Microstructure and Cs Behavior of Ba-Doped Aluminosilicate Pollucite Irradiated with F+ Ions

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• 作者：Weilin Jiang ; Libor Kovarik ; Zihua Zhu ; Tamas Varga ; Mark H. Engelhard ; Mark E. Bowden ; Tina M. Nenoff ; Terry J. Garino
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：August 7, 2014
• 年：2014
• 卷：118
• 期：31
• 页码：18160-18169
• 全文大小：627K
• ISSN：1932-7455

文摘

Radionuclide ¹³⁷Cs is one of the major fission products that dominate heat generation in spent fuels over the first 300 years. A durable waste form for ¹³⁷Cs that decays to ¹³⁷Ba is needed to minimize its environmental impact. Aluminosilicate pollucite CsAlSi₂O₆ is selected as a model waste form to study the decay-induced structural effects. Whereas Ba-containing precipitates are not present in charge-balanced Cs_0.9Ba_0.05AlSi₂O₆, they are found in Cs_0.9Ba_0.1AlSi₂O₆ and identified as monoclinic Ba₂Si₃O₈. Pollucite is susceptible to electron-irradiation-induced amorphization. The threshold density of electronic energy deposition for amorphization was determined to be 235 keV/nm³. Pollucite can be readily amorphized under F⁺ ion irradiation at 673 K. A significant amount of Cs diffusion and release from the amorphized pollucite occurs during the irradiation. However, cesium is immobile in the crystalline structure under He⁺ ion irradiation at room temperature. The critical temperature for amorphization is not higher than 873 K under F⁺ ion irradiation. If kept at or above 873 K all the time, the pollucite structure is unlikely to be amorphized; Cs diffusion and release are improbable. A general discussion regarding pollucite as a potential waste form is provided in this report.