Thermal hydraulic analysis of reactivity accidents in MTR research reactors using RELAP5
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N. El-Sahlamy
Abstract
The present paper comes in the line with the international approach which use the best estimate codes, instead of conservative codes, to get more realistic prediction of system behavior under off-normal reactor conditions. The aim of the current work is to apply this approach using the thermal-hydraulic system code RELAP5/Mod3.3 in a reassessment of safety of the IAEA benchmark 10 MW Research Reactor. The assessment is performed for both slow and fast reactivity insertion transients at initial power of 1.0 W. The reactor power is calculated using the RELA5 point kinetic model. The reactivity feedback terms are considered in two steps. In the first step the feedback from changes in water density and fuel temperature (Doppler effects) are considered. In the second step the feedback from the water temperature changes is added. The results from the first step are compared with that published in IAEA-TECDOC-643 benchmarks. The comparison shows that RELAP5 over predicts the peak power and consequently the fuel, clad and coolant temperatures in case of fast reactivity insertion. The results from the second step show unjustified values for reactor power. Therefore, the model of reactivity feedback from water temperature changes in the RELAP5 code may have to be reviewed.
Kurzfassung
Der vorliegende Beitrag verwendet, wie international üblich, Best-Estimate-Codes anstelle konservativer Codes, um realistischere Vorhersagen des Systemverhaltens unter abnormen Betriebszuständen machen zu können. Ziel dieser Arbeit ist die Anwendung des thermohydraulischen Systemcodes RELAP5/Mod3.3 bei der Neubewertung der IAEA-Benchmark-Vorgaben für die Sicherheit von 10 MW Forschungsreaktoren. Die Bewertung wird durchgeführt für langsame und schnelle Reaktivitätsinsertion bei einer Anfangsleistung von 1.0 W. Die Reaktorleistung wird berechnet mit Hilfe des RELAP5-punktkinetischen Models. Die Reaktivitätsrückwirkungen wurden in zwei Schritten betrachtet. Im ersten Schritt wurden Rückwirkungen durch Änderungen der Wasserdichte und Brennstofftemperatur betrachtet (Doppler-Effekt). Im zweiten Schritt wurden zusätzlich die Rückwirkungen durch Änderungen der Wassertemperatur berücksichtigt. Die Ergebnisse des ersten Schritts wurden verglichen mit den im IAEA-TECDOC-643 veröffentlichten Benchmark-Vorgaben. Der Vergleich zeigt, dass die Ergebnisse von RELAP5 die Leistungsspitzen überschätzt und damit die Temperaturen von Brennstoff, Hülle und Kühlmittel im Falle schneller Reaktivitätsinsertion. Die Ergebnisse des zweiten Schritts zeigen nicht gerechtfertigte Werte für die Reaktorleistung. Deshalb sollte das Modell der Reaktivitätsrückwirkungen durch Änderungen der Wassertemperatur beim RELAP5-Code überarbeitet werden.
References
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© 2015, Carl Hanser Verlag, München
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Articles in the same Issue
- Contents/Inhalt
- Contents
- Summaries/Kurzfassungen
- Summaries
- Technical Contributions/Fachbeiträge
- Considering the uncertainties in empirical correlations for vertical countercurrent flow limitation (CCFL) with TRACE
- 3RIP trip startup test simulation of TRACE/PARCS model for Lungmen ABWR under different power and flow conditions
- Development of a new analytic function expansion nodal code, HexDANM, for solving the neutron diffusion equation in hexagonal-Z geometry
- Laser cleaning of steam generator tubing based on acoustic emission technology
- Axial enrichment profile in advance nuclear energy power plant at supercritical-pressures
- Analysis of the small break loss of coolant accident in the VVER-1000/V446 reactor
- Thermal hydraulic analysis of reactivity accidents in MTR research reactors using RELAP5
- Depletion of Gadolinium burnable poison in a PWR assembly with high burnup fuel
- Nuclear model calculations on cyclotron production of 51Cr
- Radiotracer application for characterization of nuclear grade anion exchange resins Tulsion A-23 and Dowex SBR LC
- Solving the criticality problem with the reflected boundary condition for the triplet anisotropic scattering with the modified FN method
