Validation of the MC2-3/TWODANT/DIF3D code system for control rod worth via BFS-75-1 and BFS-109-2A reactor physics experiments

Abstract In this paper, validation of the MC 2 -3/TWODANT/DIF3D code system with the ENDF/B-VII.0 library was performed based on two different physics experiments: BFS-75-1 and BFS-109-2A critical assemblies. Both the BFS-75-1 and BFS-109-2A physics experiments were carried out in the Russian BFS facility with collaboration between KAERI and IPPE. The BFS-75-1 critical assembly is a metal-fueled core surrounded by a depleted uranium blanket, and the BFS-109-2A critical assembly is a metal-fueled core surrounded by a steel reflector and sodium/gas plenums. The results of the multi-group MC 2 -3/TWODANT/DF3D code were compared with experiments and results of the continuous energy as-built MCNP code. The MC 2 -3/TWODANT/DIF3D model showed excellent agreement with experiments in the reference criticality, i.e., a 70 pcm difference at the maximum. The MC 2 -3/TWODANT/DIF3D models estimated the absorber or control rod worth to be between a −6.2% and 8.6% error range vs. that of the experiments. A remarkable spatial spectrum transition effect was reported, especially for the BFS-109-2A critical assembly, and the TWODANT procedure successfully mitigated this effect by applying a global neutron spectrum during energy group condensation in MC 2 -3.