Speaker
Francois Virot
(IRSN)
Description
The ASTEC code has been recently extended to address the analysis of the main design basis accident scenarios in fusion installations, more particularly in the ITER facility. Current efforts are focused on loss of coolant accidents (LOCA) because a strong reactivity between beryllium toxic dust and steam leading to possible formation of gaseous beryllium oxide, hydroxide and hydride during the transient is expected. The accidental scenario presently considered is a wet bypass between the first and second confinement barriers. This corresponds to a multiple failure of first wall cooling loops inside the vacuum vessel coupled with a failure of both windows in a heating line. In our previous source term evaluations for different LOCA scenario, the presence of tritiated beryllium dust in modules at the transient end was put in evidence [1]. With the presently considered scenario, due to the bypass, the transport of toxic dust towards the galleries becomes possible.In this study, aerosol transport modelling has been improved, notably the material properties, i.e. density, thermodynamic data and thermal conductivity which are shown to significantly impact the aerosol behaviour. The isotopic effect and neutron damage are also taken into account. The properties of condensed beryllium hydride and hydroxide have been reviewed with a critical assessment of experimental literature data and completed by computational quantum mechanical modelling. The influence of this improvement on the transport, speciation and location is shown. A special attention is paid to compounds formed with tritium and beryllium. Moreover a parametric study on sensitive material properties is presented in order to evaluate their potential impact on the source term.
Co-authors
Francois Virot
(IRSN, Saint Paul Lez Durance, France)
Marc Barrachin
(IRSN, Saint Paul Lez Durance, France)
