Experimental modelling of core debris dispersion from the vault under a PWR pressure vessel. Pt. 3

This report principally addresses the question of whether experimental results obtained using a scaled down model of a PWR vault are affected by the size scale used. A wide range of equivalent tube geometries representing the main features of a PWR vault have been tested, using water and a liquid metal to simulate molten core debris, and high pressure air to simulate steam escaping from a hole in the pressure vessel. The experiments confirm that the dispersion phenomena occurring are not affected by the size scale of the model. This information has been used to simplify the general modelling equation, enabling a correlation of all previous data obtained from an exact 1/25 scale model (with a particular location of hole and with no internal structures) to be produced. Application of the correlation to a hypothetical severe accident in a full size reactor is discussed. (author)