The contribution of UPTF experiments to resolve some scale-up uncertainties in countercurrent two phase flow

The volume scaling of previous existing integral test facilities is up to a maximum of 1/48 of the full size power reactors (or 1/25 for the reflood integral test facility CCTF). The experimental results achieved in these facilities or in down-scaled separate effects test facilities have to be extrapolated to reactor scale in order to evaluate the full size reactor thermal hydraulic behaviour. There is some uncertainty in extrapolating the small scale results. Experimental results from the 1:1 scale UPTF test facility can considerably reduce the uncertainty of geometrical scaling. The final goal is to qualify the overall validity of computer program simulation, and to quantify the uncertainty of the computer program calculations for full size reactors. Significant scaling dependent experimental results have been found in UPTF separate effects tests in the case of heterogeneous steam-water flow conditions. This is especially the case for vertical and horizontal countercurrent flow. (authors). 18 figs., 5 tabs., 20 refs