Determination of neptunium-237 in complex matrices by high-resolution inductively coupled plasma--atomic multielement emission spectroscopy (ICP--AMES)

Np-237 is determined sensitively by inductively coupled plasma -- atomic multielement emission spectroscopy (ICP-AMES). Detection limits of intense Np emission lines and the hyperfine broadening of these lines are reported. The most sensitive line, at 382.9 nm, has a detection limit of 25 ppb (i.e., 25 ng/ml) and is split by hyperfine effects into six resolvable components. Lines at 430.7 nm and 382.9 nm can be used to determine Np in complex U-containing solutions, such as spent fuel dissolver solution, at concentrations of 0.05 and 0.1% (relative to U) respectively. ICP-AMES, with a photodiode array detector, is used for real-time, simultaneous, multielemental monitoring of solutions eluting from ion-exchange columns. The added selectively provided by combining ion-exchange chromatography with high-resolution ICP emission spectroscopy results in improved Np detectability. Np, in a simulated D5 fuel dissolver solution, was determined at a concentration of <50 ppm relative to U. The detection limit for determining Np in a U-rich matrix by monitoring its emission at 382.9 nm is estimated to be 1 ppm relative to U. 29 refs., 25 figs., 8 tabs.