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 fo r this method to put a standard calibration sample in a field of a vie w, this method has an advantage of measuring the phase-distribution of multiphase materials with unknown internal-structure and neutron-atte nuation in the object in an enlarged field of view. Although its appli cation 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 a re important materials in relation to research on the thermalhydraulic s of the nuclear reactor. The validity of the approximate method was a lso confirmed experimentally by comparing the void fraction of air-wat er Rows in round tubes measured by the approximate method with those b y the other more-accurate method.