抄録
An estimation of void fraction in tight-lattice rod bundles was carried out. Five types of void fraction experiments with 7-, 14-, 19- and 37-rod and rod-gap of 1.0 - 1.3 mm bundle and spacer effect tests were conducted ranging from 0.1 to 7.2 MPa. Extensibility of a system accident analysis code, TRAC-BF1 and one-dimensional drift-flux model to the tight-lattice rod bundle was studied. The TRAC-BF1 and the model calculated the void fraction with good agreement to the data in case of relatively high quality and void fraction region. Applicability of advanced numerical analysis codes, NASCA, ACE-3D, TPFIT to the tight-lattice rod bundle was verified by comparing with the three-dimensional void fraction data measured by neutron tomography. Tendency of the calculated void fraction by these codes and measured data was similar as same order of the measurement error. Vapor distribution and velocity profile of water and vapor were discussed based on data. The reason why a boiling transition phenomenon occurred at the center region of the 37-rod bundle test section is probably related to a lower local liquid holdup at the channel center region.
