抄録
In TOSHIBA, Uranium oxide has been handled as reactor fuel since 1958. This paper mainly deals with the fabrication process of the pellets and the yield for the applied specifications. The characteristics of the TOSHIBA PROCESS are as follows;
1. The rolling process is employed for a physical treatment of powder.
By this treatment, coagulated porous particles are divided into elementary fine particles while they are partially densified into dense particles, and then become suitable for pressing once organic additives being added. This treatment is rather effective and healthy than ball milling or others.
2. A mixed organic additives with organic solution is applied.
The additives was chosen from the following stand points:
(i) Highly lubricative ability among particles or between powder and die. (ii) Easy dewaxing property (iii) Precise evaluation of the change of the weight between before and after dewaxing in powder state.
3. The feeding mechanisms of powder from a hopper to a feeding shoe and from the shoe to the die holes were improved in the automatic pressing.
This method may control the precision of the green density within ±1.27% of the theoretical value even when a lot of pellets are treated.
4. The size with high precision may be obtained after sintering as the result mentioned above.
5. Unrecoverable loss is small even after the size of the pellet is ground so that the tolerance in diameter becomes ±0.02mm.
When the specification of the pellets was assumed to be φ=9.90±0.02mm h=15.00±0.15 and p=94.5±1% T. D., the yield was 91.10% and unrecoverable loss was 1.16%. When the specification was allowed to be φ=10.00±0.15 h=15.00±0.2 and p=94.5±2% T. D., the yield was raised to 97.15% and unrecoverable loss was decreased to 0.42%.
