A full-scale STAR-CCM+ model for VVER-1000/320 application purposes was developed in order to predict the core outlet temperature distribution, the pressure losses experienced at different locations and to investigate the mixing coefficients between loops, for in-vessel flow. The research activity was carried out in the framework of CAMIVVER project: “Code And Methods Improvements for VVER comprehensive safety assessment project”. The primary aim of this work is to compare the measured and calculated core outlet temperature and mixing coefficient distributions at nominal operating conditions assessing the predicting capabilities of some selected turbulence models. The developed geometry consists of inlet nozzles, downcomer, lower plenum, core region, upper plenum, and outlet nozzles. The numerical simulations were performed using a computational grid of approximately 27.7 million polyhedral unstructured cells. The reference design of Kozloduy Unit 6 nuclear power plant was taken into account; with respect to the actual geometry of the vessel and its internals some simplifications were established in order to reduce the computational cost. Consequently, some regions were modelled as porous media, such as the core region, core basket, upper core plate, perforated barrel section and so forth. Also, additional pressure loss coefficients were imposed in the porous regions to reproduce the design pressure losses measured at the reference locations of Kozloduy-6 NPP. The CFD results predicted the presence of an azimuthal asymmetry of the loop flow centers relative to the cold leg axes, which is also observed in the experimental data. The azimuthal asymmetry shift is affected by the adopted turbulence model. Also, the distribution of the mixing coefficients at the fuel assemblies’ outlet slightly differs based on the adopted turbulence model. The average values of the core outlet temperature distribution in the calculation are in the same range of the measured plant data. Overall, the results show a good agreement with the corresponding average plant measured parameters and provide a better understanding of the involved phenomena.
CFD Simulation of a VVER-1000/320 at Nominal Operating Conditions
Abedelhalim Ossama
;Pucciarelli Andrea;Forgione Nicola
2022-01-01
Abstract
A full-scale STAR-CCM+ model for VVER-1000/320 application purposes was developed in order to predict the core outlet temperature distribution, the pressure losses experienced at different locations and to investigate the mixing coefficients between loops, for in-vessel flow. The research activity was carried out in the framework of CAMIVVER project: “Code And Methods Improvements for VVER comprehensive safety assessment project”. The primary aim of this work is to compare the measured and calculated core outlet temperature and mixing coefficient distributions at nominal operating conditions assessing the predicting capabilities of some selected turbulence models. The developed geometry consists of inlet nozzles, downcomer, lower plenum, core region, upper plenum, and outlet nozzles. The numerical simulations were performed using a computational grid of approximately 27.7 million polyhedral unstructured cells. The reference design of Kozloduy Unit 6 nuclear power plant was taken into account; with respect to the actual geometry of the vessel and its internals some simplifications were established in order to reduce the computational cost. Consequently, some regions were modelled as porous media, such as the core region, core basket, upper core plate, perforated barrel section and so forth. Also, additional pressure loss coefficients were imposed in the porous regions to reproduce the design pressure losses measured at the reference locations of Kozloduy-6 NPP. The CFD results predicted the presence of an azimuthal asymmetry of the loop flow centers relative to the cold leg axes, which is also observed in the experimental data. The azimuthal asymmetry shift is affected by the adopted turbulence model. Also, the distribution of the mixing coefficients at the fuel assemblies’ outlet slightly differs based on the adopted turbulence model. The average values of the core outlet temperature distribution in the calculation are in the same range of the measured plant data. Overall, the results show a good agreement with the corresponding average plant measured parameters and provide a better understanding of the involved phenomena.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
