Nickel-59 and Nickel-63 Determination in Aqueous Samples

1.0 Scope and Application

This method is used to determine the activity of 59Ni and 63Ni in a solution. It describes the separation and purification of Ni using column precipitation chromatography. It also describes the subsequent determination of 59Ni and 63Ni by low energy photon spectroscopy (LEPS) and liquid scintillation counting (LSC) methods, respectively. Stable Ni is used as a carrier, and yield is determined by inductively coupled plasma optical emission spectroscopy (ICP-OES)(or equivalent) analysis of the Ni.

The method was developed for use with highly radioactive Hanford tank samples. It has also been applied to activated stainless steel samples. Variations in the radioactive isotopes present and the radioactive Ni activity will be factors used to determine aliquot size and amount of carrier added. Specific sample matrices {other than single-shell tanks (SST), double-shell tanks (DST), and activated stainless steel} may need to be tested with this procedure to ensure its applicability.

2.0 Summary of Method

A sample is equilibrated with stable Ni carrier and prepared for loading onto a dimethylglyoxime (DMG) precipitation column. The sample is loaded on the DMG column where the Ni forms a Ni-DMG complex. Other cations and anions are effectively eluted with the load and wash solutions. Nickel is stripped from the column with 3 M HNO3. It is again precipitated as the Ni-DMG complex, filtered onto a 1-in. filter paper, and washed. The filter paper Ni-DMG complex is mounted for LEPS counting where 59Ni activity is determined. The Ni-DMG complex is then oxidized in a muffle furnace leaving NiO, which is then dissolved. An aliquot of the Ni solution is then counted by LSC for 63Ni activity, and another aliquot is analyzed for total Ni to determine yield.

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