Preparation of 241Am/243Am gravimetric mixtures and development of Am isotopic and assay measurement techniques using thermal ionization mass spectrometry

Three gravimetric mixtures with 241Am/243Am isotope ratios at nominally 1:1, 20:1, and 200:1 were prepared for calibration of the thermal ionization mass spectrometer instruments used for americium isotopic and assay measurements by isotope dilution mass spectrometry. The total evaporation analytical technique that has already been demonstrated to provide accurate (within ±0.03%) 235U/238U and 240Pu/239Pu ratios was developed to obtain highly reproducible Am isotopic ratios. The technique was also applied to Am assay measurements using isotope dilution mass spectrometry. The Am isotope ratio and assay measurement techniques were utilized to characterize batches of americium oxide separated from plutonium materials in storage at Los Alamos National Laboratory in support of commercial use of 241AmO2. LA-UR-20–23098.