Pressure Drop of Tight Lattice Rod Bundle

The fuel assembly design with tightened fuel rod pitch gives a possibility of higher conversion ratio for Boiling Water Reactor (s). Pressure drop is one of the key design parameters to evaluate the possibility of BWR core with higher conversion ratio. The pressure drop test for tight lattice rod bundles under steady conditions has been done under BWR fluid conditions. The following results were obtained: (1) The present prediction method has the reasonable performance under 25% of quality at the rated mass flux, but the predicted value is larger than the measured ones for larger mass flux.(2) This method can be applied to evaluate the pressure drop for tight lattice bundles from the conservative point of view, but it is necessary to improve the predicted accuracy for larger mass flux.