Review of the representative development history on rod bundle mixing coefficient used in subchannel analysis code of PWR

Critical Heat Flux (CHF) is one of the most important indices in determining reactor core safety and economics. As well known,the Mixing Vane Grid(MVG) in the rod bundle reactor core will provide high mixing performance that could mix the coolant and increase CHF. The subchannel analysis code is widely used in predicting CHF and developing CHF correlations. To evaluate the mixing performance of the MVG in the 1-D subchannel code, the Total Diffusion Coefficient (TDC) is applied to describe the MVG's mixing performance. While the TDC mixing coefficient is the main parameter that could affect the local physical parameters calculation and ultimately affect the CHF prediction. In order to improve the prediction of local parameters and decrease the design limit, in developing new MVGs, the TDC is gaining more attention. The TDC of the MVG is usually obtained from the combination of experiments and subchannel analysis. In this paper, the representative development history of rod bundle mixing coefficient used in subchannel analysis code of PWR is critically reviewed. Firstly, the development history of subchannel code and the application of TDC in subchannel code are reviewed. Then the TDC are reviewed from the effect of bare rods, Simple Support Grid(SSG) and MVG in the rod bundle systems. In addition, key experiments developed in-house and abroad are discussed. This is also a developing process of learning the TDC physical meaning and high performance MVG. Lastly, the prospects of TDC are proposed.