Experiment Research On Physical-mechanical Properties And Radon-reduction Effect Of Solidified Uranium Tailings

Uranium tailings are formed after a series of complex processes such as solid liquid separation or extraction of uranium ore.A huge amount of waste substances are contained in uranium tailing ponds with wide varieties and high toxicity.Nearly 30% of nuclide is long-lived nuclide among which uranium tailings and heavy metal elements can be transported and diffused through the media of air,biology and water,which brings potential radiation hazard to the natural environment.The radioactive waste treatment of one uranium tailings reservoir is mainly carried out by the methods of vacuum preloading and cement mixing pile,but those two methods can not be implemented in the local area.Therefore,it is necessary to add chemical curing agent to solidify uranium tailings,in the hope of ensuring the security and reliability of uranium tailing ponds decommissioning management.Non-additive cement curing technology is used in deposing low and middle radioactive waste,which achieves good effects but has the defects of increasing capacity and high economic cost at the same time.Industrial waste granulated blast furnace slag,flyash and quicklime solidified uranium tailings are selected in this paper.Three kinds of materials instead of cement solidified uranium tailings can not only reduce the amount of cement,but also reduce the project cost because of it can be hydrated to form cementations’ substances and expansive hydrates just like cement during the curing process.The solidification of granulated blast furnace slag,quicklime and fly ash with cement and uranium tailings is studied in this research.The physical properties,mechanical properties and radon reduction effects of different ratios of uranium tailings solidified body are systematically measured.According to the experimental results,the solidification effect of granulated blast furnace slag is the best.The specific elements include:(1)The properties of uranium tailings in a uranium tailings pond are determined,including chemical composition,phase analysis,microstructure and energy spectrum analysis,water content,particle size distribution and gamma dose rate.According to other related documents,three solidified materials of granulated blast furnace slag,quicklime and fly ash which cooperating cement were selected as the base material of solidified uranium tailings.(2)Three kinds of materials are mixed with cement in equal proportions and blended into uranium tailings at blending amounts of 15%,20%,and 25%.Test specimen of 70.7× 70.7× 70 mm,50× 100 mm,(37)50× 25 mm and 150× 150× 150 mm are prepared by blending,stirring,loading,vibrating,demoulding and curing.The physical properties(including micromorphology and permeability coefficient),mechanical properties(including compressive strength,tensile strength and shear strength)and the effect of radon reduction are analyzed as well.(3)The consistency of granulated blast furnace slag specimens with granulated blast furnace slag under the same amount is the best,followed by flyash specimens which compared with the uranium tailings original sand.The permeability coefficient values of the solidified specimen No.2 of granulated blast furnace slag,the solidified specimen No.3 of granulated blast furnace slag,the solidified specimen No.3 of quickline,the solidified specimen No.2 of flyash and the solidified specimen No.3 of flyash specimens were 5.58 × 10-3 cm·s-1 and that of uranium tail sand.The field measurement value is small,all reaching 0.136×10-3cm·s-1.The solidified specimen No.2 of granulated blast furnace slag,the solidified specimen No.3 of granulated blast furnace slag,the solidified specimen No.2 of flyash,the solidified specimen No.3 of flyash,and the solidified specimen No.3 of quickline specimens have been subjected to the compressive strength requirements for decommissioning treatment.At the same time,the compressive strength(tensile strength and shear strength)of the specimen with the same amount of admixture is specimen of granulated blast furnace slag,specimen of flyash and the least is specimen of quickline.And the compressive strength of the solidified specimen is 8-10 time of the tensile strength and 3-5 times of the shear strength.(4)Radon emission rate,radon diffusion length and radon diffusion coefficient are obtained again after noise reduction based on wavelet theory.The results show that the correlation coefficient of fitting slope after noise reduction is more than 0.96 compared with the range of 0.90-0.94 before noise reduction.It is proved that Wavelet theory can provide an analytic framework for improving the accuracy of radon exhalation rate,diffusion length and diffusion coefficient.The decommissioning management of uranium tailings reservoir is provided with technical guidance by the corresponding results obtained in this research.