Postirradiation examination of GETR-IRT(B)

S.Kobay*; J.Komat*; S.Nakay*; K.Inoue*; K.Ishik*

THe GETR-1RT(B) irradiation was carried out for the purpose of examining the transient behavior of uranium-plutonium oxide fuels for fast reactow at the biginning of irradiation, especially in the course of the rise of power at the startup of the reactor. The result used as samples were different in density, plutonium content and uranium enrichment as well as in fuel form, as the annular pellet and the vibra-tory compacted fuel. The maximum linear power was 460 - 560 W/cm, the irradiation period was 3 or 24 hours, and the maximum power was reached in 30 min. The result of postirradiation examination showed that three was no columnar grain growth and no central void in both kinds of pellets having theoretical densities of 84% and 91%m, respectively, when irradiated for 3 hours. changes of structure were greater in fuels having lower density. Especially in the case of vibratory compacted fuels, the structure was changed more rapidly than in pellets and the