Numerical Simulation of Annular Dispersed Flow in Simplified Subchannel of Light Water Cooled Fast Reactor RBWR

Abstract

Abstract About the boiling transition (BT) that determines the maximum thermal output of the BWR, it is considered that the spacers have significant effects on the occurrence of BT. In the light water cooled fast reactor: RBWR, thermal-hydraulics conditions are more severe than the current BWR. Then, the effect of the spacer on BT should be sufficiently utilized in the RBWR. The RBWR is still in the design stage, therefore is not reasonable to determine the shape of the spacer by evaluation only for large-scale tests. In the occurrence of BT, it is considered that the two-phase flow pattern is the annular dispersed flow, and we want to evaluate the effects of spacer shape on annular dispersed flow in RBWR subchannels. This research uses the detailed two-phase flow simulation code TPFIT to simulate annular dispersed flow in RBWR subchannels. As the first step of this research, we performed numerical simulations of annular dispersed flow in the simplified subchannel of RBWR. We used a circular tube with the same hydraulic diameter as the RBWR subchannel to consider the basic effects of spacer on the annular dispersed flow. In this paper, we describe the result of numerical simulation. In addition, we evaluated droplets’ size and velocity based on simulation results for the spacer’s existence and non-existence cases.