Measurement of Void Fraction Distribution by Gamma-Ray Computed Tomography

Measurement of the void fraction distribution in a stainless steel pipe by a gamma -ray computed tomography (CT) scanner using simulated voids and actual two-phase flows to clarify the possibility of obtaining accurate values for void fractions in a steel pipe was attempted. A 137 Cs gamma -ray with 662 keV energy was found suitable. An acrylic resin-filled steel pipe was used for simulated void measurements. A reconstructed image of the simulated void showed a clear distinction between the acrylic resin and the void by the gamma -ray CT. The void fraction obtained by the CT scanner agreed with that obtained from the increase of liquid level within the experimental uncertainty. It was concluded that the void fraction in a steel pipe could be measured accurately by the gamma -ray CT scanner.--S.K.B.