Chemical types of bonding of natural radionuclides in technologically enhanced naturally occurring radioactive material (tenorm)

摘要

TENORM (technologically enhanced naturally occurring radioactive material) isrnan acronym for solid material containing human made elevated concentrations ofrnnaturally occurring radioactive elements. In this study, an enhancement is given if atrnleast one radionuclide exceeds 200 Bq/kg. Raw materials, wastes and products wererntaken from the following types of industry: aluminium production, refractory industry,rnfertilizer production, hard coal mining and crude oil exploitation, as well as Th contaminatedrnsoils. In order to estimate their environmental hazard dimensions, the availabilityrnand mobilization potential of the natural radionuclides stored in those materials wererninvestigated. For this purpose, the 3 step extraction procedure proposed by thernEuropean Bureau Communautaire de Référence was applied as well as the Germanrnextraction procedures DIN 19730 and 38414-S4. The reagents obtained represent thernwater soluble, easily exchangeable, plant available, reducible and oxidizable level. Thesernextraction solutions were then measured by gamma spectrometry for determining thernactivity concentrations of the following radionuclides: ~(238)U, ~(226)Ra, ~(210)Pb, ~(228)Ra and ~(228)Th.rnBy doing so, the chemical types of bonding of these radionuclides can be evaluated. Thernmeasuring geometry for gamma spectrometry strongly depends on the reagent volumesrnresulting from the extraction procedures, which are about 200 mL. Therefore, a specialrncalibration was introduced by using reference water of known radionuclide content fromrnthe German Federal Office for Radiation Protection. In order to verify the reliability ofrnthat calibration standard containing low, medium and high activity concentrations, arnmeasurement comparison was undertaken in a second, independent laboratory, whichrnconfirmed the results. The described analytical procedures provide information aboutrnpotential migration pathways of the natural radionuclides contained in TENORM, as wellrnas the radiological risks for workers dealing with TENORM and members of the publicrnwho may be affected (e.g. by dump sites, secondary use as building material).