Non-destructive determination of low-level activity radionuclides in samples of one gram powder by gamma-ray spectrometry

A nondestructive method for determination of several low-level activity radionuclides in samples of one gram powder by gamma-ray spectrometry is described. Each sample is loaded by a custom-made plastic box, forming a small disk of φ26 mm x 3 mm. Sample box are measured in a lower position, about 1 cm far from the HPGe detector. The main problem of calibration of absolute full-energy peak efficiencies for those nuclides has been resolved, including self-absorption correction. Planar sources using same boxes are prepared with radionuclides solution to measure on several different positions in order to calculate the efficiencies of disk samples. The relative uncertainties of radioactivity by this method are between 2% to 4% by discussing measurement results and confirmed by radiochemical analyses of two nuclides with partial samples. (authors)