Analysis of PROTEUS-experiments performed in support of LWHCR design

The Phase II series of tight lattice experiments carried out at the PROTEUS reactor facility in Switzerland was concentrated on physics aspects of a Light Water High Conversion Reactor (LWHCR). The dependence of reaction rate ratios and coolant void coefficients on lattice parameters was of main interest. In several cores additional experiments were carried out in support of reactor design. The reactivity worth of absorber materials proposed for reactor control were measured and the distribution of fission rates in the vicinity of core singularities, like water holes and absorber pins, was studied. These experimentals were now analysed with data and methods readily available at KfK. Main tool for these investigations was the two-dimensional transport code TWODANT. The input cross-sections were prepared from data files of the KARBUS system used at KfK for reactor design. The comparison of calculated reactivity changes with experimental data shows agreement of relative absorber worths within about 20 %. The power distribution in the vicinity of singularities can be estimated with ca. 4% accuracy. Studies have indicated that the remaining discrepancies may be partially caused by deficiencies of the transport code used for the analysis. (orig.)