Usage of FEMAXI-6 Program Code for RBMK-1500

Ignalina NPP is the only nuclear power plant in Lithuania, which is comprised of two units, commissioned in 1983 and 1987. Ignalina NPP Unit 1 was shutdown for decommissioning at the end of 2004 and Unit 2 is to be operated until the end of 2009. Both units are equipped with channel-type graphite-moderated boiling water reactors RBMK-1500. The nuclear fuel used in the Ignalina NPP is slightly enriched U235 (2 percent initially, changed to 2.4 percent, 2.6 percent and 2.8 percent at present). The fuel of enrichment higher than 2.0 percent contains erbium as burnable absorber. Up to now the analyses of process in RBMK-1500 fuel rods were prepared only by general designer of RBMK - specialists of Research and Development Institute of Power Energy using Russian in-house codes. Recently Lithuanians specialists started to model processes in fuel rods of Ignalina NPP, using the state-of-the-art FEMAXI-6 code. This code has been designed for vessel type reactors. Because the materials of fuel and cladding and design of fuel rods in RBMK-1500 have differences comparing to light water vessel type reactors, the FEMAXI-6 code should be adopted and tested before the analysis. This paper provides information about the inclusion of material properties for fuel pellets and cladding of RBMK-1500 reactor into FEMAXI-6 code. Using the developed model of RBMK-1500 fuel rod the dependency of fuel parameters from burnup was calculated. The received results were compared with calculations performed by specialists from Kurchatov Institute. The reasonable agreement of both calculation results shows that the adapted FEMAXI-6 code and developed model are suitable for future analysis of processes in fuel rods of RBMK-1500.(author)