Simultaneous non-destructive determination of long-lived radionuclides in contaminated seaweed by X-ray spectrometry

Planar high purity germanium detectors have been used for activity determination of fission nuclides, as well as transuranic elements, in a contaminated seaweed. The activity of a given isotope was deduced from the absolute detection efficiency of the detector and from the branching ratio R Nsub(K)/Nsub(β) of the K-X photons emitted by desintegration; in case of monoenergetic γ emitters, these branching ratios have been calculated from nuclear data decay. These low-energy measurements require one standard sample only for simultaneous determination of several isotopes. The data obtained in this work for the 137Cs specific activity by non-destructive analysis are in good agreement with the results of an intercomparison exercise performed by te IAEA. Moreover, this method allows us to measure in this seaweed the specific activity of the previously not detected 129I nuclide, both by destructive and non-destructive analysis, and that of 241Pu which generally needs complicated radiochemical separations. (Author)