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ISSN Online: 2377-424X

International Heat Transfer Conference 12
August, 18-23, 2002, Grenoble, France

Implementation of preventive measures against local flow degradation in the primary circuit of RBMK-1500

Get access (open in a dialog) DOI: 10.1615/IHTC12.4360
6 pages

Sinopsis

Results of "In-depth Safety Assessment of the Ignalina Nuclear Power Plant" show that the RBMK-1500 reactors are quite well protected against the breaks that might occur in the reinforced leak-tight compartments if they do not result in local flow degradation. The local flow degradation in the few Fuel Channels (FC) results the mismatch between energy generation and cooling. That could lead to the overheating of the fuel cladding and pressure tube walls, if any preventive measures will not be arranged. The reason of flow degradation in the FC could be the local flow stagnation or blockade of coolant flow path into Group Distribution Header (GDH).
The possible initiating events (partial GDH break, guillotine break of GDH accompanied with failure to close of the check valve at the adjacent GDH, or GDH flow blockade) in the primary circuit of RBMK-1500 reactor were investigated by employing thermal-hydraulic system code RELAP5 (Code Development Team, 1995). The RELAP5/MOD3.2 model of Ignalina NPP reactor primary circuit and plant safety systems was developed (Kaliatka, Uspuras, 2000). The local flow stagnation can occur at different time spans during the accidents, because the primary circuit conditions are changing and reactor protection systems are activated. The phenomena, which are responsible for flow stagnation during short and long term cooling, were discussed. The justification of the preventive measures against local flow degradation is performed. These measures, already implemented at Ignalina Nuclear Power Plant (reactor scram actuation and emergency cooling initiation signals due to decrease of coolant flow rate through GDH) ensure the safe reactor shutdown and cool down.