[en] Automatic translation: The temperature and flow processes in the core area of the THTR reactor were measured for the so-called ''5-hour case'' using the 2-dimensional. THERMIX calculation program was examined. The comparison with a 1-dimensional calculation carried out by RWTH Aachen University shows good agreement in the calculated temperatures without the occurrence of local hot spots, despite very different flow conditions in the upper core area. In particular, the heat balance over the core area and thus the gas inlet and outlet temperatures are correct very well matched. However, the maximum ceiling reflector temperature remains 200°C below that in 1-dimensional Value shown on invoice.