Prototypic corium analysis: a round robin for SEM and EDS characterisation

In case of a nuclear reactor severe accident, the core could melt, forming a high temperature mixture called corium. A uranium oxide-containing sample from a corium-concrete interaction test has been analyzed by scanning electron microscopy (SEM) and energy-dispersive X-ray spectrometry (EDS) at three different laboratories. In all the measured windows, the composition lay on or close to the line connecting the initial corium melt composition to the concrete average composition. The round robin exercise confirmed that SEM and EDS analysis can be used confidently to perform fast and good quality local corium analyses and provide local quantitative compositions in the metallic elements of corium with an uncertainty of 10 % of the measured value. Differences up to 25 % of the measured value were found for the oxygen content, although two of the laboratories provided very close results.