A fabrication technique for a UO 2 pellet consisting of UO 2 grains and a continuous W channel on the grain boundary
Abstract
A new fabrication process of UO 2-W composite fuel has been studied in order to improve the thermal conductivity of the UO 2 pellet by the addition of a small amount of W. A fabrication process was designed from the phase equilibria among tungsten, tungsten oxides and UO 2. The conventionally sintered UO 2 pellet which contains W particles is heat-treated in an oxidizing gas and then in a reducing gas. In the oxidizing heat-treatment W particles are oxidized and liquid tungsten oxide penetrates within the UO 2 grain boundary, and in the reducing heat-treatment liquid oxide is transformed to solid tungsten which forms a continuous channel along the UO 2 grain boundary. This developed technique can provide a continuous W channel covering UO 2 grains for a UO 2-W composite fuel even with a small amount of a metal phase - below 6 vol.%. The thermal diffusivity of the UO 2-6 vol.%W cermet composite increases by about 80% when compared with that of a pure UO 2 pellet.
- Publication:
-
Journal of Nuclear Materials
- Pub Date:
- July 2006
- DOI:
- 10.1016/j.jnucmat.2006.01.019
- Bibcode:
- 2006JNuM..353..202Y