Migration of fission product barium in UO(2) fuel under transient conditions
Gamma scanning and electron probe microanalysis results are reported for LWR fuels transient-tested in the first RisÝ Fission Gas Project. The fuels, supplied by RisÝ National Laboratory (R fuel) and the UKAEA (U fuel) were transient-tested to powers in the range 30.1 to 44.4 kW/m at a burn-up between 3.6 and 4.5 at%. Considerable radial redistribution of Ba occurred during the transient tests. Evaporation-condensation of BaO led to the formation of BaSiO(3) in pores and cracks at intermediate radial positions. As a result of thermal diffusion up the temperature gradient, Ba also accumulated in the centre of the fuel. Although radial redistribution of barium occurred in both the R and U fuels, only the R fuel released Ba to the rod free volume. In rods that were transient-tested to powers greater than 41 kW/m accumulations of 140 Ba were found at the pellet interfaces. The release of Ba is ascribed to the evaporation of BaO in the central region of the fuel at temperatures above 2000 C. Indications were found that the U fuel operated at a lower temperature than the R fuel. It is concluded tht the U fuel never reached 2000 C, even at the highest terminal power of 44.4 kW/m.
Bibliographic Reference: Article: Journal of Nuclear Materials, Vol. 173 (1990) pp. 14-25
Record Number: 199011410 / Last updated on: 1994-12-02
Original language: en
Available languages: en