Thermohydraulic evaluation of two downcomer rupture in drum separator compartment at Ignalina NPP

The peculiarity of Ignalina NPP is that some part of the main circulation circuit is not covered by accident localization system, which is designed to suppress the pressure rise in compartments and limit the release of radioactive materials into the environment. Drum separator compartment is outside the accident localization system and therefore is very useful to carry out thermohydraulic analysis of the adjacent rooms. In this paper the analysis of the postulated two downcomer rupture is presented. The behavior of pressure and temperature and the influence of the central hall leak tightness is presented. The calculations are performed by CONTAIN code (USA). (author)