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Instant release of fission products in leaching experiments with high burn-up nuclear fuels in the framework of the Euratom project FIRST- Nuclides
Ist Teil von
Journal of nuclear materials, 2017-02, Vol.484, p.307-323
Ort / Verlag
Amsterdam: Elsevier B.V
Erscheinungsjahr
2017
Quelle
Access via ScienceDirect (Elsevier)
Beschreibungen/Notizen
The instant release of fission products from high burn-up UO2 fuels and one MOX fuel was investigated by means of leach tests. The samples covered PWR and BWR fuels at average rod burn-up in the range of 45–63 GWd/tHM and included clad fuel segments, fuel segments with opened cladding, fuel fragments and fuel powder. The tests were performed with sodium chloride – bicarbonate solutions under oxidizing conditions and, for one test, in reducing Ar/H2 atmosphere. The iodine and cesium release could be partially explained by the differences in sample preparation, leading to different sizes and properties of the exposed surface areas. Iodine and cesium releases tend to correlate with FGR and linear power rating, but the scatter of the data is significant. Although the gap between the fuel and the cladding was closed in some high burn-up samples, fissures still provide possible preferential transport pathways.
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•Leach tests were performed to study the instant release of fission products from high burn-up UO2 fuels and one MOX fuel.•In these tests, the fission gas release given by the operator was a pessimistic estimator of the iodine and cesium release.•Iodine and cesium release is proportional to linear power rating beyond 200 W cm−1.•Closure of the fuel-cladding gap at high burn-up slows down the release.•The release rate decreases following an exponential equation.