Investigation of the thermal diffusion in the transverse flow, narrow rod cluster of a new fast breeder core with open fuel elements

This report from the research field for nuclear and new energy systems of the Ruhr University deals with one particular aspect of thermohydraulic design, namely with the effects of possible, transverse flow mixing processes in the cooling agent in the reactor core with open fuel element clusters on the core outlet temperature profile, which is significant with regard to the overall thermodyamic efficiency. The state of research and the resulting tasks yet to be performed are explained. The first point of main interest of this research report was to provide experimental data confirming the calculated data already established within the framework of the project (BENTE/14). Good agreement with calculations was found (Chapter 3). Insight had to be gained into the flow conditions in order to be able to develop a model of the mixing and exchange processes in the core, to be described by the term 'thermal diffusion'. This model and approaches for a numerical solution are presented in chapter 4 and 5. The tensor coeffieicnts quantifying the thermal diffusion had to be derived from a number of tracer measurements and by comparison with parametricised computer runs. Simple relations could be found for the dependence of these coefficients from the local impact flow angle in the fuel rod lattice. Chapter 6). Finally, a complete example was thoroughly tested by computer calculations, the results were applied to the new core design, and were compared with a measured core outlet temperature profile. Again, good agreement was achieved. Chapter 7). (orig.)