Nitrogen transport in the primary circuit of a VVER during a LOCA occurring under plant cool-down conditions

H.-M. Prasser; L. Perneczky; G. Baranyai; A. Böttger; Gy. Ézsöl; A. Guba; I. Tóth; J. Zschau

doi:10.3139/124.100206

Artikel

Nitrogen transport in the primary circuit of a VVER during a LOCA occurring under plant cool-down conditions

H.-M. Prasser , L. Perneczky , G. Baranyai , A. Böttger , Gy. Ézsöl , A. Guba , I. Tóth und J. Zschau

Veröffentlicht/Copyright: 2. Mai 2013

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Aus der Zeitschrift Kerntechnik Band 69 Heft 4

Abstract

The paper presents the results of a thermal hydraulic experiment conducted at the PMK-2 test facility within the IMPAM-VVER project. The test was dedicated to a loss-of-coolant event during the cool-down phase of the plant, when neither core flooding tanks nor safety injections systems are automatically available. Though fuel rod dryout occurs, the activation of one of four lines of low pressure emergency injection is sufficient to re-establish reliable core cooling. In the cooling-down situation, the primary circuit is pressurised with nitrogen, therefore, non-condensable gas can enter the primary circuit from the pressurizer during the blow-down phase. The transport of the nitrogen along the primary circuit was studied with a novel type of a local void probe equipped with an integrated micro-thermocouple. RELAP5 was found to be able to predict the behaviour of the non-condensable gas in the primary circuit. Despite of some delay in the prediction of the time of the appearance of the gaseous phase in the begin of the process, most details of the transient were well reproduced by the code.

Kurzfassung

Der Beitrag präsentiert die Ergebnisse eines thermohydraulischen Experiments an der Versuchsanlage PMK-2 im Rahmen des EU-Projekts IMPAM-VVER, das einem Kühlmittelverlust während der Abkühlphase der Anlage gewidmet ist, wenn weder die Kernflutbehälter zur Verfügung stehen noch die Notkühlsysteme automatisch ansprechen. Obwohl es zur zeitweiligen Überhitzung der Brennelemente kommt, kann ein von vier Niederdruck-Notkühlsystemen die zuverlässige Kernkühlung wieder herstellen. In der Abkühlungsphase der Anlage ist der Druckhalter mit Stickstoff gefüllt. Damit kann von dort ein nichtkondensierbares Gas in den Kreislauf eintreten. Die Ausbreitung des Stickstoffs wurde mit lokalen Dampfgehaltssonden untersucht, die über ein integriertes Mikrothermoelement verfügen. Rechnungen mit RELAP5 haben gezeigt, dass das Programm in der Lage ist, das Verhalten des Stickstoffs zu beschreiben. Abgesehen von einer gewissen Verspätung, mit der das Eintreffen des Stickstoffs an verschiedenen Messpositionen zu Beginn des Prozesses vorhergesagt wird, werden die meisten Details der Transiente durch die Rechnung richtig wiedergegeben.

References

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Received: 2004-7-19

Published Online: 2013-05-02

Published in Print: 2004-08-01

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https://doi.org/10.3139/124.100206