Advances in the CFD Modelling of the PBMR to Improve the Prediction of Bypass Flows

An area that has been identified as important in the development of High Temperature Reactors (HTRs) 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 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 to the operation of the PBMR. However, through a focused approach, it is shown that PBMR is able to improve the understanding of this phenomenon, to quantify the flows and the 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 empowers PBMR to address this issue already 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.