Comparative Analysis of Particle Retention Models in Filtered Containment Venting Systems

Abstract

In the European AMHYCO project which aims at an enhanced H₂/CO combustion risk management, a high -pressure accident sequence, such as a station blackout with release of high amounts of fission and activation products, is investigated. By comprehensive plant simulations using the German lumped parameter system code AC² it is shown that large amounts of steam and non-condensable gases can lead to a continuous pressurization of the containment beyond the design pressure in case of an extensive failure of safety sytems. To decrease the containment pressure with simultaneous retention of particles from the atmosphere the gas stream must be filtered before being released to the environment. Therefore, the majority of the European nuclear powerplants are equipped with a filtered containment venting system (FCVS). The most commonly used FCVS combines a venturi scrubber in a liquid pool with a metal fiber filter.

For the particle retention in a venturi scrubber inside an FCVS, different numerical models are available. These models can be broadly categorized into empirical models, which are based on experimental data, and mechanistic models, which also rely on theoretical studies. By using selected models to analyze different experiments, it is shown that they cannot reproduce the results sufficiently. In this context, based on the currently available experimental database, a comparative analysis of several models with different experiments is performed. The intention of the work is to evaluate the numerical models with regard to their applicability and quality of results, including selected experiments, and to show the limits imposed by influencing external factors.