Development of Horizontal Off-Take Model for Application to Reactor Headers of CANDU Type Reactors

摘要

In the CANDU accident analysis the header is one of the important components to be well modeled, because it has great impact on the fuel channel behavior during some accidents. The feeder void fraction, affected by thermal-hydraulic behavior in the headers, may affect the fuel bundle coolability. The liquid entrainment and vapor pull-through (off-take) phenomena in the header are considered highly important, in case where horizontal stratification is achieved inside the header. To generalize the model for application to various branch angles, a critical height correlation was reconstructed by using the point skin method, and then the constants were determined so the correlation can fit well with the previous large number of experimental data. The new model considers the effects of different branch angles on the off-take, and tested against the experimental data of various branch angles in a Separate Effect Test (SET). The verification analysis results in a conceptual blowdown problem showed that the new model gives better accuracy than the original. The new model also provided an enhancement in prediction of the experimental data selected for validation.