水热法合成铯榴石固化放射性铯的相变机理与长期浸出性能评估

doi:10.27045/j.1000-8187.202604003

摘要/Abstract

摘要： 高水平放射性废液中核素铯的安全处置是核燃料循环后端的关键挑战。铯榴石因其独特的三维笼状骨架和优异的化学耐久性,被认为是固化放射性铯的理想矿物基质。本文采用低温水热法成功制备了高纯度铯榴石晶体,并结合 X 射线粉末衍射(XRD)全谱精修、显微拉曼光谱两种表征手段,系统探究了铯榴石相变动力学及微观结构响应机理。实验结果表明,铯榴石的晶化过程遵循“溶解-重结晶”机制,铯离子作为关键结构导向剂驱动富钠亚稳相持续溶解,并在反应60 h 时完全转化为纯相铯榴石;同时,拉曼光谱低频区的本征特征峰的变化规律,证实了铯离子被成功固定在铯榴石笼状孔隙内。此外,本文构建了 Python-PHREEQC 耦合的双动力学储库模型,有效分离表面不稳定相的初期快速溶出行为,精准获取固化体长期本征稳态浸出速率,约为3.16×10^-8 g·m^-2·d^-1。本文不仅证实了温和水热法高效固化游离铯的技术可行性,也为放射性铯固化体长期地质安全风险评价,提供完备的光谱学实验依据与动力学预测模型。

关键词: 铯榴石, 水热合成, 放射性铯, 固化机理

Abstract: Safe disposal of cesium nuclides in high-level radioactive liquid waste is a critical challenge in the back-end of the nuclear fuel cycle. Pollucite possesses a unique three-dimensional cage framework and excellent chemical durability, making it an ideal mineral matrix for immobilizing radioactive cesium. In this work, high-purity pollucite crystals were successfully synthesized via a low-temperature hydrothermal method. Combined with two characterization techniques, including full-profile Rietveld refinement of X-ray powder diffraction (XRD) and micro-Raman spectroscopy, the phase transformation kinetics and microstructural evolution mechanism of pollucite were systematically investigated. The experimental results reveal that the crystallization of pollucite follows a dissolution-recrystallization mechanism. As a vital structure-directing agent, cesium ion drives the continuous dissolution of sodium-rich metastable phases, which are completely converted into pure-phase pollucite after 60 hours of reaction. Meanwhile, the variation of intrinsic characteristic peaks in the low-frequency region of Raman spectra confirms that cesium ion is successfully immobilized within the cage pores of pollucite. Furthermore, a dual kinetic reservoir model coupled with Python and PHREEQC was established. This model effectively distinguishes the initial rapid leaching behavior of unstable phases on the material surface and accurately determines the long-term intrinsic steady-state leaching rate of the solidified form, which is approximately 3.16×10^-8g·m^-2·d^-1. This study not only verifies the technical feasibility of efficiently immobilizing free cesium by a mild hydrothermal method, but also provides comprehensive spectroscopic experimental evidence and a kinetic prediction model for the long-term geological safety risk assessment of radioactive cesium solidified forms.

Key words: pollucite, hydrothermal synthesis, radioactive cesium, immobilization mechanism

中图分类号:

TL941

于伟跃, 王龙江, 谷伟刚, 刘逸飞, 孔祥银, 高超, 闫晓俊, 高凯, 李晓东. 水热法合成铯榴石固化放射性铯的相变机理与长期浸出性能评估[J]. 辐射防护, 2026, 46(4): 303-312.

YU Weiyue, WANG Longjiang, GU Weigang, LIU Yifei, KONG Xiangyin, GAO Chao, YAN Xiaojun, GAO Kai, LI Xiaodong. Phase transformation mechanism and long-term leaching behavior ofhydrothermally synthesized pollucite for radioactive cesium immobilization[J]. RADIATION PROTECTION, 2026, 46(4): 303-312.

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