| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 297439 | Nuclear Engineering and Design | 2011 | 15 Pages |
Dryout of the coolant liquid film at the upper part of the fuel pins of a boiling water reactor (BWR) core constitutes the type of heat transfer crisis relevant for the conditions of high void fractions. It is both a safety concern and a limiting factor in the thermal power and thus for the economy of BWRs. We have investigated adiabatic, air–water annular flows in a scaled-up model of two neighboring subchannels as found in BWR fuel assemblies using cold-neutron tomography. The imaging of the double suchannel has been performed at the ICON beamline at the neutron spallation source SINQ at the Paul Scherrer Institute, Switzerland. Cold-neutron tomography is shown here to be an excellent tool for investigating air–water annular flows and the influence of functional spacers of different geometries on such flows. The high-resolution, high-contrast measurements provide the spatial distributions of the coolant liquid film thickness on the fuel pin surfaces as well as on the surfaces of the spacer vanes. The axial variations of the cross-section averaged liquid hold-up and its fraction in the gas core shows the effect of the spacers on the redistribution of the two phases.
► Annular flows w/wo functional spacers are investigated by cold neutron imaging. ► Liquid film thickness distribution on fuel pins and on spacer vanes is measured. ► The influence of the spacers on the liquid film distributions has been quantified. ► The cross-sectional averaged liquid hold-up significantly affected by the spacers. ► The sapers affect the fraction of the entrained liquid hold up in the gas core.
