This paper presents numerical estimation of the relation between measured intensity of 662keV γ-ray and nonuniform distributions of
137Cs in a γ-scan of a 7×7 fuel bundle without disassembling.
In the present analysis, the intensity of 662 keV γ-ray measured on the bundle is calculated as a function of the γ-ray measurement angle which is defined as an angle between the central axis of a collimator of a γ-ray detector and the line normal to a wall of the channel box.
In the calculation, the local distribution of
137Cs in the bundle is treated as power distributions obtained by calculation at the uncontrolled bundle and at the controlled bundle. The distributioa of
137Cs in a fuel rod is assumed to be parabolic in radial directions.
The present numerical analysis shows that the content of
137Cs can be estimated from the intensity of 662 keV γ-ray at a measurement angle of 27° with an error of less than 0.7%, provided that the local distribution of
137Cs is known and the distrlbution of
137Cs in fuel rods is parabolic.
The analysis also shows that the extent of
137Cs can be estimated from the intensity of 662keV γ-ray at a measurement angle of 24° with an error of about 3.7% when the local distribution of
137Cs is unknown.
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