Comparative study of main features of some thermalhydraulic safety codes for PWR systems

Great efforts have been made for some years in the USA as well as in the Federal Republic of Germany, France and Japan, in order to develop best estimate system-codes for safety calculations of PWRs. These codes have different conceptions (structure, physical models, numerical solution schemes, etc.) which are not easily known without dividing into voluminous manuals. It was the CEC's view that a straightforward comparison of such codes based on an appropriate comparison structure would be a very useful contribution in general for meaningful comparisons between different codes and between codes and experimental data, and for a better evaluation of the confidence level of code prediction capability of NPP accidental behaviour. The CEC has proposed and sponsored the present study /1/. Work was performed in close co-operation between teams of the CEA and GRS and coordinated by the CEC. The following codes were considered: ALMOD (FRG) /2/ CATHARE (France) /3/ DRUFAN/FLUT (FRG) /4/, /5/ RELAP5/MOD 2 (USA) /6/ THYDE P2 (Japan) /7/ TRAC PF1/MOD 1 (USA) /8/ The study contains a systematic comparison of the main code features and a series of quantitative analyses of models for selected phenomena