High precision analysis of isotopic composition for samples used for nuclear cross-section measurements

For the accuracy improvement of nuclear data of minor actinides and long-lived fission products in the project of “Research and development for Accuracy Improvement of neutron nuclear data on Minor Actinides”, the isotopic compositions of two Am samples ( 241 Am sample and 243 Am sample) were analyzed by thermal ionization mass spectrometry. Only the peak of 241 Am was observed in the analysis of 241 Am sample, and level of isotopic impurities were improved from 0.1% to 0.0004%. In the analysis of 243 Am sample, the peak of unreported isotope of 242 m Am was observed in addition to the peaks of 243 Am and 241 Am. The mass spectrometry also showed that 243 Am sample has other unreported impurities such as 239 Pu and 240 Pu.