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Estimation of the uncertainty components associated with the measurement of radionuclides in air filters using γ-ray spectrometry
Abstract
This paper discusses and assesses the major sources of uncertainty arising in measurement of radionuclide activity concentrations in air. Besides counting statistics, the main contributors to the overall uncertainty of the activity concentration of long-lived radionuclides are the heterogeneities of the calibration source and the test samples (approximately 4%). In addition, in the case of radionuclides with half-lives of the order of days or shorter, a significant uncertainty results from the variability of the “source term” because the peak concentration of the radionuclide might occur either at the beginning or at the end of the sampling period. For131I (T
1/2≈8 days), for instance, the relative standard uncertainty was estimated as 17% owing to this effect. In addition, the uncertainty introduced by the software used for evaluation of the γ-ray spectra is discussed. Details of the uncertainty components, including their assessed probability distributions and degrees of freedom, and the conversion into standard uncertainties are reported in this paper, following the ISO Guide to the expression of uncertainty in measurement. A standard form for documenting and reporting the uncertainty budged is proposed and illustrated with an example.
... A realistic assessment of uncertainties is crucial for the determination of low level activity concentrations of 7 Be, 210 Pb and 22 Na. The measurements presented in this work are accompanied by a combined standard uncertainty that can be separated into type A and type B uncertainty components [19]. As far as the type A uncertainties are concerned, the peak area uncertainty that was calculated by the gamma spectroscopic analysis code was considered to be the principal component. ...
... For the analysis of air filter samples, several potential sources of type B uncertainty have been identified [19]. In this work, the uncertainty of the efficiency calibration procedure and the airflow measurement uncertainty were taken into account. ...
The activity concentration of cosmogenic radionuclides in atmospheric aerosol has been used in many applications, such as air mass transport models and solar activity reconstructions. One of the most studied cosmogenic radionuclides is 7Be which is being monitored at the Nuclear Engineering Department of the National Technical University of Athens (NED- NTUA) since many years, with high accuracy and precision. Sodium-22 is another cosmogenic radionuclide met in such studies, however less reported due to its very low activity concentration, of the order of 1 μBq/m3 [1], [2] – roughly four orders of magnitude lower than that of 7Be. Besides cosmogenic radionuclides, radionuclides of terrestrial origin like the 222Rn progeny 210Pb are also used in atmospheric aerosol studies. Lead-210 serves as an ideal tracer of continental air masses because 222Rn emission from oceans and lakes is negligible (<1%) compared to land sources. However, its deposition exhibits geographic and seasonal variations depending on 226Ra content of the top soils, soil-porosity and meteorology of a particular region [3]. Values reported for 210Pb activity in the air range from 0.1 to 3.4 mBq/m3 [4]. During this research, an investigation regarding the detection of 210Pb and 22Na in atmospheric aerosol and the determination of 7Be/22Na ratio has been conducted at NED-NTUA. Sampling and analysis methods were appropriately selected to allow for the detection of all three nuclides in aerosol samples. In order to study the role of precipitation in surface air 7Be, 210Pb and 22Na activity concentration, a procedure for collecting and analyzing rainwater was also developed. From the results obtained so far it is concluded that with the sampling and analysis procedures followed, 210Pb can be easily determined with reasonable accuracy. As far as 22Na is concerned, it was concluded that it can be detected although with high uncertainty, since its activity concentration is within the limits of detection.
... A re al is tic as sess ment of un cer tain ties is cru cial for the iden ti fi ca tion of vari a tions in 7 Be ac tiv ity concen tra tion. The mea sure ments per formed in the present work are ac com pa nied by a to tal com bined un certainty that can be sep a rated in type A and type B un cer tainty com po nents [22]. As far as type A un certain ties are con cerned, the peak area un cer tainty that was cal cu lated by the gamma spec tro scopic anal y sis code was con sid ered to be the prin ci pal com po nent. ...
... For the anal y sis of air fil ter sam ples, sev eral poten tial sources of type B un cer tainty have been iden tified [22]. In the pres ent work, the un cer tainty of the effi ciency cal i bra tion pro ce dure and the air flow mea sure ment un cer tainty were taken into ac count. ...
The activity concentration of Be-7 in atmospheric aerosol can exhibit seasonal variations due to various physical processes taking place in the troposphere and stratosphere, as well as due to solar activity. An investigation of these variations has been carried out at the Nuclear Engineering Department of the National Technical University of Athens over a two year period (3/2008-4/2010). In the framework of this study, sampling and analysis methods were appropriately selected to allow for the observation of short-term Be-7 air activity concentration variations, using a 4-hour sampling interval, while taking in consideration type A and type B uncertainties introduced in the measurements. In order to study the role of precipitation in surface air Be-7 activity concentration variations, a procedure for collecting and analyzing rainwater was developed. The techniques used in the present study allowed for the observation of seasonal and diurnal Be-7 concentration variations, as well as correlations between Be-7 activity concentration and the meteorological parameters of air temperature and relative humidity.
... A sampling of 12 h per day for a 5-day period was collected on A4 filter paper. The samples were weighed and folded into the same geometry as the calibration standard as described in Makarewicz [15] for the gamma spectrometry measurements. ...
This study presents assessment results of the hazardous materials contained in ceramic tiles used in interior decorations and construction in Saudi Arabia. Chemical compositions and radiometric characterizations of the ceramic tiles were determined by using ICP-MS, XRD, and gamma-ray spectrometer with a high-purity germanium (HPGe) detector. The results showed that the ceramic tiles and clays contained 21 elements in the ppm to ppb range, including the major elements of Ca, Si, Fe, Na, Al, Mg, Si, and K, and heavy metals that are used as tracers such as Cr, Mn, Co, Ni, Cu, Zn, Cd, and Pb. Additionally, the XRD analysis had indicated that quartz (SiO2), albilte (feldspar) in the calcium and magnesium carbonate forms, and microcline (KAlSi3O8) are also presented in the samples. The activity concentrations of ²²⁶Ra, ²³²Th, and ⁴⁰K ranged from 29 to 129 Bq kg⁻¹, 32 to 114 Bq kg⁻¹, and 83 to 1100 Bq kg⁻¹, respectively. Furthermore, an assessment of the radiological risks from exposure to these nuclides was conducted by estimating the radium equivalent activity index, activity concentration index, alpha index, outdoor absorbed gamma dose rate, and the corresponding annual effective dose rate.
... The corrections for nuclide decay are negligible, since the half-lives of natural radionuclides are much longer compared to sampling (C D1 ), storage (C D2 ) and counting (C D3 ) periods: e.g. for experimental time periods of \1 % of nuclide half-life the magnitude of the correction factor is \ \1 % and therefore can be neglected. On the other hand, when all corrections are needed, attention must be paid to the correlation among the three correction factors [19]. The correction on the random summing is considered negligible since the dead time is too low for low count rates which are of the order of few hundreds of cps. ...
The feasibility of using certified reference materials for the full energy efficiency calibration of p-type coaxial high-purity germanium detectors for the determination of radioactivity in environmental samples is discussed. The main sources of uncertainty are studied and the contributions to the total uncertainty budget for the most intense gamma lines are presented. The correction factors due to self-absorption and true coincidence summing effects are discussed in detail. The calibration procedure is validated for natural and artificial radionuclide determination in different matrices through an internal cross-validation and through the participation in a world-wide open proficiency test.
... Tuo atveju, kai impulsų skaičius smailėje (išskaičiavus foninius impulsus) > L c , smailė identifikuojama kaip statistiškai patikima: Tuo atveju, kai impulsų skaičius smailėje (išskaičiavus foninius impulsus) < L c , smailė neidentifikuojama ir apskaičiuojama impulsų skaičiaus viršutinė riba: Radionuklidų aktyvumo bandiniuose matavimų rezultatai statistikai apdorojami ORIGIN aplinkoje [117,118]. Radionuklido iškritų (stambiadispersinės frakcijos) tankis, D p (Bq m -2 ), įvertinamas aktyvumo ir bandinio surinkimo ploto santykiu: ...
For mechanical properties of titanium, oxygen content is important. In re-certifying O mass fraction in the Ti certified reference material ERM-EB090b, instrumental photon activation analysis (IPAA) was used as an alternative to the inert gas fusion technique. IPAA utilizes 15O measurable only via the nonspecific annihilation gamma line 511 keV. Interferences from other radionuclides can be suppressed by optimizing photon energy and irradiation-decay-counting times, and for most interfering radionuclides corrected via their specific gamma lines. The present re-evaluated IPAA results for O content 3.56 ± 0.59 g/kg matches closely the assigned certified value 3.57 ± 0.19 g/kg.
The activities on air filters of the radionuclides (40)K and (137)Cs were measured in an above ground laboratory and compared with the activities measured in an underground laboratory. The average relative differences were lower than 20% for (137)Cs and (40)K. The temporal series of these radionuclides in the period 2006-2010 are also presented. These results form the baseline of these radionuclides in the studied period, and are particularly interesting because they correspond to the radioactive background in Barcelona before the Fukushima accident.
This chapter describes the topics of importance for any site evaluation, providing an informed decision for remediation. It demonstrates the need to characterize the different release scenarios and to determine the radio-ecological sensibility/vulnerability of a contaminated site. It also provides very practical advice on planning, field and laboratory measurements, verification of data, and the role of quality analyst (QA) and quality control (QC) within the whole survey and remediation process. This information should help to improve the survey planning, the survey, and the pathway analysis for optimized remediation strategy. Site characterization represents the first necessary stage in the remediation of any contaminated environment. Indeed, all decisions for the evaluation of need for site remediation—further remediation planning and the implementation of remedial actions—and post remediation for the assessments (to ensure that there is compliance of the residual concentrations of radionuclides in the environment with the expected levels) are based on the site characterization.
Mass attenuation coefficients of various soil and sediment samples (density range between 1.0 and 1.7 g cm(-3)) collected from 60 sites distributed in Syrian land have been determined for gamma lines of 46.5, 59.5, 88, 122, 165, 392, 661, 1173, and 1332 keV using gamma spectrometry and simulation software program X-com. The average mass attenuation coefficients for the studied samples were found to be 0.513, 0.316, 0.195, 0.155, 0.134, 0.096, 0.077, 0.058, and 0.055 cm(2) g(-1) at previous energies, respectively. The results have shown that Ca and Fe contents of the samples have strong effect on the mass attenuation coefficient at lower energies. In addition, self-attenuation correction factors determined using mass attenuation coefficient was in good agreement with addition spiked reference material method provided that the sample thickness is 2.7 cm. However, mass attenuation coefficients determined in this study can be used for determination of gamma emitters at energy ranges from 46.5 to 1332 keV in any soil and sediment samples having density of 1.0-1.7 g cm(-3).
In the frame of an International Atomic Energy Agency Technical Cooperation project, a radiological survey was performed in
the Araks and Kura Rivers (Azerbaijan). Sediment samples, and where available, aquatic plants were collected along these two
rivers and their inflow and tributary rivers. 137Cs, 238U, 234U, 239+240Pu, 238Pu, 90Sr and 241Am activity concentrations were measured. The radionuclide levels measured were relatively low, and in most cases below the
detection limit, as compared with those from other areas of the world which have been directly affected by effluents from
nuclear installations or influenced by the Chernobyl accident. The results indicated that the radionuclides are of natural
origin or attributable to the atmospheric fallout from nuclear weapons tests or to the Chernobyl-derived deposition.
A computer program and data base are presented which can be used to calculate, with a personal computer, photon cross sections for scattering, photoelectric absorption and pair production, as well as total attenuation coefficients, in any element, compound or mixture, at energies from 1 keV to 100 GeV.
Performance of three commercial gamma-ray spectrometric systems was evaluated for precision and accuracy prior to use in characterization of reference materials. Two of the systems were based on fast processing of the analogue signal from the amplifier (EGG Ortec model 672) using a loss free counting module (Canberra model LFC 599) interfaced to one of two analog-to-digital converters (Canberra models 8713 or 8715). The third system was based on a digital signal processor (Canberra model DSP 9660). Performance of the systems was tested over a range of count rates up to a maximum of 70,000 counts per second (dead time up to 90%) using 60Co and 137Cs sources. Best resolution was achieved with an analogue system with ADC 8713. The analytical results obtained with the digital system show the lowest and well-quantified uncertainty.
Halbw-ertszeiten und photonen-Emission-swahrscheunlichkeiten von häufig ver-wendeten Radionukliden, PTB-Bericht Ra-16
- U Schötzig
- Schrader
Schötzig U, Schrader H (1993) Halbw-ertszeiten und photonen-Emission-swahrscheunlichkeiten von häufig ver-wendeten Radionukliden, PTB-Bericht Ra-16/4, Braunschweig, July 1993
Developed jointly by Guide to the expression of uncertainty in measurement
- Iso
- Bipm
- Iec
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- Iso
- Iupac
- Iupap
- Oiml
Method of the Investigation of the Air-borne Radioactive Contamination Using ASS-500 Station
- J Jagielak
- M Biernacka
- M Bysiek
- R Zarucki