Effect of curved fuel rods on liquid film flow behavior

Takase, Kazuyuki; Yoshida, Hiroyuki; Shibata, Mitsuhiko; Kitamura, Tatsuaki*; Kume, Etsuo; Zhe, X.*

Nihon Kikai Gakkai Ryutai Kogaku Bumon Koenkai Koen Rombunshu, P. 227, 2006/10

Fluid flow characteristics in a tight-lattice rod bundle with spacers were analyzed numerically using a newly developed two-phase flow analysis code under the conditions of the full bundle size and non-heated isothermal flow. Conventional analysis methods such as sub-channel codes need composition equations based on the experimental data. In case that there are no experimental data about thermal-hydraulics in the tight-lattice core, therefore, it is difficult to obtain high prediction accuracy on the thermal design of the tight-lattice core. Then the direct numerical simulations with the earth simulator were chosen. The axial velocity and void fraction distributions in a simulated tight-lattice rod bundle changed sharply around a spacer and the interface behavior between water and vapor in a narrow coolant channel was clarified using the predicted quantities. The high prospect was acquired on the possibility of establishment of the thermal design procedure of the advanced nuclear reactors with large-scale direct simulations.