摘要:
为研究钆锆烧绿石固化Pu（Ⅳ）的相变化情况及化学稳定性,以Gd2O3,ZrO2为原料,Ce（Ⅳ）作为Pu（Ⅳ）的模拟替代物质,采用冷压热烧结的方法制备出Gd2Zr2-xCexO7（0≤x≤2.0）系列样品.分别在40℃和70℃的合成海水中,对固化体的长期浸出性能进行研究.借助粉末X射线衍射仪对所制备样品的物相信息进行收集,利用等离子体质谱仪对固化体的浸出浓度数据进行分析.研究结果表明：当x≤0.08时,固化体保持为烧绿石相;当x〉0.08时,固化体转变为具有缺陷的萤石型结构相.固化体中Gd3＋,Zr4＋和Ce4＋在合成海水中,随着浸泡时间的延长浸出浓度逐渐上升,70℃下的浸出浓度高于40℃下的浸出浓度.在42 d时,固化体中Gd3＋的最大浸出浓度在0.032μg.ml.-1以下,Zr4＋的最大浸出浓度在0.003μg.ml.-1以下;Ce4＋的最大浸出浓度在0.032μg.ml.-1以下.
关键词:
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烧绿石
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固化体
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物相
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化学稳定性
Abstract:
In order to investigate phase change and chemical stability of pyrochlore Gd2Zr2O7 used for immobilizing Pu（Ⅳ）,tetravalent cerium is used as the simulacrums for plutonium with tetravalence,and Gd2Zr2-xCexO7（0≤x≤2.0） series samples are successfully synthesized by high temperature solid reaction and using Gd2O3 and ZrO2 powders as starting materials.The experiments of long-term chemical stability are conducted in synthetic seawater at 40℃and 70℃separately.The XRD diffractive data and extraction ratio of as-gained samples are collected by the help of X-ray diffraction（XRD） instrument and inductively coupled plasma mass spectrometry. The results indicate that the phases of compounds change from pyrochlore to fluorite-type phase when the value of x is more than 0.08. Extraction ratios of Gd3＋,Zr4＋ and Ce4＋ in waste forms increase with the increase of immersion time in synthetic seawater.The extraction ratio of waste form at 70℃is higher than at 40℃.The highest extraction ratios of Gd3＋,Zr4＋ and Ce4＋ for 42 days are no more than 0.032,0.003 and 0.032μgml-1 respectively.
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