Thermal-hydraulic estimation in tight-lattice rod bundles for development of the innovative water reactor for flexible fuel cycle

Kureta, Masatoshi   ; Yoshida, Hiroyuki  ; Tamai, Hidesada; Onuki, Akira; Akimoto, Hajime

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 TRAC-BF1 code 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 data in case of relatively high quality and void fraction region. Applicability of a NASCA, ACE-3D, TPFIT codes 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. Vapor distribution and velocity profile of water and vapor were discussed based on data.