Gamma-ray spectrometry of radon in water and the role of radon to representatively sample aquifers.

Measurement of radon in water by gamma-ray spectrometry using a HPGe detector has been investigated to determine aquifer characteristics. The radon activity concentration is determined by taking the weighted average of the concentrations derived from gamma-ray lines associated with (214)Pb and (214)Bi decay. The role of accurate radon data to representatively sample aquifers was also investigated by studying a semi-cased borehole. A simplified physical model describing the change of radon concentration with the pumping time, reproduces the data and predicts the time for representative sampling of the aquifer.

Determination of soil, sand and ore primordial radionuclide concentrations by full-spectrum analyses of high-purity germanium detector spectra.

The full-spectrum analysis (FSA) method was used to determine primordial activity concentrations (ACs) in soil, sand and ore samples, in conjunction with a HPGe detector. FSA involves the least-squares fitting of sample spectra by linear combinations of (238)U, (232)Th and (40)K standard spectra. The differences between the FSA results and those from traditional windows analyses (using regions-of-interest around selected photopeaks) are less than 10% for all samples except zircon ore, where FSA yielded an unphysical (40)K AC.

Radioactivity levels of staple foodstuffs and dose estimates for most of the Tanzanian population.

Levels of natural radioactivity in staple food products (maize and rice) from various localities of Tanzania have been studied. The average activity concentrations of 40K, 232Th and 238U in maize were 48.79 +/- 0.11, 4.08 +/- 0.01 and 13.23 +/- 0.10 Bq kg(-1), respectively. In rice the concentrations of 40K, 232Th and 238U were 24.67 +/- 0.03, 3.82 +/- 0.02 and 5.02 +/- 0.02 Bq kg(-1), respectively. 137Cs was detected in only one sample collected in Zanzibar. The sample, with activity concentration of 5.57 +/- 0.01 Bq kg(-1), had been imported from Thailand. The relatively high average concentrations of the radionuclides in maize compared to rice may be attributed to the extensive use of phosphate fertilizers in maize production in Tanzania. Total annual committed effective doses due to total 232Th and 238U intakes as a result of consumption of staple foodstuffs for infants, children and adults were 0.16, 0.29 and 0.36 mSv y(-1), respectively, which are lower than the annual dose guideline for the general public.