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1.
Anal Chem ; 93(35): 11937-11945, 2021 09 07.
Artigo em Inglês | MEDLINE | ID: mdl-34432435

RESUMO

Plutonium, americium, and uranium contribute to the radioactive contamination of the environment and are risk factors for elevated radiation exposure via ingestion through food or water. Due to the significant environmental inventory of these radioelements, a sampling method to accurately monitor their bioavailable concentrations in natural waters is necessary, especially since physicochemical factors can cause significant temporal fluctuations in their waterborne concentrations. To this end, we engineered novel diffusive gradients in thin-film (DGT) configurations using resin gels, which are selective for UO22+, Pu(IV + V), and Am(III) among an excess of extraneous cations. In this work, we also report an improved synthesis of our in-house ion-imprinted polymer resin, which we used to manufacture a resin gel to capture Am(III). The effective diffusion coefficients of Pu, Am, and U in agarose cross-linked polyacrylamide were determined in freshwater and seawater simulants and in natural seawater, to calibrate these configurations for environmental deployments.


Assuntos
Plutônio , Urânio , Amerício/análise , Difusão , Água Doce , Plutônio/análise , Urânio/análise
2.
Spectrochim Acta A Mol Biomol Spectrosc ; 261: 120082, 2021 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-34153551

RESUMO

Cosmic rays, nuclear accidents, and neutron therapy could be sources for exposure to low-dose fast neutrons. However, the study of low dose effects needs sentient techniques to detect slight alteration happen by this low dose. Herein, the effects of low-dose fast neutrons on the structure of hemoglobin (Hb) using spectroscopic techniques, namely, Fourier transform infrared (FTIR), Raman, and ultraviolet-visible (UV-Vis) spectroscopic. Forty (20 control/20 irradiated) female Wistar rats were used in this work. The irradiated rats were irradiated to low-dose at a total dose of 10 mGy from a fast neutron source (241Am-Be, 0.2 mGy/h). Multivariate analyses were applied to differentiate between the control and irradiated rats' Raman spectra. The erythrocytes samples were isolated from whole blood to explore the Hb structure. FTIR results revealed changes in the ν(S-H) bond of α-104 and ß-93 cysteines by low-dose fast neutrons. Raman spectra showed changes in the spin state and oxidation state of the iron atom of the Hb. Besides, deformation in methine C-H was recorded. UV-Vis spectroscopy disclosed that the irradiated rats might be more susceptive to oxidation than control rats. The study deduced that the low dose fast neutron could cause tiny Hb structure changes by indirect effects. Besides, the spectroscopic techniques showed a potent ability to reveal tiny changes in the Hb structure that happened by a low dose of fast neutrons.


Assuntos
Amerício , Nêutrons Rápidos , Animais , Feminino , Hemoglobinas , Ratos , Ratos Wistar
3.
J Chromatogr A ; 1641: 461999, 2021 Mar 29.
Artigo em Inglês | MEDLINE | ID: mdl-33611122

RESUMO

Low molecular weight diglycolamide (DGA) extractants were tested for the extraction of europium(III) and americium(III) from nitric acid solutions in n-dodecane, a molecular diluent and 1-butyl-3-methylimidazolium bis(trifluoromethanesulphonyl) imide (C4mim⋅NTf2), a room temperature ionic liquid, as the diluents. N,N,N',N'-tetra-n-butyl diglycolamide (TBDGA) was selected for extraction chromatography (XC) studies involving Eu(III) and Am(III). While the TBDGA resin containing n-dodecane gave reasonably high Kd values, that containing the ionic liquid showed higher Eu(III) uptake values. Compared to Eu(III), Am(III) was extracted by the resins to a lower extent. The loaded Eu(III) was back extracted from the resin using 0.05 M EDTA solutions in a buffered medium containing 1 M guanidine carbonate. Reusability studies indicated that, while the ionic liquid-based resin can be conveniently recycled five times with very marginal decrease in the percentage extraction values, there was a sharp decrease in the percent extraction after three cycles with the n-dodecane-based resin. The uptake data was fitted into different isotherm models and the results conformed to the Langmuir model. Based on the batch uptake studies, columns were prepared and the breakthrough as well as elution profiles were obtained. The elution profiles were found to be sharp without any significant tailing.


Assuntos
Cromatografia/métodos , Glicolatos/química , Líquidos Iônicos/química , Ácido Nítrico/química , Resinas Sintéticas/química , Amerício/química , Cátions , Európio/química , Imidazóis/química , Ligantes , Solventes/química , Temperatura , Termogravimetria , Fatores de Tempo
4.
J Environ Radioact ; 229-230: 106540, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-33503559

RESUMO

The new data on 239+240Pu, 238Pu, 241Pu, 241Am vertical distribution in the deep western Black Sea sediments was analyzed. The sediment dating, obtained by means of 238Pu/239+240Pu activity ratio vertical distribution, suggested the upper 3 cm layer of sediments to be formed during 27 years after the Chernobyl accident and the deeper layers to be formed earlier in pre-Chernobyl time (before 1986). The whole data set on profiles of radionuclides studied was shown to reflect the history of their input into the basin and elimination of these radionuclides from the water column. Analysis of inventories of plutonium alpha-emitting nuclides ensured a more significant contribution of Chernobyl fallout into the present total 238Pu inventory than into 239+240Pu one. The 241Am inventory after-deposition enhancement due to 241Pu decay was estimated at 74% in pre-Chernobyl sediment layer and the general contribution of 241Pu support in the total 241Am inventory in situ enhancement was estimated at 49%.


Assuntos
Plutônio , Monitoramento de Radiação , Poluentes Radioativos da Água , Amerício/análise , Mar Negro , Sedimentos Geológicos , Plutônio/análise , Poluentes Radioativos da Água/análise
5.
J Environ Radioact ; 227: 106459, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-33221564

RESUMO

The 238Pu, 239+240Pu, 241Am, 242Cm, 243+244Cm and 90Sr concentrations in seafloor surface sediments collected at three sampling stations off the Fukushima Daiichi Nuclear Power Plant (FDNPP) site during the period from 2012 to 2019 were determined to elucidate the impacts of the FDNPP accident onto their concentrations in coastal sediments and to discuss the sources of the measured radionuclides. The 239+240Pu, 241Pu and 241Am concentrations and 240Pu/239Pu atom ratios in a sediment core were also determined to allow comparison of their inventories between this study and previously reported values and to identify the Pu sources. The 238Pu, 239+240Pu, 241Am and 90Sr concentrations showed no remarkable temporal variations; no significant increases in concentrations after the FDNPP accident were observed; these concentrations were comfortably within the previously reported concentration range; and no detectable 242Cm and 243+244Cm amounts were observed in surface sediments. The observed 238Pu/239+240Pu activity ratios were approximately two orders of magnitudes lower than those for the damaged FDNPP reactor core inventories and the observed values in terrestrial samples after the accident. The 239+240Pu, 241Pu and 241Am inventories in the sediment core were 389 ± 5, 503 ± 33 and 214 ± 3 Bq m-2, respectively. The 239+240Pu inventory was about an order of magnitude greater than the expected cumulative deposition density of global fallout from atmospheric nuclear weapons testing due to an enhanced scavenging effect. The 240Pu/239Pu atom ratios in the sediment core ranged from 0.239 to 0.246 with a mean value of 0.242 ± 0.002; these ratios were clearly greater than the mean global fallout ratio of 0.18. The results for 238Pu/239+240Pu activity ratios and 240Pu/239Pu atom ratios reflected a mixture of global fallout and Pacific Proving Grounds (PPG) close-in fallout Pu rather than Fukushima accident-derived Pu. The sediment column inventory for 239+240Pu originating from the PPG close-in fallout was calculated as 166 Bq m-2, which corresponded to 43% of the total inventory. A significant amount of the PPG-derived Pu has been transported by ocean currents and then preferentially scavenged in the coastal waters of Japan.


Assuntos
Acidente Nuclear de Fukushima , Monitoramento de Radiação , Poluentes Radioativos da Água , Amerício/análise , Cúrio/análise , Japão , Centrais Nucleares , Plutônio/análise , Radioisótopos de Estrôncio , Poluentes Radioativos da Água/análise
6.
Health Phys ; 120(1): 24-33, 2021 01.
Artigo em Inglês | MEDLINE | ID: mdl-32427639

RESUMO

Biokinetics underlies the basis for assessment of internal exposures. This paper develops a biokinetic method on simultaneous intake of radionuclides from multiple intake scenarios in internal exposures. With numerical techniques that transform the whole biokinetics between the coupled and decoupled representations of the same problem, this method applies to coupled biokinetics with complex structures and has no restrictions of practical importance on the number of intake scenarios, the number of intake parent radionuclides and decay products, and the complexity of decay relationships between parent and progeny nuclides. For illustration, this method is applied to an assumed case of mixed inhalation and ingestion of weapon-grade plutonium material for reference workers that is focused on Pu and Am. Due to coupled biokinetics between the direct intake and ingrowth parts in different intake pathways, the multiple intake results (the contents of lungs, daily excretions, and cumulative contents) display richer behaviors as compared to single intake cases. This method benefits both the prospective and retrospective assessment of internal exposures for complex intake cases in actual applications.


Assuntos
Exposição à Radiação , Radioisótopos/administração & dosagem , Radioisótopos/farmacocinética , Algoritmos , Amerício/administração & dosagem , Amerício/farmacocinética , Ingestão de Alimentos , Humanos , Exposição por Inalação , Pulmão/metabolismo , Pulmão/efeitos da radiação , Modelos Biológicos , Exposição Ocupacional , Plutônio/administração & dosagem , Plutônio/farmacocinética , Estudos Prospectivos , Doses de Radiação , Proteção Radiológica , Estudos Retrospectivos , Medição de Risco , Software
7.
Health Phys ; 120(1): 94-97, 2021 01.
Artigo em Inglês | MEDLINE | ID: mdl-32496326

RESUMO

NCRP Report 156 describes soluble radionuclide retention kinetics in a wound, segregated into four retention categories: weak (W), moderate (M), strong (S), and avid (A). An alternate single-parameter model, the negative power function, t, is presented in this paper to describe the time behavior of radionuclide retention. With this mathematical description, γ is a single parameter that can be used to assign the wound retention category rapidly. Using the power function description of wound retention, the various wound categories present as straight lines on log scales with different slopes corresponding to the various retention categories. Regression analysis of average retention values in NCRP 156 shows γ = 0.735 ± 0.132, 0.514 ± 0.015, 0.242 ± 0.016, and 0.053 ± 0.023 for the weak, moderate, strong, and avid categories, respectively. A case study is presented (REAC/TS Registry case 1284) where a power function is shown to fit retention data in a Pu/Am hand wound up to 2,000 d (5.4 y) post-accident.


Assuntos
Lesões por Radiação/metabolismo , Liberação Nociva de Radioativos , Radioisótopos/efeitos adversos , Radioisótopos/farmacocinética , Ferimentos Penetrantes/metabolismo , Idoso , Amerício/efeitos adversos , Amerício/farmacocinética , Quelantes/administração & dosagem , Simulação por Computador , Humanos , Masculino , Modelos Biológicos , Ácido Pentético/administração & dosagem , Plutônio/efeitos adversos , Plutônio/farmacocinética , Lesões por Radiação/terapia , Solubilidade , Polegar/lesões , Polegar/efeitos da radiação , Ferimentos Penetrantes/terapia
8.
Ecotoxicol Environ Saf ; 207: 111191, 2021 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-32890947

RESUMO

To elucidate the features of bioaccumulation and phytotoxic effects of long-lived artificial radionuclides, a hydroponic experiment was carried out with the cultivation of onion (Allium cepa L.) in low-mineralized solutions spiked with 137Cs (250 kBq L-1) or 243Am (9 kBq L-1). After the 27-day growth period, ≈70% of 137Cs and ≈14% of 243Am were transferred from the solutions to onion biomass with transfer factor values ≈ 400 and ≈ 80, respectively. Since the bioaccumulation of both radionuclides mainly took place in the roots of onion (77% 137Cs and 93% 243Am of the total amount in biomass), edible organs - bulbs and leaves - were protected to some extent from radioactive contamination. At the same time, the incorporation of the radionuclides into the root tissues caused certain changes in their biometric (geometric and mass) traits, which were more pronounced under the 243Am-treatment of onion. Exposure to 243Am significantly reduced the number, length, and total surface area of onion roots by 1.3-2.6 times. Under the influence of 137Cs, the dry-matter content in roots decreased by 1.3 times with a corresponding increase in the degree of hydration of the root tissues. On the whole, the data obtained revealed the specific features of 137Cs and 243Am behaviour in "hydroponic solution - plant" system and suggested that biometric traits of onion roots could be appropriate indicators of phyto(radio)toxicity.


Assuntos
Amerício/toxicidade , Radioisótopos de Césio/toxicidade , Cebolas/efeitos da radiação , Biomassa , Hidroponia , Cebolas/crescimento & desenvolvimento , Folhas de Planta , Raízes de Plantas/crescimento & desenvolvimento
9.
J Environ Radioact ; 223-224: 106378, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32911270

RESUMO

The solid-liquid distribution coefficient (Kd) is a key input parameter in radioecological risk models. However, its large variability hampers its usefulness in modelling transport processes as well as its accuracy in representing soil-radionuclide interactions. To assist in the selection of Kd values and their cumulative distribution functions for study areas without site specific information, a critically reviewed dataset was developed, containing more than 5000 soil Kd entries for 83 elements and an additional 2000 entries of Kd data for 75 elements gathered from a selection of other geological materials. For the specific case of americium (Am), the dataset contained 109 entries for soils and 33 additional entries for sediment and subsoils. The analysis of the Am Kd soil dataset showed that values varied 4-orders of magnitude, and consequently the resulting Am Kd best estimate (geometric mean (GM): 4.6 × 103 L kg-1) lacked sufficient reliability. The objective of this study was to calculate cumulative distribution functions and statistically evaluate this dataset to determine if the Am Kd variability in soils could be reduced by considering various factors, including: 1) measurement methods, 2) key soil properties, 3) the use of chemical analogue data, and 4) the use of analogue data. Accounting for Am Kd experimental method (i.e., sorption vs. desorption; long-vs. short-term experiments) had little effect on reducing variability. However, accounting for key soil factors (i.e., organic matter content (OM), pH, soil texture) succeeded in reducing variability of Am Kd, especially when combining pH and OM. While previous data sets have used 20% OM content as a critical value to distinguish between mineral and organic soils, this study shows that this critical value should be reduced to 10% OM to minimize Am Kd variability. The inclusion in the dataset of Am Kd from other geological materials (e.g., gyttjas, tills, and subsoils) and Kd values from trivalent lanthanides (Ln (III)) and actinides (An (III)) (172 additional entries) did not statistically affect the Am Kd geometric means of the various pH and OM partial datasets. The larger composite dataset (> 310 entries), with both chemical analogues and geological material analogues to address data gaps, increased the statistical power for calculating Kd best estimates with lower variability, thereby enhancing their usefulness for radionuclide risk calculations.


Assuntos
Monitoramento de Radiação , Solo , Adsorção , Amerício/análise , Reprodutibilidade dos Testes , Poluentes do Solo/análise
10.
PLoS One ; 15(7): e0235109, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32609724

RESUMO

Data on the transfer of artificial radionuclides from the environment to the food supply is necessary for internal dose assessment. There is a necessity for expanding and improving the available information on these factors in order to make better dose models for specific scenarios. This paper describes the results of a field experiment with broiler chickens on the transfer factor (Ff) and concentration ratio (CR) for the long-term intake of 241Am and 137Cs with grass meal and soil. The broilers were divided into two groups, each group had nine subgroups and each subgroup had three broilers. The radionuclide concentrations in the feed and the thigh muscle, thigh bone, and liver of 54 broilers divided between the grass meal and soil groups were evaluated by gamma spectrometry for 241Am and 137Cs. The duration of feeding with "contaminated" sources ranged between 1-70 days. The equilibrium stage of 241Am in muscle and bone occurs on the 1st and 40th day, respectively; for 137Cs in muscle- 30th days of intake and for liver and bone- 7th days. For 241Am, the liver did not reach equilibrium stage during the 70 days of intake. Ff of 137Cs in the "forage-muscle" and "soil-muscle" systems were determined as 1.9±0.3 and 0.18±0.05; Ff of 241Am in the "soil-muscle" system was-7.5×10-5.


Assuntos
Amerício/análise , Radioisótopos de Césio/análise , Galinhas , Contaminação Radioativa de Alimentos/análise , Aves Domésticas , Poluentes Radioativos do Solo/análise , Amerício/metabolismo , Ração Animal/análise , Animais , Radioisótopos de Césio/metabolismo , Galinhas/metabolismo , Abastecimento de Alimentos , Aves Domésticas/metabolismo , Poluentes Radioativos do Solo/metabolismo
11.
Radiat Prot Dosimetry ; 190(2): 125-131, 2020 Aug 28.
Artigo em Inglês | MEDLINE | ID: mdl-32607545

RESUMO

A set of five Bonner spheres was used to measure the ambient neutron H*(10) dose around an orphan 241Am-Be neutron source shielded with different arrangements and types of neutron-absorbing materials. These results were compared to measurements obtained using a portable radiation dosemeter. The Bonner sphere measurement results identified the presence of a large thermal and intermediate neutron component from the shielded 241Am-Be source that was not revealed using the portable instrument.


Assuntos
Amerício , Exposição Ocupacional , Desenho de Equipamento , Nêutrons , Exposição Ocupacional/análise , Doses de Radiação , Análise Espectral
12.
Appl Radiat Isot ; 163: 109194, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32392167

RESUMO

In this work, the benefits in terms of dose enhancement and dose sparing via radiation shielding are evaluated, for a combined irradiation scheme with sources of 241Am and tumor-infused with Gd agents, regarding conventional 192Ir treatment. Monte Carlo simulations using PENELOPE code were implemented for endocavitary brachytherapy geometries, configuring a pelvis phantom of 15 cm radius and 30 cm length. Inside, it was defined cylindrical tumor phantoms of 2 cm radius and 4 cm-6 cm length (simulating initial stages) as well as tumors of extensive volume (2.5 and 3.0 cm radius) and difficult coverage. Tumor phantoms were doped with 68 mM and 138 mM of Gd in order to assess the effects of enhancement and protection based on the concentration and emission energy of the isotope. Obtained results for the first tumor group, shown the feasibility of achieving dose enhancements of 94.3%-117% and 160%-194% for 68 mM and 138 mM of Gd infused into the tumor and irradiation with 241Am, respectively. Similarly, reduced dose enhancements of 3.5-5.7% y 8.9%-11.2% for 68 mM and 138 mM of Gd are attained with 192Ir. In terms of dose sparing outer the tumor, the radiation shielding and dose enhancement allowed a higher reduction in the dose by 241Am of 17%-24% for 68 mM and 21%-32% for 138 mM of Gd, and non-negligible dose sparing are produced too by 192Ir of 2% and 5% for the same concentration of Gd. For the second tumors group, the combined use of 241Am and Gd agents simultaneously allowed to improve coverage and reduce the healthy tissue dose, showing the obtained results the possibility of achieving coverage of 95% of the prescribed dose in 100% of tumor volume together with dose sparing factor of 6-21% reduction in isodose of the studied point and dose enhancements of 75%-158% at the prescription point.


Assuntos
Amerício/administração & dosagem , Braquiterapia/métodos , Gadolínio/administração & dosagem , Neoplasias/radioterapia , Dosagem Radioterapêutica , Humanos , Método de Monte Carlo , Imagens de Fantasmas
13.
Health Phys ; 119(2): 252-260, 2020 08.
Artigo em Inglês | MEDLINE | ID: mdl-32332419

RESUMO

A large volume gamma spectrometer was designed and constructed to analyze foodstuffs and environmental samples having low radionuclide concentrations. This system uses eight 11-cm × 42.5-cm × 5.5-cm NaI(Tl) detectors, chosen due to their relatively high sensitivity and availability and arranged in an octagonal configuration. The sensitive volume of the system is ~28 cm in diameter and ~42 cm deep. Shielding consists of an 86-cm × 86-cm square, 64-cm-tall lead brick enclosure with 18-cm-thick lead walls lined by 0.3-cm-thick copper plates. An aluminum top was machined to suspend the detectors within this shield. The shielding reduces background counts by 72% at 100 keV and 42% at 1,000 keV. The positional variability in sensitivity of the well was determined by both simulation and experiment. A 2.1-L volume of nearly uniform sensitivity, varying less than 10%, exists in the well's center. Energy resolutions of 14.6% and 7.8% were measured for Am and Cs, respectively. Energy resolution shows a 0.2% variation for both Am and Cs as a function of position within all regions of the well's central sensitive volume. Dead time was also determined to be less than 35% for all sources measured in the system, the largest of which had an activity of 1,760 kBq. Simulated results for various source geometries show higher counts for smaller samples, especially at lower energies due to less attenuation of low energy photons. Minimum detectable activities were determined for all source energies used, less than 5.1 Bq kg for reasonable background and sample counting times.


Assuntos
Amerício/análise , Césio/análise , Exposição Ambiental/análise , Radioisótopos/análise , Espectrometria gama/métodos , Simulação por Computador , Desenho de Equipamento , Raios gama , Humanos , Modelos Químicos , Método de Monte Carlo , Fótons
14.
J Radiol Prot ; 40(2): 381-392, 2020 06.
Artigo em Inglês | MEDLINE | ID: mdl-32045888

RESUMO

Routine monitoring is an important element of any occupational radiation protection programme to be able to determine how effective this protection is in practice. As well as providing information on normal operational conditions and routine worker dose uptakes, these programmes are also required to be able to detect the occurrence of abnormal or unexpected exposures to radionuclides, where these risks are deemed to be present in the workplace. Various monitoring techniques and methods are available and can be applied to the direct monitoring of workers or of the workplace. For many of the less radio-toxic radionuclides simple monitoring programmes are often more than sufficient to demonstrate compliance with operational and regulatory controls; however, multiple programmes, operated in parallel, are often required for the more radio-toxic radionuclides-e.g. Plutonium and americium-to be able to provide assurance that the potential risks of exposure are reliably and adequately controlled. When a potential exposure event is detected then further investigations are instigated to confirm whether an intake has occurred and to estimate the resultant dose. This paper presents an empirical review of the records of all such investigations over an eighteen-year period at the Harwell site, Oxfordshire, UK. The purposes of this review were to determine the relative effectiveness of different monitoring methods in being able to detect potential exposure events; and how efficient each method was in detecting potential exposures which, following investigation, were confirmed as real intakes. The analyses revealed that routine faecal sampling provided the better performance characteristics in terms of combined effectiveness and efficiency; and that the ability to detect potential exposures (at levels of up to 6 mSv) in the absence of any routine monitoring programme was limited. There was a very low incidence of potential exposures being detected by more than one monitoring technique, which emphasises the importance of operating multiple monitoring methods in order to optimise the probability and confidence of detecting potential exposures.


Assuntos
Amerício/análise , Exposição Ocupacional/análise , Monitoramento de Radiação/métodos , Contaminação Radioativa do Ar/análise , Humanos , Laboratórios , Plutônio , Doses de Radiação , Proteção Radiológica/métodos , Medição de Risco/métodos , Reino Unido
15.
J Radiol Prot ; 40(2): 477-486, 2020 06.
Artigo em Inglês | MEDLINE | ID: mdl-32045889

RESUMO

The detection of internal contamination may be carried out by direct or indirect methods. The lung counting technique using an array of High Purity Germanium (HPGe) detectors is one of such direct detection methods. It is known from the literature that the estimation of activity by organ counting can lead to erroneous results if an amount of activity is possessed by an adjacent organ. In the case of HPGe-based lung monitoring, the estimation could be misleading if the activity is possessed by the liver, which is a proximal organ. In such cases the measured activity should be modified using cross-talk coefficients which account for the contribution from adjacent organs. The determination of cross-talk coefficients for 241Am was carried out by placing the detectors over inactive lungs of an Lawrence Livermore National Laboratory phantom when the source activity was contained in the liver and vice versa. A calibration matrix was formulated with calibration coefficients as diagonal elements and cross-talk coefficients as off-diagonal elements. The measured activities may be modified by matrix multiplication with the inverse of the calibration matrix to nullify the contribution from adjacent organs. The current work has empirically determined the fitting equations which relate calibration and cross-talk coefficients for lungs and liver measurement geometries with muscle-equivalent chest wall thickness (MEQ-CWT) values. The values of these coefficients were determined for an average MEQ-CWT of 1.77 cm for lungs and 1.33 cm for liver. The calculations showed that the activity contribution from liver to lungs was 29% higher than that of lungs to liver. A verification exercise was conducted to demonstrate this method. For the given calibration source, the percent overestimation was reduced for lung activity, while the liver activity was slightly underestimated. In the case of old exposure follow-up monitoring cases, the 241Am activity built up in liver could interfere with the lung monitoring results and this method using the calibration matrix may be used for estimation of more accurate results.


Assuntos
Amerício/análise , Fígado/química , Pulmão/química , Monitoramento de Radiação/instrumentação , Calibragem , Germânio , Humanos , Modelos Anatômicos , Modelos Biológicos , Doses de Radiação
16.
J Environ Radioact ; 216: 106181, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32056789

RESUMO

The methodology for determination of 241Pu in soils of the main test sites of the Semipalatinsk Test Site (STS) has been developed. The results of 241Am and 241Pu activity determination in soil samples sampled at the main testing sites of the STS are presented. 241Pu/241Am activity ratio is calculated. In most cases, on local sites, 241Pu/241Am activity ratio is in a rather narrow range, which makes it possible to estimate 241Pu activity based on the results of 241Am gamma-spectrometric analysis. The accuracy of 241Pu activity estimation using this method will be about 50%, which is quite enough in most cases.


Assuntos
Monitoramento de Radiação , Poluentes Radioativos do Solo/análise , Amerício , Cazaquistão , Plutônio , Solo , Espectrometria gama
17.
Radiat Prot Dosimetry ; 188(4): 486-492, 2020 Jul 02.
Artigo em Inglês | MEDLINE | ID: mdl-31950186

RESUMO

As a reference photon field, several radionuclides have been used frequently, such as 241Am,137Cs and60 Co for calibration. These nuclides provide mono-energy photons for dosemeters covering few tens of keV-MeV. The main energy around 200 keV is important for both environmental and medical fields since the former should consider scattering photons and the later should measure photons from X-ray generator. In our previous work, a backscattered layout can provide a uniform photon field spectra and dose rate with an energy of 190 keV by using an affordable intensity 137 Cs gamma source. Several other quasi-monoenergetic photon fields in the range of 100-200 keV could be obtained by using several available gamma sources. Two calibrated environmental CsI(Tl) survey meters, Horiba PA-1000 and Mr. Gamma A2700, had been measured with the developed backscattered photon field to understand energy-dependent features in order to confirm dosemeter readings. Consequently, both scintillator instruments are sensitive for measurements of the relatively low dose rates at 190 keV.


Assuntos
Radioisótopos de Césio , Fótons , Amerício , Calibragem
18.
Radiat Prot Dosimetry ; 188(1): 117-122, 2020 Jun 12.
Artigo em Inglês | MEDLINE | ID: mdl-31747040

RESUMO

A current-mode neutron detector with a pair of 6Li- and 7Li-glass scintillators has been developed to measure high-flux neutrons in a boron neutron capture therapy field. Neutrons are basically measured by subtracting gamma-ray component using current outputs from the 7Li-glass scintillator. In the present study, the difference in the gamma-ray sensitivity between the 6Li- and 7Li-glass scintillators and the neutron sensitivity for the 7Li-glass scintillator due to the 6Li contamination were also considered to improve the gamma-ray subtraction precision. The gamma-ray subtraction procedure was experimentally investigated in thermal neutron fields with 252Cf and 241Am-Be neutron sources, which have different gamma-ray intensities per unit neutron fluence. A linear relation between neutron fluence and current output was obtained for the neutron detector in the two types of thermal neutron fields with different gamma-ray intensities. It was found that the gamma-ray subtraction procedure is useful for current-mode neutron detectors.


Assuntos
Terapia por Captura de Nêutron de Boro , Vidro , Isótopos , Lítio , Contagem de Cintilação/instrumentação , Amerício , Califórnio , Desenho de Equipamento , Raios gama , Humanos , Nêutrons
19.
Int J Radiat Biol ; 96(2): 206-213, 2020 02.
Artigo em Inglês | MEDLINE | ID: mdl-31682776

RESUMO

Purpose: We present an α-irradiation setup for the irradiation of primary human cell cultures under controlled conditions using 241Am α-particles.Materials and Methods: To irradiate samples with α-particles in a valid manner, a reliable dosimetry is a great challenge because of the short α-range and the complex energy spectrum. Therefore, the distance between α-source and sample must be minimal. In the present setup, this is achieved by cells growing on a 2 µm thick biaxially-oriented polyethylene terephthalate (boPET) foil which is only 2.7 mm apart from the source. A precise and reproducible exposure time is realized through a mechanical shutter. The fluence, energy spectra and the corresponding linear energy transfer are determined by the source geometry and the material traversed. They were measured and calculated, yielding a dose rate of 8.2 ± 2.4 Gy/min. To improve cell growth on boPET foils, they were treated with air plasma. This treatment increased the polarity and thus the ability of cells attaching to the surface of the foil. Several tests including cell growth, staining for a marker of DNA double-strand breaks and a colony-forming assay were performed and confirm our dosimetry.Conclusion: With our setup, it is possible to irradiate cell cultures under defined conditions with α-particles. The plasma-treated foil is suitable for primary human cell cultures as shown in cell experiments, confirming also the expected number of particle traversals.


Assuntos
Partículas alfa , Amerício , Transferência Linear de Energia , Cultura Primária de Células , Animais , Células CHO , Linhagem Celular , Colágeno/química , Cricetinae , Cricetulus , Relação Dose-Resposta à Radiação , Histonas/metabolismo , Humanos , Queratinócitos/citologia , Oxigênio/metabolismo , Polietilenotereftalatos , Radiometria , Reprodutibilidade dos Testes
20.
Radiat Prot Dosimetry ; 188(2): 191-198, 2020 Jun 13.
Artigo em Inglês | MEDLINE | ID: mdl-31845739

RESUMO

This article highlights the issues of exposure inhomogeneity that are relative to eye lens monitoring for low-energy photons from 241Am and beta-rays from 90Sr/90Y including a personal protective equipment because eye lens exposure has been concerned more than before due to the proposed reduction of relevant dose limit. These nuclides are common and concerned sources in the nuclear industry. Our previous study presented a quantitative estimation of exposure inhomogeneity, which was applied to simple but typical exposure situations. For the present study, exposure inhomogeneity of 241Am was approximately within a factor of 1.6, implying a more homogeneous situation than expected. Regarding 90Sr/90Y exposure, estimation from both Hp(10) and Hp(0.07) on trunk would lead to an over- or underestimation by a factor of more than 10. In contrast, Hp(3) measurement on trunk will improve by up to a factor of 2. With respect to the personal protective equipment, lead apron and protective glasses are effective for the 60-keV photons for both anterior-posterior and rotational irradiations, while a full-face respirator can reduce the eye lens dose by approximately 17% for 90Sr/90Y betas. As a whole, this study demonstrated that the effect of protective equipment could be effectively incorporated into the homogeneity evaluation.


Assuntos
Cristalino , Exposição Ocupacional , Amerício , Exposição Ocupacional/análise , Exposição Ocupacional/prevenção & controle , Doses de Radiação , Radioisótopos de Estrôncio/análise , Radioisótopos de Ítrio/análise
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