模拟高放玻璃体在高温湿气中的蚀变行为
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摘要
模拟地下水穿透地质处置多重屏障情形下,地下水会以高温蒸气的形式与高放玻璃体发生反应,加速玻璃体的蚀变。采用纯水和特定的盐溶液作为浸泡剂以控制体系的相对湿度分别在100%和90%左右。模拟高放玻璃体样片用聚四氟乙烯线悬挂在浸泡剂上方并在低氧箱中平衡,分别在120℃和150℃的干燥箱内反应。通过测试浸泡液中各元素的浓度和分析玻璃体表面的腐蚀产物,以表征玻璃的蚀变速率。实验发现,温度对玻璃腐蚀的影响最为明显,湿度的影响较弱。玻璃体中大多数元素在150℃下的浸出速率高于120℃下的浸出速率2～3个数量级。90 d时,玻璃体在150℃下已观察到显著的腐蚀。900 d后,150℃下玻璃体已基本完全腐蚀;而在120℃下的玻璃腐蚀程度很小,900 d时腐蚀厚度仍小于50μm。150℃时随着腐蚀的发生,玻璃表面的SiO_2腐蚀层逐渐形成以钙的硅酸盐为主的二次矿相。
Alteration of simulated high-level waste(HLW) glass in humid vapor at high temperature was investigated to simulate the penetration of groundwater to geological disposal barrier and accelerated hydration of HLW glass. Glass samples were hanged in the autoclaves in a hypoxia cell. Pure water and special saline solution were placed in the autoclave to maintain the relative humidity at 90% and 100%, respectively. The autoclaves were sealed and placed at 120 ℃ and 150 ℃ to maintain the vapor humidity. The concentration of the key elements and corrosion products are analyzed to determine the alteration rate of glass. The results show that the effect of temperature on alteration rate of glass is more remarkable than that of humidity. The leaching rate of most elements in glass at 150 ℃ are 2-3 orders of magnitude higher than those at 120 ℃. There is obvious alteration phenomenon after 90 days at 150 ℃. After 900 days experiment, the thickness of corrosion layers is 800-1 000 μm at 150 ℃, while the corrosion occurrs slightly at 120 ℃ with a thickness less than 50 μm. With the occurrence of alteration at 150 ℃, the SiO_2 corrosion layer on the surface of glass turns to silicate of calcium and forms secondary minerals.
Alteration of simulated high-level waste(HLW) glass in humid vapor at high temperature was investigated to simulate the penetration of groundwater to geological disposal barrier and accelerated hydration of HLW glass. Glass samples were hanged in the autoclaves in a hypoxia cell. Pure water and special saline solution were placed in the autoclave to maintain the relative humidity at 90% and 100%, respectively. The autoclaves were sealed and placed at 120 ℃ and 150 ℃ to maintain the vapor humidity. The concentration of the key elements and corrosion products are analyzed to determine the alteration rate of glass. The results show that the effect of temperature on alteration rate of glass is more remarkable than that of humidity. The leaching rate of most elements in glass at 150 ℃ are 2-3 orders of magnitude higher than those at 120 ℃. There is obvious alteration phenomenon after 90 days at 150 ℃. After 900 days experiment, the thickness of corrosion layers is 800-1 000 μm at 150 ℃, while the corrosion occurrs slightly at 120 ℃ with a thickness less than 50 μm. With the occurrence of alteration at 150 ℃, the SiO_2 corrosion layer on the surface of glass turns to silicate of calcium and forms secondary minerals.
引文
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[2] 盛嘉伟,罗上庚,汤宝龙.高放废液的玻璃固化及固化体的浸出行为与发展情况[J].硅酸盐学报,1997,25(1):83-88.
[3] 张华,罗上庚,姜耀中,等.低氧条件下浸出剂和温度对固化体浸出行为的影响[J].核化学与放射化学,2005,27(4):144-151.
[4] ASTM C1663-17 Standard test method for measuring waste glass or glass ceramic durability by vapor hydration test[S].West Conshohocken:ASTM international,2017.
[5] Neeway J,Abdelouas A,Grambow B,et al.Vapor hydration of SON68 glass from 90 ℃ to 200 ℃:a kinetic study and corrosion products investigation[J].J Non-Cryst Solids,2012,358(21):2894-2905.
[6] Frugier P,Gin S,Minet Y,et al.SON68 nuclear glass dissolution kinetics:current state of knowledge and basis of the new GRAAL model[J].J Nucl Mater,2008,380(1):8-21.
[7] Godon N,Delaye J M,Deneele D,et al.Dossier de référence sur le comportement à long terme des verres nucléarires,DTCD/2004/06[R].Commissariat à l′énergie Atomique,2004.
[8] Gong W L,Wang L M,Ewing R C,et al.Analytical electron microscopy study on surface layers formed on the French SON68 nuclear waste glass during vapor phase alteration at 200 ℃[J].J Nucl Mater,1998,2-3:249-265.
[9] Cunnane J C,Bates J K,Ebert W L,et al.High-level nuclear-waste borosilicate glass:a compendium of characteristics[C]∥MRS Proceedings.Cambridge University Press,1992,294:225.
[10] Abrajano T A,Bates J K,Mazer J J.Aqueous corrosion of natural and nuclear waste glasses Ⅱ:mechanisms of vapor hydration of nuclear waste glasses[J].J Non-Cryst Solids,1989,108(3):269-288.
[11] Strachan D.Defense HLW glass degradation model,ANL-EBS-MD-000016,REV 02[R].Yucca Mountain Project,Las Vegas,USA,2004.
[12] Ebert W L,Hoburg R F,Bates J K.The sorption of water on obsidian and a nuclear waste glass[J].Phys Chem Glasses,1991,32(4):133-137.
[13] Abdulagatov I M,Azizov N D.Experimental vapor pressures and derived thermodynamic properties of aqueous solutions of lithium sulfate from 423 to 573 K[J].Fluid Phase Equilib,2004,216(2):189-199.
[14] Sako T,Hakuta T,Yoshitome H.Vapor pressures of binary (water-hydrogen chloride,-magnesium chloride,and -calcium chloride) and ternary (water-magnesium chloride-calcium chloride) aqueous solutions[J].J Chem Eng Data,1985,30(2):224-228.