Gamma Spectrometric Measurement of Uranium Isotopic Composition and Mass in Sintered UO Pellets Using the Efficiency Transfer Method

Gamma spectrometric measurements to determine the isotopic composition and total uranium mass in UO pellets (D = 7.5 mm; H = 3.5 mm, ρ = 10 g/cm) were carried out. The required efficiency curve was obtained by applying the efficiency transfer method from a calibration standard (D = 65 mm; H = 20 mm) of a slightly acidified water solution. The average isotopic composition of ten UO pellets was consistent with values of natural uranium given by IUPAC. The average relative bias for the U/U amount ratio was -0.73% using the 1001 keV gamma line for U and 0.50% using the 63 keV gamma line (186 keV was always used for U). For the total uranium mass, the mean deviation as compared to mass determinations using a balance was 5.5% using the 1001 keV gamma line for U and 4.3% using the 63 keV gamma line.