Theoretical assessment of particle generation from sodium pool fires

Abstract

Potential sodium discharge in the containment during postulated Beyond Design Basis Accidents (BDBAs)

in Sodium-cooled Fast Reactors (SFRs) would have major consequences for accident development in

terms of energetics and source term. In the containment, sodium vaporization and subsequent oxidation

would result in supersaturated oxide vapours that would undergo rapid nucleation creating toxic aerosols.

Therefore, modelling this vapour nucleation is essential to proper source term assessment in

SFRs. In the frame of the EU-JASMIN project, a particle generation model to calculate the particle generation

rate and their primary size during an in-containment sodium pool fire has been developed. Based

on a suite of individual models for sodium vaporization, oxygen natural circulation (3D modelling),

sodium-oxygen chemical reactions, sodium-oxides-vapour nucleation and condensation, its consistency

has been partially validated by comparing with available experimental data. As an outcome, large temperature

and vapour concentration gradients set over the sodium pool have been found which result

in large particle concentrations in the close vicinity of the pool.