ADVANCED ANALYSIS OF THE CEA-NEA/OECD VVER-1000 COOLANT TRANSIENT BENCHMARK WITH THE COUPLED SYSTEM CODE ATHLET-BIPR-VVER
17th Symposium of AER on VVER Reactor Physics and Reactor Safety (2007, Yalta, Crimea (Ukraine, back then))
REACTOR DYNAMICS, THERMAL HYDRAULICS AND SAFETY ANALYSIS
Recent studies showed the necessity of a detailed modelling of the core outlet region of the VVER-1000 reactor where the thermocouples are located. Solving of this problem is of primary importance for the validation of the coupled system code ATHLET/BIPR-VVER on local parameters. Therefore, special attention is paid on the reactor pressure vessel model and its nodalization schema and in particular the fluid mixing phenomena at assemblies? outlets. For this purpose additional thermal-hydraulic channels modelling the flow along the guide tubes are introduced in the reactor core.
With the new advanced modelling again the benchmark problems of Phase 1 of the CEA-NEA/OECD VVER-1000 Coolant Transient Benchmark are analysed. On the base of data comparison with the experimental measurements (Phase 2, Exercise 1) the mixing phenomena at assembly head is estimated and mixing coefficients are introduced in the thermal-hydraulic core outlet models of the coupled system code ATHLET/BIPR-VVER.