The mechanism of the hydrothermal alteration of cerium- and plutonium-doped zirconolite
The mechanism of the hydrothermal alteration of cerium- and plutonium-doped zirconolite
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DOI：
10.1016/j.jnucmat.2010.12.218
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发表时间：
2011-03
影响因子：
3.1
通讯作者：
P. Pöml;T. Geisler;J. Cobos-Sabaté;T. Wiss;P. Raison;P. Schmid-Beurmann;X. Deschanels;C. Jegou;J. Heimink;A. Putnis
中科院分区：
文献类型：
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作者：
P. Pöml;T. Geisler;J. Cobos-Sabaté;T. Wiss;P. Raison;P. Schmid-Beurmann;X. Deschanels;C. Jegou;J. Heimink;A. Putnis
对Ce和Pu掺杂锆英石的水稳定性进行了综合研究。用Ce掺杂的锆沸石粉末进行四个系列的水热实验：（1）溶液系列（1 M HCl、2 M NaCl、1 M NaOH、1 M NH3、纯H2O），（2）温度系列（T=100-300°C），（3）表面积与流体体积比系列，和（4）使用不同反应器材料（Teflon ®、Ni和Ag）的系列。此外，还对238 Pu和239 Pu掺杂的锆英石陶瓷在1 M HCl溶液中的生长进行了实验研究。238 Pu掺杂的锆英石已经积累了显著的辐射损伤，并且是X射线非晶的，而239 Pu掺杂的锆英石仍然是结晶良好的。不同实验系列的结果可以总结如下：（1）14天后，除了1 M HCl之外的所有溶液的改变程度都不显著，因此1 M HCl用于所有其他实验系列;（2）TiO 2和m-ZrO 2在1 M HCl溶液中不同程度地取代了锆英石颗粒，即，（3）蚀变程度随温度的升高而略有增加，（4）蚀变速率与表体积比无关;（5）从银反应器中溶解的Ag显著提高了反应速率，而从Ni反应器中溶解的Ni降低了Ti和Zr在HCl溶液中的溶解度，表明背景电解质对改变速率具有强烈的影响。从在200°C下在1 M HCl溶液中用Pu掺杂的样品进行的实验中发现，非晶238 Pu掺杂的锆英石的改变程度明显大于晶体对应物。结果表明，耦合溶解-再沉淀机制，这是详细讨论。
A comprehensive study on the aqueous stability of Ce- and Pu-doped zirconolite has been performed. Four series of hydrothermal experiments were carried out with Ce-doped zirconolite powders: (1) a solution series (1M HCl, 2M NaCl, 1M NaOH, 1M NH3, pure H2O), (2) a temperature series (T=100–300°C), (3) a surface area-to-fluid volume ratio series, and (4) a series using different reactor materials (Teflon©, Ni, and Ag). In addition, experiments on238Pu- and239Pu-doped zirconolite ceramics in a 1M HCl solution have been performed. The238Pu-doped zirconolite had already accumulated significant radiation damage and was X-ray amorphous, while the239Pu-doped zirconolite was still well-crystalline. The results of the different experimental series can be summarized as follows: (1) After 14 days the degree of alteration is insignificant for all solutions other than 1M HCl, which was therefore used for all other experimental series; (2) TiO2and m-ZrO2replaced the zirconolite grains to varying degrees in the 1M HCl solution, i.e., zirconolite dissolution is incongruent; (3) the degree of alteration increases only slightly with increasing temperature; (4) the alteration rate is independent on the surface to volume ratio; (5) Ag dissolved from the silver reactors dramatically increases the reaction rate, while Ni from the Ni reactors reduces the solubility of Ti and Zr in the HCl solution, indicating that background electrolytes have a strong effect on the alteration rate. From the experiment with the Pu-doped samples at 200°C in a 1M HCl solution it was found that the amorphous238Pu-doped zirconolite was altered to a significantly greater extent than the crystalline counterparts. The results suggest a coupled dissolution-reprecipitation mechanism, which is discussed in detail.