NEUTRON FLUX RATIO MEASURING METHOD FOR NEUTRON EMISSION BODY SYSTEM

摘要

PURPOSE:To remove background components and to find an accurate neutron flux ratio having no systematic error by finding a difference in measured value obtained by using two kinds of neutron detectors. CONSTITUTION:The 1st and 2nd kinds of neutron detectors 1 and 2 are used to detect emitted neutrons as to a 1st object 3 of measurement which is a spent fuel assembly 10. The detector 1 is equipped with a neutron detector 8 in water 7 as a moderator surrounded with a large-diameter Cd cover 6 and the detector 2 is constituted by surrounding the detector 8 directly with a small-diameter Cd cover 9. Then, similar detection is performed for a 2nd object 4 of measurement provided with a Cd plate 11 at the periphery of the assembly 10. Then the difference between the outputs of both detectors 1 and 2 with respect to the objects 3 and 4 of measurement is found and the ratio of both differences is regarded as the neutron flux ratio. Consequently, the background components are removed and accurate measurement is taken.