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Science and Technology of Nuclear Installations
Volume 2007 (2007), Article ID 87834, 7 pages
Research Article

Thermal-Hydraulic Analysis of Coolant Flow Decrease in Fuel Channels of Smolensk-3 RBMK during GDH Blockage Event

1Departamento de Engenharia Nuclear, Universidade Federal de Minas Gerais (UFMG), Avenue Antônio Carlos 6627 Campus of the Universidade Federal de Minas Gerais, Pré dio PCA1 Anexo Engenharia, Pampulha, CEP 31270-90, Belo Horizonte, MG, Brazil
2Dipartimento di Ingegneria Meccanica, Nucleare e della Produzione, Università di Pisa, Via Diotisalvi 2, Pisa 56126, Italy
3N. A. Dollezhal Research and Development Institute of Power Engineering (NIKIET), P.O. Box 788, Moscow 101000, Russia

Received 4 September 2007; Accepted 27 November 2007

Academic Editor: Ali Hainoun

Copyright © 2007 A. Lombardi Costa et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


One of the transients that have received considerable attention in the safety evaluation of RBMK reactors is the partial break of a group distribution header (GDH). The coolant flow rate blockage in one GDH might lead to excessive heat-up of the pressure tubes and can result in multiple fuel channels (FC) ruptures. In this work, the GDH flow blockage transient has been studied considering the Smolensk-3 RBMK NPP (nuclear power plant). In the RBMK, each GDH distributes coolant to 40–43 FC. To investigate the behavior of each FC belonging to the damaged GDH and to have a more realistic trend, one (affected) GDH has been schematized with its forty-two FC, one by one. The calculations were performed using the 0-D NK (neutron kinetic) model of the RELAP5-3.3 stand-alone code. The results show that, during the event, the mass flow rate is disturbed differently according to the power distribution established for each FC in the schematization. The start time of the oscillations in mass flow rate depends strongly on the attributed power to each FC. It was also observed that, during the event, the fuel channels at higher thermal power values tend to undergo first cladding rupture leaving the reactor to scram and safeguarding all the other FCs connected to the affected GDH.