Theoretical and experimental estimation of self-attenuation corrections in determination of 210Pb by -spectrometry with well Ge detector

Abstract

This paper aims at giv ing a practical method for rou tine measu rements of the activ ity of 210 Pb in solids b y gamma spectrometry w ith a w ell G e cry stal. S ince the gamma ray s emitted b y 210 Pb hav e a low energy , 4 6 .5 k eV , the proportion of pu lses cou nted in the cry stal depends strongly on the sample composition trou gh self-attenu ation w ithin the sample itself. S elfattenu ation can b e calcu lated b y u se of a M onte C arlo method b ased on a model. I n the present w ork tw o codes, namely G E AN T 4 and a L ab oratory code gav e resu lts in agreement. H ow ev er, b oth necessitate a good k now ledge of the sample composition, of the detector geometry and of the compu ting programs. I n order to circu mv ent su ch draw b ack s, w as dev eloped an experimental techniq u e, w here the ov erall cou nting efficiency can b e deriv ed directly from the transmission of 4 6 .5 k eV γ−ray s throu gh the sample, b y means of a linear relationship. S u ch correlation w as ob serv ed experimentally w ith samples of k now n activ ity and the approach w as v alidated b y v erification that a linear relation preliminary exists b etw een the transmission and the calcu lated self-ab sorption.

Well GeHP detector calibration for environmental measurements using reference materials

“…The detector full energy peak efficiency (FEPE) calibration is always required to reach accurate measurements and still represents a subject of considerable interest for the gamma spectrometry [1][2][3][4][5][6][7][8][9][10]. In this work, the measurements were carried out with a well highpurity germanium (HPGe) detector, situated in the underground Laboratory of Modane (LSM, located along the Frejus Tunnel Rood in Savoy) where the reachable sensitivity depends on the ultra-low background.…”

“…In this work, the measurements were carried out with a well highpurity germanium (HPGe) detector, situated in the underground Laboratory of Modane (LSM, located along the Frejus Tunnel Rood in Savoy) where the reachable sensitivity depends on the ultra-low background. The FEPE calibration of the well detector [1][2][3][4]7,8,10] is required for environmental measurements, mainly the determination of fallout radionuclides in lake sediments such as 210 Pb (half-life 22.3 years) and 137 Cs (half-life 30.05 years) for dating methods. To determine the FEPE function, standard calibration sources, with the same size and composition as the samples, should be used to have the same matrix effects (concerning mainly the auto-absorption due to the density and the chemical composition) that will be corrected.…”

An intercomparison of Monte Carlo codes used for in-situ gamma-ray spectrometry

“…The present work reports the results obtained during the intercomparison of a commercial calculation code LabSOCS/ISOCS (Bronson and Wang, 1996;Bronson et al, 1998) and a free-available and general-purpose GEANT4 (Agostinelli et al, 2003;Hurtado et al, 2004;Pilleyre et al, 2006;Villa et al, 2007). Calculated efficiency curves, in the gamma-ray energy range of 59e1460 keV, were compared with the experimental ones obtained through standard samples in more general measurement configurations.…”

Calibration of an HPGe detector and self-attenuation correction for 210Pb: Verification by alpha spectrometry of 210Po in environmental samples

“…Measuring its activity in air and in surface soils will provide quantitative information about the flux of 222 Rn and its daughters in the atmosphere [2]. Especially 210 Pb and 210 Po (T 1/2 ¼ 138.4 d) can be of great concern from the standpoint of radiation protection due to their radiotoxicity, as 210 Pb and 210 Po can accumulate in some foods and contribute significantly to the dose from total internal irradiation by ingested natural radionuclides [3,4].…”

“…This low energy requires one to apply a selfattenuation factor to take into account the difference in composition of the sample with regard to the calibration standard solution [1]. In this work we use experimental, theoretical and Monte Carlo methods to determine the selfattenuation correction for the environmental solid samples in the cylindrical geometry [2,6]. The chemical composition of each analysed sample is determined by X-ray fluorescence and the experimental self-attenuation correction is based on the method proposed by San Miguel et al [6] while theoretical and Monte Carlo approaches [2] are used for checking for coherence with the experimental method.…”