CN102276231A - Method for curing radioactive waste resin by NaAlO2 coagulant cement - Google Patents

Abstract

The invention discloses a method for curing a radioactive waste resin by NaAlO2 coagulant cement, and belongs to the technical field of radioactive waste resin cement curing. The method comprises the following steps of mixing sulfoaluminate cement, a composite mineral additive, NaAlO2 and NaOH well, stirring the mixture and a radioactive waste resin in a stirring kettle, transferring the mixture obtained by the previous step into a mold and maintaining for curing. The method is utilized for curing a radioactive waste resin, improves a capacity and compressive strength of cured waste, and shortens coagulation time.

Description

A method of using NaAlO₂ coagulant cement to solidify radioactive waste resin

technical field

The invention belongs to the technical field of radioactive waste resin cement solidification, and in particular relates to a method for solidifying radioactive waste resin by using _NaAlO2 coagulant cement.

Background technique

In nuclear power plants, ion exchange technology is widely used in auxiliary systems of the primary and secondary circuits and radioactive waste liquid treatment systems. Due to the high radioactive level of the loaded nuclides or the saturation of the exchange capacity, the resin in the equipment needs to be replaced regularly. Waste resin must be cured before final disposal. Cement solidification technology is the main solidification method of radioactive waste resin, but the waste containment capacity is low. Especially when solidifying the boron-containing waste resin produced by the pressurized water reactor nuclear power plant, the increase in the containment capacity will increase the amount of boron contained in the solidified body per unit volume, resulting in a sharp extension of the coagulation time of the slurry or even failure to coagulate. At present, the solidified body of C1 concrete barrels produced by domestic pressurized water reactor nuclear power plants has a waste resin volume containment capacity of about 35%.

Sulphoaluminate cement is a cement series with independent intellectual property rights in my country, and the research on radioactive waste solidification has been reported. Eettite is one of the main hydration products of sulfoaluminate cement. There is [Al(OH) ₆ ] ^3- octahedral structure in its crystals, and its nucleation requires a certain degree of supersaturation to complete the crystallization process. . When boron exists in the hydration system, boron reacts with calcium in cement components to form calcium borate which is slightly soluble in water. Calcium borate crystals gather on the surface of cement clinker particles, hindering the contact between cement and water, which is not conducive to ettringite crystals formation, thus delaying the hydration reaction of cement. The addition of NaAlO ₂ to the formula of sulphoaluminate cement solidified boron-containing resin can increase the concentration of Al(OH) ₄ ^- in the liquid phase, increase the formation rate of [Al(OH) ₆ ] ^3- , and promote the crystallization of ettringite formation, so as to achieve the purpose of promoting coagulation.

The types and components of waste processed by cement solidification technology are diverse, and have complex effects on the cement hydration process. Coagulants are often used to adjust the setting time of cement. Patent No. 200810097228.1 provides a curing agent for solid waste concrete, in which a coagulant is used but its specific composition is not disclosed. No. 200810036184.1 patent discloses that the type of cement used in the curing agent for municipal sewage treatment plant drainage sludge and river sludge is sulfoaluminate cement, and the coagulant is lithium salt or lithium hydroxide. In the application of radioactive waste cement solidification, the addition of coagulant can shorten the coagulation time and improve the performance of solidified body. Patent No. 201010269158.0 discloses a curing agent for curing borate-containing radioactive waste. The type of cement used is Portland cement or sulphoaluminate cement, and the coagulation accelerator is sodium silicate. When Wang Ren and others used ordinary Portland cement, pozzolanic cement, high alumina cement and zeolite cement to solidify radioactive waste liquid, they used sodium metaaluminate as a coagulant to shorten the solidification time of the slurry (the radioactive waste liquid of pressurized water reactor nuclear power plant Research on cement curing, Radiation Protection, 1982, 2(5): 352-360).

Contents of the invention

The object of the present invention is to provide a kind of method that uses NaAlO _coagulant cement to solidify radioactive waste resin.

A method of using NaAlO ₂ coagulant cement to solidify radioactive waste resin. Mix sulphoaluminate cement, composite mineral additives, NaAlO ₂ , and NaOH evenly, stir with radioactive waste resin in a stirring pot for 3 minutes, and move to Φ50mm×50mm In the mold, it is cured for 7 days, the curing temperature is 25±5°C, and the relative humidity is ≥90%.

The composite mineral additive is a mixture of zeolite, slag, silica fume and fly ash, and the mass ratio of zeolite, slag, silica fume and fly ash is 5:10:9:4.

The consumption ratio of described radioactive waste resin, sulfoaluminate cement, composite mineral additive, NaAlO _and NaOH is: 1L: (1455～1674) g: (45～126) g: (8～16) g: (1 ~ 4) g. Among them, the composite mineral additive accounts for 3%-7% of the total mass of the sulphoaluminate cement and the composite mineral additive, and the mass ratio of NaAlO ₂ to NaOH is 6:1-4:1.

Beneficial effects of the present invention: the method of the present invention solidifies the radioactive waste resin, improves the waste containment capacity and compressive strength of the solidified body, and shortens the coagulation time.

Detailed ways

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

The following examples adopt the mixed resin as the simulated radioactive waste resin, the volume ratio of anion and cation resins in the mixed resin is 3:2, and the boron content on the anion resin is about 1.2mol/L (calculated as B).

Example 1

Mix 1505g sulfoaluminate cement, 95g composite mineral additive (zeolite: slag: silica fume: fly ash = 5:10:9:4), 15g NaAlO ₂ , 3g NaOH, and stir with 1L simulated radioactive waste resin Stir in the pot for 3 minutes, fill the stirred slurry once to measure the coagulation time test mold, vibrate several times to scrape the surface and put it into the curing box. The curing temperature is 20±1°C and the relative humidity is ≥90%. Measure the initial setting time after curing until 30 minutes after the start of stirring. After the initial setting time is measured, turn the setting time test mold over to continue curing, and measure the final setting time. The measured initial and final setting times were 4.7h and 19.0h, respectively.

Example 2

Mix 1505g sulfoaluminate cement, 95g composite mineral additive (zeolite: slag: silica fume: fly ash = 5:10:9:4), 15g NaAlO ₂ , 3g NaOH, and stir with 1L simulated radioactive waste resin Stir in the pot for 3 minutes, move to a Φ50mm×50mm mold, prepare a cured body, calculate the total volume of the cured body and calculate the volume inclusion capacity of the waste resin in the cured body, and the value of the inclusion capacity is 65%.

Example 3

Mix 1505g sulfoaluminate cement, 95g composite mineral additive (zeolite: slag: silica fume: fly ash = 5:10:9:4), 15g NaAlO ₂ , 3g NaOH, and stir with 1L simulated radioactive waste resin Stir in the pot for 3 minutes, move to a Φ50mm×50mm mold, and cure. The curing temperature is 25±5°C and the relative humidity is ≥90%. After curing for 48 hours, remove the mold, and after curing for 7 days, the upper and lower surfaces 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 7d compressive strength is 14.5MPa.

Example 4

Mix 1505g sulfoaluminate cement, 115g composite mineral additive (zeolite: slag: silica fume: fly ash = 5:10:9:4), 14.2g NaAlO ₂ , 2.8g NaOH, and mix them with 1L simulated radioactive waste resin Stir in the stirring pot for 3min, use the same coagulation time measurement method as in Example 1, the same waste resin volume inclusion calculation method as in Example 2, the same curing body preparation method and 7d compressive strength test method as in Example 3 , the obtained values of final setting time, inclusion capacity and 7d compressive strength were 17.5h, 61% and 12.7MPa respectively.

Example 5

Mix 1515g sulfoaluminate cement, 65g composite mineral additive (zeolite: slag: silica fume: fly ash = 5:10:9:4), 14.2g NaAlO ₂ , 3g NaOH, and mix them with 1L simulated radioactive waste resin in Stir in the stirring pot for 3min, use the same coagulation time measuring method as in Example 1, the same waste resin volume inclusion capacity calculation method as in Example 2, the same curing body preparation method and 7d compressive strength test method as in Example 3, The obtained values of final setting time, inclusion capacity and 7d compressive strength are 20.3h, 65% and 11.3MPa respectively.

Claims (3)

1. A method of using NaAlO coagulant cement to solidify radioactive waste resin _, characterized in that, sulphoaluminate cement, composite mineral additives, NaAlO ₂ , NaOH are mixed uniformly, and the radioactive waste resin is stirred in a stirring pot for 3min , moved to a Φ50mm×50mm mold, cured for 7 days, the curing temperature was 25+5°C, and the relative humidity was ≥90%. 2. according to claim 1, a kind of use NaAlO _coagulant cement solidifies the method of radioactive waste resin, it is characterized in that, described composite mineral additive is the mixture of zeolite, slag, silica fume and fly ash, zeolite, slag , The mass ratio of silica fume to fly ash is 5:10:9:4. 3. according to claim 1, a kind of use NaAlO _coagulant cement is used to solidify radioactive waste resin method, it is characterized in that, described radioactive waste resin, sulfoaluminate cement, composite mineral additive, NaAlO ₂ and the consumption of NaOH The ratio is: 1L: (1455-1674) g: (45-126) g: (8-16) g: (1-4) g.