Modernization of cross section library for VVER-1000 type reactors internals and pressure vessel dosimetry

The broad-group library BGL1000-B7 (417 nuclides, 47 neutron and 20 gamma groups) has been developed from ENDF/B-VII data files, for dosimetry calculations of VVER-1000 type reactor internals. Previous broad-group libraries BUGLE-96 and BGL1000 used for VVER-1000 calculations were based on ENDF/B-6. Calculations show that the library BGL1000-B7 provides better agreement with fine-group calculations than BGL1000 but all broad-group libraries give approximately the same discrepancy from experimental values measured in the VVER-1000 mock-up on the LR-0 reactor. The use of fine-group cross-sections is preferable for neutron flux calculations in the regions over the level of the weld No. 4 and below the level of the weld No. 3 of the VVER-1000 as well as in calculations of the VVER-1000 type reactors with enlarged downcomer and pressure vessel