Filtration tests of gaseous ruthenium tetroxide by sand bed and metallic filters

This work presents laboratory tests on gaseous RuO₄ filtration carried out at IRSN in Cadarache. The objective is to determine if gaseous ruthenium tetroxide can be trapped by metallic filter and sand bed filter, both elements being used in filtered containment venting systems implemented on French pressurized water reactors. The results show no ruthenium tetroxide trapping by physical or chemical adsorption but certain retention is observed resulting from its thermal decomposition into solid ruthenium dioxide. A thermodynamic analysis of the system tends to confirm this conclusion. Chemical stability of RuO_4(g) has to be considered as it strongly impacts potential filtration and so potential releases.