IMPROVEMENT OF THE THERMAL-HYDRAULIC FEEDBACK MODEL IN BAMBOO-CORE FROM SINGLE-CHANNEL TO SUB-CHANNEL

The thermal-hydraulic feedback is critical for PWR-core analysis. The real flow distribution at the core inlet shows some non-uniformity and varies with operating conditions. Most core analysis codes assume that the core inlet flow distribution is uniform. To minimize the power distribution variations due to different core inlet flow distributions, the sub-channel model is employed to replace the single-channel model in the thermal-hydraulic feedback module of Bamboo-Core, which is a full-core reactor core analysis code for the Pressurized Water Reactor (PWR). The new sub-channel thermal-hydraulic feedback model is validated by comparing its calculation results with the measured data from the first three operational cycles of M310. When both uniform and non-uniform core inlet flow distribution were used to calculate the CNP650. The maximum bias between two core inlet flow distribution is 8.2%. Subsequently, the bias of 3D power distribution due to two different flow distributions was calculated. For single-channel thermal feedback, the maximum bias is 0.598%, while for sub-channel feedback, the maximum is 0.205%. The Changes in core inlet flow distribution have less impact on the results with sub-channel thermal feedback than single-channel thermal feedback. Therefore, the sub-channel thermal feedback is more suitable for the case of approximate processing of coolant flow distribution at the core inlet than the single-channel thermal feedback.