On the Method of Moving of Incomplete Coolant Mixing Correction in the Top Nozle of VVER-440 Assembly. Correction of Power Assemblies Using Thermocouples Readings,

A. Brik, D. Oleksiuk / RRC “Kurchatov Institute” / Russia

16th Symposium of AER on VVER Reactor Physics and Reactor Safety (2006, Bratislava, Slovakia)
Core Operation, Experiments and Code Validation


In the RRC “Kurchatov Institute” during 3 last years it was realized work package directed to development of the method of power assemblies correction using thermocouples readings.
This entire works include the experimental and calculation ones. The main result of the experiment investigations is fact of incomplete coolant mixing in the head of VVER-440 assembly. Furthermore experimental data were used for validation of CFD code PHOENICS and modernized subchannel code SC-1 (SC-1 is analogue of COBRA-IV code).
Modernized SC-1 code is capable to calculate the coolant temperature distribution in not only the fuel part of assembly but the head of assembly too.
In the future the modernized SC-1 code was used for calculation analysis of the thermocouples data that were obtained from 3-d and 4-th units of the Kola NPP.
At the results of this analysis were developed the method of the moving of incomplete coolant mixing correction in the nozzle of VVER-440 assembly.
The developed corrective functions were used for compare of calculated and measured relative assemblies power using thermocouples readings.
The main result of such comparison is that the differences between calculated and measured relative assembly powers for representative sample are reduced as a whole. Total amount of the considered variants were more than 1200 (different units, campaigns, assemblies and time moments).

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