PREDICTION OF TRANSIENT NONEQUILIBRIUM TWO-PHASE FLOWS: AN EXTENSION TO THE FAST TECHNIQUE.

The present report describes a code (FAST, Finite-Interval Analytic Solution Technique) that has been developed to analyze channels with heat sources, as opposed to entire systems, in a rapid and efficient fashion. As such as it is useful for the analysis and interpretation of experiments, application of out-of-pile data to reactor flow conditions, and calculation of core behavior in reactor transients. The objective of this work was to extend a rapid, existing calculation methodology, applicable to transient two-phase flow, to include more physical realism. This required the introduction of a fuel conduction model and a capability to handle subcooled boiling and flow reversals.