Thermal-hydraulic analysis of Ignalina NPP compartments response to group distribution header rupture using RALOC4 code

The Accident Localisation System of Ignalina NPP is a containment of pressure suppression type designed to protect the environment from the dangerous impact of the radiation. In this paper the analysis of guillotine Group Distribution Header break in the Lower Water Piping compartment of ALS of Ignalina NPP is presented. The purpose of this analysis is to perform the long-term thermal-hydraulic analysis of compartments response to Group Distribution Header rupture and to verify if design pressure values in the compartments are not exceeded. The operation of CTCS, sprays, drainages and the make-up of hot condensate chamber are considered in the model. According to the calculation results all the pressures in ALS compartments are below the maximum allowed design values. (authors)