On the nature of aerosols produced during a severe accident of a water-cooled nuclear reactor

Particle behaviour depends strongly on classic characteristics, e.g., size, and less macroscopic ones involving structure and composition these being especially important in situations of strong differential forces on a particle, i.e., surface impact or intensely-shearing flows. The former situation may lead to particle deposition or break-up and re-entrainment (with potential accident-management implications). This paper reviews information on aerosols from prototypical experiments identifying common features and typical variations. It emerges that a particle comprising one-third metal, one-third metal oxide and one-third a mixture of fission-product species would not be out of place in any potential reactor-accident sequence. Particle shapes appear relatively compact without branching chain-like structures. On size and structure, aerosols in the upstream part of the primary circuit would comprise a near-lognormal population with AMMD no more than 2 μm and geometric standard deviation around 2, particles comprising agglomerates of highly-coordinated clusters as small as 0.1 μm. In the containment, aerosols can typically be represented by primary-circuit particles and their agglomerates though particular circumstances (core–concrete interaction, hot-leg accident sequence) can alter this simple picture.