FORO Iberoamericáno de Organismos Reguladores Radiológicos y Nucleares

Descripción

Clearance values were derived for natural and artificial radionuclides. The radiological basis followed for their derivation was the same for both cases, i.e. practically not to modify the natural radiation background, but the approach to obtain the numerical figures was different. For natural radionuclides the values have been chosen by experts judgments as the optimum boundary between, on the one hand, the ubiquitous unmodified soil concentrations and, on the other hand, activity concentrations in ores, mineral sands, industrial residues and wastes. For artificial radionuclides the clearance levels have been derived from the scenarios postulated in the document “Safety Reports Series N° 44” of the IAEA considering quantitative exemption criterion. A set of 8 scenarios were postulated covering external irradiation, ingestion and inhalation exposure pathways. For each radionuclide, the generic clearance level was derived as the more restrictive value obtained from the scenarios, that is the lowest ratio between the applicable individual dose criterion and the dose per unit activity concentration (Bq/g). It was concluded that the clearance levels are conservative given the fact that the scenarios in which they are based are generic, covering a wide range of possible exposure situations. (6th Intenational Symposium on Release of Radioactive Material from Regulatory Requirements Provisions for Exemption and Clearance Wiesbaden, Alemania, 21 al 23 de setiembre de 2009)