Abstract
Development of a steady-state model is the first step in nuclear safety analysis. The developed model should be qualitatively analyzed first, then a sensitivity analysis is required on the number of nodes for models of different systems to ensure the reliability of the obtained results. This contribution aims to show through sensitivity analysis, the independence of modeling results to the number of nodes in a qualified MELCOR model for a Westinghouse type pressurized power plant. For this purpose, and to minimize user error, the nuclear analysis software, SNAP, is employed. Different sensitivity cases were developed by modification of the existing model and refinement of the nodes for the simulated systems including steam generators, reactor coolant system and also reactor core and its connecting flow paths. By comparing the obtained results to those of the original model no significant difference is observed which is indicative of the model independence to the finer nodes.
Kurzfassung
Die Entwicklung eines Modells für einen stationären Zustand ist der erste Schritt bei der Sicherheitsanalyse. Das entwickelte Modell sollte zuerst qualitativ analysiert werden, dann ist eine Sensitivitätsanalyse zur Anzahl der Knoten für Modelle verschiedener Systeme erforderlich, um die Zuverlässigkeit der erhaltenen Ergebnisse sicher zu stellen. Dieser Beitrag zielt darauf, durch eine Sensitivitätsanalyse die Unabhängigkeit der Modellergebnisse von der Anzahl der Knoten in einem qualifizierten MELCOR-Modell für einen Westinghouse-Druckwasserreaktor zu zeigen. Dafür und zur Minimierung von Anwenderfehlern wird die Analysesoftware SNAP verwendet. Verschiedene Sensitivitätsfälle wurden entwickelt durch Modifizierung des vorhandenen Modells und Verfeinerung der Knoten für die simulierten Systeme Dampferzeuger, Reaktorkühlsystem und Reaktorkern mit seinen verbundenen Strömungswegen. Durch Vergleich der erhaltenen Ergebnisse mit denen des ursprünglichen Modells wurde kein signifikanter Unterschied festgestellt, was bezeichnend ist für die Unabhängigkeit des Modells von den verfeinerten Knoten.
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