阅读说明：本技术 用于核素固化的高稳定性复合型地质水泥及其应用方法 (High-stability composite geological cement for nuclide solidification and application method thereof ) 是由 张培 胡梅娟 苏伟 孟宪东 潘社奇 尹安毅 颜家伟 刘天伟 于 2020-05-07 设计创作，主要内容包括：本发明公开了一种用于核素固化的高稳定性复合型地质水泥,按质量分数计,包括复合铝硅酸盐30-80份,碱性激发剂5-45份,添加剂0-10份；所述复合铝硅酸盐包括含钙铝硅酸盐、偏高岭土和膨润土；一种用于核素固化的高稳定性复合型地质水泥的应用方法,包括以下步骤：步骤a：按质量分数计将复合铝硅酸盐30-80份,碱性激发剂5-45份,添加剂0-10份混合均匀,制得地质水泥；步骤b：将含铀、钚的放射性废物与地质水泥搅拌混合,慢速搅拌1-3分钟,暂停5-15秒,再快速搅拌1-3分钟,持续5-10次循环,制得含铀、钚放射性废物的浆体；步骤c：将含铀、钚放射性废物的浆体移至磨具,进行养护。采用本发明的一种用于核素固化的高稳定性复合型地质水泥及其应用方法,能够将含铀、钚的放射性废物安全处理。(The invention discloses high-stability composite geological cement for nuclide curing, which comprises 30-80 parts of composite aluminosilicate, 5-45 parts of an alkaline activator and 0-10 parts of an additive by mass fraction; the composite aluminosilicate comprises calcium-containing aluminosilicate, metakaolin and bentonite; an application method of high-stability composite geological cement for nuclide curing comprises the following steps: step a: uniformly mixing 30-80 parts of composite aluminosilicate, 5-45 parts of alkaline activator and 0-10 parts of additive by mass fraction to prepare geological cement; step b: stirring and mixing the radioactive waste containing uranium and plutonium with geological cement, stirring slowly for 1-3 minutes, pausing for 5-15 seconds, stirring rapidly for 1-3 minutes again, and continuing for 5-10 cycles to prepare slurry containing the radioactive waste containing uranium and plutonium; step c: and (4) transferring the slurry containing the radioactive wastes of uranium and plutonium to a grinding tool for maintenance. By adopting the high-stability composite geological cement for nuclide solidification and the application method thereof, the radioactive wastes containing uranium and plutonium can be safely treated.)

1. A high-stability composite geological cement for nuclide solidification is characterized in that: according to mass fraction, comprises 30-80 parts of composite aluminosilicate, 5-45 parts of alkali activator and 0-10 parts of additive; the composite aluminosilicate comprises calcium-containing aluminosilicate, metakaolin and bentonite.

2. The high stability composite geological cement for nuclide solidification as claimed in claim 1, wherein: the composite aluminosilicate comprises 30-80% of calcium-containing aluminosilicate, 10-35% of metakaolin and 10-35% of bentonite by mass.

3. The high stability composite geological cement for nuclide solidification as claimed in claim 1, wherein: in the calcium-containing aluminosilicate, the mass fraction of calcium is more than 5%.

4. The high stability composite geological cement for nuclide solidification as claimed in claim 1, wherein: the metakaolin is prepared by adding hydroxide with the mass fraction of 0-10% into kaolin and calcining at 600-1000 ℃ for 1-3 hours.

5. The high stability composite geological cement for nuclide solidification as claimed in claim 1, wherein: the alkali activator comprises sodium water glass, sodium hydroxide solution and/or potassium hydroxide solution.

6. The high stability composite geological cement for nuclide solidification as claimed in claim 1, wherein: the additive is one or more of reinforcing fiber, a toughening agent, a water reducing agent, an early strength agent, a waterproof agent, a foam stabilizer and a pumping agent.

7. An application method of high-stability composite geological cement for nuclide curing is characterized by comprising the following steps: the method comprises the following steps:

step a: uniformly mixing 30-80 parts of composite aluminosilicate, 5-45 parts of alkaline activator and 0-10 parts of additive by mass fraction to prepare geological cement;

step b: stirring and mixing the radioactive waste containing uranium and plutonium with geological cement, stirring slowly for 1-3 minutes, pausing for 5-15 seconds, stirring rapidly for 1-3 minutes again, and continuing for 5-10 cycles to prepare slurry containing the radioactive waste containing uranium and plutonium;

step c: and (4) transferring the slurry containing the radioactive wastes of uranium and plutonium to a grinding tool for maintenance.

8. The method of applying a high stability composite geological cement for nuclide curing as claimed in claim 7 wherein: in the step b, the mass ratio of the radioactive waste to the geological cement is 0.75-0.95: 1.

9. The method of applying a high stability composite geological cement for nuclide curing as claimed in claim 7 wherein: in step b, the specific activity of the radioactive waste is 10⁴～10⁶Bq/kg。

10. The method of applying a high stability composite geological cement for nuclide curing as claimed in claim 7 wherein: in the step c, the curing conditions are as follows: firstly, covering a film on the surface of the slurry, curing for one day at room temperature, then demoulding, and curing for 1-28 days under the conditions that the temperature is 20-80 ℃ and the humidity is 80-100%.

Technical Field

The invention relates to high-stability composite geological cement for nuclide curing and an application method thereof, belonging to the technical field of nuclide curing.

Background

Following the accident of the nuclear power plant in fukushima, the safe development and utilization of nuclear energy has become a hot spot of research in various countries. Safety supervision in various national and nuclear fields is increasingly strengthened, stricter requirements are also put on treatment and disposal of radioactive wastes, and the corresponding curing process, the stability of a cured body, the safety of long-term disposal and the like also face new challenges. Along with the development process of China nuclear military industry for more than half a century and the development and utilization of civil nuclear energy, more and more radioactive wastes containing specific nuclides (uranium, plutonium, cesium and strontium) are accumulated, and the safe treatment and disposal of the radioactive wastes become the key problems facing the further development of China nuclear industry. How to safely and effectively process the biological energy, and to isolate the biological energy from the biosphere to the maximum extent becomes a problem which needs to be solved urgently at home and abroad at present, and the health and the sustained development of the nuclear military industry and the nuclear energy in China are directly influenced.

Because the characteristics of high strength, high hardness, corrosion resistance and the like of cement are considered as the preferred materials for curing radioactive nuclide, cement curing is the most mature process applied to curing treatment of low-and-medium-level waste at present and is widely applied in the world. The traditional cement curing method is to use silicate cement as a curing body to cure the radioactive nuclide. However, in recent years, according to the ukrainian-based structure and the simulation calculation result of the professor Krivenko of architecture university, the ordinary portland cement solidified body containing the radioactive waste of different nuclides has a service life of even less than 100 years in the disposal environment, and the requirement of safe disposal of long-life radionuclides such as uranium and plutonium is far from being met. Therefore, the ordinary portland cement curing technology and process adopted for the medium-low-level waste containing uranium, plutonium and other long-life nuclides risks that the radioactive nuclides are continuously released to the environment in the disposal process of the cured body.

The geological cement material originated from research of Ukrainian scientists on the success of alkali-activated slag in the fifties of the last century, and is mainly represented by research work of professor Ukraghovsky. The most important research is the research of Geopolymer (Geopolymer), which contains amorphous SiO under strong alkali or strong acid condition²And Al²O³The silicate mineral is mixed with alkali, water glass or phosphate, and is subjected to condensation polymerization to form an amorphous three-dimensional network gel consisting of alundum and siloxate, which is a main component of geological cement. The geological cement is a novel material which not only has the excellent performances of organic high polymers, ceramics and cement, but also has the advantages of wide material source, simple process, less energy consumption, small environmental pollution and the like. The high-temperature-stability geological cement has high thermal stability, can be applied to a high-temperature environment, has the advantages that the long-term chemical stability of geological cement can absorb toxic wastes and nuclear wastes, and the like, and is widely concerned at home and abroad recently.

At present, geological cement on the market can only be generally used for treating low radioactive waste due to high nuclide leaching rate, and has the problems of poor stability, radiation intolerance, low thermal stability and the like.

Disclosure of Invention

The invention aims to: aiming at the existing problems, the invention provides the high-stability composite geological cement for nuclide solidification and the application method thereof, and the invention can safely treat radioactive wastes containing uranium and plutonium.

The technical scheme adopted by the invention is as follows:

a high-stability composite geological cement for nuclide curing and an application method thereof are disclosed, wherein the high-stability composite geological cement comprises 30-80 parts of composite aluminosilicate, 5-45 parts of an alkaline activator and 0-10 parts of an additive by mass;

the composite aluminosilicate comprises calcium-containing aluminosilicate, metakaolin and bentonite.

In the present invention, the complexity of the network structure is increased by the calcium-containing aluminosilicate; an amorphous substance with chemical reaction activity at normal temperature and normal pressure is formed by metakaolin, so that the reaction activity is improved; various polyhedral network structures can be formed by bentonite, and cations in the polyhedral network structures can be replaced. The calcium-containing aluminosilicate, the metakaolin and the bentonite can react with the alkaline activator to form geological cement, the geological cement has a certain calcium content to form a complex network structure and high reactivity to improve the strength of the cement by combining the calcium-containing aluminosilicate, the metakaolin and the bentonite, and cations in a large-surface-area network can be replaced by U, Pu and other radioactive particles to form a better solidification effect, so that uranium and plutonium-containing radioactive wastes can be safely treated.

The calcium-containing aluminosilicate refers to an aluminosilicate containing calcium, or an aluminosilicate to which a calcium-containing compound is added.

Preferably, the composite aluminosilicate comprises, by mass, 30-80% calcium-containing aluminosilicate, 10-35% metakaolin and 10-35% bentonite.

In the scheme, better effect can be achieved by combining the calcium-containing aluminosilicate, the metakaolin and the bentonite in a certain proportion.

Preferably, the calcium-containing aluminosilicate has a calcium mass fraction of more than 5%.

In the scheme, the low calcium content can not achieve a good effect, and the problems of long coagulation time, low compressive strength, poor freezing resistance and the like can be caused.

Preferably, the metakaolin is prepared by adding 0-10 mass percent of hydroxide into kaolin and calcining at 600-1000 ℃ for 1-3 hours.

Preferably, the hydroxide is one or more of sodium hydroxide, potassium hydroxide, calcium hydroxide, aluminum hydroxide, and the like.

In the scheme, after 0-10% of hydroxide by mass is added into the metakaolin, the metakaolin is prepared after calcination at 600-1000 ℃ for 1-3 hours. The structural water in the kaolin escapes through calcination, but the silica skeleton structure still remains, and Al-OH octahedrons are formed by adding sodium hydroxide; al in Al-OH octahedron³⁺Diffusing and rearranging to form Al-O bond, changing six times of coordination into four times of coordination to form amorphous substance with chemical reaction activity at normal temperature and pressure, so as to improve the reaction activity.

Preferably, the alkali activator includes sodium water glass, a sodium hydroxide solution and/or a potassium hydroxide solution.

Preferably, the sodium water glass is prepared into an alkali activator with a modulus of 1.8-2.2 by using a sodium hydroxide solution and/or a potassium hydroxide solution.

Preferably, the particle size of the composite aluminosilicate is 1 to 100 μm.

In the scheme, the smaller the particle size, the larger the specific surface area, the more surface reaction sites and the higher the activity, so that the reaction speed and the reaction uniformity in the cement curing process are improved, and the more sufficient the reaction is, the more sufficient and firmer the formed three-dimensional network structure is, so that the hardness and the curing performance are better.

Preferably, the additive is one or more of reinforcing fiber, a toughening agent, a water reducing agent, an early strength agent, a waterproof agent, a foam stabilizer and a pumping agent.

In the scheme, the performance of the geological cement is adjusted by adding different additives according to needs.

The invention also provides an application method of the high-stability composite geological cement for nuclide curing, which comprises the following steps:

step a: uniformly mixing 30-80 parts of composite aluminosilicate, 5-45 parts of alkaline activator and 0-10 parts of additive by mass fraction to prepare geological cement;

step b: stirring and mixing the radioactive waste containing uranium and plutonium with geological cement, stirring slowly for 1-3 minutes, pausing for 5-15 seconds, stirring rapidly for 1-3 minutes again, and continuing for a plurality of cycles to prepare slurry containing the radioactive waste containing uranium and plutonium;

step c: and (4) transferring the slurry containing the radioactive wastes of uranium and plutonium to a grinding tool for maintenance.

In the scheme, in the step b, the slow stirring and the fast stirring are matched to better uniformly disperse the radioactive ions into the slurry, the pause in the middle is to ensure that the ions have certain sedimentation, and the mixture is more uniform through 5-10 times of circulation. Wherein, the slow stirring refers to 30-60rpm, and the fast stirring refers to 90-120 rpm.

Preferably, in step b, the mass ratio of the radioactive waste to the geological cement is 0.75-0.95: 1.

Preferably, in step b, the radioactive waste has a specific activity of 10⁴～10⁶Bq/kg。

Preferably, in step c, the curing conditions are as follows: firstly, covering a film on the surface of the slurry, curing for one day at room temperature, then demoulding, and curing for 1-28 days under the conditions that the temperature is 20-80 ℃ and the humidity is 80-100%.

The common geological cement is only suitable for treating radioactive waste with lower radioactivity level because of high leaching rate of a solidified body, but the high-calcium geological cement for nuclide solidification and the application method can treat the radioactive waste containing uranium and plutonium, wherein the uranium and plutonium are medium and high radioactive waste and cannot be treated by the common geological cement.

In the present invention, an amorphous three-dimensional network gel composed of alundum and siloxate, which is formed by mixing an aluminosilicate mineral with alkali, water glass or phosphate and carrying out polycondensation, is further formed into Ca-Si-H by adding a calcium-containing aluminosilicate₂O or Ca-Al-H₂The O network structure increases the complexity of the network structure, so that the geological cement can be hardened more quickly, and the compressive strength, freezing resistance and other properties are improved; the metakaolin is formed by sintering kaolin, the structural water in the kaolin escapes, and the silica skeletonStructure remaining, Al in Al-OH octahedron³⁺Diffusing and rearranging to form an Al-O bond, changing six-time coordination into four-time coordination to form an amorphous substance with chemical reaction activity at normal temperature and normal pressure, and increasing and improving the reaction activity; bentonite is a layered silicate, which is composed of structural units formed by two silicon-oxygen tetrahedrons with an aluminum-oxygen octahedron wafer sandwiched in the center, and has the characteristics of absorbing hydrated cations into interlayer regions by electrostatic attraction for self charge balance, and ions in the interlayer regions are exchanged to different degrees as long as the concentration of other cations in a medium is higher than that of the cations absorbed in the interlayer, so the bentonite has the characteristics of large specific surface area, capability of forming various polyhedral network structures, capability of replacing the cations and the like.

By combining calcium-containing aluminosilicate, metakaolin and bentonite, the high-stability composite geological cement for nuclide solidification has a complex network structure formed by a certain calcium content, has high reactivity to improve the strength of the cement, and simultaneously cations in a large-surface-area network can be replaced by U, Pu and other radioactive particles to form a better solidification effect.

The high-stability composite geological cement for nuclide curing has a mixed structure of C-S-H type geological cement and zeolite type geological cement, has strong physical and chemical dual curing effects on long-life radionuclides uranium, plutonium and the like, and also has high strength and stable properties.

In summary, due to the adoption of the technical scheme, the invention has the beneficial effects that:

1. the nuclide content is high, and the weight ratio of the radioactive waste liquid to the glue material is more than 0.75;

2. the leaching rate of nuclide is low, and the leaching rate of radionuclide uranium and plutonium is less than 5.0 × 10 in 50 days^-6cm/d；

3. The crystal structure is stable, and the crystal lattice parameter change of a tetrahedral structure of uranium and plutonium replacing silicon and aluminum is less than 5% within 2 years;

4. the radiation resistance is realized, after the radiation resistance test of the solidified body sample is carried out under the radiation dosage rate lower than 10KGy/h, the appearance has no obvious crack, the compressive strength loss is lower than 25 percent, and the radiation resistance test is superior to the national standard;

5. high thermal stability, and linear expansion coefficient less than 10 at 0-1000 deg.C^-6/K。

Detailed Description

All of the features disclosed in this specification, or all of the steps in any method or process so disclosed, may be combined in any combination, except combinations of features and/or steps that are mutually exclusive.

Any feature disclosed in this specification may be replaced by alternative features serving equivalent or similar purposes, unless expressly stated otherwise. That is, unless expressly stated otherwise, each feature is only an example of a generic series of equivalent or similar features.