制备致密UO_2微球的全胶凝方法  

A TOTAL GELATION PROCESS FOR THE PREPARATION OF DENSE UO_2 MICROSPHERES FOR HTGR

作　　者：徐志昌[1] 张萍[1] 唐亚平[1] 张富宏[1] 秦长生[1] 刘家祥[1] 

机构地区：[1]清华大学核能技术设计研究院

出　　处：《核科学与工程》1994年第1期50-57,7,共8页Nuclear Science and Engineering

摘　　要：为了制备高温气冷反应堆用燃料芯核,致密UO_2微球,研究了一种新的溶胶-凝胶工艺.该流程具有经典的溶胶-凝胶工艺的优点,但克服了它们的缺点.已经知道,合理的配方设计和良好的干燥条件是克服破裂困难的关键因素.影响胶滴尺寸及其分布的控制因素是:极限流量、几何因子、物理因子和振动因子.微球干燥和焙烧参数的优化是依据热分析曲线来确定的.用SEM方法观察了热处理过程中的微观结构的变化.观察了真空烧结的重结晶现象.观察了UO_2·nH_2O的化学气相沉积.结果表明:晶粒大小随烧结温度增加而增加.本工艺适合于制备500μm直径的微球.其产率为90%.球度优于1.08.球径范围为470-530μm.1400-1450℃真空条件下的烧结密度范围为10.71-10.76 g/cm^3.A new kind of sol - gel process for preparation of dense UO2 kernels used for HTGR (High Temperature Gas cooled Reactor) has been developed in our institute. This achievement is based on the typical sol - gel process (external gelation process and internal gelation process). Hower, this process not only has advantages of the typical sol - gel process, but also overcomes their disadvantages. It has been shown that an reasonable prescription design and the good condition of drying is the critical factor to overcome the difficulty of cracking. Controlled factors effect on the drop size and it's distribution are as follows: critical flow, geometric factor, physical factor and vibration factor. Optimization of parameters for drying and calcination of microsphers, such as temperature rate and atmospheres were determined by TG and DTA thermal analysis. Mi-crostructure in the course of heat treatment was observed by SEM. Recrystallization phynomenon during sintering in vacuum was found out, Chemical vapour deposition (CVD) in the form of UO2 nH2O was observed by SEM SEM analysis indicates that crystal grain increases regularly with the temperature sintered. TGU process is suitable for preparing UO2 microspheres which diameter is about 500μm. In the products sintered, about 10% of the deformation kernels are rejected by a vibratory shape separator. The sphericity of the accepted kernels is better than 1.08. The average diameter which can be produced by the TGU process is about 470 - 530μm. The density of kernels is the range of 10. 71 - 10. 76 g/cm3, sintered at the temperature of 1400 - 1450℃ in vacuam.

关 键 词：全胶凝 工艺 燃料球 二氧化铀 

分 类 号：TL213.2[核科学技术—核燃料循环与材料]