膨润土-砂混合物碱热耦合老化后的膨胀性能

Study on Expansion Properties of Bentonite-sand Mixture after Alkali-thermal Coupling Aging

在高放射核废物地质处置中,膨润土-砂混合物作为其人工屏障的一种缓冲回填材料,长期受到含盐地下水与地热、化学衰变热的双重碱热耦合作用,导致该材料封闭性能衰退。为了研究膨润土-砂混合物在碱热耦合作用后的膨胀性能,将膨润土分别放入密封容器中用1 mol/L的Na OH溶液浸泡并置于90℃的高温烘箱中进行2~12个月的碱热耦合反应,模拟膨润土在地质库中的运行情况,考察了碱热耦合老化后膨润土-砂混合物恒体积膨胀力与膨润土自由膨胀率指标。结果表明,碱热耦合老化作用会显著降低膨润土-砂混合物的膨胀性能,随着老化时间的延长,膨润土-砂混合物的膨胀力和膨润土的自由膨胀率都明显减小。研究成果可为高废处置库长期运行的稳定性和安全性预测提供参考。

In the geological disposal of high radiation nuclear waste,bentonite-sand mixture,as a buffer backfilling material of its artificial barrier,has been subjected to the double alkali-thermal coupling of salty groundwater,geothermal and chemical decay heat for a long time,resulting in the decline of sealing performance of the material.In order to study the expansion performance of bentonite-sand mixture after alkali-thermal coupling,the bentonite was put into a sealed container and bubbled with NaOH solution of 1mol/L and placed at 90℃for 2-12 months to simulate the operation of bentonites in geological depots.The constant volume expansion force and free expansion rate of bentonite-sand mixture after coupling aging were studied.The results show that the alkali-thermal coupling aging can significantly reduce the expansion performance of bentonite-sand mixture,but with the prolongation of aging time,the expansion force of bentonite-sand mixture and the free expansion rate of bentonite decrease obviously.The research results can provide a reference for the stability and safety prediction of long-term operation of high waste disposal library.