A CFD method to evaluate the integrated influence of leakage and bypass flows on the PBMR Reactor Unit

An area that has been identified as significantly important in the development of a High Temperature Reactor (HTR) is the prediction of leakage and bypass flows through such a reactor. It is therefore essential to understand the causes of bypass flows and to determine the effect on the predicted fuel and component temperatures.This paper discusses the identification of leakage flows that are applicable to the Pebble Bed Modular Reactor (Pty) Ltd. (PBMR) design and the ranking of these leakage flows. The modeling methodology and results are also discussed.Similar to previous HTR's, it was found that leakage and bypass flows are important parameters to consider for safe and efficient operation of the PBMR. Through a focused approach, it is shown that PBMR is able to improve the understanding of this phenomenon and quantify the flows and subsequent influence on the operation of the system. This has resulted in a reduction of leakage and bypass from approximately 46% to 20%. The improved understanding of leakage and bypass flows allows PBMR to address this issue during the design phase of the project, which subsequently results in a vast improvement over historical HTR designs. This gives PBMR a distinct advantage over previous High Temperature Reactors.

Research highlights▶ Research and analysis to identify and rank different leakage flow paths in a HTR. ▶ Development of integrated CFD methodology for the prediction of leakage flows. ▶ Development of a methodology to simulate flow resistances in above CFD model. ▶ Validation of predicted flow results against different numerical methodology. ▶ Illustration of the significant improvement achieved through this methodology.