Development of design technology on thermal-hydraulic performance in tight-lattice rod bundles, 5; Estimation of void fraction

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

An estimation of void fraction in a tight-lattice rod bundle was needed of the design of the Innovative Water Reactor for Flexible Fuel Cycle (FLWR). For this purpose, we measured the void fraction and studied the behaviors of boiling flow. The void fraction was measured by a neutron radiography, a quick-shut-valve technique, and an electro void fraction meter. The data were taken using the 7-, 14-, 19- and 37-rod bundle test sections with the rod gap of 1.0 or 1.3 mm under from atmospheric pressure to 7.2 MPa. Followings were made clear: (1) numerical analysis codes calculate the similar distribution to the data, and (2) TRAC-BF1 code and drift-flux model tends to overestimate the void fraction at lower quality region.