Temperature and fission rate effects on the rim structure formation in a UO(2) fuel with a burnup of 7.9% FIMA
A boiling water reactor (BWR) design uranium dioxide fuel irradiated to a burnup of 7.9% FIMA was selected for calculational and experimental analysis because the rod had an unusual power history: it had two high power periods at 1.7% FIMA and between 4 and 5% FIMA causing increased fuel temperatures and thus increased gas release and damage recovery. As a consequence, two parameters generally considered to be important for grain subdivision were locally different from normal fuel (ie fission gas inventory and extent of radiation damage). Histories of temperature, fission rate and fission gas release were calculated at different radial positions. Microstructure observations revealed the typical high burnup grain subdivision process which extended to a maximum of 1.65 mm from the pellet surface inwards. For this radial position, the calculations yielded a local temperature of 1200 C and predicted that more than half of the fission gas was released during the second high power period for this radial position. The results give importance information on the fission gas inventory for the burnup threshold of restructuring.
Bibliographic Reference: Article: Journal of Nuclear Materials
Record Number: 199810490 / Last updated on: 1998-05-05
Original language: en
Available languages: en