外凝胶法制备UO_2核芯工艺中胶液沉淀分析与微球直径控制

Analysis of Precipitation in Broth Preparation and Size Control of Liquid Microspheres in UO_2 Kernels Production by External Gelation Process

简述了清华大学核研院使用外凝胶法大批量制备高温气冷堆燃料元件UO2核芯工艺,以及工艺中遇到的煮胶步骤发生沉淀和产品粒径控制问题。对沉淀物的XRD分析得到了沉淀物的主要物相,研究发现煮胶步骤中煮胶温度和尿素的加入速度是造成煮胶沉淀的主要原因,通过工艺改进解决了煮胶沉淀问题。另外,通过精确控制分散步骤的压力,有效避免了二次球的产生,保证了UO2核芯粒径的精确控制。

This paper briefly described the process of UO2 kernels preparation by external-gelation for high temperature gas cooled reactor (HTR) fuel elements at Institute of Nuclear and New Energy Technology, Tsinghua University (INET). Precipitation in the broth preparation and the size control of the products were investigated. The precipitate was analyzed by X-ray Diffraction. The results indicate that the temperature and the speed of urea addition are the key causes of precipitation in the broth preparation. The precipitation could be avoided by optimization of the process. By precisely controlling the pressure for casting, microspheres with more uniform size could be produced.