Method for solidifying radioactive waste ion-exchange resin by using phosphoric acid-based geopolymer raw material, and radioactive waste ion-exchange resin solidified body obtained using same

Abstract

The present invention relates to a method for solidifying a radioactive waste ion-exchange resin by using a phosphoric acid-based geopolymer raw material, the method comprising the steps of: (a) generating a mixture in which a radioactive waste ion-exchange resin, metakaolin, water and an acidic activator are mixed; and (b) curing the mixture, wherein the acidic activator is phosphoric acid (H3PO4).

Description

A method for solidifying radioactive waste ion exchange resin using phosphoric acid-based geopolymer raw materials and a solidified body of radioactive waste ion exchange resin obtained thereby

[0001] The present invention relates to a method for solidifying radioactive waste using a phosphoric acid-based geopolymer raw material and a radioactive waste solidification body thereof, and relates to a method for solidifying radioactive waste such as radioactive waste ion exchange resins by using a phosphoric acid-based geopolymer solidification body having a compressive strength higher than the acceptance standards of a radioactive waste disposal facility while maximizing the loading rate of radioactive waste.

[0002]

[0003] In general, most of the reactor devices and equipment used in nuclear power plants and then disposed of after their lifespan has ended are contaminated with radioactive materials.

[0004] Buildings, facilities, machinery, structures, etc. contaminated with radioactive materials cannot be simply buried or incinerated. They must be decontaminated and cut to remove the radioactive materials, and then disposed of in accordance with the provisions of the Atomic Energy Act and the Environmental Protection Act.

[0005] According to these processing regulations, low- and intermediate-level radioactive waste, such as radioactive concentrated waste powder generated from nuclear power plants, radioactive waste ion exchange resin, and radioactive acid waste generated from chemical decontamination processes, are solidified with solidifying materials such as cement (concrete), paraffin, asphalt, and geopolymer and placed in storage drums for safe storage in a fixed form.

[0006] These radioactive wastes are permanently disposed of in radioactive waste disposal facilities, and it is important to stably solidify them to prevent the fixed nuclides contained in the disposed radioactive wastes from leaking into the surrounding environment. It is common to stabilize low- and intermediate-level radioactive wastes by solidifying them using cement.

[0007] However, radioactive waste ion exchange resins, which together with radioactive concentrated liquid waste account for over 90% of Korea's low- and intermediate-level radioactive waste, are composed of organic materials and emit high levels of radioactivity depending on the nuclide, making cement solidification difficult. In particular, due to the organic ion exchange resin's tendency to absorb water and swell, problems such as cement solidification falling off or cracking continue to be reported.

[0008] To overcome the limitations of cement, several solutions have been proposed, including solidifying the waste with an organic polymer solidifier, converting the radioactive waste ion exchange resin into a liquid for disposal using the Fenton process, and solidifying it by drying and crushing. However, these solutions have not been adopted due to issues such as cost-effectiveness, heterogeneity of the solidified waste, and the potential for secondary waste generation. Consequently, the radioactive waste ion exchange resin is currently temporarily stored within nuclear power plants.

[0009]

[0010] Accordingly, there is an urgent need for research on a method that can maximize the retention rate of radioactive waste, such as radioactive waste ion exchange resin, while solidifying it into a solidified body with a compressive strength higher than the acceptance standards of a radioactive waste disposal facility.

[0011]

[0012] (Patent Document 1) KR 10-2375027 B

[0013] (Patent Document 2) KR 10-2181217 B

[0014]

[0015] In order to solve the problems of the above-mentioned conventional technology, a method is proposed that can maximize the loading rate of radioactive waste when disposing of radioactive waste such as radioactive waste ion exchange resin by solidification, while solidifying it into a solidified body having a compressive strength higher than the acceptance standard of a radioactive waste disposal facility.

[0016]

[0017] In order to solve the problems of the prior art described above, the method for solidifying a radioactive waste ion exchange resin according to the present invention comprises: (a) a step of producing a mixture of a radioactive waste ion exchange resin, metakaolin, water, and an acid activator; and (b) a step of curing the mixture.

[0018] The above acid activator may be phosphoric acid (H3PO4).

[0019]

[0020] Preferably, the ratio of the weight of the water and the water contained in the acidic activator to the weight of the remainder excluding the water and the water contained in the acidic activator in the mixture may be 0.6 to 1.3.

[0021]

[0022] Preferably, the weight parts of the radioactive waste ion exchange resin may be 10 to 50 for 100 weight parts of the mixture.

[0023]

[0024] Preferably, the ratio of the molar concentration of phosphorus to the molar concentration of aluminum in the mixture may be 0.6 to 1.2.

[0025]

[0026] Preferably, the molar concentration of phosphorus in the above phosphoric acid may be 8 to 12 mol / L.

[0027]

[0028] Preferably, the ratio of the weight of the water and the water contained in the acidic activator to the weight of the remainder excluding the water and the water contained in the acidic activator in the mixture may be 0.6 to 0.8.

[0029]

[0030] Preferably, the weight parts of the radioactive waste ion exchange resin may be 40 to 50 per 100 parts by weight of the mixture.

[0031]

[0032] Preferably, the ratio of the molar concentration of phosphorus to the molar concentration of aluminum in the mixture may be 0.6 to 0.8.

[0033]

[0034] Preferably, the molar concentration of phosphorus in the above phosphoric acid may be 8 to 12 mol / L.

[0035]

[0036] Preferably, the ratio of the weight of the water and the water contained in the acidic activator to the weight of the remainder excluding the water and the water contained in the acidic activator in the mixture may be 0.65 to 0.75.

[0037]

[0038] Preferably, the weight parts of the radioactive waste ion exchange resin may be 45 to 50 for 100 weight parts of the mixture.

[0039]

[0040] Preferably, the ratio of the molar concentration of phosphorus to the molar concentration of aluminum in the mixture may be 0.65 to 0.75.

[0041]

[0042] Preferably, the molar concentration of phosphorus in the above phosphoric acid may be 8 to 12 mol / L.

[0043]

[0044] Preferably, in the step (b), the mixture can be cured for 5 to 7 days.

[0045]

[0046] In order to solve the problems of the above-described prior art, the solidified radioactive ion exchange resin according to the present invention may be a solidified radioactive ion exchange resin manufactured according to the above-described method for solidifying the radioactive ion exchange resin.

[0047]

[0048] By means of the above-described problem-solving means, it is possible to efficiently solidify and dispose of radioactive waste ion exchange resin using a solidification method that minimizes the occurrence of problems caused by conventional technologies and maximizes the loading rate of radioactive waste while maintaining a compressive strength higher than the acceptance criteria of a radioactive waste disposal facility.

[0049]

[0050] FIG. 1 is a drawing showing an example of a mixing ratio for manufacturing a geopolymer solidified body according to the present invention.

[0051] FIG. 2 is a drawing schematically illustrating a process for manufacturing a radioactive waste ion exchange resin sample used in manufacturing a geopolymer solidified body according to the present invention.

[0052] Figures 3 to 8 are drawings showing test data for a geopolymer solidified body according to the present invention.

[0053]

[0054] Hereinafter, preferred embodiments of the method according to the present invention will be described with reference to the attached drawings. Throughout this process, the thickness of lines and the sizes of components depicted in the drawings may be exaggerated for clarity and convenience. Furthermore, the terms described below are defined based on their functions in the present invention and may vary depending on the intent or custom of the user or operator. Therefore, the definitions of these terms should be based on the overall content of this specification.

[0055]

[0056] Referring to FIGS. 1 to 8, a method for solidifying radioactive waste ion exchange resin into a geopolymer solidified body using a raw material for manufacturing a phosphoric acid-based geopolymer is described.

[0057] A mixture of radioactive waste ion exchange resin, metakaolin, water, and an acid activator can be produced, and then the mixture produced in this manner can be cured to produce a geopolymer solidified body in which the radioactive waste ion exchange resin is solidified.

[0058] Here, the acid activator may be phosphoric acid (H3PO4).

[0059]

[0060] Among the mixing ratios of the mixture, we first look at the weight ratio between water and the remainder in the mixture.

[0061] The ratio of the weight (L) of water containing water and acid activator to the weight (S) of the remainder excluding water and water contained in the acid activator in the mixture may be from 0.6 to 1.3. That is, the L / S ratio may be from 0.6 to 1.3, where L is the weight of water in the mixture including water and water contained in the acid activator, and S is the weight of the remainder excluding water and water contained in the acid activator in the mixture.

[0062] More preferably, the L / S ratio may be 0.6 to 0.8, and even more preferably, 0.65 to 0.75.

[0063] Next, looking at the weight of the radioactive waste ion exchange resin mixed into the mixture, the weight parts of the radioactive waste ion exchange resin may be 10 to 50 for 100 parts by weight of the entire mixture. More preferably, it may be 40 to 50. Even more preferably, it may be 45 to 50.

[0064] Next, looking at the molar concentration ratio of aluminum and phosphorus in the mixture, the ratio of the molar concentration of phosphorus to the molar concentration of aluminum in the mixture may be 0.6 to 1.2. More preferably, it may be 0.6 to 0.8. Even more preferably, it may be 0.65 to 0.75.

[0065] Next, the molar concentration of phosphorus in phosphoric acid mixed as an oxidation activator may be 8 to 12 mol / L.

[0066]

[0067] Looking at the curing conditions, the mixture mixed at the above-described mixing ratio can be cured for 5 to 7 days. Specifically, the mixture can be cured at room temperature for 4.5 to 5.5 days, and then at 55 to 65°C for 0.5 to 1.5 days.

[0068]

[0069] Describe the experiment and its results.

[0070] Figure 1 is about the mixing ratio and curing conditions of a mixture for producing a geopolymer solidified body in which a radioactive waste ion exchange resin solidifies.

[0071] In Figure 1, P molarity represents the concentration of phosphorus in phosphoric acid, which is an acid activator. In the Liquid / Solid ratio, Liquid represents the weight of the water in the mixture plus the water contained in the acid activator, and Solid represents the weight of the remainder of the mixture minus the water in the mixture plus the water contained in the acid activator.

[0072] The P / Al molarity ratio represents the ratio of the molar concentration of phosphorus to the molar concentration of aluminum in the mixture, and the waste loading (wt%) represents the weight percentage of radioactive waste ion exchange resin mixed in the mixture (radioactive waste ion exchange resin loading rate).

[0073] Figure 2 illustrates the conditions under which the radioactive waste ion exchange resin sample used in the experiment was manufactured. The manufactured radioactive waste ion exchange resin sample was a radioactive waste ion exchange resin sample saturated with water. In Figure 1, in the Liquid / Solid ratio, Liquid is the weight of water and water contained in the acid activator in the mixture, and is the weight of water contained in the radioactive waste ion exchange resin without water. In Figure 1, Solid is the weight of the remainder of the radioactive waste ion exchange resin with water contained.

[0074] Figure 3 shows the compressive strength of each sample (geopolymer solidified body manufactured according to the mixing ratio shown in Figure 1) at an L / S ratio (Liquid / Solid ratio in Figure 1) of 1.2.

[0075] In Fig. 3, the compressive strength of the geopolymer solidified body manufactured without mixing in the radioactive spent ion exchange resin (Spent IER loading (wt%) = 0) is shown to be significantly higher than the compressive strengths of the remaining samples (geopolymer solidified bodies manufactured by mixing in the radioactive spent ion exchange resin, Spent IER loading (wt%) = 10, 20, 30, 40, 50).

[0076] Radioactive spent ion exchange resins have low mechanical strength, which is attributed to their porous structure. For this reason, the compressive strength of geopolymer solidified bodies mixed with radioactive spent ion exchange resins with a porous structure appears to be lower than that of geopolymer solidified bodies without radioactive spent ion exchange resins.

[0077] In Fig. 3, except for the case where the loading ratio is 50 wt%, the remaining samples show a compressive strength exceeding the compressive strength of 3.445 MPa, which is the standard compressive strength for a radioactive waste disposal facility.

[0078] Figure 4 shows the compressive strength of samples according to each L / S ratio. When the L / S ratio is 0.7, it shows a higher compressive strength than when the L / S ratio is 1.2, and even when the loading ratio of the radioactive waste ion exchange resin is 50 wt%, it shows a compressive strength that exceeds the compressive strength (3.445 MPa) of the acceptance criteria for a radioactive waste disposal facility.

[0079] Looking at Figures 3 and 4, the L / S ratio appears to affect the compressive strength of the manufactured geopolymer solidified body. This is because the greater the amount of water mixed into the mixture (the higher the L / S ratio), the more diluted the concentration of the acid activator becomes, which in turn reduces the compressive strength of the geopolymer solidified body.

[0080] The geopolymer solidified body manufactured according to the present invention was subjected to gamma irradiation, water immersion, and thermal cycling tests, which are radioactive waste disposal facility acceptance criteria tests, and Fig. 5 shows the compressive strength of the geopolymer solidified body according to the loading ratio before the test (control) and after the test (gamma irradiation, water immersion, thermal cycling). Considering the standard deviation of the compressive strength, it appears that the radioactive waste disposal facility acceptance criteria test did not induce structural decomposition of the geopolymer solidified body. Gamma rays can cause changes in the structure of organic substances, but it appears that the geopolymer solidified body manufactured according to the present invention has no effect. The geopolymer solidified body according to the present invention exhibits excellent water resistance and freeze-thaw stability.

[0081] Figure 6 shows the leachability index. Cobalt (Co), cesium (Cs), and strontium (Sr) show leachability indices that satisfy the radioactive waste disposal site acceptance criteria of higher than 6.0 according to ANSI / ANS. Silicon (Si), aluminum (Al), and phosphorus (P), which are the main components of geopolymer solidified bodies, show good leachability indices of 12 or higher, which are much higher than the radioactive waste disposal site acceptance criteria of higher than 6.0 according to ANSI / ANS. In the case of leachability indices of cobalt (Co), cesium (Cs), and strontium (Sr), the solidified alkali-based geopolymer solidified body with radioactive waste ion exchange resin shows a lower leachability indices than the solidified alkali-based geopolymer solidified body. The attractive force between the structural negative charge and positively charged nuclides in the alkali-based geopolymer solidified body effectively prevents the movement of positively charged nuclides, resulting in a high leachability indices. On the other hand, the repulsive force between the positive charge and positively charged nuclides in the geopolymer solidified body appears to cause a low leachability indices.

[0082] Figure 7 shows the microstructure of geopolymer solidified bodies according to the present invention before (control) and after (gamma irradiation, water immersion, thermal cycling) testing. The radioactive waste disposal facility acceptance criteria test did not appear to affect the microstructure of the geopolymer solidified bodies. All geopolymer solidified bodies exhibited a dense and well-connected microstructure.

[0083] FIG. 8 shows XRD analysis data of a geopolymer solidified body before (control) and after (gamma irradiation, water immersion, thermal cycling) testing according to the present invention. Amorphous protrusions appearing at 2 theta 18-35 degrees indicate the geopolymer structure. While the crystalline structure of the geopolymer solidified body after water immersion and thermal cycling tests was not changed, aluminum phosphate (AlPO4) crystals were confirmed as new crystals in the geopolymer solidified body after leaching and gamma irradiation tests. Anatase appears to be an impurity contained in metakaolin. Overall, it appears that the amorphous structure of the geopolymer solidified body manufactured according to the present invention is maintained even after the radioactive waste disposal site acceptance standard test is performed.

[0084]

[0085] While the present invention has been described with reference to the embodiments illustrated in the drawings to facilitate understanding and reproduction by those skilled in the art, these are merely exemplary, and those skilled in the art will appreciate that various modifications and equivalent embodiments are possible based on the embodiments of the present invention. Therefore, the scope of protection of the present invention should be defined by the claims.

Claims

1. (a) a step of producing a mixture of radioactive waste ion exchange resin, metakaolin, water and an acid activator; and (b) comprising a step of curing the mixture; The above acid activator is a method for solidifying a radioactive waste ion exchange resin, which is phosphoric acid (H3PO4).

2. In paragraph 1, A method for solidifying a radioactive waste ion exchange resin, wherein the weight ratio of the water contained in the acid activator and the water contained in the acid activator to the weight of the remainder excluding the water and the water contained in the acid activator in the mixture is 0.6 to 1.

3.

3. In paragraph 2, A method for solidifying a radioactive waste ion exchange resin, wherein the weight parts of the radioactive waste ion exchange resin are 10 to 50 for 100 weight parts of the above mixture.

4. In paragraph 3, A method for solidifying a radioactive waste ion exchange resin, wherein the ratio of the molar concentration of phosphorus to the molar concentration of aluminum in the above mixture is 0.6 to 1.

2.

5. In paragraph 4, A method for solidifying a radioactive waste ion exchange resin, wherein the molar concentration of phosphorus in the above phosphoric acid is 8 to 12 mol / L.

6. In paragraph 1, A method for solidifying a radioactive waste ion exchange resin, wherein the weight ratio of the water contained in the acid activator and the water contained in the acid activator to the weight of the remainder excluding the water and the water contained in the acid activator in the mixture is 0.6 to 0.

8.

7. In paragraph 6, A method for solidifying a radioactive waste ion exchange resin, wherein the weight parts of the radioactive waste ion exchange resin are 40 to 50 parts per 100 parts by weight of the above mixture.

8. In paragraph 7, A method for solidifying a radioactive waste ion exchange resin, wherein the ratio of the molar concentration of phosphorus to the molar concentration of aluminum in the above mixture is 0.6 to 0.

8.

9. In paragraph 8, A method for solidifying a radioactive waste ion exchange resin, wherein the molar concentration of phosphorus in the above phosphoric acid is 8 to 12 mol / L.

10. In paragraph 1, A method for solidifying a radioactive waste ion exchange resin, wherein the weight ratio of the water contained in the acid activator and the water contained in the acid activator to the weight of the remainder excluding the water and the water contained in the acid activator in the mixture is 0.65 to 0.

75.

11. In paragraph 10, A method for solidifying a radioactive waste ion exchange resin, wherein the weight parts of the radioactive waste ion exchange resin are 45 to 50 parts per 100 parts by weight of the mixture.

12. In paragraph 11, A method for solidifying a radioactive waste ion exchange resin, wherein the ratio of the molar concentration of phosphorus to the molar concentration of aluminum in the above mixture is 0.65 to 0.

75.

13. In paragraph 12, A method for solidifying a radioactive waste ion exchange resin, wherein the molar concentration of phosphorus in the above phosphoric acid is 8 to 12 mol / L.

14. In paragraph 1, A method for solidifying a radioactive waste ion exchange resin, wherein the mixture is cured for 5 to 7 days in the above step (b).

15. A solidified radioactive waste ion exchange resin manufactured according to the solidification method of radioactive waste ion exchange resin according to Article 1.

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