THMC耦合作用下温度对硼硅酸盐玻璃固化体抗浸出性能的影响

Influence of Temperature on Leaching Resistance of Borosilicate Glass Waste Forms Under THMC Couplings Condition

硼硅酸盐玻璃固化体在深地质处置环境会受到"热-水-力-化学"(THMC)多场耦合作用的影响。采用单通道流通法,利用自主研发的装置,研究了THMC耦合作用下(流速~0.01mL/min,压力~10 MPa)不同温度(40~150℃)对硼硅酸盐玻璃固化体在模拟地下水侵蚀后的表面形貌和抗浸出性能的影响。结果表明:在90℃、150℃浸泡后的玻璃固化体表面形成了明显的蚀变层,其主要成分为含Mg、Al、Fe、Si的层状硅酸盐,并首次观察到蚀变层表面板状或片状BaSO_(4)晶体的生成;Si、B的浸出速率在7d后基本达到稳定,U的浸出速率随着时间的延长而增加,28d后Si、B、U在150℃的浸出速率比90℃下高约一个数量级。90℃、150℃下,Cs在3d快速浸出后有所降低,其浸出速率处于同一数量级。

Borosilicate glass waste forms would suffer from the influences due to the multi-field couplings of Thermodynamics-Hydrodynamics-Mechanics-Chemistry(THMC)in the deep geological disposal environment.Using a self-developed device based on the Single-Pass Flow-Through Test Method,the effects of temperatures(40~150℃)on the surface morphology and leaching resistance of borosilicate glass waste forms under THMC couplings(flow rate~0.01 mL/min,pressure~10 MPa)are studied in this work.The results show that the alteration layer with main composition of the phyllosilicate that is constituted by Mg,Al,Fe and Si is observed on the glass surface after leaching at 90℃and 150℃.Moreover,the plate-like or flake-like BaSO_(4)crystals,which are first observed and reported,stably forms on the surface of the alteration layer.The leaching rates of Si and B are approximately constant after 7 days,while the leaching rate of U gradually increases with time.After leaching 28 days,the leaching rates of Si,B and U elements at 150℃are approximate one order of magnitude higher than those at 90℃.At 90℃and 150℃,for Cs element,its leaching rate increases rapidly in the first 3 days,and then decreases slightly with time.Interestingly,the temperature has little influence on the leaching rate of Cs,resulting in similar leaching values at 90℃and 150℃.