RESUMO
The procedure followed by the Nuclear Metrology Laboratory (LMN) at the IPEN-CNEN/SP, in São Paulo, for the primary standardization of 166Ho is described. The activity of 166Ho was determined by the efficiency extrapolation technique applied to a 4πß(PC)-γ coincidence system using a gas flow proportional counter in 4π geometry coupled to a 76 × 76 mm NaI(Tl) crystal. The results for the γ-rays intensities at 80.57 and 1379.45 keV were 0.0651(11) and 0.00904(11), respectively.
Assuntos
Raios gama , Hólmio/normas , Radioisótopos/normas , Padrões de Referência , Espectrometria gama/normasRESUMO
The Laboratory for Neutron Activation Analysis and Gamma Spectrometry at the VSB-Technical University of Ostrava was equipped with the neutron generator MP320 operating on the principle of the deuterium-tritium fusion and producing 108 neutrons/s at maximum. To ensure radiation protection of radiation workers and public outside the laboratory, the concrete shielding was designed and its protection efficiency was validated by MCNP simulations. Three approaches to calculate the dose rates were compared. The dose rates were estimated for the ORNL MIRD phantom located at the relevant positions (Tally F6 and *F8) and using the MCNPX mesh tally feature with the new ICRP Publication 116 flux-to-dose conversion factors. It was proven that the Approach II in which the absorbed dose rates due to neutrons for all organs are computed using the cell tally F6 and the photon dose calculation is performed by the *F8 energy deposition tally is the most valuable one.
Assuntos
Laboratórios/normas , Modelos Estatísticos , Análise de Ativação de Nêutrons/normas , Imagens de Fantasmas , Proteção Radiológica/normas , Espectrometria gama/normas , Simulação por Computador , República Tcheca , Humanos , Método de Monte Carlo , Análise de Ativação de Nêutrons/instrumentação , Doses de Radiação , Radiometria/métodos , Espectrometria gama/instrumentaçãoRESUMO
In Japan, we conducted proficiency testing of activity measurement by using high-purity germanium detectors for 134Cs and 137Cs in brown rice grains. Among 176 reported results, 86 % (for 134Cs) and 93 % (for 137Cs) of the results satisfied |En| ⦠1. However, 58 reports for 134Cs and 51 reports for 137Cs had some failures in their evaluations of uncertainties. The proficiency testing was effective to improve the ability of uncertainty evaluation.
Assuntos
Radioisótopos de Césio/análise , Contaminação Radioativa de Alimentos/análise , Oryza/química , Radiometria/métodos , Radioisótopos de Césio/normas , Acidente Nuclear de Fukushima , Germânio , Humanos , Japão , Ensaio de Proficiência Laboratorial/métodos , Ensaio de Proficiência Laboratorial/normas , Ensaio de Proficiência Laboratorial/estatística & dados numéricos , Radiometria/normas , Radiometria/estatística & dados numéricos , Padrões de Referência , Espectrometria gama/métodos , Espectrometria gama/normas , Espectrometria gama/estatística & dados numéricos , IncertezaRESUMO
In situ gamma spectrometry (ISGS) is a technique mainly focused on the determination of man-made radionuclides deposited on soils. It is widely used for the radioactive characterization of soils in which there has been an incorporation of such radionuclides, especially 137Cs. Its use for the activity determination of naturally occurring radionuclides in soils has been more limited, and the accuracy associated with those measurements has yet to be treated extensively. There are numerous factors affecting the accuracy of the activity determination of naturally occurring radionuclides, such as the assumed soil geometry, the soil's geological and mineral composition, its moisture content, etc. The present work studies the accuracy associated with the ISGS determination of the activity concentrations of natural radionuclides in soils using a portable HPGe detector. For 40K and 232Th activity determinations, the uncertainties associated with ISGS are generally of the order of 15%. However, 226Ra activity determined from its daughters 214Pb and 214Bi can be significantly overestimated when there is a major presence of 222Rn in the air around the detector. Finally, absorbed dose rate in air values were calculated from the naturally occurring radionuclide concentration in soils. The results showed good correspondence between the values obtained from ISGS and those obtained from laboratory determinations with the same soils.
Assuntos
Monitoramento de Radiação/normas , Radioisótopos/análise , Poluentes Radioativos do Solo/análise , Espectrometria gama/normasRESUMO
This work investigated the utility of performing efficiency calibration for environmental gamma spectrometry using the Monte Carlo based, free of charge GATE toolbox. The validity of this approach was tested by comparing output efficiency values of an in-house developed GATE-based program with experimental measurements covering various geometries and primary photon energies. The results of this comparison revealed relative deviations within ±20%, thus validating the employed computational approach. Moreover, the GATE-based method was able to predict quantities that are generally difficult to measure experimentally, such as the number of interactions preceding full energy absorption. These computationally obtained predictions were found to be in agreement with theory.
Assuntos
Calibragem/normas , Método de Monte Carlo , Monitoramento de Radiação/instrumentação , Monitoramento de Radiação/normas , Espectrometria gama/instrumentação , Espectrometria gama/normas , Algoritmos , Simulação por Computador , Desenho de Equipamento , Análise de Falha de Equipamento/normas , Modelos Estatísticos , Linguagens de Programação , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , SoftwareRESUMO
(124)I is a radionuclide used in the diagnosis of tumors. The National Health Agency requires identification and activity measurement of impurities. Using gamma spectrometry with an efficiency calibrated high-purity germanium detector, impurities (125)I and (126)I in an (1)(24)I production sample were identified. Activity ratios of (125)I and (126)I to (124)I were approximately 0.5% and 98%, respectively.
Assuntos
Contaminação de Medicamentos/prevenção & controle , Radioisótopos do Iodo/análise , Radioisótopos do Iodo/normas , Radiometria/métodos , Radiometria/normas , Espectrometria gama/normas , Brasil , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Espectrometria gama/métodosRESUMO
Reference materials were used to assess measurement result uncertainty in determination of (210)Pb by gamma-ray spectrometry, liquid scintillation counting, or indirectly by alpha-particle spectrometry, using its daughter (210)Po in radioactive equilibrium. Combined standard uncertainties of (210)Pb massic activities obtained by liquid scintillation counting are in the range 2-12%, depending on matrices and massic activity values. They are in the range 1-3% for the measurement of its daughter (210)Po using alpha-particle spectrometry. Three approaches (direct computation of counting efficiency and efficiency transfer approaches based on the computation and, respectively, experimental determination of the efficiency transfer factors) were applied for the evaluation of (210)Pb using gamma-ray spectrometry. Combined standard uncertainties of gamma-ray spectrometry results were found in the range 2-17%. The effect of matrix composition on self-attenuation was investigated and a detailed assessment of uncertainty components was performed.
Assuntos
Radioisótopos de Chumbo/análise , Radioisótopos de Chumbo/normas , Contagem de Cintilação/métodos , Contagem de Cintilação/normas , Espectrometria gama/métodos , Espectrometria gama/normas , Algoritmos , Valores de Referência , Reprodutibilidade dos Testes , Sensibilidade e EspecificidadeRESUMO
The paper describes the measurements performed at IFIN-HH regarding the creation of a Romanian (124)I standard, consisting of: absolute standardization of the solution by the application of the 4πß(PC)-γ coincidence method; Calibration of the CENTRONIC IG12/20A ionization chamber with a standardised solution and comparison with a calculated efficiency; γ-ray spectrometry activity measurement and determination of the impurity levels; Comparison of the results of the three methods.
Assuntos
Calibragem/normas , Radioisótopos do Iodo/análise , Radioisótopos do Iodo/normas , Dosímetros de Radiação/normas , Espectrometria gama/instrumentação , Espectrometria gama/normas , Desenho de Equipamento , Análise de Falha de Equipamento , Valores de Referência , Reprodutibilidade dos Testes , Romênia , Sensibilidade e EspecificidadeRESUMO
A novel method has been developed for the activity measurement of large-area beta reference sources. It makes use of two emission rate measurements and is based on the weak dependence between the source activity and the activity distribution for a given value of transmission coefficient. The method was checked experimentally by measuring the activity of two ((60)Co and (137)Cs) large-area reference sources constructed from anodized aluminum foils. Measurement results were compared with the activity values measured by gamma spectrometry. For each source, they agree within one standard uncertainty and also agree within the same limits with the certified values of the source activity.
Assuntos
Algoritmos , Partículas beta , Radioisótopos/análise , Radioisótopos/normas , Espectrometria gama/métodos , Espectrometria gama/normas , Internacionalidade , Análise Numérica Assistida por Computador , Reprodutibilidade dos Testes , Sensibilidade e EspecificidadeRESUMO
The determination of radionuclide activity concentration requires a prior knowledge of the full-energy peak (FEP) efficiency at all photon energies for a given measuring geometry. This problem has been partially solved by using procedures based on Monte Carlo simulations, developed in order to complement the experimental calibration procedures used in gamma-ray measurements of environmental samples. The aim of this article is to apply GEANT4 simulation for calibration of two HPGe detectors, for measurement of liquid and soil-like samples in cylindrical geometry. The efficiencies obtained using a simulation were compared with experimental results, and applied to a realistic measurement. Measurement uncertainties for both simulation and experimental values were estimated in order to see whether the results of the realistic measurement fall within acceptable limits. The trueness of the result was checked using the known activity of the measured samples provided by IAEA.
Assuntos
Calibragem/normas , Modelos Estatísticos , Monitoramento de Radiação/instrumentação , Monitoramento de Radiação/normas , Manejo de Espécimes/normas , Espectrometria gama/instrumentação , Espectrometria gama/normas , Algoritmos , Simulação por Computador , Desenho de Equipamento , Análise de Falha de Equipamento , Raios gama , Internacionalidade , Método de Monte Carlo , Doses de Radiação , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Sérvia , SoftwareRESUMO
In this study, we investigated the correlation between 2-dimensional (2D) and 3D gamma analysis using the new PTW OCTAVIUS 4D system for various parameters. For this study, we selected 150 clinically approved volumetric-modulated arc therapy (VMAT) plans of head and neck (50), thoracic (esophagus) (50), and pelvic (cervix) (50) sites. Individual verification plans were created and delivered to the OCTAVIUS 4D phantom. Measured and calculated dose distributions were compared using the 2D and 3D gamma analysis by global (maximum), local and selected (isocenter) dose methods. The average gamma passing rate for 2D global gamma analysis in coronal and sagittal plane was 94.81% ± 2.12% and 95.19% ± 1.76%, respectively, for commonly used 3-mm/3% criteria with 10% low-dose threshold. Correspondingly, for the same criteria, the average gamma passing rate for 3D planar global gamma analysis was 95.90% ± 1.57% and 95.61% ± 1.65%. The volumetric 3D gamma passing rate for 3-mm/3% (10% low-dose threshold) global gamma was 96.49% ± 1.49%. Applying stringent gamma criteria resulted in higher differences between 2D planar and 3D planar gamma analysis across all the global, local, and selected dose gamma evaluation methods. The average gamma passing rate for volumetric 3D gamma analysis was 1.49%, 1.36%, and 2.16% higher when compared with 2D planar analyses (coronal and sagittal combined average) for 3mm/3% global, local, and selected dose gamma analysis, respectively. On the basis of the wide range of analysis and correlation study, we conclude that there is no assured correlation or notable pattern that could provide relation between planar 2D and volumetric 3D gamma analysis. Owing to higher passing rates, higher action limits can be set while performing 3D quality assurance. Site-wise action limits may be considered for patient-specific QA in VMAT.
Assuntos
Raios gama , Neoplasias/radioterapia , Assistência Centrada no Paciente/normas , Garantia da Qualidade dos Cuidados de Saúde/normas , Planejamento da Radioterapia Assistida por Computador/normas , Radioterapia de Intensidade Modulada/normas , Espectrometria gama/normas , Humanos , Índia , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Estatística como AssuntoRESUMO
In the framework of environmental measurements by gamma-ray spectrometry, some laboratories need to characterize samples in geometries for which a calibration is not directly available. A possibility is to use an efficiency transfer code, e.g., ETNA. However, validation for large volume sources, such as Marinelli geometries, is needed. With this aim in mind, ETNA is compared, initially to a Monte Carlo simulation (PENELOPE) and subsequently to experimental data obtained with a high-purity germanium detector (HPGe).
Assuntos
Algoritmos , Modelos Estatísticos , Monitoramento de Radiação/métodos , Monitoramento de Radiação/normas , Software , Espectrometria gama/métodos , Espectrometria gama/normas , Simulação por Computador , Internacionalidade , Transferência Linear de Energia , Doses de RadiaçãoRESUMO
The article describes the development of a KX-γ-coincidence method implemented in the prototype setup developed at the ionizing radiation department of the D.I. Mendeleyev Institute for Metrology. The first part was presented at Third European IRPA Congress (2010 June 14-18, Helsinki, Finland). NaI(Tl) crystals of 100 µm × 40 mm and 80 mm × 80 mm are used for photon radiation detection. A set of "ORTEC NIM" units and ADC "MKGB-01" are used for coincident pulse processing. The activity of electron-capture radionuclides (54)Mn, (57)Co, (65)Zn, (85)Sr, (88)Y, (139)Ce and (119m)Sn was measured. The expanded uncertainty (k=2) of activity was estimated in the range of 1-2%. The main metrological characteristics of the setup were determined: long-term stability, background, dead time, resolving time. The results obtained are in good agreement with international comparisons results and the Russian national standard of radioactivity.
Assuntos
Radioisótopos/análise , Radioisótopos/normas , Radiometria/instrumentação , Radiometria/normas , Espectrometria gama/instrumentação , Espectrometria gama/normas , Elétrons , Meia-Vida , Internacionalidade , Doses de Radiação , Radioisótopos/química , Padrões de Referência , Valores de ReferênciaRESUMO
The effect of radon diffusion and distribution between a (226)Ra matrix and the top air gap inside sample containers for gamma-ray spectrometry was studied. Containers filled at almost 100% or just 70% of total capacity yielded correction factors of about 7% and 20% respectively. Applying these correction factors allowed activity values calculated from (226)Ra or radon decay products to agree within 2%.
Assuntos
Algoritmos , Artefatos , Radiometria/normas , Radônio/análise , Radônio/normas , Espectrometria gama/métodos , Espectrometria gama/normas , Ar , Meia-Vida , Internacionalidade , Transição de Fase , Doses de Radiação , Radiometria/métodos , Radônio/química , Padrões de Referência , Valores de Referência , SoluçõesRESUMO
The procedure followed by the Nuclear Metrology Laboratory, at IPEN, for the primary standardization of (99m)Tc is described. The primary standardization has been accomplished by the coincidence method. The beta channel efficiency was varied by electronic discrimination using a software coincidence counting system. Two windows were selected for the gamma channel: one at 140 keV gamma-ray and the other at 20 keV X-ray total absorption peaks. The experimental extrapolation curves were compared with Monte Carlo simulations by means of code ESQUEMA.
Assuntos
Radiometria/métodos , Radiometria/normas , Software , Espectrometria gama/normas , Tecnécio/análise , Tecnécio/normas , Brasil , Meia-Vida , Internacionalidade , Doses de Radiação , Padrões de Referência , Valores de ReferênciaRESUMO
A software package is presented to calculate the total counting efficiency for the decay of radionuclides in a well-type γ-ray detector. It is specifically applied to primary standardisation of activity by means of 4πγ-counting with a NaI(Tl) well-type scintillation detector. As an alternative to Monte Carlo simulations, the software combines good accuracy with superior speed and ease-of-use. It is also well suited to investigate uncertainties associated with the 4πγ-counting method for a variety of radionuclides and detector dimensions. In this paper, the underlying analytical models for the radioactive decay and subsequent counting efficiency of the emitted radiation in the detector are summarised.
Assuntos
Radioisótopos/análise , Radioisótopos/normas , Radiometria/instrumentação , Radiometria/normas , Software/normas , Espectrometria gama/instrumentação , Espectrometria gama/normas , Algoritmos , Meia-Vida , Internacionalidade , Doses de Radiação , Radioisótopos/química , Padrões de Referência , Valores de ReferênciaRESUMO
Several problems concerning (133)Ba activity distribution in a cylindrical source were addressed by measurements with a 47% n-type HPGe detector and by simulation. Within-sample homogeneity was tested using the count rates from normal and from pure sum peaks. The sensitivity of front versus back source measurements to deviations from uniform distribution was studied. In the case of distributions symmetric with respect to the median plane of the source quantities that can provide information on the distribution of the activity were proposed.
Assuntos
Algoritmos , Artefatos , Radioisótopos de Bário/análise , Radioisótopos de Bário/normas , Radiometria/normas , Manejo de Espécimes/instrumentação , Espectrometria gama/normas , Brasil , Doses de Radiação , Tamanho da AmostraRESUMO
Gamma-ray measurements in terrestrial/environmental samples require the use of high efficient detectors because of the low level of the radionuclide activity concentrations in the samples; thus scintillators are suitable for this purpose. Two scintillation detectors were studied in this work; CsI(Tl) and NaI(Tl) with identical size for measurement of terrestrial samples for performance study. This work describes a Monte Carlo method for making the full-energy efficiency calibration curves for both detectors using gamma-ray energies associated with the decay of naturally occurring radionuclides (137)Cs (661keV), (40)K (1460keV), (238)U ((214)Bi, 1764keV) and (232)Th ((208)Tl, 2614keV), which are found in terrestrial samples. The magnitude of the coincidence summing effect occurring for the 2614keV emission of (208)Tl is assessed by simulation. The method provides an efficient tool to make the full-energy efficiency calibration curve for scintillation detectors for any samples geometry and volume in order to determine accurate activity concentrations in terrestrial samples.
Assuntos
Césio/efeitos da radiação , Monitoramento Ambiental/instrumentação , Iodetos/efeitos da radiação , Radioisótopos/análise , Radiometria/instrumentação , Iodeto de Sódio/efeitos da radiação , Espectrometria gama/instrumentação , Transdutores , Calibragem , Monitoramento Ambiental/normas , Desenho de Equipamento , Análise de Falha de Equipamento , Raios gama , Método de Monte Carlo , Doses de Radiação , Radiometria/normas , Sensibilidade e Especificidade , Espectrometria gama/normasRESUMO
This paper describes an electrochemical method for deposition of a thin layer of (57)Co on the outer surface of a copper sphere of 5mm diameter intended to be used as a point radioactive source. A description of the electrolytic cell, the process of deposition and the assay of the (57)Co activity are presented. About 1.48MBq (â¼40µCi) of (57)Co could be deposited using the described method. The quality of the prepared source in terms of nonleachability, uniform distribution of activity and stability, which are necessary attributes to be ensured before application were evaluated and found to be satisfactory.
Assuntos
Radioisótopos de Cobalto/química , Cobre/química , Galvanoplastia/instrumentação , Espectrometria gama/instrumentação , Adsorção , Calibragem , Raios gama , Espectrometria gama/normasRESUMO
This article brings the results of a method for quality assurance in gamma-ray spectrometry of seabed sediments. Sediments were collected in selected locations of the South and Middle Adriatic Sea using grab and corer tools. Using our own experimental design, we determined the self-attenuation factors of selected samples. The article also discusses sources of uncertainty in gamma-ray spectrometry, which is another important issue in quality assurance. Together with self-attenuation correction sources of uncertainty are used to calculate the activity concentration for a given sample. The presented procedure demonstrates how a gamma-ray spectrometry experiment should be approached in order to properly account for errors and uncertainties specific to a particular sample.