KR20180126820A - Borate glass wasteform to immobilize rare-earth oxides from pyro-processing and manufacturing method thereof - Google Patents

Abstract

The present disclosure relates to a borate glass wasteform to immobilize radioactive rare earth waste generated in a pyrogenic process and a manufacturing method thereof. The borate glass wasteform includes: a glass medium containing boron oxide (B_2O_3), calcium oxide (CaO), and aluminum oxide (Al_2O_3); and a radioactive rare earth waste. It is possible to maintain a process temperature.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a boric acid glass solid body for carrying rare-earth waste, and a method for manufacturing the same. BACKGROUND ART [0002]

The present disclosure relates to a boric acid glass solid for immobilizing radioactive rare earth waste generated in a pyrogen process and a method for producing the same.

Spent fuel reprocessing technology is divided into wet process and dry process. The wet process (PUREX) is a technology for separating uranium and plutonium by dissolving spent nuclear fuel with nitric acid, organic solvent and so on. In the wet process, there is a possibility of separating plutonium and the like and used for the development of nuclear weapons. Therefore, in Korea, there is no technology for reprocessing spent fuel by wet process in terms of nuclear nonproliferation.

Pyro processing, a dry process, is a technique for electrolyzing spent fuel using molten salt. The dry process is remarkable in terms of nuclear nonproliferation since it is a technology that can not separate only plutonium due to electrochemical characteristics of each material.

In pyrolytic processes, radioactive waste is separated by characteristics. In the pretreatment process, volatile nuclei such as Tc and I, LiCl salts containing fission products of Cs and Sr such as Cs and Sr in the electrolytic reduction process, rare earth nuclides and very small quantities of actinide nuclides in the refining / The included LiCl-KCl eutectic salts are each generated as waste. The LiCl-KCl eutectic salt generated during the double electrolytic refining / smelting process can be reused in the pyrogen process by removing the contained nuclides in oxide form. That is, the waste to be finally disposed in the above step has a rare-earth oxide form.

The conventional technology for producing the radioactive rare earth waste as a solid body is disclosed in Korean Patent Laid-Open No. 10-2010-0133089 (manufactured by Korea Atomic Energy Research Institute), a method for producing a ceramic solidified body containing radioactive rare earth waste, Stability and erosion resistance) and Korean Patent Laid-Open No. 10-2016-0049564 (vitrification method of radioactive rare earth waste) invented by Korea Hydro & Nuclear Power Co., Ltd. The Korea Atomic Energy Research Institute (KAERI) synthesized ZIT (Zinc Titante) ceramic solid after synthesizing rare earth oxides with rare earth monazite (RE-monazite). This solidification process improved leaching and physico - chemical properties. However, this solidification process is difficult to commercialize due to the impossibility of continuous process and the complexity of the process. The alumina-containing glass solids invented by Korea Hydro & Nuclear Power Co., Ltd. can be applied to actual vitrification process, but the amount of rare earth waste is only about 20% by weight.

The viscous condition of the glass for smoothly performing the melting step during the vitrification process is 10-100 poise. However, rare earths have the property of increasing the viscosity in the glass manufacturing process. Therefore, if the amount of rare earth waste is increased, the melting temperature may increase and the operation cost of the melting furnace may increase.

Accordingly, there is a growing need for a boric acid glass solid that can maintain the process temperature while improving the amount of rare earth support in the glass, and a method for producing the same.

The present invention intends to provide a boric acid glass solid body capable of maintaining the process temperature while improving the amount of the radioactive rare earth waste in the glass and a method of manufacturing the same.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not intended to limit the invention to the precise form disclosed. It can be understood.

The boric acid glass solids according to one embodiment of the present invention include glass medium and radioactive rare earth waste including boron oxide (B ₂ O ₃ ), calcium oxide (CaO) and aluminum oxide (Al ₂ O ₃ ).

The glass medium may contain from 35 mol% or more to 60 mol% or less of the boron oxide, 10 mol% or more and 25 mol% or less of the calcium oxide, and 1 mol% or more and 20 mol% or less of the aluminum oxide.

The radioactive rare earth waste may be contained in an amount of 1 wt% or more and 60 wt% or less.

The radioactive rare earth waste may be selected from the group consisting of Lanthanum, La, Cesium, Praseodymium Pr, Neodymium Nd, Promethium, Pm, Samarium, (Europium, Eu), Gadolinium (Gd), Terbium, Tb, Dysprosium, Dy, Holmium, Ho, Erbium, Er, Thulium, Terbium, Tb, Lutetium, Lu, and Yttrium (Y) oxides.

A method of manufacturing a boric acid glass solidified body according to another embodiment of the present invention includes the steps of (1) introducing radioactive rare earth waste into a melting furnace, (2) introducing a glass medium into the furnace to vitrify the radioactive rare earth waste, (3) melting the radioactive rare earth waste and the glass medium together to produce a melt, and (4) solidifying the melt to produce a boric acid glass solid.

The radioactive rare earth waste may be selected from the group consisting of Lanthanum, La, Cesium, Praseodymium Pr, Neodymium Nd, Promethium, Pm, Samarium, (Europium, Eu), Gadolinium (Gd), Terbium, Tb, Dysprosium, Dy, Holmium, Ho, Erbium, Er, Thulium, Terbium, Tb, Lutetium, Lu, and Yttrium (Y) oxides.

The melt of step (3) may comprise from 1 wt% to 60 wt% of radioactive rare earth waste, and the remainder may be the glass medium.

The glass medium in the step (2) includes boron oxide (B ₂ O ₃ ), calcium oxide (CaO) and aluminum oxide (Al ₂ O ₃ ), and may not contain silicon oxide (SiO ₂ ) .

At this time, the molten material in the step (3) may include 35 mol% or more and 60 mol% or less of the boron oxide, 10 mol% or more and 25 mol% or less of the calcium oxide, and 1 mol% or more and 20 mol% or less of the aluminum oxide And the remainder may be the radioactive rare earth waste.

In the step (3), the temperature in the melting furnace may be elevated from 1100 DEG C to 1400 DEG C to melt the radioactive rare earth waste and the glass medium.

According to the present invention, the radioactive rare earth waste can be stably vitrified, which is effective in terms of volume. In addition, the increase of the melting point, which may occur when treating with a borosilicate glass system, can be blocked by using boric acid glass.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a photograph of a real object of a boric acid glass solidified body according to Experimental Examples 1 to 4 of the present invention. FIG.
2 is a graph showing an X-ray diffraction (XRD) pattern of Experimental Examples 3 and 4 of the present invention.
3 is an XRD result of evaluating the thermal stability of a boric acid glass solidified body according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, the well-known functions or constructions will not be described in order to clarify the present invention.

The boric acid glass solids according to one embodiment of the present invention include glass medium and radioactive rare earth waste including boron oxide (B ₂ O ₃ ), calcium oxide (CaO) and aluminum oxide (Al ₂ O ₃ ).

The glass medium according to this embodiment may contain 35 mol% or more and 60 mol% or less of boron oxide, 10 mol% or more and 25 mol% or less of calcium oxide, and 1 mol% or more and 20 mol% or less of aluminum oxide. Other portions of the other boric acid glass solids may include radioactive rare earth waste and other unavoidable impurities.

At this time, the glass medium according to the present embodiment is characterized in that silicon oxide (SiO ₂ ) in the borosilicate glass increases the viscosity, and does not contain silicon oxide.

The amount of the radioactive rare earth waste according to this embodiment can be included in the boric acid glass solid matter in an amount of 1 wt% or more and 57 wt% or less, when the content based on the mol% is converted into the weight percentage (wt%). In terms of mol%, the radioactive rare earth waste is 1 mol% or more and 22 mol% or less, and the radioactive rare earth waste of this embodiment can be contained in the boric acid glass solid matter in an amount of 1 mol% or more and 22 mol% or less. In particular, according to the present embodiment, it is possible to provide a boric acid glass solid body comprising a high content of radioactive rare earth waste of 50 wt% or more.

Radioactive rare earth wastes include Lanthanum, La, Cesium, Ce, Praseodymium, Pr, Neodymium, Nd, Promethium, Pm, Samarium, , Eu, Gadolinium, Gd, Terbium, Tb, Dysprosium, Dy, Holmium, Ho, Erbium, Er, Thulium, Tm, Terbium, Tb), lutetium (Lu), and yttrium (Y) oxide.

According to another embodiment of the present invention, there is provided a method for producing a molten glass, comprising the steps of injecting radioactive rare earth waste into a furnace, introducing a glass medium into the furnace to vitrify the radioactive rare earth waste, melting the radioactive rare earth waste and the glass medium together to produce a melt And solidifying the melt to produce a boric acid glass solidified body.

The step of injecting the radioactive rare earth waste into the melting furnace may be carried out by using lanthanum, La, cesium, Praseodymium, Pr, Neodymium, Nd, Promethium, Pm, Gadolinium, Gd, Terbium, Tb, Dysprosium, Dy, Holmium, Ho, Erbium, Er, A method for melting and heating a radioactive rare earth waste comprising at least one material selected from the group consisting of Thulium (Tm), Terbium (Tb), Lutetium, Lu and Yttrium (Y) .

The step of introducing the glass medium into the melting furnace is a step of introducing the glass medium into the melting furnace into which the radioactive rare earth waste is introduced in order to vitrify the radioactive rare earth waste. The glass medium according to this embodiment may include boron oxide (B ₂ O ₃ ), calcium oxide (CaO), and aluminum oxide (Al ₂ O ₃ ). In addition, attention is paid to the point that silicon oxide (SiO ₂ ) increases viscosity in borosilicate glass, and silicon oxide is not included.

After the radioactive rare-earth waste and the glass medium are put into the melting furnace, they are melted together to produce a melt. The step of melting the radioactive rare earth waste and the glass medium together to produce a melt is a step of raising the temperature in the melting furnace to 1100 ° C. or more and 1400 ° C. or less to melt the radioactive rare earth waste and the glass medium injected into the melting furnace.

At this time, the glass medium present in the melt may contain 35 mol% or more and 60 mol% or less of boron oxide, 10 mol% or more and 25 mol% or less of calcium oxide, and 1 mol% or more and 20 mol% or less of aluminum oxide. Other portions of the other boric acid glass solids may include radioactive rare earth waste and other unavoidable impurities.

Or the melt may contain 1 wt% or more and 57 wt% or less of the radioactive rare earth waste, and the mol% thereof corresponds to 1 mol% to 22 mol%. The remainder may include glass medium and other unavoidable impurities.

Boric acid glass containing radioactive rare earth waste Solid body  Produce

Table 1 shows molar ratios of the glass medium and the radioactive rare earth waste according to Experimental Examples 1 to 4 according to the embodiments of the present invention. (100-x) (0.25 calcium oxide (CaO) - 0.19 aluminum oxide (Al ₂ O ₃ ) - 0.56 boron oxide (B ₂ O ₃ )) - x Nd ₂ O ₃ (Mol%, x = 0, 10, 20, 30)) is evenly mixed. 25 g of the powder mixture was immersed in an alumina crucible and then melted in an electric furnace at 1300 ° C for 30 minutes and quenched to prepare a boric acid glass solidified body.

FIG. 1 is a photograph of a real object of a boric acid glass solidified body according to Experimental Examples 1 to 4 shown in Table 1, FIG. 2 is a graph showing X-ray diffraction (XRD) patterns of Experimental Examples 3 and 4 of the present invention Graph. Referring to FIGS. 1 and 2, when the content of Nd ₂ O ₃ exceeds 22 mol% (about 57 wt%) in the composition shown in Table 1, crystallization is carried out under the above-mentioned melting conditions. Can be confirmed.

Mole ratio Experimental Example 1 Experimental Example 2 Experimental Example 3 Experimental Example 4
(Comparative Example) CaO 25.0 22.5 20.0 17.5 Al ₂ O ₃ 18.8 16.9 15.0 13.1 B ₂ O ₃ 56.2 50.6 45.0 39.4 Nd ₂ O ₃ 0 10 20 30 total 100 100 100 100 Vitrification possible possible possible Impossible

Boric acid glass containing radioactive rare earth waste Solid  Thermal Stability Analysis

In order to analyze the passivity stability of the boric acid glass solid body containing the radioactive rare earth waste, the boric acid glass solid body corresponding to Experimental Example 3 among the boric acid glass solid bodies prepared by the method of Example 1 was heated at 600 and 700 ° C for 5 hours Respectively. The time to reach each temperature was set to 1 hour, and after the heat treatment, it was low temperature.

FIG. 3 is an XRD result of evaluating the thermal stability of the boric acid glass solidified according to each experimental example manufactured through the above-described process. Referring to FIG. 3, it can be seen that the boric acid glass solidified body according to the present invention is thermally stable since there is no phase change of the boric acid glass solidified body when the heat treatment is performed at 700 ° C or lower.

Boric acid glass containing radioactive rare earth waste Solid Leaching characteristics  analysis

Table 2 shows the result of performing a standard test, product consistency test (PCT), in order to evaluate the leaching characteristics of boric acid glass solid bodies containing radioactive rare earth waste.

In the above experiment, the boric acid glass solid prepared according to Experimental Examples 1 to 4 of Example 1 was changed to 75-150um powder, and then 1.5g of powder and 15ml of distilled water were immersed in a 50ml Teflon container at 90 ° C for 7 days. The leachate was then sampled and subjected to ICP-AES analysis to determine the concentrations of leached elements in the leachate and normalized. In the case of Experimental Example 4, the vitrification did not proceed stably and the leaching experiment was not carried out.

g / m ² Ca B Al Nd Experimental Example 1 0% 0.469 0.677 0.002 - Experimental Example 2 10% 0.473 0.406 0.016 Below detection limit Experimental Example 3 20% 0.073 0.067 0.009 Below detection limit

As a result, as shown in Table 2, the leaching rate of all the elements showed a regulatory standard of 2 g / m ² or less. Especially, the leaching amount of neodymium (Nd) Or less. As a result, it can be seen that the boric acid glass solid body prepared according to Experimental Examples 1 to 4 of the present invention satisfies the international leaching standards for radioactive waste.

The boric acid glass solid body and the method of manufacturing the same according to an embodiment of the present invention have been described above. According to the present invention, it is possible to stabilize vitrification by containing up to 57% by weight of radioactive waste, which is effective from the viewpoint of bulkiness, and which can inhibit the increase of the melting point, which can occur when treating with a borosilicate glass system, Glassy solid and a method for producing the same.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, It is obvious to those who have. Accordingly, it should be understood that such modifications or alterations should not be understood individually from the technical spirit and viewpoint of the present invention, and that modified embodiments fall within the scope of the claims of the present invention.

Claims (10)

A glass medium containing boron oxide (B ₂ O ₃ ), calcium oxide (CaO) and aluminum oxide (Al ₂ O ₃ ); And
Boric acid glass solids containing radioactive rare earth waste. The method of claim 1,
Wherein the glass medium comprises,
From 35 mol% to 60 mol% of the above boron oxide;
10 mol% or more and 25 mol% or less of the calcium oxide; And
From 1 mol% to 20 mol% of the aluminum oxide. The method of claim 1,
From 1 wt% to 57 wt% of the radioactive rare earth waste. The method according to claim 1,
The radioactive rare-
Lanthanum, La, Cesium, Ce, Praseodymium Pr, Neodymium Nd, Promethium, Pm, Samarium, Sm, Europium, Eu, (Gadolinium, Gd), Terbium, Tb, Dysprosium, Dy, Holmium, Ho, Erbium, Er, Thulium, Tm, Terbium, (Lutetium, Lu) and yttrium (Y) oxides. (1) introducing radioactive rare earth waste into a furnace;
(2) introducing a glass medium into the melting furnace to vitrify the radioactive rare earth waste;
(3) melting the radioactive rare earth waste and the glass medium together to produce a melt; And
(4) solidifying the melt to produce a boric acid glass solidified body. 6. The method of claim 5,
The radioactive rare-
Lanthanum, La, Cesium, Ce, Praseodymium Pr, Neodymium Nd, Promethium, Pm, Samarium, Sm, Europium, Eu, (Gadolinium, Gd), Terbium, Tb, Dysprosium, Dy, Holmium, Ho, Erbium, Er, Thulium, Tm, Terbium, (Lutetium, Lu), and yttrium (Y) oxide. 6. The method of claim 5,
Wherein the melt in step (3) comprises 1 wt% or more and 57 wt% or less of the radioactive rare earth waste, and the remainder is the glass medium. 6. The method of claim 5,
The glass medium in the step (2)
(B ₂ O ₃ ), calcium oxide (CaO) and aluminum oxide (Al ₂ O ₃ )
A method for producing a boric acid glass solidified body, which does not contain silicon oxide (SiO ₂ ). 9. The method of claim 8,
The melt of step (3)
From 35 mol% to 60 mol% of the above boron oxide;
10 mol% or more and 25 mol% or less of the calcium oxide; And
And 1% by mol or more and 20% by mol or less of the aluminum oxide,
And the remainder is the radioactive rare earth waste. 6. The method of claim 5,
The step (3)
And raising the temperature in the melting furnace from 1100 DEG C to 1400 DEG C to melt the radioactive rare earth waste and the glass medium.

Images