CN102208224A - Method for solidifying radioactive boron-containing residual distillate by sulphoaluminate cement - Google Patents

Abstract

The invention discloses a method for solidifying radioactive boron-containing distillation raffinate with sulphoaluminate cement, which belongs to the technical field of radioactive waste cement solidification. The method is to mix sulfoaluminate cement, zeolite, lime, and early strength agent evenly, stir with the radioactive boron-containing steamed raffinate in a stirring pot for 3 minutes, move it to a Φ50mm×50mm mold, and cure it for 28 days to make a solidified body . The method of the present invention solidifies the boron-containing distillate, and the volume of the distillate in the cured body reaches 60% to 65%, and the cured body can obtain high compressive strength, meeting the national standard GR14569.1-2011.

Description

A method for solidifying radioactive boron-containing distillation raffinate with sulphoaluminate cement

technical field

The invention belongs to the technical field of radioactive waste cement solidification, and in particular relates to a method for solidifying radioactive boron-containing distillation raffinate with sulphoaluminate cement.

Background technique

During the operation of the pressurized water reactor nuclear power plant, boric acid needs to be added to the primary circuit to control the reaction rate, and a large amount of boric acid solution will be added to the core during refueling or maintenance to ensure safety. When it is no longer needed, the boron solution is flushed out with deionized water, resulting in radioactive boron-containing waste liquid. After these boron-containing waste liquids are evaporated, most nuclides are enriched in the raffinate to form radioactive boron-containing raffinate. A 1 million-kilowatt pressurized water reactor nuclear power plant discharges approximately 23m ³ of boron-containing 4% distilled residue every year (Radiation Protection, 1995, 15(1): 33-41). These distilled residues are generally solidified by cement to form a solidified body with stable performance for final disposal. The performance of the solidified body of the steamed raffinate is stable, but the presence of boron may cause the setting time of the cement to be too long, which in turn affects the strength of the solidified body and the waste inclusion capacity.

Qinshan No. 2 Nuclear Power Plant and Daya Bay Nuclear Power Plant adopt the cement solidification process to treat the boron-containing 40g/L concentrate. The formula components include ordinary Portland cement, sand and lime, and its inclusion capacity is about 40%. Patent No. 00100596.0 discloses a cement solidification method for boron-containing waste liquid. The type of cement used may be Portland cement, a mixture of Portland cement and blast furnace slag cement, or a mixture of Portland cement and soot. First add alkali metal and alkaline earth metal compounds to the waste liquid, then dry the waste liquid into powder, and then solidify with cement. This process can increase the containment capacity of the waste liquid in the solidified body, but the operation steps are complicated and the cost is high. Patent No. 201010269158.0 uses Portland cement or sulphoaluminate cement, and sodium silicate is added to solidify boron-containing waste liquid, with a holding capacity of 45% to 55%.

In recent years, there have been many reports on the use of sulfoaluminate cement to solidify radioactive waste (Atomic Energy Science and Technology, 2006, 40(3): 288-291). The main clinker mineral of sulfoaluminate cement is anhydrous calcium sulfoaluminate (3CaO·3Al2O3·CaSO4), which makes the cement have the advantages of early strength, high strength, frost resistance, impermeability, corrosion resistance and low alkalinity. Zeolite is a group of hydrous aluminosilicate minerals with a framework structure. It contains alkali and alkaline earth metal ions in its crystal framework. The connection between the cation and the framework is weak, and it has a large adsorption capacity and strong ion interaction for other cations. ability; when it fills the gaps between cement hydrate particles, it can enhance the cohesion and compactness of cement to a certain extent (Nuclear Science and Engineering, 1994, 14(2): 134-140; Radiation Protection, 1982, 2(5):352-360). With the sulfoaluminate cement solidified body mixed with zeolite, the leaching rate of Cs and Co is greatly reduced (Atomic Energy Science and Technology, 2006, 40(3): 288-291), and the addition of no more than 10% is also beneficial Improve the strength of the cured body and improve its microstructure (Journal of Jinan University (Natural Science Edition), 2006, 20(4): 293-295).

Contents of the invention

The purpose of the present invention is to provide a method for solidifying radioactive boron-containing distillation raffinate with sulphoaluminate cement, so as to solve the problems of low waste containment capacity and long coagulation time when solidifying radioactive boron-containing distillation raffinate.

A method for solidifying radioactive boron-containing steam raffinate with sulphoaluminate cement, mixing sulphoaluminate cement, zeolite, lime, and early strength agent uniformly, stirring with radioactive boron-containing steam raffinate in a stirring pot for 3 minutes, and moving to In the mold of Φ50mm×50mm, curing for 28 days, the curing temperature is 25±5℃, and the relative humidity is ≥90%.

The dosage ratio of the radioactive boron-containing distillation raffinate, sulphoaluminate cement, zeolite, lime, and early strength agent is: (0.4-0.5) L: 1000g: (30-70) g: (100-150) g: (20～30) g.

The zeolite is clinoptilolite; the main component of the early strength agent is Li ₂ CO ₃ .

Beneficial effects of the present invention: when the method of the present invention is used to solidify the boron-containing distilled liquid, the volume of the distilled liquid in the cured body reaches 60% to 65%, and the cured body can obtain higher compressive strength, meeting the national standard GB14569.1 -2011.

Detailed ways

The present invention will be further described below with specific examples.

Example 1

Mix 1000g of sulphoaluminate cement, 50g of clinoptilolite, 110g of lime, and 20g of early strength agent (the main component is Li ₂ CO ₃ ) evenly, stir with 0.45L of radioactive boron-containing steam raffinate in a stirring pot for 3 minutes, and move to In the mold of Φ50mm×50mm, cure for 28 days, the curing temperature is 25±5°C, and the relative humidity is ≥90%, to make a cured body. Calculate the total volume of the solidified body and use it to calculate the waste inclusion capacity in the solidified body, and obtain a value of 60%.

Example 2

Mix 1000g of sulphoaluminate cement, 50g of clinoptilolite, 110g of lime, and 20g of early strength agent (the main component is Li ₂ CO ₃ ) evenly, stir with 0.45L of radioactive boron-containing steam raffinate in a stirring pot for 3 minutes, and move to In the mold of Φ50mm×50mm, cure for 28 days, the curing temperature is 25±5°C, and the relative humidity is ≥90%, to make a cured body. The upper and lower surfaces of the cured body are properly polished with sandpaper to keep the upper and lower surfaces parallel, and then the unconfined compressive strength is measured on a pressure testing machine. The measured 28d compressive strength is 31.0MPa.

Example 3

Mix 1000g of sulphoaluminate cement, 40g of clinoptilolite, 110g of lime, and 25g of early strength agent (the main component is Li ₂ CO ₃ ) evenly, stir with 0.42L of radioactive boron-containing steam raffinate in a stirring pot for 3 minutes, and move to In the mold of Φ50mm×50mm, cure for 28 days, the curing temperature is 25±5°C, and the relative humidity is ≥90%, to make a cured body. The inclusion capacity and 28d compressive strength of the cured body are 60% and 29.7MPa, respectively.

Example 4

Mix 1000g of sulphoaluminate cement, 40g of clinoptilolite, 120g of lime, and 30g of early strength agent (the main component is Li ₂ CO ₃ ) evenly, stir with 0.5L of radioactive boron-containing steam raffinate in a stirring pot for 3 minutes, and move to In the mold of Φ50mm×50mm, cure for 28 days, the curing temperature is 25±5°C, and the relative humidity is ≥90%, to make a cured body. The inclusion capacity and 28d compressive strength values of the cured body are 65% and 28.3MPa respectively.

Claims (3)

1. A method for sulphoaluminate cement solidifying radioactive boron-containing steam raffinate is characterized in that, sulphoaluminate cement, zeolite, lime, early strength agent are mixed uniformly, and radioactive boron-containing steam raffinate is mixed in a stirring pot Stir for 3 minutes, move to a Φ50mm×50mm mold, and cure for 28 days at a temperature of 25±5°C and a relative humidity of ≥90%. 2. according to the method for a kind of sulphoaluminate cement curing radioactive boron-containing steam raffinate according to claim 1, it is characterized in that, the radioactive boron-containing steam raffinate, sulphoaluminate cement, zeolite, lime, early strength The consumption ratio of agent is: (0.4～0.5) L: 1000g: (30～70) g: (100～150) g: (20～30) g. 3. A method for solidifying radioactive boron-containing distilled raffinate with sulphoaluminate cement according to claim 1, wherein the zeolite is clinoptilolite; the main component of the early strength agent is Li ₂ CO ₃ .