Results of Modeling Benchmark Problem V1000CT2 for Exercise 1 of the Phase 2 with the System Code ATHLET-BIPR8KN
16th Symposium of AER on VVER Reactor Physics and Reactor Safety (2006, Bratislava, Slovakia)
Reactor Dynamics, Thermal Hydraulics and Safety Analysis
The coupled code system ATHLET-BIPR8KN is being developed to perform realistic simulation of three-dimensional neutron kinetics and thermal-hydraulic processes in VVER reactors. The detailed description of the flow mixing in the all reactor vessel is of great importance for the correct modeling and simulation of many NPP transients. As contribution to the validation of the system code ATHLET-BIPR8KN for asymmetric core inlet conditions, the CEA-NEA/OECD VVER-1000 Coolant Transient Benchmark (V1000CT) – vessel mixing problems are analyzed.
Results are presented for Exercise 1 of the Phase 2 of the Benchmark obtained with the system code ATHLET-BIPR8KN, supplemented by sensitivitiy studies done on the variation of the number of the thermo-hydraulic channels with cross flows (CF) in down comers and bottom plenums under the core with CF and with 163 (1:1 mapping schema) parallel thermal-hydraulic channels (PTHC) without of CF in the core and 48 PTHC without of CF for the core bypass. The transient is a simultaneous isolation of one steam generator from the steam line and the feed water supply at low power level. It causes a temperature rise in the affected loop and leads to a non-uniform temperature distribution at core inlet. The results of the simulation are compared with experimental data from NPP Kozloduy Unit 6 collected during the plant-commissioning phase.