Studies on supercritical hydrothermal syntheses of uranium and lanthanide oxide particles and their reaction mechanisms
Studies on supercritical hydrothermal syntheses of uranium and lanthanide oxide particles and their reaction mechanisms
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DOI：
10.1016/j.jnucmat.2015.06.020
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发表时间：
2015-11
影响因子：
3.1
通讯作者：
Do-Huak Hwang;Takehiko Tsukahara;Kosuke Tanaka;M. Osaka;Y. Ikeda
中科院分区：
文献类型：
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作者：
Do-Huak Hwang;Takehiko Tsukahara;Kosuke Tanaka;M. Osaka;Y. Ikeda
为了发展超临界水热法制备低污染MOX燃料用金属氧化物粗颗粒的方法，我们研究了U（VI）、Ln（III）（Ln：镧系元素= Ce、Pr、Nd、Sm、Tb）、Cs（I）和Sr（II）的硝酸盐或氯化物化合物在SH条件下（温度= 400-500 ℃，压力= 30-40 MPa）。结果发现，Ln（NO3）3（Ln = Ce、Pr、Tb）化合物生成LnO 2，Ln（NO3）3（Ln = Nd、Sm）化合物几乎不转化为它们的氧化物，而LnCl 3（Ln = Ce、Pr、Nd、Sm、Tb）、CsNO 3和Sr（NO3）2不形成它们的氧化物。此外，在SH条件下处理含有Ln（NO3）3（Ln = Ce，Pr，Tb）的HNO 3水溶液后，在液相中检测到HNO 2物种，并发现HNO 3分解产生NO2和NO化合物。根据这些结果，提出了Ln氧化物（LnO 2）颗粒是通过SH体系中的HNO 3和HNO 2物种将Ln（III）氧化成Ln（IV）而直接形成的。此外，发现铀酰离子形成U3 O 8和UO 3取决于HNO 3的浓度。根据这些结果，预期通过SH方法有效地制备用于低去污MOX燃料的原料金属氧化物颗粒。
In order to develop preparation method of raw metal oxide particles for low decontaminated MOX fuels by supercritical hydrothermal (SH) treatments, we have investigated behavior of aqueous solutions dissolving U(VI), Ln(III) (Ln: lanthanide = Ce, Pr, Nd, Sm, Tb), Cs(I), and Sr(II) nitrate or chloride compounds under SH conditions (temperature = 400–500 °C, pressure = 30–40 MPa). As a result, it was found that Ln(NO3)3(Ln = Ce, Pr, Tb) compounds produce LnO2, that Ln(NO3)3(Ln = Nd, Sm) compounds are hardly converted to their oxides, and that LnCl3(Ln = Ce, Pr, Nd, Sm, Tb), CsNO3, and Sr(NO3)2do not form their oxide compounds. Furthermore, HNO2species were detected in the liquid phase obtained after treating HNO3aqueous solutions containing Ln(NO3)3(Ln = Ce, Pr, Tb) under SH conditions, and also NO2and NO compounds were found to be produced by decomposition of HNO3. From these results, it was proposed that the Ln oxide (LnO2) particles are directly formed with oxidation of Ln(III) to Ln(IV) by HNO3and HNO2species in the SH systems. Moreover, the uranyl ions were found to form U3O8and UO3depending on the concentration of HNO3. From these results, it is expected that the raw metal oxide particles for low decontaminated MOX fuels are efficiently prepared by the SH method.