Grant: NSERC/NRCan/AECL Generation IV Energy Technologies Program

In the preceding proposed work scope, experimental and analytical studies of supercritical flow in a natural-convection loop were undertaken. The studies focused on pressure drop and the onset of flow instability in natural circulation. Also, analytical studies were conducted of parallel-channel flow instability. Non-dimensional parameters defining the instability boundary of static as well as dynamic instability were developed and tested using a linear stability program and studying a large number of cases. The further studies proposed here will extend the previous studies to assess, experimentally and analytically, the stability of supercritical flow in vertical parallel-channels and to test the non-dimensional parameters developed by various authors. A new down-flow facility is planned. The experimental results obtained will be useful for validating licensing codes, as well as can be used to assess other analytical models. This would be relevant to predicting the flow instability in down-flow channels -- the current Gen IV design -- as well as up-flow channels.Vertical flow is essentially two-dimensional and, therefore, must be shown to be within the modeling capability of a 1-D code, which invariably licensing codes are. A separate CFI proposal will be submitted to acquire funding for a vertical down-flow facility. A pump will be required, which is not presently a component of the existing facility. CFD analyses will also be done, as the complex nature of supercritical flow may likely require a more detailed analysis a 1-D code can give. The accuracy margin needs to be defined clearly; that is, how accurate a numerical model is, and the confidence an engineer can place in its predictions, is of paramount importance to the reactor design engineer.