Void fraction measurement in channels with internal metallic structures using neutron scattering

Two-phase flow through complex internal metallic geometries is encountered in many industrial installations. Boiling water flow through steam generators and nuclear reactor cores and gas-liquid flow through packed and fluidized bed reactors are typical examples. Measuring the volume fraction of each phase in the flow channel is difficult to perform nonintrusively using acoustic or electromagnetic radiation because of the strong attenuating effect of the metal. Neutrons, on the other hand, are well suited for this purpose as they can easily penetrate metal and are very susceptible to the usually low-mass number flow material. This paper shows how a neutron device, called a scatterometer, can be used for measuring the void fraction of a water-gas flow in a channel containing a significant amount of metallic inclusions.