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A low-level high-purity Ge detection system was used to investigate samples of volcanic rock from different locations. A lead shield surrounded the 100 cm3 germanium crystal and reduced the background radioactivity by a factor of 100 within the energy interval 70 to 3000 keV; an integrated count rate of (0.498 +/- 0.001)/s was achieved over this interval, which was mainly attributable to the influence of cosmic rays. Although sample volumes up to 2 litres could be measured, the volcanic samples, held in cylindrical containers, varied in volume from 16 to 20 cm3. A powdered solid source was prepared of similar chemical composition to the samples, and spiked with suitable radionuclides to calibrate the detector system. The resulting efficiency calibration was compared with a Monte Carlo simulation of the detector efficiency for extended sources. Corrections were made for the given geometry, self-absorption and absorption in calculating the full energy-peak efficiency. The concentrations of various radionuclides originating from the decay chains in the different samples were compared to a well known reference sample. A wide variation of the concentrations of the measured radionuclides and a breaking of the secular equilibrium was observed.

Additional information

Authors: WORDEL R, JRC Geel (BE);MOUCHEL D, JRC Geel (BE);SOLÉ V A, JRC Geel (BE);HOOGEWERFF J, University of Utrecht, Institute of Earth Sciences, Department of Geochemistry (NL);HERTOGEN J, University of Leuven, Fysico-chemische Geologie (BE)
Bibliographic Reference: Paper presented: ICRM Conference and International Symposium on Radionuclide Metrology and its Applications, Teddington (GB), June 7-11, 1993
Availability: Available from (1) as Paper EN 37657 ORA
Record Number: 199311039 / Last updated on: 1994-11-29
Original language: en
Available languages: en