Low-temperature curing method of borate glass ceramics coated with copper / silver aerogel

Abstract

The present invention discloses a method for low-temperature solidification of borate glass ceramics coated with copper / silver aerogel, and belongs to the technical field of radioactive waste treatment. The radioactive iodine-coated copper / silver aerogel is mixed with borate glass ceramic powder, and deionized water is added and then ground to obtain a wet mixture; the wet mixture is dried to obtain a dry mixture; the dry mixture is placed in a sintering device for sintering, and after sintering, it is cooled to obtain a glass ceramic sintered body. The glass ceramic sintered body has the advantages of higher volume density and lower nuclide leaching rate, and can well inhibit the migration of radioactive iodine in nature. In addition, the low-temperature solidification method of the present application has the characteristics of simple process, energy saving and environmental protection, safety and reliability. In summary, the present invention has important application value in the field of radioactive waste treatment technology.

Description

Technical Field

[0001] The invention belongs to the technical field of radioactive waste treatment, and in particular relates to a low-temperature solidification method for copper / silver aerogel-coated borate glass ceramics. Background Art

[0002] In recent years, the field of nuclear technology has developed rapidly. Nuclear energy, as a clean and efficient energy source, has been favored by people. However, in the development and utilization of nuclear technology, various radioactive wastes will inevitably be produced. Considering the living environment and life and health of human beings, the safe treatment and disposal of radioactive wastes is imminent. The safe use of nuclear technology and the control of radioactive pollution have become topics of great concern to the world.

[0003] During the post-processing of spent fuel (irradiated nuclear fuel), waste gas containing iodine-129 is generated. Because iodine-129 is chemically active, has a long half-life, and is easily accumulated in organisms and causes long-term damage, it needs to be disposed of urgently. Some existing methods such as cement and asphalt solidification can dispose of radioactive iodine to a certain extent, but the solidified body has poor stability and high solidification conditions; and radioactive iodine cannot be disposed of for a long time. Therefore, the safe disposal of iodine-containing waste has become an important task we are currently facing.

[0004] The existing methods for treating radioactive gaseous iodine will eventually form certain iodine-containing wastes. If these iodine-containing wastes are not treated safely and effectively, the radioactive iodine in them may be desorbed and enter the environment. Therefore, we should pay great attention to the treatment of iodine-containing wastes generated after the separation of radioactive gaseous iodine, put the protection of the ecological environment and human health in the first place, and it is very important to invent a method with good adsorption performance, low solidification conditions, and long-term disposal of radioactive iodine. Summary of the invention

[0005] The purpose of the present invention is to overcome the defects of the prior art and provide a low temperature curing method for borate glass ceramics coated with copper / silver aerogel.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A method for low-temperature curing of copper / silver aerogel-coated borate glass ceramics comprises the following steps:

[0008] S1, mixing radioactive iodine-containing copper / silver aerogel particles with borate glass ceramic powder, adding deionized water and grinding to obtain a wet mixture;

[0009] S2, drying the wet mixture to obtain a dry mixture;

[0010] S3, placing the dried mixture into a sintering device for sintering, and cooling after sintering to obtain a glass ceramic sintered body.

[0011] Furthermore, the radioactive iodine-containing copper / silver aerogel particles in step S1 are composed of AgI, CuI and silica aerogel.

[0012] Furthermore, in step S1, the maximum outer diameter of the radioactive iodine-containing copper / silver aerogel is less than or equal to 50 μm.

[0013] Furthermore, in step S1, the borate glass ceramic powder is prepared by sintering and grinding boron oxide, aluminum oxide and barium oxide in the mass percentage of 40-65% boron oxide, 15-20% aluminum oxide and 12-20% barium oxide; the sintering temperature is 1000°C-1300°C.

[0014] Furthermore, the specific method of the drying treatment in step S2 is: ventilation drying at a temperature between 25° C. and 100° C. for 1 h to 5 h.

[0015] Furthermore, in the mixture dried in step S3, the radioactive iodine-containing copper / silver aerogel particles account for 35%-55% and the borate glass ceramic powder accounts for 30%-55% by mass; the mass of the radioactive iodine does not exceed 20% of the total mass of the mixture.

[0016] Furthermore, the sintering device in step S3 is a high-temperature muffle furnace or a microwave sintering furnace.

[0017] Furthermore, in step S3, the sintering temperature is 800° C.-900° C., and the sintering time is 1 h-3 h.

[0018] Copper and silver are coated on the silica aerogel at the same time. The binding force of copper and silver to iodine ions is stable and strong, which effectively inhibits the migration of radioactive iodine. In addition, the specific surface area and porosity of silica aerogel are much larger than those of silica gel, zeolite and other materials, and the adsorption performance is much higher than those of silica gel, zeolite and other materials, which significantly improves the adsorption performance of glass-ceramic sintered bodies to iodine. Moreover, silica aerogel is not easily affected by external environmental factors, which improves the stability of glass-ceramic sintered bodies. In addition, boron as a flux depressant can better reduce the melting point, and by limiting the amount of boron oxide used, the sintering temperature during the sintering process can be effectively reduced, so low-temperature sintering can be achieved and the curing conditions are reduced, which is safe, reliable, energy-saving and environmentally friendly.

[0019] It should be noted that by limiting the outer diameter of the radioactive iodine-containing copper / silver aerogel particles, grinding is easier, ensuring that the radioactive iodine-containing copper / silver aerogel and borate glass ceramic powder are mixed and ground more fully.

[0020] Beneficial effects of the present invention:

[0021] The present invention obtains a glass ceramic sintered body by solidifying the iodine-adsorbed aerogel into glass ceramics. The aerogel can effectively inhibit the migration of radioactive iodine in nature by simultaneously coating copper and silver; silica aerogel is selected, which has a large specific surface area and high porosity, strong adsorption performance, is less affected by environmental factors, and has stable performance; boron as a flux reducer can reduce the melting point and effectively reduce the sintering temperature during the sintering process, and can achieve low-temperature sintering, which is safe, reliable, energy-saving and environmentally friendly. In addition, the low-temperature solidification method has the advantages of simple process, energy-saving, environmental protection, safety and reliability. In summary, the present invention has important application value in the field of radioactive waste treatment technology. DETAILED DESCRIPTION

[0022] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] The following experimental methods are conventional methods unless otherwise specified.

[0024] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0025] In the following embodiments, the high-temperature muffle furnace used is the KM30 / 13 high-temperature muffle furnace of THERMCONCEPT; and the microwave sintering furnace is the HY-MF1512 microwave high-temperature muffle furnace.

[0026] The silica aerogel used was purchased from Jicui Organic Functional Materials Institute, and the SiO2 content exceeded 99.5%.

[0027] The AgI, CuI, boron oxide (B2O3), aluminum oxide (Al2O3) and barium oxide (BaO) used were purchased from Sinopharm Group Co., Ltd.

[0028] Example

[0029] In this embodiment, common iodine-127 is used to simulate the radioactive nuclide iodine-129. A method for low-temperature curing of copper / silver aerogel-coated borate glass ceramics comprises the following steps:

[0030] S1. Mix and grind the silica aerogel, AgI, and CuI, and filter through a filter to obtain an iodine-containing copper / silver-coated aerogel having a maximum outer diameter of less than or equal to 50 μm;

[0031] S2. Mix boron oxide, aluminum oxide and barium oxide and put them into a high-temperature muffle furnace, sinter them at 1000℃-1300℃ to obtain glass ceramics, and grind the glass ceramics to obtain borate glass ceramic powder. In the borate glass ceramic powder, by mass percentage, in this embodiment, boron oxide is 65%, aluminum oxide is 15%, and barium oxide is 20%. In actual use, boron oxide is 40-65%, aluminum oxide is 15-20%, and barium oxide is 12-20%;

[0032] S3. Mix the iodine-containing copper / silver aerogel with borate glass ceramic powder, add deionized water and grind to obtain a wet mixture; dry the wet mixture at 25°C-100°C for 1h-5h to obtain a dry mixture; in the dry mixture, by mass fraction, the copper / silver aerogel is 50.44%, the iodine element is 10.56%, and the borate glass ceramic powder is 39.00%. In actual use, in order to achieve a better curing effect, by mass fraction, the iodine-containing copper / silver aerogel is 35%-55%, the borate glass ceramic powder is 30%-55%, and the mass of radioactive iodine does not exceed 20% of the total mass of the mixture.

[0033] S4, placing the dried mixture in a high-temperature muffle furnace, heating it from room temperature to 800°C, keeping it at 800°C for 3 hours, and then naturally cooling it to room temperature to obtain a borate glass ceramic sintered body containing iodine-coated copper / silver aerogel. In actual use, cooling after sintering can also be carried out by cooling at different rates, the sintering temperature can be controlled at 800°C-900°C, and the sintering time can be 1h-3h.

[0034] After taking out the sample for testing, the volume density of the borate glass ceramic sintered body containing iodine-coated copper / silver aerogel was 3.082 g / cm 3 After sintering, the thermal release rate of iodine was 3.28%, and the normalized leaching rate of radionuclide I under the PCT standard was less than 2.86×10 -4 g / m 2 / d 1 .

[0035] It can be seen from the test results that the obtained iodine-containing copper / silver aerogel glass ceramic sintered body has the advantages of high volume density and low nuclide leaching rate, and can effectively inhibit the migration of radioactive iodine in nature. In addition, boron can be used as a flux reducer to reduce the melting point and effectively reduce the sintering temperature during the sintering process, so that low-temperature sintering can be achieved, which is safe, reliable, energy-saving and environmentally friendly. The low-temperature curing method of the present application has the characteristics of simple process, energy-saving and environmental protection, safety and reliability. In summary, the present invention has important application value in the field of radioactive waste treatment technology.

[0036] In the description of the specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0037] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the invention or exceed the scope defined by the claims, they shall all fall within the protection scope of the present invention.

Claims

1. A low temperature curing method for borate glass ceramics coated with copper / silver aerogel, characterized in that: The following steps are involved: S1, mixing radioactive iodine-containing copper / silver aerogel particles with borate glass ceramic powder, adding deionized water and grinding to obtain a wet mixture; S2, drying the wet mixture to obtain a dry mixture; S3, placing the dried mixture into a sintering device for sintering, and cooling after sintering to obtain a glass ceramic sintered body; The radioactive iodine-containing copper / silver aerogel particles in step S1 are composed of AgI, CuI and silicon dioxide aerogel; the maximum outer diameter of the radioactive iodine-containing copper / silver aerogel is less than or equal to 50 μm; the borate glass ceramic powder is sintered and ground with boron oxide, aluminum oxide and barium oxide in a mass percentage of 40-65%, aluminum oxide of 15-20% and barium oxide of 12-20%; and the sintering temperature is 1000° C.-1300° C.

2. The low temperature curing method of copper / silver aerogel-coated borate glass ceramics according to claim 1, characterized in that: The specific method of the drying treatment in step S2 is: ventilation drying at a temperature between 25° C. and 100° C. for 1 h to 5 h.

3. The low temperature curing method of copper / silver aerogel-coated borate glass ceramics according to claim 1, characterized in that: The mixture dried in step S3 contains 35%-55% of radioactive iodine-containing copper / silver aerogel particles and 30%-55% of borate glass ceramic powder in terms of mass percentage; the mass of radioactive iodine in the dried mixture does not exceed 20% of the total mass of the mixture.

4. The low temperature curing method of copper / silver aerogel-coated borate glass ceramics according to claim 1, characterized in that: The sintering device in step S3 is a high-temperature muffle furnace or a microwave sintering furnace.

5. The low temperature curing method of copper / silver aerogel-coated borate glass ceramics according to claim 1, characterized in that: In step S3, the sintering temperature is 800°C-900°C, and the sintering time is 1h-3h.