¹²⁹I determination by direct gamma-X spectrometry and its application to concentration variations in two seaweed species

Abstract

Abstract. The quantification of radionuclides by direct gamma-X spectrometry with energy below 100 keV requires knowledge the elementary composition of the sample or the development of a device for determining the mass attenuation coefficients. This is especially true for 129 I which is characterised by a 29.8 keV X-ray and 39.6 keV gamma ray. Experimental equipment has been developed in order to obtain this mass attenuation coefficient as a function of energy. 129 I concentrations were measured in samples of seaweed (Fucus serratus and Laminaria digitata) collected monthly over a period of one year nearby La Hague reprocessing plant in France. This paper describes the measurement methodology used to determine 129 I concentrations and variations in the two seaweeds over a one-year period. Mean mass attenuation coefficients for 129 I energies were established in order to determine the self-attenuation corrective factor for both seaweed species, regardless of the sampling date.

Methods and Application of ¹²⁹I Determination by Accelerator Mass Spectrometry

“…II sú uvedené detekčné limity pre zmienené metódy stanovenia 129 I (cit. [14][15][16] ). Z vyššie uvedeného a z tab.…”

“…Preto je nutné zabezpečiť také podmienky odprašovania v céziovom iónovom zdroji, aby sa vnútorný priestor iónového zdroja nekontaminoval samotnou vzorkou, a aby bolo zároveň možné zmerať čo najnižší pomer 129 I/ 127 I. Vzorky obsahujúce napr. 10 Be, 14 C alebo aktinoidy sa analyzujú pri teplote cézia v rezervoári iónového zdroja ≥140 °C. Pri meraní 129 I táto teplota nepresahuje hodnotu 100 °C.…”

“…Rádioizotop 129 I vstupuje do globálnych cyklov jódu od atmosféry cez biosféru a hydrosféru, až do geosféry. Jeho prirodzená produkcia bola rádovo prekročená ľudskou jadrovou činnosťou a 129 I sa tak stal ďalším rádioaktívnym stopovačom prírodných procesov podobne ako 14 C v bombovom píku alebo 236 U a 99 Tc. Jeho chemické správanie dovoľuje postihnúť omnoho širšie spektrum prírodných i antropogénnych cyklov než umožňujú posledné dva uvedené rádioizotopy a je možné ho detegovať na úrovniach izotopových pomerov až 10 -15 v submiligramových terčových vzorkách.…”

The Potential Of I-129 as an Environmental Tracer

“…It is used for monitoring of environmental samples collected in vicinity of NFRP such as thyroid, urine, seaweed, and for nuclear waste by using high purity Ge or plenary Si detector (Suarez et al, 1996;Bouisset et al, 1999;Frechou et al, 2001;Lefevre et al, 2003;Frechou & Calmet, 2003;Barker et al, 2005). To lower the detection limits normally big samples (50−500 g) are used, which induces considerable attenuation at low energies.…”

“…Therefor the mass energyattenuation coefficient (self-absorption correction) at a given energy must be measured for all sample matrices with respect to that of the standard source. Experimentally obtained selfabsorption correction factors are used to obtain accurate results (Bouisset et al, 1999;Lefevre et al, 2003, Barker et al, 2005. To quantify self-absorption correction factors 210 Pb (46.5 keV) and 241 Am (59.6 keV), with gamma lines close to 129 I are used.…”