The analyses of samples were carried out using a p-type coaxial
HPGe detector (EG&G Ortec; 57.5-mm crystal diameter and 51.5-mm
thickness, 30% efficiency relative to a 7.62 cm7.62 cm NaI (Tl)
detector). This was connected to an ADCAM data acquisition system,
a PCAII multichannel analyzer and Gamma Visison spectrum analyzer.
For the measurement of low level radioactivity, a counting system
retained within a well shielded arrangement is essential. Gross
reduction of background radiation was accomplished using a lead
shielding arrangement of thickness 7.5 cm. A cylindrical multi-nuclide
source (
241
Am (59.541 keV),
109
Cd (88.040 keV),
57
Co (122.061 keV;
136.474 keV),
203
Hg (279.1952 keV),
113
Sn (391.698 keV),
85