Simultaneous Determination of ²²⁶Ra, ²³³U and ²³⁷Np by Liquid Scintillation Spectrometry

A method has been developed for the simultaneous determination of ²²⁶Ra, ²³³U and ²³⁷Np by liquid-scintillation (LS) spectrometry. This method consists in the evaluation of strongly overlapped multi peak spectra by a special peak fit function, considering the deviation of the LS-peak shape from the pure Gaussian distribution. First ²³⁷Np is determined using its daughter ²³³Pa by analyzing the ß-spectrum. ²²⁶Ra follows from the α-spectrum recorded 6 weeks after sample preparation. The peak of the three short-lived daughters ²²²Rn, ²¹⁸Po and ²¹⁴Po corresponds to the ²²⁶Ra activity under radioactive equilibrium conditions. Finally the ²³³U activity results from the joint α-peak at 4.8 MeV of the deconvoluted spectrum by subtracting the activity of ²²⁶Ra and ²³⁷Np. A second option uses the characteristic double peak of ²³⁷Np near 4.8 MeV. Due to the fact that the position is accurately known the pure α-spectrum can be analyzed for the determination of the given nuclides.