Light elements microanalysis of steel/B4C melts for nuclear power plants accident studies

Out of pile small scale tests have been carried out to study the steam oxidation of B4C-steel liquid mixtures. Microstructures and composition of the mixes were investigated by electron probe microanalysis (EPMA). Quantitative analysis of the light B and C elements in complex B4C-stainless steel mixtures was approached gradually starting with the simplified Fe-B system. Measurements of boron contents in Fe-B phases were achieved with an absolute error of 2 %. In addition, phase area ratio determination by BSE images analysis was coupled to quantitative analysis data to estimate the global composition of the samples. For non oxidized samples, a good correlation was obtained between this microanalysis determination and actual composition of the samples. The evolution of this global composition during the oxidation process was studied by performing successive tests with increasing oxidation duration. A preferential oxidation of boron and chromium was revealed. (author)