Hydrodynamic Stability and Thermal Performance Test of a 1-MWt Sodium-Heated Once-Through Steam Generator Model

Abstract

The 1-MWt Heat Transfer Model (HTM-1) test program was directed to the development of techniques to predict, and thereby avoid, water-side instabilities in sodium-heated once-through and recirculating steam generators. Water-side performance instabilities in steam generators have been an underlying problem through decades of experience. This subject is of particular concern to sodium-heated units due to the severe performance deterioration that can result from such instability. The 1-WMt test model contains nine 0.50 in. OD 130 ft long serpentine tubes. Thermocouples and low-pressure-drop orifice flow meters were installed at the feedwater inlet end of each of the three active tubes to disclose instabilities. These measurements were recorded on a high-speed oscillograph. Instabilities were deliberately induced in order to determine the inception condition of instability. The model was dynamically stable for a range of operating conditions. The model was statically stable (uniform static feedwater flow distribution) at all steam outlet conditions tested. The model was generally more stable than predicted especially at higher loads.