Approximate method for measurement of phase-distribution in multiphase materials with small neutron-attenuation using a neutron beam as a probe

An approximate method for the quantification of a neutron radiography image was proposed for measuring the phase-distribution of multiphase materials with small neutron-attenuation. Since it is not necessary for this method to put a standard calibration sample in a field of a view, this method has an advantage of measuring the phase-distribution of multiphase materials with unknown internal-structure and neutron-attenuation in the object in an enlarged field of view. Although its application is limited to an object with small neutron-attenuation, it was revealed from a numerical analysis that the approximate method can be applicable to heavy water, liquid sodium and liquid potassium, which are important materials in relation to research on the thermalhydraulics of the nuclear reactor. The validity of the approximate method was also confirmed experimentally by comparing the void fraction of air-water flows in round tubes measured by the approximate method with those by the other more-accurate method.