CHATENA Simulation of Thermosiphoning in a Pressurized-Water Test Facility

Abstract

Under some postulated accident conditions, decay heat is removed from a reactor core by two-phase natural circulation or "thermosiphoning" of the primary coolant. To assess the ability of the computer code CATHENA (Canadian Algorithm for Thermalhydraulics Network Analysis, formerly ATHENA) to predict such events, simulations were performed of thermosiphoning tests conducted in the RD-14 facility at the Whiteshell Nuclear Research Establishment. Predictions for three test conditions are presented. In general, CATHENA predictions agree well with the observed results. Non-oscillating two-phase thermosiphoning and the onset of oscillatory flow are well predicted. Channel heater temperatures are also well predicted. The periods and amplitudes of oscillatory flows were not always well predicted, but it is thought that a more detailed representation of the steam generators will correct this problem.