Influence of Scattered Neutrons on Void Fraction Measurement of Two-Phase Flow Using Thermal Neutron Radioscopy
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The purpose of this study was to study the influence of scattered neutrons on void fraction measurement of two-phase flow using thermal neutron radioscopy and to develop a practical correction method for scattered neutrons. Experimental and analytical studies resulted in the followings. (1) It was confirmed that neutrons scattered in the object could be smoothed out by taking an appropriate distance between the object and the converter. The distance was roughly estimated to be greater than the object width and was independent of the object thickness. The maximum distance was estimated to be the product of the spatial-resolution and L/D ratio of the neutron radiography facility in view of the image unsharpness due to unparallelness of an incident neutron beam. (2) The previously proposed method for correcting scattered neutrons (∑-scaling method) was verified experimentally. (3) In such a system that neutrons scattered in surrounding shields cannot be ignored, it was pointed out analytically that void fraction measured without no corrections of scattered neutrons might include a large measurement error. This measurement error depended on the void fraction, the object material, and the flux of scattered neutrons.
- Journal of Nuclear Science and Technology
Journal of Nuclear Science and Technology 34(10), 996-1005, 1997-10-25
Atomic Energy Society of Japan