“…3 Due to the long half-life and its mobility in the environment, 237 Np will be one of the most hazardous elements in high-level nuclear waste when in geological repositories for at least 10 4 to 3 6 10 7 years after disposal. 4 The main methods employed for the determination of 237 Np are a-spectrometry, [5][6][7] inductively-coupled mass spectrometry (ICP-MS), 1,[8][9][10][11][12][13] neutron activation analysis (NAA) 14,15 and a liquid scintillation with rejection of b-c emitters. 16 The major drawback in 237 Np measurement by a-spectrometry is the need of extensive sample preparation prior to counting, in particular to remove 234 U, which has a similar a decay energy.…”