γ辐照和热老化对高庙子膨润土自由基的影响

The Influence ofγ-rays Irradiation and Thermal Aging on the Radicals of Gaomiaozi Sodium Bentonite

为了明确γ辐照和热老化对高庙子天然钠基膨润土中自由基的影响,拓展高放地质处置缓冲材料性能评价范围,以内蒙古高庙子天然钠基膨润土和北山地下水为研究对象,利用电子自旋共振波谱仪、红外光谱仪和穆斯堡尔谱仪分析了不同γ辐照剂量(500、1000、1500、2000、2500、3000 kGy)照射、不同老化温度(90、150、170、190、210℃)和老化时间(2、4、6、8、10、12个月)热老化以及γ辐照3000 kGy后,开展不同老化温度(90、150、170、190、210℃)和老化时间(2、4、6、8、10、12月)热老化后的高庙子天然钠基膨润土中自由基浓度、官能团和Fe的赋存状态以及含量的变化,并对其机理进行了初步分析。结果表明:随着累积辐照剂量和老化温度(时间)的增加,膨润土中自由基含量先增大后减小,且辐照和老化作用存在明显的叠加效应;老化后膨润土中Fe(Ⅱ)含量减小,Fe(Ⅲ)含量增大,老化过程发生了结构Fe(Ⅱ)向Fe(Ⅲ)的转变,而这种转变在黑暗条件下可以活化O 2产生·OH,且·OH的生成与Fe(Ⅱ)的氧化趋势一致。总体而言,γ辐照和热老化引起了高庙子天然钠基膨润土中自由基的显著变化,在此试验条件下Fe(Ⅱ)活化O^2产生·OH对膨润土中自由基含量的影响较大。

The research aimed to expand the characterization scope of high-level radioactive geological disposal buffer materials,and clarify the effects of gamma irradiation and thermal aging on radicals in Gaomiaozi natural sodium bentonite.The Gaomiaozi natural sodium bentonite in Inner Mongolia and Beishan groundwater was taken as research objects.The changes of free radical concentration,functional group,the state and content of Fe were analyzed by electron spin resonance spectrometer,fourier transform infrared spectrometer and Mossbauer spectrometer under differentγ-rays irradiation dose(500,1000,1500,2000,2500,3000 kGy),aging temperature(90,150,170,190,210℃),and aging time(2,4,6,8,10,12 months).Additionally,these four parameters were analyzed under different aging temperature(90,150,170,190,210℃)and aging time(2,4,6,8,10,12 months)with the accumulative radiation doses of 3000 kGy.The preliminary analysis of mechanism was also discussed.The results indicate that the content of radicals firstly increases and then decreases with the accumulative irradiation dose,thermal aging time and temperature increasing.There is a significant superimposed effect of irradiation and aging.During the aging process,the Fe(Ⅱ)content in the bentonite decreases,and the Fe(Ⅲ)content increases.Fe(Ⅱ)is transformed to Fe(Ⅲ),and this transition can activate O^2 to·OH under dark conditions,the formation trend of·OH is consistent with the oxidation of Fe(Ⅱ).In general,the radicals of the Gaomiaozi natural sodium-based bentonite are obviously varied after theγ-ray irradiation and thermal aging on the bentonite,So the impact of·OH that produce by Fe(Ⅱ)activation was very important under above condition.