The issue of the temperature measurement in a nuclear reactor is an important element to ensure safe operation of the nuclear power plant. To prevent damages and radioactive releases the fuel in the reactor must be continuously cooled. The coolant temperature field of the VVER-440 reactor is measured with thermocouples installed at the outlet part of fuel assemblies. Since the power output of the fuel pins is not equal, a non-uniform temperature field at the inlet of the fuel assembly head is formed. Next, the temperature field is subsequently mixed by passing through the assembly head, which contains some constructional elements helping to mixing coolant flow. This mixing is not perfect and due to the effect described above, the signal on the thermocouple can be affected. This phenomenon was introduced in 2009 Atomic Energy Research (AER) Symposium in Bulgaria. 7 international institutions participated with the main goal to explain the mixing character of the coolant and to compare results. For further study of this phenomenon the new detailed computational model of the upper part of the fuel assembly was created and subsequently on the ANSYS FLUENT CFD code verified. The main output of these simulations is study of the coolant temperature distribution on the thermocouple. Computational model, based on the source geometry given by AER symposium, was created in preprocessor GAMBIT 2.4.6. Model contains over 13 million hexahedral cells. Thermohydraulic simulations where performed in ANSYS FLUENT v14.5 and results were compared with data from AER Symposium. There were considered two cases with different pins power outputs. With compare to AER symposium results the achieved resultant temperature on the thermocouple position for both cases indicate comparable accuracy. Furthermore, some flow fluctuations in the assembly head area where found.
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2014 22nd International Conference on Nuclear Engineering
July 7–11, 2014
Prague, Czech Republic
Conference Sponsors:
- Nuclear Engineering Division
ISBN:
978-0-7918-4594-3
PROCEEDINGS PAPER
Coolant Mixing in the VVER-440 Fuel Assembly Head Available to Purchase
Pavel Zacha
Pavel Zacha
CTU, Prague, Czech Republic
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Tomas Romsy
CTU, Prague, Czech Republic
Pavel Zacha
CTU, Prague, Czech Republic
Paper No:
ICONE22-30823, V004T10A036; 7 pages
Published Online:
November 17, 2014
Citation
Romsy, T, & Zacha, P. "Coolant Mixing in the VVER-440 Fuel Assembly Head." Proceedings of the 2014 22nd International Conference on Nuclear Engineering. Volume 4: Radiation Protection and Nuclear Technology Applications; Fuel Cycle, Radioactive Waste Management and Decommissioning; Computational Fluid Dynamics (CFD) and Coupled Codes; Reactor Physics and Transport Theory. Prague, Czech Republic. July 7–11, 2014. V004T10A036. ASME. https://doi.org/10.1115/ICONE22-30823
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