Out-of-Pile Transient Blowdown Experiment

Abstract

Accurate prediction of critical heat flux (CHF) during transients like loss of coolant accidents (LOCAs) stresses the bounds of current models. The common approach is the quasi-steady method which assumes that the CHF phenomenon can be accurately predicted with the use of steady-state correlations without accounting for hysteresis. This has been demonstrated to provide discrepant but conservative predictions in LOCA transients and, therefore, has been deemed safe. However, the application of more accurate predictive models may aid the safety margins of novel fuel designs. Therefore, new testing with quality data at prototypic conditions is needed to test available approaches to predict the conditions necessary for transient CHF to occur during a LOCA The Transient Reactor Test Facility (TREAT) has developed a testing apparatus architecture to test such transient phenomena in-pile. TREAT has already demonstrated efficient testing of advanced fuels in dry capsule environments. To support the design and development of a LOCA-specific experiment - called Super-Static Experiment Rodlet Transient Testing Apparatus (Super-SERTTA), Oregon State University has built an out-of-pile prototype of Super-SERTTA (O-SERTTA). O-SERTTA, a natural circulation loop, operates at prototypic PWR pressures and temperatures. It can simulate different LOCA progressions of different break sizes. With instrumentation to characterize temperature, pressure, and flow, it can be coupled with computer modeling, RELAP5-3D, to estimate the margin of error for transient CHF due to LOCAs.