The influence of nuclear cross section data bases on the neutron physics of high converting PWRs

The fuel utilization of present PWRs can be considerably optimized by modifications exclusively in the core design. Leaving most other well approved system components unchanged and largely maintaining the existing licensing procedures, higher burnups and a reduction of fissionable material consumption can be achieved with a tighter hexagonal fuel rod lattice core and a higher plutonium content in the fissionable material. Programs for the calculation of such high-converting pressurized water reactors (HCR) have been developed and improved during the preceding years. Therefore, experiments for the verification of programs and nuclear cross section libraries are carried out at the PROTEUS reactor today on the basis of a Swiss-German cooperation. An additional international comparison of calculation results is provided by a numerical NEACRP benchmark. Recalculations were performed and interpreted at the IfRR using the code SPEKTRA, developed there, with two different nuclear cross section libraries. The findings obtained hence, flow into first parametric design calculations for a flexible high converter design. Core designs realizable today show a fuel utilization improved by a factor 2 compared with existing pressurized water reactors. (orig.)