在放射性废物地质处置中, 为确保废物容器较长时间内的完整性, 防止容器内放射性核素扩散, 采用在容器表面涂装防腐蚀涂层, 并用压实膨润土填埋的方式进行处理。考虑到膨润土膨胀、收缩过程中产生的应力会破坏容器表面防腐蚀涂层, 而回填材料和地下水中含有的氯离子, 可侵入钢与膨润土界面, 使钢去钝化而发生局部腐蚀。本工作取地下水和柯尔碱膨润土对16MnR钢试片进行浸泡腐蚀试验, 研究亚硝酸钠对膨润土中16MnR钢的缓蚀效果。另外, 由于压实膨润土的非饱和渗透特性对于评价缓冲回填材料性能具有重要意义, 故采用压力膜仪分别测量添加亚硝酸钠膨润土和原土的土水特征曲线。结果表明, 当添加亚硝酸钠浓度大于临界浓度时, 缓蚀效率与亚硝酸钠浓度成正比, 0.60%后, 缓蚀效率可达95%; 添加亚硝酸钠膨润土的吸水/脱水速度较慢, 持水性能较好。

In order to ensure the integrity of the waste container over an extended period and prevent the proliferation of radionuclide in the container, anti-corrosion coating was painted on the surface of the container and bentonite land fill was compacted for the disposal of high level waste (HLW). Stress produced in expansion and contraction process of bentonite would destroy the anticorrosion coating of waste container. Cl- contained in the backfill material and groundwater can invade the steel/bentonite interface, resulting in damaying the passivation and localized corrosion of the steel. Immersion corrosion experiment of 16MnR steel was carried out in mixed solution of groundwater and cole alkali bentonite. The inhibition effect of NaNO2 on 16MnR steel in bentonite was studied. In addition, considering that unsaturated permeability of compacted bentonite is significant to the evaluation of backfill and buffer material properties, pressure plate extractors were used to measure the soil-water characteristic curves of the original bentonite and NaNO2 added bentonite. The experimental results showed that the inhibition efficiency was proportional to the concentration of NaNO2 when the concentration of added NaNO2 was greater than the critical concentration. The inhibition efficiency was up to 95% when the concentration increased to 0.60%. Water-absorption/holding rate of NaNO2 added bentonite was slower than that of the original bentonite, and the water holding capacity of NaNO2 added bentonite was relatively good.