A model considering quality distribution in transverse profile for critical power prediction in different scale tight lattice bundles

In this paper, a critical power model is proposed among different size tight lattice bundles. The model takes into account quality distribution in cross-sectional profile. A quality distribution factor is introduced and is written as a function of mass velocity and radial power distribution in divided sub-channels. Boiling Transition (BT) is assumed occurring in the sub-channel that possesses highest quality distribution factor. Around RMWR operating conditions, for bundles that has same axial heated pattern but being different size, BT is assumed occurring when local quality reach local critical quality. Based on the model, critical power in JAERI 37-rod tight lattice bundle is predicted from JAERI 7-rod tight lattice bundle data. The predicted values are compared with experimental data. The model then is applied to predict critical power in 127-rod and 217-rod bundles. At last, scale factors are evaluated. (author)