scholarly journals Attenuation of beta radiation in granular matrices: implications for trapped-charge dating

2021 ◽  
Author(s):  
Alastair Charles Cunningham ◽  
Jan-Pieter Buylaert ◽  
Andrew Sean Murray
Keyword(s):  
Grain Size ◽  
Dose Rate ◽  
Radiation Transport ◽  
Beta Radiation ◽  
Host Matrix ◽  
Beta Particles ◽  
Dose Rates ◽  
Homogenous Medium ◽  
Beta Dose ◽  
Trapped Charge

Abstract. Mineral grains within sediment or rock absorb a radiation dose from the decay of radionuclides in the host matrix. For the beta dose component, the estimated dose rate must be adjusted for the attenuation of beta particles within the mineral grains. Standard calculations, originally designed for thermoluminescence dating of pottery, assume that the grain is embedded in a homogenous medium. However, most current applications of trapped-charge dating concern sand- or silt-sized dosimeters embedded in granular sediment. In such cases, the radionuclide sources are not homogeneous, but are localized in discrete grains or held on grain surfaces. We show here that the mean dose rate to dosimeter grains in a granular matrix is dependent on the grain-size distributions of the source grains, and of the bulk sediment, as well as on the grain size of the dosimeters. We further argue that U and Th sources are likely to be held primarily on grain surfaces, which causes the dose rate to dosimeter grains to be significantly higher than for sources distributed uniformly throughout grains. For a typical well-sorted medium sand, the beta dose rates derived from surface U and Th sources are higher by 9 % and 14 %, respectively, compared to a homogenous distribution of sources. We account for these effects using an expanded model of beta attenuation, and validate the model against Monte Carlo radiation transport simulations within a geometry of packed spheres.

Electron and Beta Dose Rates of UO2 Pellet and Fuel Rod

2013 ◽  
Author(s):  
Guoqing Zhang ◽  
Xuexin Wang ◽  
Jiangang Zhang ◽  
Dajie Zhuang ◽  
Chaoduan Li ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Dose Rate ◽  
Radiation Protection ◽  
High Dose Rate ◽  
High Dose ◽  
Electron Dose ◽  
Dose Rates ◽  
Fuel Rod ◽  
Calculation Results ◽  
Beta Dose

The isotopes of uranium and their daughter nuclides inside the UO2 pellet emit mono-energetic electrons and beta rays, which generate rather high dose rate near the UO2 pellet and could cause exposure to workers. In this work calculations of electron dose rates have been carried out with Monte Carlo codes, MCNPX and Geant4, for a UO2 pellet and a fuel rod. Comparisons between calculations and measurements have been carried out to verify the calculation results. The results could be used to estimate the dose produced by electrons and beta rays, which could be used to make optimization for radiation protection purpose.

Gamma-Ray Imaging for Generating 3D Dose Rate Maps

2011 ◽  
Author(s):  
Karl Hughes ◽  
Edmund Cracknell
Keyword(s):  
Dose Rate ◽  
Source Term ◽  
Gamma Ray ◽  
Radiation Transport ◽  
Simple Procedure ◽  
Two Dimensions ◽  
Nuclear Industry ◽  
Dose Rates ◽  
Physical Measurements ◽  
Gamma Ray Imaging

The use of gamma-ray imaging has become established in the nuclear industry, especially in the fields of decommissioning and clean-up, for identifying the origins of elevated gamma dose rates. Since their first use in the mid 1990s, gamma-ray imaging devices, such as the Babcock RadScan, have been used to produce colour overlay plots that indicate, in two dimensions, the locations and distribution of radioactive contaminants. This information is invaluable in helping project managers to plan clean-up and shielding activities, ensuring that all work carried out is cost effective and ALARP. Recent work undertaken by Babcock demonstrates the capability to generate 3D maps of dose rate fields from the output of gamma-ray imaging work. The combination of gamma-ray imaging survey and resultant dose map is a very powerful tool for planning decommissioning. The conventional gamma-ray image provides an unambiguous identification of the origins of the dose rates present whilst the 3D dose map allows the dose uptake to personnel to be determined. Furthermore, the ability to quantify the effect of clean-up or shielding on the dose rates is possible, providing project teams with a metric for determining the best option available. A simple procedure is followed to generate 3D dose maps from gamma-ray imaging data. Firstly a model of the plant area is constructed. This model can be generated from existing plant drawings, from laser scan surveys, or from simple physical measurements taken on plant. The model includes information about the shielding properties of the plant structures, and can be easily modified to demonstrate the effect of adding more shielding, or of reducing any of the source terms. The data from a gamma-ray imager, such as RadScan, are analysed to generate distributions of radionuclide specific activities. These activities are entered into the model and form the source term. The advantage of using a gamma ray imager to generate the source term is that the location and distribution of the source is accurately represented in the model, thus ensuring that accurate dose maps are generated. Once the model has been completed it is analysed using a radiation transport modelling code such as Attila to produce the 3D dose maps (although other codes are available which could perform the same function). This paper describes an example of how this technique has been used to generate 3D dose maps for a customer and builds on earlier work with RadScan which provides quantitative in-cell assay.

scholarly journals Distribution in SAR palaeodoses due to spatial heterogeniety of natural beta dose

2011 ◽  
Vol 38 (3) ◽  
pp. 190-198 ◽  
Author(s):  
Naveen Chauhan ◽  
Ashok Singhvi
Keyword(s):  
Radiation Dose ◽  
Luminescence Dating ◽  
Beta Radiation ◽  
Beta Particles ◽  
Beta Emitters ◽  
Minimum Number ◽  
Sensitivity Changes ◽  
Individual Grains ◽  
Beta Dose ◽  
Quartz Grains

Abstract In luminescence dating of sediments, Mayya et al. (2006) pointed out that at single grain level, the beta dose for quartz grains is heterogeneous. This heterogeneity arises due the fact that the total potassium in sediment is contributed by few feldspar grains with up to 11–14% stoichiometric potassium (Huntley and Baril, 1997). Beta particles have a range of ∼2 mm, which is comparable to grain sizes and inter-grain distances. This fact implies that the spatial fluctuation of beta emitters (K-feldspars) around individual quartz grains results in heterogeneous dose deposition. These fluctuations therefore, lead to an inherent spread in palaeodoses received by individual quartz grains. In this study, we compute the spread in single aliquot palaeodoses that arises exclusively due to heterogeneity in beta radiation dose received by individual grains. We thus postulate that ‘single aliquots’ (comprising several — typically 100 — heterogeneously irradiated single grains) would have an inherent spread in the palaeodose. In this work, we used Monte Carlo simulations to quantify the extent of spread in palaeodoses arising due to heterogeneity of beta dose and hence put a limit on the precision of age estimation. Simulations results indicated, that, 1) the average of the single aliquot palaeodoses provides the closest approximation to the true palaeodose, 2) the minimum number of aliquots that are needed to obtain a robust estimate of average palaeodose value depend upon desired precision and the concentration of K, and 3) the ratio of maximum to minimum single aliquot palaeodose values for a given K concentration provides a measure of inherent spread arising due to beta dose heterogeneity. Any spread over and above this range, can be ascribed to other sources such as heterogeneous bleaching and sensitivity changes. Radiation dose from other uniformly distributed sources of beta particles (U, Th and Rb) however would reduce this spread.

scholarly journals Radiation Awareness for Endovascular Abdominal Aortic Aneurysm Repair in the Hybrid Operating Room: An Instant Operator Risk Chart for Daily Practice

2021 ◽  
pp. 152660282110074
Author(s):  
Quirina M. B. de Ruiter ◽  
Frans L. Moll ◽  
Constantijn E. V. B. Hazenberg ◽  
Joost A. van Herwaarden
Keyword(s):  
Radiation Dose ◽  
Dose Rate ◽  
Effect Size ◽  
Radiation Risk ◽  
Dose Limit ◽  
Access Site ◽  
Femoral Access ◽  
Dose Rates ◽  
Rate Prediction ◽  
Operator Dose

Introduction: While the operator radiation dose rates are correlated to patient radiation dose rates, discrepancies may exist in the effect size of each individual radiation dose predictors. An operator dose rate prediction model was developed, compared with the patient dose rate prediction model, and converted to an instant operator risk chart. Materials and Methods: The radiation dose rates (DRoperator for the operator and DRpatient for the patient) from 12,865 abdomen X-ray acquisitions were selected from 50 unique patients undergoing standard or complex endovascular aortic repair (EVAR) in the hybrid operating room with a fixed C-arm. The radiation dose rates were analyzed using a log-linear multivariable mixed model (with the patient as the random effect) and incorporated varying (patient and C-arm) radiation dose predictors combined with the vascular access site. The operator dose rate models were used to predict the expected radiation exposure duration until an operator may be at risk to reach the 20 mSv year dose limit. The dose rate prediction models were translated into an instant operator radiation risk chart. Results: In the multivariate patient and operator fluoroscopy dose rate models, lower DRoperator than DRpatient effect size was found for radiation protocol (2.06 for patient vs 1.4 for operator changing from low to medium protocol) and C-arm angulation. Comparable effect sizes for both DRoperator and DRpatient were found for body mass index (1.25 for patient and 1.27 for the operator) and irradiated field. A higher effect size for the DRoperator than DRpatient was found for C-arm rotation (1.24 for the patient vs 1.69 for the operator) and exchanging from femoral access site to brachial access (1.05 for patient vs 2.5 for the operator). Operators may reach their yearly 20 mSv year dose limit after 941 minutes from the femoral access vs 358 minutes of digital subtraction angiography radiation from the brachial access. Conclusion: The operator dose rates were correlated to patient dose rate; however, C-arm angulation and changing from femoral to brachial vascular access site may disproportionally increase the operator radiation risk compared with the patient radiation risk. An instant risk chart may improve operator dose awareness during EVAR.

Kinetics of DNA Repair Under Chronic Irradiation at Low and Medium Dose Rates in Repair Proficient and Repair Compromised Normal Fibroblasts

2021 ◽  
Author(s):  
Elena K. Zaharieva ◽  
Megumi Sasatani ◽  
Kenji Kamiya
Keyword(s):  
Dna Damage ◽  
Dna Repair ◽  
Dose Rate ◽  
Dose Response ◽  
Chronic Irradiation ◽  
Dose Rates ◽  
Chronic Radiation ◽  
Damage Repair ◽  
Kinetics Of ◽  
Medium Dose

We present time and dose dependencies for the formation of 53BP1 and γH2AX DNA damage repair foci after chronic radiation exposure at dose rates of 140, 250 and 450 mGy/day from 3 to 96 h, in human and mouse repair proficient and ATM or DNA-PK deficient repair compromised cell models. We describe the time/dose-response curves using a mathematical equation which contains a linear component for the induction of DNA damage repair foci after irradiation, and an exponential component for their resolution. We show that under conditions of chronic irradiation at low and medium dose rates, the processes of DNA double-strand breaks (DSBs) induction and repair establish an equilibrium, which in repair proficient cells manifests as a plateau-shaped dose-response where the plateau is reached within the first 24 h postirradiation, and its height is proportionate to the radiation dose rate. In contrast, in repair compromised cells, where the rate of repair may be exceeded by the DSB induction rate, DNA damage accumulates with time of exposure and total absorbed dose. In addition, we discuss the biological meaning of the observed dependencies by presenting the frequency of micronuclei formation under the same irradiation conditions as a marker of radiation-induced genomic instability. We believe that the data and analysis presented here shed light on the kinetics of DNA repair under chronic radiation and are useful for future studies in the low-to-medium dose rate range.

scholarly journals Serum Metabolomic Alterations Associated with Cesium-137 Internal Emitter Delivered in Various Dose Rates

Metabolites ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 270
Author(s):  
Heng-Hong Li ◽  
Yun-Tien Lin ◽  
Evagelia C. Laiakis ◽  
Maryam Goudarzi ◽  
Waylon Weber ◽  
...  
Keyword(s):  
Dose Rate ◽  
Cumulative Dose ◽  
Low Dose ◽  
Biological Effects ◽  
Serum Samples ◽  
Dose Rates ◽  
Sphingosine 1 Phosphate ◽  
Cesium 137 ◽  
Dose Rate Effect ◽  
Medium Dose

Our laboratory and others have use radiation metabolomics to assess responses in order to develop biomarkers reflecting exposure and level of injury. To expand the types of exposure and compare to previously published results, metabolomic analysis has been carried out using serum samples from mice exposed to 137Cs internal emitters. Animals were injected intraperitoneally with 137CsCl solutions of varying radioactivity, and the absorbed doses were calculated. To determine the dose rate effect, serum samples were collected at 2, 3, 5, 7, and 14 days after injection. Based on the time for each group receiving the cumulative dose of 4 Gy, the dose rate for each group was determined. The dose rates analyzed were 0.16 Gy/day (low), 0.69 Gy/day (medium), and 1.25 Gy/day (high). The results indicated that at a cumulative dose of 4 Gy, the low dose rate group had the least number of statistically significantly differential spectral features. Some identified metabolites showed common changes for different dose rates. For example, significantly altered levels of oleamide and sphingosine 1-phosphate were seen in all three groups. On the other hand, the intensity of three amino acids, Isoleucine, Phenylalanine and Arginine, significantly decreased only in the medium dose rate group. These findings have the potential to be used in assessing the exposure and the biological effects of internal emitters.

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