waste or the residual actinides can be recovered by complete electrolysis. The waste molten salt after complete electrolysis still contains at least 0.1 wt.% uranium element. The finally unloaded waste salt contains a large amount of chloride ions, more fission products, some corrosion products, and low contents of residual actinides (U, Pu, Am, etc.).

[0003] The types and properties of elements in the waste salt are complex, and there is high radioactivity, threatening the ecological environment of the earth. Therefore, it is necessary to find a solidification matrix with stable structure and radiation resistance to form a stable and leach-resistant solid waste, isolating it from the human living environment. The traditional solidification methods mainly include cement solidification, asphalt solidification, and glass solidification. The cement and asphalt solidifications are simple mechanical combinations with poor solidification stability. For the chloride molten salt system, since the compatibility of conventional silicate glass with chlorides is relatively low, the waste salt cannot be disposed of by simple glass solidification.

[0004] In order to immobilize the waste salt generated from the electrorefining treatment of EBR-II fast reactor spent fuel, Argonne National Laboratory in the United States developed the CWF (Ceramic Waste Form) waste form. The first step is to utilize the "cage-shaped" crystal structure of zeolite to adsorb metal chlorides into these "cages" to form salt-loaded zeolite. The second step is to use borosilicate glass as a binder to wrap the salt-loaded zeolite transformed into sodalite while dissolving other radioactive cations. The final reaction equation for obtaining the CWF solidified body is: Na 12 (AlSiO4) 12 +4NaCl → 2Na8(AlSiO4)6Cl2.

[0005] However, under the influence of water and heat in geological conditions, the glass matrix will undergo a transformation from the non-crystalline state to the crystalline state, thereby releasing radioactive cations. To improve the stability of radioactive cations in the CWF solidified body, according to the principle of "isomorphism", fixing them in the crystal lattice of artificial ore can achieve the purpose of reducing the leaching rate and improving chemical and geological stability.

[0006] Monazite (alias, monazite) is a monoclinic orthophosphate (Ce, RE, Th, U, Ca)PO4 containing Ce and other rare earth elements. Monazite as a ceramic matrix is a single-phase material with a flexible structure, and almost all elements of HLW can be accommodated as solid solutions in its crystal structure. And its outstanding performance in radiation resistance and chemical durability is considered a safe and reliable solidification form for disposing of radioactive fission elements and actinide waste.

[0007] There is no report on the research of directly synthesizing monazite ceramics through precipitation products applicable to the chloride molten salt system at home and abroad. There is also no report on the research of using monazite single-phase ceramics to strengthen the solidification performance of CWF glass-ceramic solidified bodies. This method directly uses the precipitation products of fission products as raw materials, and solidifies fission products and actinides through pressureless sintering, so that the ceramic solidified body has a large embedding rate. The glass-ceramic solidified body with monazite ceramic phase prepared by this method has a uniform element distribution, realizes the embedding of RE, Sr, Ba, U, and Cl elements, and has good solidification performance. This method is committed to realizing the one-stop treatment of electrolytic refining waste salt from unloading to burial, and provides an economically feasible solution for industrial application. The CWF glass-ceramic designed with monazite as the ceramic phase in this method can simultaneously treat LiCl-KCl, RECl3 (RE = Nd, Ce, La, Pr, Sm), SrCl2, BaCl2, and UCl4 in the waste salt, which is of great significance for the safe treatment and disposal of radioactive waste salt generated in the electrolytic refining process. Summary of the Invention

[0008] The purpose of the present invention is to provide a solidification method for the waste salt generated during the treatment of spent fuel using the electrolytic refining method, and further to describe a method for solidifying chloride molten salt, fission products and actinides in the waste salt; this waste salt contains LiCl-KCl, RECl3 (RE = Nd, Ce, La, Pr, Sm), SrCl2, BaCl2, and UCl4.

[0009] The present invention provides a method for solidifying electrolytic refining waste salt with a glass-ceramic having monazite as the ceramic phase, comprising the following steps:

[0010] Step 1: Add precipitants K3PO4 and K2CO3 to the LiCl-KCl molten salt containing fission product chlorides and actinide chlorides, separate and retain the bottom precipitate by liquid separation; wash the cooled precipitate with deionized water to separate the precipitate and the salt-containing filtrate; evaporate the water from the salt-containing filtrate to obtain recrystallized LiCl-KCl; dry the precipitate to obtain a pure precipitate.

[0011] Step 2: Mix the precipitate obtained in Step 1 with a curing agent NH4H2PO4 and sinter it by pressureless sintering to obtain a pre-sintered monazite ceramic body.

[0012] Step 3: Perform chloride ion adsorption on the recrystallized LiCl-KCl obtained in Step 1 and 4A zeolite in a pit furnace to obtain salt-loaded zeolite.

[0013] Step 4: Mix the pre-sintered monazite ceramic body obtained in Step 2 with the salt-loaded zeolite obtained in Step 3, add glass powder, grind them in a ball mill, and then send them to a muffle furnace for final sintering to obtain a glass-ceramic solidified body with monazite as the ceramic phase.

[0014] Further, in Step 1, the fission product elements include rare earth elements RE and alkaline earth metal elements; the rare earth elements RE are selected from one or more of La, Nd, Ce, Sm, and Pr; the alkaline earth metal elements are selected from one or two of Sr and Ba; the actinide element is U.

[0015] Further, in Step 1, the temperature at which the precipitant is added to the molten salt is 450 - 550 °C; the precipitate is three or more of REPO4, UO 2、 SrCO3, and BaCO3.

[0016] Further, Step 2 is specifically to mix the precipitate with NH4H2PO4, place it in a corundum crucible and put it into a muffle furnace for pressureless sintering. With a heating rate of 1 - 10 °C / min, first heat it to 900 °C, hold for 2 h, then heat it to 1200 - 1400 °C, hold for 3 h, and cool it to room temperature with the furnace to obtain a pre-sintered monazite ceramic body; the mass ratio of NH4H2PO4 to the precipitate is not less than 0.2; the molar ratio of NH4H2PO4 to the total molar number of alkaline earth metal elements and actinide elements in the precipitate is 1:1.

[0017] Further, in Step 2, the chemical composition general formula of the pre-sintered monazite ceramic body is: A x B y M yPO4, where x = 1 - y, 0.5 < x < 1, A is one or more of trivalent lanthanide elements Nd, Ce, La, Pr, Sm, B is one or two of divalent alkaline earth metal elements Sr, Ba, and M is tetravalent actinide element U.

[0018] Further, in step 3, the 4A zeolite is dried in an oven before being added; the drying temperature is 90 °C, and the drying time is greater than 24 h; the mass of recrystallized LiCl-KCl in the salt-loaded zeolite accounts for 10 - 12 wt.%.

[0019] Further, in step 3, the adsorption temperature is 500 °C, the adsorption time is 12 - 24 h, and stirring is performed in the furnace every 4 h during adsorption.

[0020] Further, in step 4, the glass powder is selected from one of borosilicate glass or iron phosphate glass; the composition mass ratio of the borosilicate glass is SiO2:B2O3:Al2O3:ZrO2:Na2O = 51:20:9:4:16; the composition mass ratio of the iron phosphate glass is B2O3:Fe2O3:P2O5 = 5:34:61.

[0021] Further, in step 4, the mass ratio of the pre-sintered monazite ceramic body, salt-loaded zeolite, and glass powder is one of 1:1:8, 2:2:6, 3:3:4, 4:4:2; the rotation speed of the ball mill is 300 r / min, and the forward and reverse rotation times are each 2 h; the muffle furnace is heated to 900 - 1200 °C and sintered for 5 h, with a heating rate of 1 - 10 °C / min, and then naturally cooled to room temperature to obtain a glass-ceramic solidified body with a uniform element distribution and monazite as the ceramic phase.

[0022] The present invention also provides a method for vitrifying electrolytically refined waste salt with monazite as the ceramic phase, which is applied to the ceramic solidification of high-level radioactive nuclear waste.

[0023] The principle and specific description of the present invention are as follows:

[0024] The reactions involved after adding the precipitant K3PO4 in step (1) are: RECl3 + K3PO4 = REPO4↓ + 3KCl, and the reactions involved after adding the precipitant K2CO3 are: SrCl2 + K2CO3 = SrCO3↓ + 2KCl, BaCl2 + K2CO3 = BaCO3↓ + 2KCl, UCl4 + 2K2CO3 = UO2↓ + 4KCl + 2CO2↑.

[0025] The beneficial effects of the present invention are as follows:

[0026] 1. The method of the present invention can be applied to the solidification treatment of waste salt generated in the dry reprocessing of spent fuel by molten salt electrolysis.

[0027] 2. The method of the present invention is to directly add a precipitant to the molten waste salt of LiCl-KCl, and use the precipitation product of fission products to embed fission products and actinides, obtaining a monazite single-phase ceramic solidified body. Utilizing the chloride ion adsorption ability of 4A zeolite and the bonding effect of glass powder, radioactive nuclides and chloride molten salt are co-solidified. The method is simple and has the prospect of industrial application. The glass-ceramic solidified body designed in the present invention with monazite as the ceramic phase combines the high compatibility of monazite-type ceramics with nuclides and the high solidification ability of CWF glass-ceramics with chlorides, successfully co-solidifying various radioactive elements such as fission products and actinides with chlorine element, having a large encapsulation capacity and a low leaching rate. The implementation method of the present invention is simple and can provide an economically feasible solution for industrial application.

[0028] 3. The borosilicate glass-ceramic with monazite as the ceramic phase prepared by the method of the present invention at a waste salt encapsulation capacity of 30 wt.% has very stable chemical properties and uniform element distribution in the solidified body. The normalized leaching rate of La element is 2.75×10 -5 g·m 2 ·d -1 , the normalized leaching rate of Sr element is 7.26×10 -5 g·m 2 ·d -1 , the normalized leaching rate of Ce element is 7.26×10 -5 g·m 2 ·d -1 , the normalized leaching rate of Cl element is 6.72×10 -3 g·m 2 ·d -1 , and the solidification effect is good. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is the implementation roadmap of the present invention;

[0030] Figure 2 is the XRD pattern of La 0.6 Sr 0.2 U 0.2 PO4 monazite ceramic;

[0031] Figure 3 is the XRD pattern of the glass-ceramic with La 0.6 Sr 0.2 Ce 0.2 PO4 monazite as the ceramic phase;

[0032] Figure 4 is the XRD pattern of the glass-ceramic with La 0.6 Sr 0.2 Ce 0.2Physical photo, SEM and EDS scanning pictures of glass-ceramics with monazite as the ceramic phase and PO4 Detailed implementation mode

[0033] The present invention will be described in more detail below with reference to the accompanying drawings;

[0034] The present invention discloses a method for solidifying electrolytic refining waste salt with glass-ceramics using monazite as the ceramic phase. As Figure 1 shown, it includes the following steps:

[0035] (1) Purifying molten salt by precipitation method: Adding precipitants K3PO4 and K2CO3 to the LiCl-KCl molten salt containing RECl3 (RE = La, Nd, Ce, Sm, Pr), SrCl2, BaCl2, and UCl4 to generate REPO4, SrCO3, BaCO3, and UO2 precipitates in the molten salt. After cooling, wash with water and filter to separate the precipitates from the salt-containing filtrate. Evaporate the water from the salt-containing filtrate to obtain recrystallized LiCl-KCl for further treatment.

[0036] (2) Pre-sintering of the ceramic body: Mix the precipitates REPO4, SrCO3, BaCO3, and UO2 in step (1) with the curing agent NH4H2PO4, place them in a corundum crucible and put it into a muffle furnace. With a heating rate of 1 - 10 °C / min, first heat to 900 °C and hold for 2 hours, then heat to 1200 - 1400 °C and hold for 3 hours, and then cool to room temperature with the furnace to obtain a monazite pre-sintered ceramic material (A x B y M y PO4).

[0037] (3) Adsorbing chloride ions with 4A zeolite: Place the LiCl-KCl obtained in step (1) and 4A zeolite in a corundum crucible and put it into a pit furnace. With a heating rate of 1 - 10 °C / min, heat to 500 °C and hold for 12 - 24 hours, and stir in the furnace every 4 hours during this period to obtain salt-loaded zeolite.

[0038] (4) Solidifying the glass-ceramic body: Add the monazite single-phase pre-sintered ceramic material in step (2) and the salt-loaded zeolite in step (3) to the glass powder. After mixing with a planetary ball mill, place it in a corundum crucible and put it into a muffle furnace. With a heating rate of 1 °C / min - 10 °C / min, heat to 915 - 1200 °C and hold for 3 - 5 hours to obtain a glass-ceramic solidified body.

[0039] The main components of the salt-containing precipitate in step (1) are REPO4, SrCO3, BaCO3, UO2, and LiCl-KCl.

[0040] The molten salt in step (1) mainly consists of LiCl-KCl, and the temperature of the molten salt is 450°C to 550°C.

[0041] The general chemical composition formula of the monazite ceramic body in step (2) is: A x B y M y PO4, where x = 1 - y, 0.5 < x < 1, A is one or more of the trivalent lanthanide elements Nd, Ce, La, Pr, Sm, B is one or more of the divalent alkaline earth metal elements Sr, Ba, and M is the tetravalent actinide element U.

[0042] The reaction involved after adding NH4H2PO4 in step (2) is: yAPO4 + xBCO3 + xMO2 + 2xNH4H2PO4 = A y B x M x PO4 + 2xNH3↑ + 3xH2O↑

[0043] In step (2), the mass ratio of NH4H2PO4 to the precipitate should not be less than 0.2, and the molar ratio of the addition amount of NH4H2PO4 to the total molar amount of B and M is 1:1.

[0044] For the salt-loaded zeolite obtained in step (3), the mass of recrystallized LiCl-KCl accounts for 10 - 12 wt.%, and the mass of 4A zeolite accounts for 88 - 90 wt.%. The 4A zeolite should be placed in an oven at 90°C to remove water for more than 24 hours before adding.

[0045] In step (4), the glass powder can be one of borosilicate glass or iron phosphate glass. The composition mass ratio of borosilicate glass is SiO2:B2O3:Al2O3:ZrO2:Na2O = 51:20:9:4:16. The composition mass ratio of iron phosphate glass is B2O3:Fe2O3:P2O5 = 5:34:61.

[0046] In step (4), the mass ratio of the pre-fired ceramic material, salt-loaded zeolite, and glass powder can be one of 1:1:8, 2:2:6, 3:3:4, 4:4:2.

[0047] Example 1

[0048] Use Ce 4+ to replace U 4+ for the simulated solidification of U (Note: The ionic radii of Ce 4+ and U 4+ are very close, and they have similar reaction characteristics). The implementation process can refer to the appendix Figure 1, specifically: LaCl3, SrCl2, and CeCl4 exist in the LiCl-KCl (mass ratio 38:45, the same below) molten salt. After adding K3PO4 and K2CO3, precipitates LaPO4, SrCO3, and CeO2 are obtained. The precipitate is separated from the salt by washing and filtration. The precipitate and NH4H2PO4 are mixed and ground in a mortar in a ratio of LaPO4:SrCO3:CeO2:NH4H2PO4 = 3:1:1:2 (molar ratio) until uniform, then transferred to a corundum crucible, placed in a muffle furnace, heated at 5 °C / min (the same below) to 900 °C, held for 2 hours, then heated to 1200 °C and held for 2 hours, and taken out after cooling to room temperature with the furnace, obtaining a pre-fired ceramic material, which is a yellow-green block, and its chemical formula is La 0.6 Sr 0.2 Ce 0.2 PO4. After recrystallizing the separated salt and mixing and grinding it with 4A zeolite, it is transferred to a muffle furnace, heated to 500 °C, and held for 12 h, with stirring in the furnace every 4 h during this period. After the adsorption is completed, it is cooled to room temperature with the furnace to obtain a salt-loaded zeolite. The obtained pre-fired ceramic material, salt-loaded zeolite, and borosilicate glass powder are mixed in a mass ratio of 3:3:4, placed in a planetary ball mill at 300 r / min, with the forward and reverse rotation times each being 2 hours. After mixing evenly, it is transferred to a muffle furnace, heated to 1200 °C, held for 5 hours, and taken out after cooling, obtaining a glass-ceramic solid (XRD see Figure 3 , SEM photos and EDS surface scanning photos see attached Figure 4 ).

[0049] Leaching rate performance test of the solid: Soak the powder with deionized water according to the PCT (Product conformance testing) standard, soak it statically at 90 °C for 28 days, the normalized leaching rate of La element is 2.75×10 -5 g·m 2 ·d -1 , the normalized leaching rate of Sr element is 7.26×10 -5 g·m 2 ·d -1 , the normalized leaching rate of Ce element is 7.26×10 -5 g·m 2 ·d -1 , the normalized leaching rate of Cl element is 6.72×10 -3 g·m 2 ·d -1 , and the solidification effect is good. (Specific normalized leaching rate data are shown in Table 1)

[0050] Example 2

[0051] The difference from Example 1 is that the borosilicate glass powder is replaced with iron phosphate glass powder. The powder is soaked in deionized water according to the PCT standard and left standing at 90 °C for 28 days. The normalized leaching rate of La element is 2.64×10 -6 g·m 2 ·d -1 , the normalized leaching rate of Sr element is 8.14×10 -4 g·m 2 ·d -1 , the normalized leaching rate of Ce element is 3.63×10 -6 g·m 2 ·d -1 , the normalized leaching rate of Cl element is 3.65×10 -3 g·m 2 ·d -1 , and the solidification effect is good, as shown in Table 1.

[0052] Table 1 Normalized leaching rate data of the present invention under PCT standard

[0053]

[0054] Example 3

[0055] The difference from Example 1 is that the pre-fired ceramic material, salt-loaded zeolite and borosilicate glass powder are mixed in a mass ratio of 2:2:6, put into a planetary ball mill and ground and mixed evenly, and then transferred into a muffle furnace and heated to 915 °C at a rate of 5 °C / min, and finally a glass-ceramic solidified body is obtained (XRD is shown in the appendix Figure 3 ).

[0056] Example 4

[0057] The difference from Example 1 is that BaCl2 is added to the molten salt composition, and the chemical formula of the monazite ceramic is La 0.6 Sr 0.1 Ba 0.1 Ce 0.2 PO4.

[0058] Example 5

[0059] The difference from Example 1 is that SmCl3 is added to the molten salt composition, and the chemical formula of the monazite ceramic is La 0.3 Sm 0.3 Sr 0.2 Ce 0.2 PO4.

[0060] Example 6

[0061] The difference from Example 1 is that CeCl4 in the molten salt composition is replaced with UCl4, and the chemical formula of the monazite ceramic is La 0.6 Sr0.2 U 0.2 PO4 (XRD see attached Figure 2 ).

[0062] In summary, the electrolytically refined LiCl-KCl molten salt contains chlorides of fission products (RE, Sr, Ba) and actinides (U). In the present invention, precipitants K3PO4 and K2CO3 are added to the molten salt to precipitate the fission products and actinides in the form of REPO4, SrCO3, BaCO3, and UO2 in the molten salt respectively. After cooling, the precipitate and the LiCl-KCl molten salt are separated by washing with water, filtering, and recrystallization, and then processed separately. After mixing the above precipitate with the curing agent NH4H2PO4, a monazite single-phase pre-sintered ceramic material is obtained by pressureless sintering, and its chemical general formula is: A x B y M y PO4, where x = 1 - y, 0.5 < x < 1, A is one or more of trivalent lanthanide elements Nd, Ce, La, Pr, Sm, B is one or more of divalent alkaline earth metal elements Sr, Ba, and M is tetravalent actinide element U. The above recrystallized LiCl-KCl adsorbs chloride ions using 4A zeolite to obtain salt-loaded zeolite. After mixing the above monazite single-phase ceramic body and the salt-loaded zeolite with the glass frit and sintering, a glass-ceramic solidified body with uniform element distribution with monazite as the ceramic phase is obtained. The present invention has carried out precipitation purification and glass-ceramic solidification treatment on the radioactive waste salt generated after electrolytic refining of the LiCl-KCl molten salt system, and uses the precipitation product REPO4 of the fission product (RE) to embed other fission products (Sr, Ba) and actinides (U), successfully solidifying various simulated radioactive elements such as fission products and actinides and chlorine element at the same time, with a large embedding capacity and a low leaching rate. The implementation method of the present invention is simple and can provide an economically feasible solution for industrial application.

[0063] The embodiments described above are only for describing the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for solidifying electrolytic refining waste salt with glass ceramics using monazite as the ceramic phase, characterized in that: The following steps are involved: Step 1: adding precipitants K3PO4 and K2CO3 to LiCl-KCl molten salt containing chlorides of fragment elements and chlorides of actinide elements, separating the liquids to retain the bottom precipitate; washing the cooled precipitate with deionized water to separate the precipitate and the salt-containing filtrate; evaporating the water from the salt-containing filtrate to obtain recrystallized LiCl-KCl; and drying the precipitate to obtain a pure precipitate; Step 2: Mix the precipitate in step 1 with a curing agent NH4H2PO4 and sinter them by pressureless sintering to obtain a pre-sintered monazite ceramic body; Step 3: The recrystallized LiCl-KCl obtained in step 1 and 4A zeolite are subjected to chloride ion adsorption in a pit furnace to obtain salt-loaded zeolite; Step 4: Mix the pre-sintered monazite ceramic body of step 2 with the salt-loaded zeolite of step 3, add glass powder and grind in a ball mill, then send into a muffle furnace for final sintering to obtain a glass ceramic solidified body with monazite as the ceramic phase.

2. The method for solidifying electrolytic refining waste salt with glass ceramics having monazite as the ceramic phase according to claim 1, characterized in that: In step 1, the fragment elements include lanthanide elements RE and alkaline earth metal elements; the lanthanide elements RE are selected from one or more of La, Nd, Ce, Sm, and Pr; the alkaline earth metal elements are selected from one or two of Sr and Ba; and the actinide elements are U.

3. The method for solidifying electrolytic refining waste salt with glass ceramics having monazite as the ceramic phase according to claim 2, characterized in that: In step 1, the temperature of adding the precipitant to the molten salt is 450-550°C; the precipitate is REPO4, UO 2、 Three or more of SrCO3 and BaCO3.

4. The method for solidifying electrolytic refining waste salt with glass ceramics having monazite as the ceramic phase according to claim 3, characterized in that: The step 2 is specifically as follows: after mixing the precipitate with NH4H2PO4, placing the mixture in a corundum crucible and placing it in a muffle furnace for pressureless sintering, heating the mixture to 900°C at a heating rate of 1 to 10°C / min, keeping the mixture for 2 hours, then heating the mixture to 1200 to 1400°C, keeping the mixture for 3 hours, and cooling the mixture to room temperature to obtain a pre-sintered monazite ceramic body; the mass ratio of the NH4H2PO4 to the precipitate is not less than 0.2; the ratio of the molar number of the NH4H2PO4 to the total molar number of the alkaline earth metal elements and actinide elements in the precipitate is 1:

1.

5. The method for solidifying electrolytic refining waste salt with glass ceramics having monazite as the ceramic phase according to claim 4, characterized in that: In step 2, the chemical composition formula of the pre-sintered monazite ceramic body is: x B y M y PO4, wherein x=1-y, 0.5<x<1, A is one or more of the trivalent lanthanide elements Nd, Ce, La, Pr, Sm, B is one or two of the divalent alkaline earth metal elements Sr and Ba, and M is the tetravalent actinide element U.

6. The method for solidifying electrolytic refining waste salt with glass ceramics having monazite as the ceramic phase according to claim 1, characterized in that: In step 3, the 4A zeolite is placed in an oven for drying before being added; the drying temperature is 90° C., and the drying time is greater than 24 hours; the mass of recrystallized LiCl-KCl in the salt-loaded zeolite accounts for 10 to 12 wt.%.

7. The method for solidifying electrolytic refining waste salt with glass ceramics having monazite as the ceramic phase according to claim 1, characterized in that: In step 3, the adsorption temperature is 500° C., the adsorption time is 12 to 24 hours, and the mixture is stirred in the furnace every 4 hours during the adsorption period.

8. The method for solidifying electrolytic refining waste salt with glass ceramics having monazite as the ceramic phase according to claim 1, characterized in that: In step 4, the glass powder is selected from one of borosilicate glass and iron phosphate glass; the mass ratio of the borosilicate glass is SiO2:B2O3:Al2O3:ZrO2:Na2O=51:20:9:4:16; the mass ratio of the iron phosphate glass is B2O3:Fe2O3:P2O5=5:34:

61.

9. The method for solidifying electrolytic refining waste salt with glass ceramics having monazite as the ceramic phase according to claim 1, characterized in that: In step 4, the mass ratio of the pre-sintered monazite ceramic body, salt-loaded zeolite, and glass powder is one of 1:1:8, 2:2:6, 3:3:4, and 4:4:2; the ball mill speed is 300 r / min, and the forward and reverse times are 2 h each; the muffle furnace is heated to 900-1200°C and sintered for 5 h, with a heating rate of 1-10°C / min, and naturally cooled to room temperature to obtain a glass ceramic solidified body with uniform element distribution and monazite as the ceramic phase.

10. An application of the method for solidifying electrolytic refining waste salt by glass ceramics with monazite as the ceramic phase as claimed in any one of claims 1 to 9, characterized in that: Used in ceramic solidification of high-level radioactive nuclear waste.

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