APPLICATION OF QUANTITATIVE MEASUREMENT METHOD TO VOID FRACTION OF TWO-PHASE FLOW IN A ROD BUNDLE BY NEUTRON RADIOGRAPHY

Abstract Quantitative void fraction measurement method based on the umbra method using a neutron absorber grid was applied to the void fraction measurement of two-phase flow in a 4 x 4 rod bundle. The grid 3mm in width and 3mm in interval was made from B4C. The details of the method was discussedin another paper of the present conference. The two-phase flow direction was vertical and the gridwas placed vertically between the rod bundle and the neutron source. A cooled-CCO camera in the JRR-3M thermal neutron radiography system was used. CT reconstruction was carried out for sixty horizontal slices with a vertical interval of 3 mrn. Cross sectionally averaged one-dimensional void fraction distributions along the flow direction were also calculated with 3 mrn interval. Quantitative measurement with spatial resolution O.18mm, size of the image element, horizontally and 3mm vertically was carried out. keywords: Neutron radiographyTwo-phase flowVoid fractionQuantitative measurementRod bundleSpacerCT reconstruction