Gamma spectrometric measurement of uranium isotopic composition and mass in sintered UO2 pellets using the efficiency transfer method.

Gamma spectrometric measurements to determine the isotopic composition and total uranium mass in UO2 pellets (D = 7.5 mm; H = 3.5 mm, ρ = 10 g/cm3) 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 UO2 pellets was consistent with values of natural uranium given by IUPAC. The average relative bias for the 235U/238U amount ratio was -0.73% using the 1001 keV gamma line for 238U and 0.50% using the 63 keV gamma line (186 keV was always used for 235U). 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 238U and 4.3% using the 63 keV gamma line.

Alpha spectrometry and liquid scintillation counting for the measurement of 238Pu, 239Pu, 240Pu, 241Pu, 242Pu and age.

A method for the measurement of the isotopic composition and time since last chemical separation (age) of plutonium is presented. The method includes alpha spectrometric measurement of 238Pu, 239Pu and 240Pu where the ratio of 239Pu and 240Pu was determined using spectral deconvolution, and liquid scintillation counting of 241Pu, after chemical separation of plutonium and americium. For the age determination, the 241Pu determined using liquid scintillation counting was combined with alpha spectrometric measurement of 241Am. The results of the isotopic composition were compared with certified reference materials with known isotopic composition, and the results of the age determination were compared with literature values of the separation dates.