Modelling of low-pressure subcooled flow boiling using ATHLET code

Subcooled flow boiling for low pressure conditions is important in nuclear reactors. Many studies are concerned with safety analyses of safety systems operating at low pressure, such as the external reactor vessel cooling (ERVC) system which is widely adopted as a part of in-vessel retention (IVR) in severe accident management strategies. The best-estimate thermal-hydraulic computer code ATHELT (Analysis of Thermal-Hydraulics of Leaks and Transients) is developed by the GRS (Gesellschaft fur Anlagen-und Reaktorsicherheit). The set of available correlations in the ATHLET code is mostly based on experiments at high pressure conditions. So, the use of some of these correlations may be questionable. The present study identifies the most important influential parameters in the ATHLET code which affect the void fraction course at low pressure conditions. (author)