Tests in “Kurchatov Institute” on Research of Coolant Mixing in Fuel Exit Channel of VVER-440 Reactor,

L. Kobzar, D. Oleksu / RRC “Kurchatov Institute” / Russia

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


RRC “Kurchatov Institute” has performed coolant mixing investigation in a head of a full-size simulator of VVER-440 fuel assembly. The experiments were focused on obtaining the data important for investigating the trends in temperature difference between the value registered by a ICIS thermocouple and the value of average temperature. The completed experiments ensure representability of configuration simulation by reproducing every construction peculiar feature of flow part of fuel assembly in the domain between the lower spacing grid and thermocouple location, and also by slightly modified fuel assembly regular elements (or analogues thereof).
For the purpose of effectiveness of coolant mixing assessment within the head cross section of FA simulator, we measured coolant temperature distribution both in the place where coolant flow leaves the rod bundle simulator (in 39 data points along the cross section) and in the cross section location of regular ICIS thermocouple simulator (30 data points).
The testing was conducted with pressure of 90 – 95 Bar, mass coolant flow rates up to· 2000 kg/(m2⋅s), temperature of coolant heating in “hot” parts of the bundle up to 35оС and differences between coolant temperature extremes measured in rod bundle simulator outlet up to 20оС. Temperature fields were registered in 63 conditions that differ in coolant flow and inlet coolant temperature, electrical heating rate of FA simulator, and radial coolant distribution. In certain registered conditions we simulated coolant leakage to the space between the fuel assemblies.
The received test data may be important both for investigation of dependencies between the coolant temperature in regular thermocouple location or average outlet temperature in assembly head, and for validation of CFD codes or subchannel codes.

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