Determination of Np-237 in marine sediment and seawater

Procedures for determination of neptunium in marine sediment and seawater s amples are described. Iron hydroxide Fe(OH)(2)-Fe(OH)(3) is used for prelim inary pre-concentration of neptunium. Secondly, neptunium Np4+ and Pu3+ are separated by tri-isooctylamine-(TIOA) extraction in 8-10M HCl by redox wit h SO32--Fe3+. Neptunium Np4+ and uranium U6+ are separated by back extracti on the Np4+ with 2M HCl. Finally, the neptunium is purified from the uraniu m and thorium by anion exchange in 8M HNO3 and 12M HCl. The stripping of 6M HCl + NH2OH . HCl further separates the neptunium Np3+ and uranium. Reduct ion by SO32--Fe3+ appeared to be an efficient way to obtain Np4+. The decon tamination factors of the procedure are 4.0 . 10(4) for Th-232. 5.6 . 10(4) for uranium and 1.6 . 10(4) for plutonium.