SEQUENTIAL DETERMINATION OF NEPTUNIUM-237, PLUTONIUM-238, PLUTONIUM-239,240, AMERICIUM-241, AND CURIUM-244 IN PLANT MATERIAL

We describe a procedure for the sequential determination of 237Np, 238Pu, 239,240Pu, 241 Am, and 244Cm in plant material. The plant sample is decomposed completely by a combination of dry ashing and wet digestion; the radionuclides are then coprecipitated with ferric hydroxide. Americium-curium, plutonium, and neptunium fractions are sequentially extracted with tri-isooctylamine (TIOA). Excess salts are then removed from the americium-curium fraction by ferric hydroxide precipitations in a two-step procedure, first using ammonium hydroxide and then sodium hydroxide, followed by iron removal by cation exchange. Trace amounts of iron are removed from the plutonium and neptunium fractions by ion exchange. Each fraction is electrodeposited and analyzed by alpha spectrometry. Recovery for the neptunium fraction is about 80 percent, and for plutonium, americium, and curium, better than 90 percent. Yields are corrected by recovery of added tracers.