Numerical Modelling of Debris Bed Water Quenching

Debris beds may be formed during a nuclear reactor severe accident and coolability of these beds is important to avoid release of radioactive materials into the environment. However, debris bed water quenching is challenging to understand, and model, because of the complex multi-phase flow and heat transfer physics involved which may include boiling. This paper develops a modelling method for boiling and demonstrates its abilities with some applications. The model is based on a multi-fluid approach, in which one phase represents the liquid, the second phase the gas phase the third phase represents the solid debris bed. In each fluid phase a set of conservation equations for mass, energy and momentum are solved with appropriate inter-phase exchange terms coupling the fluid phases.