Investigation of coolant mixing in head parts of VVER-440 fuel assemblies with burnable poison
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S. Tóth
Abstract
Detailed CFD model for the head parts of the VVER-440 fuel assemblies with burnable poison has been developed. The coolant mixing was analyzed in some typical assemblies with this model and the signals of the in-core thermocouples above the selected assemblies were calculated. The investigations pointed out that the mixing is intensive in these assembly heads but the coolant is not perfectly mixed before reaching the thermocouples. Significant differences between the outlet average coolant temperatures and the thermocouple signals were revealed in the case of the fresh fuels. These deviations can cause about 6 % underestimations in the online monitored assembly powers unless a proper correction is introduced. The coolant mixing was also studied by means of numerical tracers and weight factors of selected rod bundle regions for the in-core thermocouple were determined. Using these weight factors and the outlet enthalpies of the assemblies' subchannels, the thermocouple signals can be corrected.
Kurzfassung
Für die Kopfteile von WWER-440 Brennelementen wurde ein detailliertes CFD-Modell entwickelt, das die Berücksichtung von Neutronengiften ermöglicht. Mithilfe dieses Modells wurde die Kühlmittelvermischung für typische Brennelemente berechnet. Dabei wurden auch die Temperaturen an den Stellen innerhalb der Brennelemente bestimmt, an denen Thermoelemente im Reaktorkern angeordnet sind. So konnte nicht nur die Kühlmittelvermischung, sondern auch lokale Temperaturen verglichen werden. Die Untersuchungen zeigten, dass die Mischung innerhalb der Brennelementkopfstücke sehr intensiv ist jedoch vor Erreichen der Thermoelementpositionen noch nicht perfekt ist. Bei Berücksichtigung von frischem Brennstoff wurden signifikante Unterschiede zwischen den mittleren Kühlmittelaustrittstemperaturen und den Messwerten festgestellt. Diese Abweichungen können zur Unterschätzung der online berechneten Brennelementleistung von 6 % führen ohne Berücksichtigung einer sinnvollen Korrektur. Des Weiteren wurde die Kühlmittelvermischung auch bei Verwendung von numerischen Tracern and Einflussgrößen in ausgewählten Brennstabbündelregionen untersucht. Dabei wurden die gemessenen lokalen Temperaturen im Kern richtig berechnet. Aus dieser Untersuchung wurden die notwendigen Einflussgrößen (u. a. Austrittsenthalpien der Brennelementunterkanäle) für eine angemessene Korrektur der Leistungsberechnung abgeleitet.
References
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© 2009, Carl Hanser Verlag, München
Articles in the same Issue
- Contents/Inhalt
- Contents
- Summaries/Kurzfassungen
- Summaries
- Technical Contributions/Fachbeiträge
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- CFD modelling of insulation debris transport phenomena in water flow
- Investigation of coolant mixing in head parts of VVER-440 fuel assemblies with burnable poison
- Prediction of time dependent standby failure rates for periodically tested components taking into account the operational history
- Closed loop auto control system software for Miniature Neutron Source Reactors (MNSRs)
- Numerical simulation of passive catalytic recombiner
- Some affine solutions for CANDLE burn-up waves in 1D-geometry
- Assessment of radiological consequences due to routine atmospheric discharges from nuclear power plants
- Chebyshev acceleration of criticality calculations in boundary element applications to neutron diffusion
- Legendre polynomial series of the infinite medium Green's Function in neutral particle transport theory: the half-space albedo problem
- A model for calculation of forward isotropic scattering with application to transport equation in slab geometry
- Training and retraining programme for research reactor operating personnel
Articles in the same Issue
- Contents/Inhalt
- Contents
- Summaries/Kurzfassungen
- Summaries
- Technical Contributions/Fachbeiträge
- Main results of the European project NURESIM on the CFD-modelling of two-phase Pressurized Thermal Shock (PTS)
- Simulation of H2 distribution and combustion in LWR containments using Lumped Parameter Codes
- CFD modelling of insulation debris transport phenomena in water flow
- Investigation of coolant mixing in head parts of VVER-440 fuel assemblies with burnable poison
- Prediction of time dependent standby failure rates for periodically tested components taking into account the operational history
- Closed loop auto control system software for Miniature Neutron Source Reactors (MNSRs)
- Numerical simulation of passive catalytic recombiner
- Some affine solutions for CANDLE burn-up waves in 1D-geometry
- Assessment of radiological consequences due to routine atmospheric discharges from nuclear power plants
- Chebyshev acceleration of criticality calculations in boundary element applications to neutron diffusion
- Legendre polynomial series of the infinite medium Green's Function in neutral particle transport theory: the half-space albedo problem
- A model for calculation of forward isotropic scattering with application to transport equation in slab geometry
- Training and retraining programme for research reactor operating personnel
