A sensitivity study of the heat transfer processes involved in a hot-leg rupture in a pressurised water-cooled system.

Series of computer experiments was performed, using the reactor thermal analysis code THETAl-B, to ascertain the significance and relative importance of the various heat transfer processes in relation to the prediction of maximum surface temperatures for: (i) the fuel cladding during the blowdown phase of a loss of coolant accident (LOCA) for a hot-leg rupture in a pressurised water reactor system; and (ii) an electrically heated tube of a simple water-cooled test assembly, subjected to a corresponding hot-leg blowdown, for which experimental results have been published. The significance of several factors was considered, including the choice of heat transfer correlation for a particular heat transfer regime, and inlet coolant flow conditions. For both cases the predicted maximum surface temperature was sensitive to a number of factors, including choice of heat transfer correlations for (i) critical heat flux, (ii) flow boiling transition region and, in particular, (iii) stable film boiling