Abstract
In this paper, the analysis of a Small Break Loss of Coolant Accident (SBLOCA) in the VVER-1000/V446 nuclear power plant is presented. For a conservative analysis of the accident, the loss of power to the NPP and failure of one accumulator, and also of two emergency core cooling systems (ECCS) in loops 2 and 3 of the primary and secondary circuits are considered when SBLOCA has occurred. The RELAP5/MOD3.2 computer code has been used in performing the analyses. Two cases of accident scenarios as 25 mm and 100 mm breaks are analyzed. The results are in good agreement with those reported in the plant's FSAR. The results of liquid velocity show that in both cases, the flow of hot legs after the break is reversed, which provides the potential for reflux condensation phenomena. Furthermore, in the 25 mm break, the flow rate in the broken and intact side downcomer remains in the downward motion while in the 100 mm break, the broken and intact side flow rate changes to the reversed state alternatively.
Kurzfassung
In diesem Betrag wird die Analyse eines SBLOCA im WWER-1000/V446-Kernkraftwerk vorgestellt. Für eine konservative Analyse des Störfalls werden der Spannungsverlust und der Ausfall einer Batterie sowie von 2 Notfall-Kernkühlsystemen in den Strängen 2 und 3 des Primär- und des Sekundärkreises nach Eintritt eines SBLOCA betrachtet. Der RELAP5/MOD3.2-Rechencode wurde zur Durchführung der Analyse verwendet. Zwei Störfall-Szenarien, für ein 25-mm- und ein 100-mm-Leck wurden analysiert. Die Ergebnisse stimmen gut überein mit dem Endbericht zur Sicherheitsanalyse der Anlage (FSAR). Die Ergebnisse der Strömungsgeschwindigkeit zeigen in beiden Fällen, dass sich der Fluss des heißen Strangs nach dem Leck umkehrt, was potentiell zu Rücklauf-Kondensationsphänomenen führt. Des Weiteren bleibt der Durchfluss beim 25-mm-Leck in der gebrochenen und intakten Seite des Downcomers in Abwärtsbewegung, während sich beim 100-mm-Leck der Durchfluss in der gebrochenen und intakten Seite in die umgekehrte Richtung ändert.
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