膨润土在核废料处置环境中的膨胀衰减规律研究

利用Phreeqc软件模拟了核废料处置库中高压实膨润土中发生的化学反应，建立了K+、Ca2+、Na+、Mg2+ 4种阳离子的离子交换和矿物溶解沉淀的一维运移反应模型。模拟了核废料处置环境中，膨润土化学组分在不同流体环境下随时间和空间的变化规律，验证了膨胀性的衰减主要是由Na基蒙脱石转变为Ca基蒙脱石引起。结合膨润土化学组分变化结果，对膨润土膨胀性衰减程度进行了评估。得到1万年后海水和地下水环境下的高庙子膨润土膨胀性衰减系数分别达到0.83和0.92，MX80膨润土达到0.79和0.90。

NUMERICAL SIMULATION FOR DECAY OF SWELLING CAPACITY OF BENTONITE IN HIGH-LEVEL NUCLEAR WASTE REPOSITORY

The hydrogeochemical reaction of the high-pressure bentonite in the high-level nuclear waste repository was simulated with the software Phreeqc. A one-dimensional transport model is established in consideration of the cation exchange of K+,Ca2+,Na+,Mg2+ and mineral dissolution and precipitation reactions. The curves of the bentonite chemical components changing over time and space are obtained, which verifies that the decay in swelling capacity is mainly caused by the transformation from Na-montmorillonite into Ca-montmorillonite. The degree of decay in swelling capacity is evaluated. Decay coefficients of the GMZ and MX80 bentonite respectively reach 0.83 and 0.79 in the seawater and 0.91 and 0.90 in the underground water after 10000 years.