Instabilities in a Passive Moderator Cooling System of SCWR-CANDU

Abstract

This paper presents the results from the examination of instability mechanisms in a Passive Moderator Cooling System of a SCWR (SuperCritical Water-cooled Reactor) - CANDU®. Such a passive system is being developed at AECL using a flashing-driven natural circulation loop. Unstable intermittent and sinusoidal oscillations were identified from available data of the flashing-driven natural circulation in a passive moderator cooling system. The oscillation periods were correlated with the boiling delay time. A stability map was established from available natural circulation test data in the Calandria Subcooling-Power plane, and depicted boundaries between the stable and unstable areas.