Recent improvements in PSU-LEOPARD/MCRAC code package

The PSU-LEOPARD/MCRAC code package was benchmarked against operational data of the first three cycles of the Yugoslav NPP Krsko reactor and used to determine the loading pattern for cycle 4. As the NPP Krsko switched to low leakage cores, modifications were made in the PSU-LEOPARD code to model classical burnable absorbers as well as integral fuel burnable absorbers. Changes were also made in the MCRAC code: to provide a fast and convenient fuel assembly interchange for loading pattern search; to calculate local power peaking factors; to print out core map with all the relevant data in a self-explanatory form; to automatise mesh definition; to convert the code to FORTRAN 77 standard. Further development, now in progress, will enable: following quarter-assembly burnups: more accurate local peaking factor determination; thermal hydraulic feedback modeling; conversion of the code package for PC. The described improvements will make this code package a reliable tool in loading pattern determination. (author). 13 refs, 6 figs