Metrological Determination of Natural Radioactive Isotopes {sup 226}Ra, {sup 228}Ra and {sup 210}Pb by Means of Ge Detector
- Laboratorio Nacional de Metrologia das Radiacoes Ionizantes, Instituto de Radioprotecao e Dosimetria, Comissao Nacional de Energia Nuclear(SEMRA/LNMRI/IRD/CNEN) Av. Salvador Allende s/n, Recreio, Rio de Janeiro, CEP 22780-160, RJ (Brazil)
A metrological method to determine the activity per mass unity (activity concentration) of {sup 226}Ra and {sup 210}Pb ({sup 238}U decay series) and {sup 228}Ra ({sup 232}Th series) by gamma-ray spectrometers based on hyper-pure coaxial germanium detector was developed. In the soil the {sup 22}Ra (half-life = 1600 years) exhibits the same level of radioactivity as {sup 238}U (half-life 4.5x10{sup 9} years) because of a natural phenomenon called secular equilibrium. {sup 226}Ra decays into {sup 222}Rn (half-life = 3.8 days), a radioactive inert gas. After several days, the {sup 222}Rn naturally decays to {sup 218}Po (half-life = 3 minutes), where finally {sup 210}Pb (half-life = 22 years) is produced. The metrological capability of high-resolution gamma-ray spectrometry for naturally occurring radionuclides at environmental levels is showed, with emphasis on the use of 2 mL standard sources volume in a glass ampoule. Source preparation and calibration procedures are described. Radionuclide standards in an activity range of 10 to 250 Bq/g were produced which can be applied in a variety of environmental sample analysis (water, plant material, sediment, etc.). Uncertainties for {sup 226}Ra and {sup 210}Pb around 3% (k = 1) were obtained.
- OSTI ID:
- 21152485
- Journal Information:
- AIP Conference Proceedings, Journal Name: AIP Conference Proceedings Journal Issue: 1 Vol. 1034; ISSN 0094-243X; ISSN APCPCS
- Country of Publication:
- United States
- Language:
- English
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