Void Fraction in a Four by Four Rod Bundle under a Stagnant Condition

Abstract

In the case of a hypothetical failure of a residual heat removal (RHR) systems under mid-loop operation, vapor generated in a reactor core forms two-phase flow in a stagnant liquid and rises the water level in the core. The vapor flows into a steam generator through a hot leg, and condenses in the steam generator. Since the flow rate of vapor from the reactor core to the hot leg depends on the water level and the void fraction α in the reactor core, the reliable analysis of the RHR failure cannot be carried out without accurately estimating the void fraction in the reactor core. Although a number of studies on void fractions in two-phase flows in rod bundles have been carried out, there are few experimental data on void fractions in rod bundles under the stagnant condition. Void fractions in four by four rod bundles under the stagnant condition were measured for a wide range of gas volume fluxes to examine the validity of available void correlations. Flow patterns were visualized by using a high-speed video camera to examine the effects of flow pattern on the void fraction. As a result, the following conclusions were obtained: (1) Dependence of the void fraction on the gas volume flux J G changed at J G 1.5 m/s due to the flow pattern transition. (2) Murase's correlation agreed well with the void fraction in the two kinds of rod bundles having different dimensions under the stagnant condition.

Void distribution and bubble motion in bubbly flows in a 4×4 rod bundle. Part I: Experiments

“…Anklam and Miller [4] measured volume-averaged void fractions in an 8 × 8 rod bundle using pressure transducers. Kamei et al [5] measured volume-averaged void fractions in a 4 × 4 rod bundle under a stagnant condition using pressure transducers. Morooka et al [6] measured area-averaged void fractions in subchannels (subchannel void fractions) using an X-ray scanner system.…”

Effect of channel geometries on two-phase mixture level swell and its fluctuation amplitude

“…Regarding the two-phase mixture level swell, researchers have conducted two-phase flow experiments in stagnant water (Osakabe et al, 1984;Suzuki and Murase, 1986;Kataoka et al, 1987;Kamei et al, 2010;Chen et al, 2012). Boiling experiments also have been conducted to evaluate the void fraction and actual water level during boil-off condition when water level drops due to evaporation (Shires et al, 1980;Seedy and Muralidoran, 1982;Anklam and Miller, 1983;Kumamaru et al, 1994;Qazi et al, 1994).…”

CFD Analysis of Subcooled Flow Boiling in 4 × 4 Rod Bundle

“…Thus, experiments and measurements on multiphase turbulent flow in pipes or rod bundles have been conducted, and numerous fluid properties have been studied. In recent years, various simulations have been conducted in various papers [1][2][3][4][5]. Numerical analysis of subcooled two-phase flow at high pressure has confirmed that the Eulerian multiphase model including a Reynolds stress turbulence model is suitable for predicting the actual phenomenon [6][7][8][9][10].…”