模拟高放玻璃固化体在低氧地下水中的长期蚀变行为研究

Study on Long-term Alteration Behavior of the Simulated HLW Glass in the Low-oxygen Underground Water

高放废物玻璃固化体的长期蚀变行为对深地质处置场的安全评价非常重要。玻璃蚀变在正常条件下发展缓慢,为了能够预测玻璃的长期蚀变行为,本研究采用了150℃下,玻璃体表面积与浸泡溶液体积比(S/V)为6 000 m-1的粉末静态浸泡法(PCT法)来加快腐蚀进度,用扫描电子显微镜-X射线能谱仪(SEM-EDS)和X射线衍射仪(XRD)分析了固体样品表面形貌和二次矿物相,用电感耦合等离子体发射光谱仪(ICP-AES)分析了浸出液中的元素含量。结果表明,模拟高放废物玻璃体在遭受苦咸地下水长期浸泡的后果是表面生成蜂窝状富Mg和Fe的页硅酸盐和铝硅酸盐矿相,这些二次矿相主要是绿脱石[Na0.3Fe2Si4O1(0OH)2.4H2O]、蒙脱石[Ca0.(2Al,Mg)2Si4O1(0OH)2.4H2O]、发光沸石([Na2,K2,Ca)Al2Si10O24.7H2O]和斜发沸石([Na,K,Ca)5Al6Si30O7.218H2O]等矿物。玻璃的溶解进一步加深后,B和Na会以硼砂形式浸出。页硅酸盐矿物的形成会加快玻璃的溶解速度,重新恢复的最大速率要比之前稳定的速率高出约4倍。

The long-term alteration behavior of HLW glasses is very important in the safety assessment of the deep geological repository.In order to predict the behavior under normal conditions,which is difficult to be obtained within a relative short period for the slow reaction between the glasses and aqueous medias,the static leaching method（PCT） was employed to accelerate the corrosion evolution of the glass with S/V=6 000 m-1 at 150 ℃.SEM-EDS and XRD,respectively,were used for the analysis of the glass surface micro-morphological characterization and the secondary minerals produced by the alteration of the glass,and ICP-AES for the concentration determination of the elements in the leaching solution.In our experiments,the aluminosilicates and phyllosolicates with honeycomb structure rich in Mg and Fe were found to form on the simulated HLW glass surface when it was subjected to a long-term leaching in the high brine groundwater.The major secondary minerals are nontronite（Na0.3Fe2Si4O10（OH）2·4H2O）,montmorillonite（Ca0.2（Al,Mg）2Si4O10（OH）2·4H2O）,mordenite（（Na2,K2,Ca）Al2Si10O24·7H2O）） and clinoptilolite（（Na,K,Ca）5Al6Si30O72·18H2O）.As further dissolution of the glass,both B and Na in the glass were found to leach out as borax form.Appearance of the phyllosilicates resumes the dissolution rate of the simulated HLW glass.The maximum renewal rate is increased by about 4 times the stable rate.