搅拌参数对放射性废液水泥固化体性能的影响

Effect of Mixing Parameter on Property of Cement Solidified Radioactive Waste Form

目前,国内核电站或核设施产生的中低放废液都采用水泥固化进行处理,水泥浆及水泥固化体性能是水泥固化技术重点研究内容。本文采用普通硅酸盐水泥固化中低放废液模拟料液,研究不同液灰比条件下,搅拌时间和搅拌速度对水泥浆流动度和固化体28 d抗压强度、孔结构、显微结构和抗浸出性能的影响。结果表明:在相同液灰比下,随着搅拌时间的延长(10～50 min),水泥浆的流动度和固化体抗压强度呈现先增大后减小的趋势,而固化体的孔隙率和Sr^(2+)浸出率随搅拌时间的延长呈递减的趋势,搅拌50 min的固化体的结构较搅拌10 min的固化体致密;用较大搅拌速度制备的固化体的抗压强度较高,且在搅拌30 min内,提高搅拌速度可提高浆料的流动度;然而长时间用较大速度搅拌制备的固化体的孔隙率较高,同时核素浸出率也较大。由于固化工艺过程中搅拌速度和搅拌时间会影响水泥浆的流动性和固化体性能,因此在水泥固化装置投入使用前,应通过大量实验来确定满足工艺要求且满足固化体性能的最佳搅拌参数。

Cement solidification is the mainly technology used to treat low and intermediate level radioactive waste from nuclear power plants or nuclear facilities in China nowadays,among which the properties of cement paste as well as cement solidified radioactive waste forms are key focus.In this paper,the effect of mixing speed and mixing time on the fluidity of cement paste and the properties of cement solidified radioactive waste forms,such as 28 d compressive strength,pore structure,microstructure and anti-leaching performance,were studied under different mixing conditions to simulate the low and intermediate radioactive waste by using ordinary Portland cement.The results show that the fluidity of cement slurry and the compressive strength of cement solidified waste form increase firstly and then decrease with the increase of mixing time(10-50 min),while the porosity and Sr^2+leaching rate of solidified body decrease with the increase of mixing time.Compared with the solidified body prepared by mixing for 10 min,the structure of 50 min solidified body is more compact.The compressive strength of solidified body prepared by the larger mixing speed is higher and the fluidity of slurry could be improved by raising the mixing speed during 30 min mixing time.However,the porosity of the solidified body prepared by mixing with large velocity is higher,as well as radionuclide leaching rate.As the mixing speed and mixing time will affect the fluidity of cement paste and the properties of cement solidified waste form,a series of experiments must be carried out before the cement solidification device is put into use,to determine the optimum mixing parameters satisfying the process requirements and the properties of the cement solidified waste form.