| 초록 |
The UO2 ceramic microspheres, which have led to the development of sol-gel processes for making spherical particles of nuclear fuel, are the most important materials in fuel elements for the application to high temperature gas cooled reactors. Sol-gel processes have a number of advantages, such as the simple processes and facilities, higher sphericity and density. Sol-gel methods based on their gelation process include external gelation, internal gelation and total gelation. In this experiments external gelation method was employed. First, U3O8 powders are dissolved with nitric acid to form stock solutions of UN. The UN solutions are then mixed with additives (PVA, THFA, urea and NH4NO3) and the broth solutions for casting and dropping are prepared. Vibrating nozzle system was applied to obtain the large droplet size when broth solution was casted in air, NH3 gas and NH4OH spraying zone. As a result, we could be fabricate spherical dried ADU particles of 1800um and droplets of 3400um in size. With strict control of subsequent heat treatment such as calcination, reduction and sintering and sampling including sieving and sorting, dense UO2 kernels with uniform diameter of approximately 900um were prepared. |
