Extraction and DFT study on the complexation of the methylammonium cation with a hexaarylbenzene-based receptor

In methods for quantification of ⁶³Ni, in e.g. reactor coolant water, a chemical separation is required due to ⁶³Ni being a pure beta emitter with limited means of quantification. ⁶⁰Co, a common radionuclide in reactor coolant water, is not completely separated with the commonly used separation procedure, and it is not resolved from ⁶³Ni in the beta spectrum. The separation method discussed in this work consists of TRU resin (Eichrom) and Ni resin (Eichrom). After running the separation procedure, depending on the initial activity of ⁶⁰Co, there may still remain enough ⁶⁰Co to interfere in the measurement of ⁶³Ni. The ⁶⁰Co interference is corrected for via a gamma spectrometric measurement. This correction may, depending on the ⁶³Ni/⁶⁰Co ratio, introduce a large contribution to the measurement uncertainty. The aim of this work was to evaluate the possibility to reduce the measurement uncertainty of ⁶³Ni measurements by adding a second Ni separation to the method. Double Ni separations were performed on reactor coolant water having a ⁶⁰Co activity much higher than the ⁶³Ni activity (⁶³Ni/⁶⁰Co = 0.01), in order to decrease the radioactivity of ⁶⁰Co in the sample. The measurement uncertainty of the ⁶³Ni measurement result was reduced by a factor of about three.