Modelling of Ru behaviour in oxidative accident conditions and first source term assessments

The 7th European Review Meeting on Severe Accident Research (ERMSAR-2015), Marseille (France), 24-26 mars 2015

For oxidative conditions in the core fuel in case of severe accident, ruthenium compounds can be released in large amount through oxides formation, next transported through the Reactor Coolant System (RCS) and reach the nuclear containment building either in particulate form or under gaseous form as supported by the available experimental database.

A review of the experiments concerning

     - Ru release from degraded fuel ;

     - Ru transport in a thermal gradient tube simulating the RCS ;

     - Ru behaviour inside the nuclear containment building;
allows us developing a first draft modelling for Ru chemistry behavior in severe accident for PSA-2 applications. First Ru Source Terms (ST) have been calculated with the associated radiological consequences and, it lead to potentially high radiological consequences knowing that conservatism assumptions were made due to some remaining high uncertainty concerning Ru behavior. Additional experimental data combined with more fundamental works based on theoretical chemistry computations are ongoing to be able to build a mechanistic modelling which will be further implemented in ASTEC software as well as PSA-2 tools. At last, the R&D priorities which look necessary to close the issue are given.