Behaviour of Fission Gas in the Rim Region of High Burn-up UO2 Fuel Pellets with Particular Reference to Results from an XRF Investigation.

XRF and EPMA results for retained xenon from Battelle's High Burn-up Effects Program are re-evaluated. The data reviewed are from commercial low enriched BWR fuel with burn-ups of 44.8 to 54.9 GWd/tU and high enriched PWR fuel with burn-ups from 62.5 to 83.1 GWd/tU. It is found that the high burn-up structure penetrated much deeper than initially reported. The local burn-up threshold for the formation of the high burn-up structure in those fuels with grain sizes in the normal range lay between 60-75 GWd/tU. The high burn-up structure was not detected by EPMA in a fuel that had a grain size of 78um although the local burn-up at the pellet rim had exceeded 80 GWd/tU. It is concluded that fission gas had been released from the high burn-up structure in the PWR fuel sections with the two highest burn-ups of 70.4 and 83.1 GWd/tU. In the rim region of these sections at the locations where XRF indicated gas release the local burn-up was greater than 75 GWd/tU.

MOGENSEN M.;  PEARCE J.H.;  WALKER Clive Thomas; 

1998-04-24

JRC15973

https://publications.jrc.ec.europa.eu/repository/handle/JRC15973,