Experiments on Choking Flow of Subcooled Liquid Through a Simulated Steam Generator Tube Crack

The ability to estimate the leak rates from the through wall cracks in a steam generator tube is important in terms of radiological source terms and overall operational management of steam generators as well as demonstration of the leak-before-break condition. A literature survey showed that there are few data sets available on crack geometries related to steam generator tubing. In this study an experimental program was developed to measure the choking flow rate of subcooled water through well defined simulated steam generator tube crack geometries with L/D < 5.5, and results are compared with models in literature. Two types of test specimens were used in the experimental program. One, a round orifice like hole is created to simulate a pitting type flaw. The others are laser cut slits representing axial cracks. A pressure differential across the crack/break of 6.8 MPa is achieved. As subcooling increasing the flashing discharge rate also increases. A modified Burnel model was identified which predicts experimentally observed choking discharge rates from such geometries well.Copyright © 2012 by ASME