采用CaO、Mg(OH)2、Ca3(PO4)2、海泡石、CaCO3 等碱性材料对放射性独居石废渣进行稳定化处理,进行不同投加比试验与长期浸出试验,监测U、Th、pH 的变化规律,借助XRD、SEM-EDS、组分形态变化等手段揭示U、Th稳定化机理.结果表明,在 5.0%、7.5%的投加比条件下,各材料试验组浸出液均满足 pH= 6~9的要求;在长期浸出试验中,仅有Ca3(PO4)2 具备对U、Th核素的长期稳定能力;短期内废渣 pH 升高对U 具有稳定化效应,稳定后U的活化重新溶出是一个长期过程,与反酸无关;Th 的稳定性主要受 pH 影响,pH>6即可实现Th长期稳定.稳定化过程中,废渣表面由于沉淀的生成而变得粗糙,沉淀的U、Th 次生相多为无定形态;U、Th核素的稳定化主要与促进可交换态、碳酸盐结合态向铁锰氧化态、残余态转变有关.
Several materials such as CaO,Mg(OH)2,Ca3(PO4)2,sepiolite,CaCO3 were used to stabi-lize radioactive monazite waste residue.Different dosing ratios and long-term leaching experiments were carried out,the changes in U,Th,and pH were monitored,and the stabilization mechanism of U and Th was revealed by means of XRD,SEM-EDS,and variation of the distribution and forms.The results show that under the condition of 5.0%and 7.5%dosage ratio,the leaching solution of all experimental groups meet the standard requirements of pH= 6~9.In subsequent long-term leaching experiments,only Ca3(PO4)2 has the long-term stability ability for U and Th nuclides.In the short term,the increase in pH of waste residue has a stabilizing effect on U,and the activation and redisso-lution of U after stabilization is a long-term process unrelated to acid reflux.The stability of Th is mainly affected by pH,pH>6 can achieve long-term stability of Th.During the stabilization process,the surface of the waste residue become rough due to the formation of precipitation,and the precipita-ted U and Th secondary phases are mostly amorphous.The stabilization of U and Th nuclides is main-ly related to promoting the transition of exchangeable state and carbonate complex state to iron-man-ganese oxidation state and residual state.