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1.
Environ Sci Pollut Res Int ; 27(20): 25057-25068, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32347488

RESUMO

In the Chinese high-level radioactive waste geological disposal program, Gaomiaozi (GMZ) bentonite has been selected as the potential buffer/backfill material. After the closure of the repository, the Ca-OH-type alkaline solution (evolved cement water) released by cement degradation may last for more than 100,000 years. The bentonite will undergo the corrosion of evolved cement water (ECW) for a long period. This work focuses on the sorption property of GMZ bentonite altered by ECW. Firstly, the corrosion experiments on compacted GMZ specimens with the dry density of 1.70 Mg/m3 were carried out under constant volume conditions at two temperatures. Then, the sorption of europium (Eu (III)) onto the corroded GMZ bentonite was studied by batch experiments. The results of batch sorption tests indicate that the altered GMZ bentonite keeps an effective removal property with the uptake of Eu (III) more than 99%. The effect of high-temperature conditions of the repository on the sorption property of bentonite is not significant. The results also suggest that the evolved cement water presents no detrimental effect on the long-term adsorption performance of bentonite even under higher temperature conditions.


Assuntos
Bentonita , Resíduos Radioativos/análise , Adsorção , Európio , Temperatura , Água
2.
Chemosphere ; 241: 124964, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31604195

RESUMO

Around former glass factories in south eastern Sweden, there are dozens of dumps whose radioactivity and physico-chemical properties were not investigated previously. Thus, radiometric and physico-chemical characteristics of waste at Madesjö glass dump were studied to evaluate pre-recycling storage requirements and potential radiological and environmental risks. The material was sieved, hand-sorted, leached and scanned with X-Ray Fluorescence (XRF). External dose rates and activity concentrations of Naturally Occurring Radioactive Materials from 238U, 232Th series and 40K were also measured coupled with a radiological risk assessment. Results showed that the waste was 95% glass and dominated by fine fractions (<11.3 mm) at 43.6%. The fine fraction had pH 7.8, 2.6% moisture content, 123 mg kg-1 Total Dissolved Solids, 37.2 mg kg-1 Dissolved Organic Carbon and 10.5 mg kg-1 fluorides. Compared with Swedish EPA guidelines, the elements As, Cd, Pb and Zn were in hazardous concentrations while Pb leached more than the limits for inert and non-hazardous wastes. With 40K activity concentration up to 3000 Bq kg-1, enhanced external dose rates of 40K were established (0.20 µSv h-1) although no radiological risk was found since both External Hazard Index (Hex) and Gamma Index (Iγ) were <1. The glass dump needs remediation and storage of the waste materials under a safe hazardous waste class 'Bank Account' storage cell as a secondary resource for potential future recycling.


Assuntos
Fenômenos Químicos , Vidro/análise , Poluentes Radioativos/análise , Resíduos Radioativos/análise , Resíduos/análise , Resíduos Perigosos , Radioisótopos de Potássio/análise , Reciclagem , Espectrometria por Raios X , Suécia , Tório/análise , Urânio/análise
4.
Health Phys ; 118(1): 1-17, 2020 01.
Artigo em Inglês | MEDLINE | ID: mdl-31703016

RESUMO

A dose-based compliance methodology was developed for Waste Control Specialists, LLC, low-level radioactive waste facility in Andrews, Texas, that allows routine environmental measurement data to be evaluated not only at the end of a year to determine regulatory compliance, but also throughout the year as new data become available, providing a continuous assessment of the facility. The first step in the methodology is a screening step to determine the potential presence of site emissions in the environment, and screening levels are established for each environmental media sampled. The screening accounts for spatial variations observed in background for soil and temporal fluctuations observed in background for air. For groundwater, the natural activity concentrations in groundwater wells at the facility are highly variable, and therefore the methodology uses ratios for screening levels. The methodology compares the ratio of gross alpha to U + U to identify potentially abnormal alpha activity and the ratio of U to U to identify the potential presence of depleted uranium. Compliance evaluation is conducted for any samples that fail the screening step. Compliance evaluation uses the radionuclide-specific measurements to first determine (1) if the dose exceeds the background dose and if so, (2) the dose consequences, so that the appropriate investigation or action occurs. The compliance evaluation is applied to all environmental samples throughout the year and on an annual basis to determine regulatory compliance. The methodology is implemented in a cloud-based software application that is also made accessible to the regulator. The benefits of the methodology over the existing system are presented.


Assuntos
Monitoramento Ambiental/normas , Modelos Teóricos , Monitoramento de Radiação/métodos , Proteção Radiológica/normas , Resíduos Radioativos/análise , Urânio/análise , Instalações de Eliminação de Resíduos/normas , Poluentes Radioativos do Ar/análise , Água Subterrânea/química , Humanos , Proteção Radiológica/legislação & jurisprudência , Instalações de Eliminação de Resíduos/legislação & jurisprudência , Poluentes Radioativos da Água/análise
6.
Mar Pollut Bull ; 146: 454-461, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31426180

RESUMO

This work is a first contribution to the knowledge of natural radionuclides (226Ra, 238U, 40K, and 232Th) activities in phosphate rock (NORM), phosphogypsum, and phosphogypsum foam (TENORM) from the coastal fertilizer plants of Gabes (Southeastern Tunisia) and the assessment of their radiation hazards on human health and the surrounding environment. In the three studied materials, activities were found to be in the range of 35.4 (40K)-375.1 (226Ra), 10.0 (40K)-220.2 (226Ra), and 79.2 (232Th)-1168.6 Bq kg-1 (226Ra), respectively. Considering the studied radionuclides and materials, the corresponding decreasing activity orders were found to be 226Ra > 238U > 40K > 232Th and PGF > PR > PG, respectively. All human health hazard indices exceeded the worldwide recommended safety limits, which show that the workers in Gabes phosphate fertilizer plants as well as the neighboring human community may potentially be exposed to significant radiation, which may cause several diseases and malformations. It is therefore recommended to avoid and/or reduce the potential fertilizer industry radioactive impact in the area.


Assuntos
Fertilizantes/análise , Resíduos Industriais/análise , Fosfatos/química , Resíduos Radioativos/análise , Radioisótopos/análise , Sulfato de Cálcio/análise , Sulfato de Cálcio/química , Humanos , Mar Mediterrâneo , Fósforo/análise , Fósforo/química , Medição de Risco , Tunísia
8.
Environ Pollut ; 252(Pt B): 1491-1499, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31265960

RESUMO

Understanding the influence of colloids on radionuclide migration is of significance to evaluate environmental risks for radioactive waste disposals. In order to formulate an appropriate modelling framework that can quantify and interpret the anomalous transport of Strontium (Sr) in the absence and presence of colloids, the continuous time random walk (CTRW) approach is implemented in this work using available experimental information. The results show that the transport of Sr and its recovery are enhanced in the presence of colloids. The causes can be largely attributed to the trap-release processes, e.g. electrostatic interactions of Sr, colloids and natural sediments, and differences in pore structures, which gave rise to the varying interstitial velocities of dissolved and, if any, colloid-associated Sr. Good agreement between the CTRW simulations and the column-scale observations is demonstrated. Regardless of the presence of colloids, the CTRW modelling captures the characteristics of non-Fickian anomalous transport (0 < ß < 2) of Sr. In particular, a range of 0 < ß < 1, corresponding to the cases with greater recoveries, reveal strongly non-Fickian transport with distinctive earlier arrivals and tailing effects, likely due to the physicochemical heterogeneities, i.e. the repulsive interactions and/or the macro-pores originating from local heterogeneities. The results imply that colloids can increase the Sr transport as a barrier of Sr sorption onto sediments herein, apart from often being carriers of sored radionuclides in aqueous phase. From a modelling perspective, the findings show that the established CTRW model is valid for quantifying the non-Fickian and promoted transport of Sr with colloids.


Assuntos
Coloides/química , Resíduos Radioativos/análise , Eliminação de Resíduos/métodos , Poluentes Radioativos do Solo/análise , Estrôncio/análise , Poluentes Radioativos da Água/análise , Radioisótopos/análise
9.
Environ Sci Pollut Res Int ; 26(24): 25235-25246, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31256394

RESUMO

We explored the effect of the presence or absence of humic acid (HA) on the sorption behaviour of Sr onto soil. We examined three different experimental cases for Sr sorption: (1) sorption in the presence of only colloidal HA, (2) sorption in the presence of only soil and (3) sorption in the presence of both colloidal HA and soil (HS). A batch technique was used to study the influencing factors, including the amount of colloidal HA, solid content, pH, initial concentration of Sr and contact time. The experiments showed that the influencing factors significantly affected the sorption process. For example, in the case of soil and HS, the sorption percentage increased rapidly with increasing solid content at m/V < 20 g/L, changing from 8.35% and 37.54% to 49.09% and 77.03%, respectively. Moreover, scanning electron microscopy and Fourier transform infrared spectroscopy were used to characterize samples. The kinetics and isotherms of Sr were best described by the pseudo-second-order and Langmuir models, which indicated that the process was controlled by chemisorption and uniform monolayer sorption with constant energy on the outer surface. These findings provide valuable information for predicting strontium migration in radioactive waste disposal sites.


Assuntos
Coloides/química , Substâncias Húmicas , Resíduos Radioativos/análise , Poluentes do Solo/química , Estrôncio/química , Instalações de Eliminação de Resíduos , Adsorção , Geologia , Cinética , Radioatividade , Solo/química , Poluentes do Solo/análise , Espectroscopia de Infravermelho com Transformada de Fourier
10.
Sci Total Environ ; 692: 219-232, 2019 Nov 20.
Artigo em Inglês | MEDLINE | ID: mdl-31349163

RESUMO

The multi-barrier deep geological repository system is currently considered as one of the safest option for the disposal of high-level radioactive wastes. Indigenous microorganisms of bentonites may affect the structure and stability of these clays through Fe-containing minerals biotransformation and radionuclides mobilization. The present work aimed to investigate the behavior of bentonite and its bacterial community in the case of a uranium leakage from the waste containers. Hence, bentonite microcosms were amended with uranyl nitrate (U) and glycerol-2-phosphate (G2P) and incubated aerobically for 6 months. Next generation 16S rRNA gene sequencing revealed that the bacterial populations of all treated microcosms were dominated by Actinobacteria and Proteobacteria, accounting for >50% of the community. Additionally, G2P and nitrate had a remarkable effect on the bacterial diversity of bentonites by the enrichment of bacteria involved in the nitrogen and carbon biogeochemical cycles (e.g. Azotobacter). A significant presence of sulfate-reducing bacteria such as Desulfonauticus and Desulfomicrobium were detected in the U-treated microcosms. The actinobacteria Amycolatopsis was enriched in G2P­uranium amended bentonites. High-Angle Annular Dark-Field Scanning Transmission Electron Microscopy analyses showed the capacity of Amycolatopsis and a bentonite consortium formed by Bradyrhizobium-Rhizobium and Pseudomonas to precipitate U as U phosphate mineral phases, probably due to the phosphatase activity. The different amendments did not affect the mineralogy of the bentonite pointing to a high structural stability. These results would help to predict the impact of microbial processes on the biogeochemical cycles of elements (N and U) within the bentonite barrier under repository relevant conditions and to determine the changes in the microbial community induced by a uranium release.


Assuntos
Bactérias/metabolismo , Bentonita/análise , Glicerofosfatos/metabolismo , Microbiota/efeitos dos fármacos , Resíduos Radioativos/análise , Urânio/metabolismo , Bactérias/classificação
11.
J Environ Radioact ; 205-206: 61-71, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31102907

RESUMO

Assessments of the environmental impact of C-14 disposal often assume that C-14 is converted into gases that are able to migrate to the surface, where they pose a radiological risk. However, uncertainties, associated with the long-term release of C-14 from graphite and the evolution in the post-closure environment of a geological disposal facility (GDF), exist. In this paper, an integrated modelling framework has been developed to investigate these uncertainties. The modelling framework consists of a biogeochemical near field model which interfaces with a geosphere/biosphere model and it is verified by comparing the results to those obtained from other models. A sensitivity analysis discloses that a faster mid chain scission rate of stopped cellulose about four orders of magnitude assesses a twice higher effective dose. In another scenario, which is related to the control of microbial activity by pH and the availability of carbon dioxide to microbes, the effective dose is two orders of magnitude higher compared with a reference scenario. This modelling work illustrates also the importance of far field parameters, such as the rock permeability and the release area of gas pathway, to the assessment of effective dose.


Assuntos
Radioisótopos de Carbono/análise , Monitoramento de Radiação , Resíduos Radioativos/análise , Instalações de Eliminação de Resíduos , Meio Ambiente , Modelos Teóricos , Doses de Radiação , Medição de Risco
12.
Health Phys ; 117(4): 378-387, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-30958804

RESUMO

Waterborne releases to the Techa River from the Mayak plutonium facility in Russia during 1949-1956 resulted in significant doses to persons living downstream. The dosimetry system Techa River Dosimetry System-2016D has been developed, which provides individual doses of external and internal exposure for the members of the Techa River cohort and other persons who were exposed to releases of radioactive material to the Southern Urals. The results of computation of individual doses absorbed in red bone marrow and extraskeletal tissues for the Techa River cohort members (29,647 persons) are presented, which are based on residence histories on the contaminated Techa River and the East Urals Radioactive Trace, which was formed in 1957 as a result of the Kyshtym Accident. Available Sr body-burden measurements and available information on individual household locations have been used for refinement of individual dose estimates. Techa River Dosimetry System-2016D-based dose estimates will be used for verification of risk of low-dose-rate effects of ionizing radiation in the Techa River cohort.


Assuntos
Exposição Ambiental/análise , Monitoramento de Radiação/métodos , Resíduos Radioativos/análise , Rios/química , Radioisótopos de Estrôncio/análise , Poluentes Radioativos da Água/análise , Carga Corporal (Radioterapia) , Estudos de Coortes , Feminino , Humanos , Masculino , Doses de Radiação , Radioisótopos de Estrôncio/farmacocinética , Distribuição Tecidual , Poluentes Radioativos da Água/farmacocinética
13.
Chemosphere ; 224: 776-785, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-30851529

RESUMO

A simple one-step approach for fabricating copper ferrocyanide-embedded magnetic hydrogel beads (CuFC-MHBs) was designed, and the beads were applied to the effective removal of cesium (Cs) and then magnetically separated from water. The polyvinyl alcohol (PVA)-coated CuFC (PVA-CuFC) was first synthesized using PVA as a stabilizer and subsequently embedded in magnetic hydrogel beads made of a cross-linked network between the PVA and magnetic iron oxide nanoparticles that was prepared through the simple dropwise addition of a mixed solution of PVA-CuFC, PVA and iron salt into an ammonium hydroxide solution. The synthesis and chemical immobilization of the PVA-CuFC in the magnetic beads were simple, facile and achieved in one pot, and the process is scalable and convenient for the large-scale treatment of Cs-contaminated water. The resulting CuFC-MHBs showed effective Cs removal performance with a high Kd value of 66,780 mL/g and excellent structural stability without the release of CuFC for at least 1 month and could be effectively separated from water by an external magnet. Moreover, the CuFC-MHBs selectively adsorbed Cs with high Kd values in the presence of various competing ions, such as in simulated groundwater (24,500 mL/g) and seawater (8290 mL/g), and maintained their Cs absorption ability in a wide pH range from 3 to 11. The convenient fabrication method and effective removal of Cs from various aqueous media demonstrated that the CuFC-MHBs have great potential for practical application in the decontamination of Cs-contaminated water sources caused by nuclear accidents and radioactive liquid waste in various nuclear industry fields.


Assuntos
Césio/química , Ferrocianetos/química , Ferrocianetos/síntese química , Hidrogéis/química , Resíduos Radioativos/análise , Poluentes Químicos da Água/análise , Poluentes Radioativos da Água/análise , Purificação da Água/métodos , Adsorção , Monitoramento Ambiental/métodos , Cinética , Imãs/química , Álcool de Polivinil/química , Água do Mar , Água/química
14.
Environ Pollut ; 248: 82-89, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-30780070

RESUMO

One of the most important reasons for the controversy over the development of nuclear energy is the proper disposal of spent fuel. Separation of actinide and lanthanide ions is an important part of safe long-term storage of radioactive waste. Herein, a three-dimensional (3D) graphene-based macrostructure (GOCS) was utilized to remove actinide thorium and lanthanide europium ions from aqueous solutions. The adsorption of Eu(III) and Th(IV) on the GOCS was evaluated as a function of adsorption time, solution pH, initial ion concentrations, and ionic strength. The experimentally determined maximum adsorption capacities of this GOCS for Eu(III) (pH 6.0) and Th(IV) (pH 3.0) are as high as 150 and 220 mg/g, respectively. By using Fourier transformation infrared (FT-IR), X-ray photoelectron (XPS), and extended X-ray absorption fine structure (EXAFS) spectroscopy, we concluded that the Eu(III) and Th(IV) adsorption was predominantly attributed to the inner-sphere coordination with various oxygen- and nitrogen-containing functional groups on GOCS surfaces. Our selective adsorption results demonstrate that the actinide and lanthanide ions can be effectively separated from transition metal ions. This study provides new clues to the overall recycling of actinide and lanthanide ions in radioactive environmental pollution treatments.


Assuntos
Quitosana/química , Recuperação e Remediação Ambiental/métodos , Európio/química , Grafite/química , Resíduos Radioativos/análise , Tório/química , Adsorção , Concentração de Íons de Hidrogênio , Centrais Nucleares , Concentração Osmolar , Espectroscopia de Infravermelho com Transformada de Fourier , Espectroscopia por Absorção de Raios X
15.
Phys Med Biol ; 64(5): 055008, 2019 02 25.
Artigo em Inglês | MEDLINE | ID: mdl-30669132

RESUMO

Past and prospective shortages of medical radioisotopes have driven recent developments in the direct production of 99mTc via the 100Mo(p,2n)99mTc reaction. The cyclotron-based production method has been shown to successfully produce 99mTc, however trace impurities present in the enriched molybdenum target can also lead to the unintended creation of other radioisotopes which constitute waste. The isotopic composition of the waste has to be investigated in order to determine how it can be handled, transported and safely stored. In this article, we report which waste radioisotopes are created alongside 99mTc during target irradiation. Results are based on the gamma spectroscopy of waste produced. Significant complexities in the emission spectra made automated identification of radioisotopes inaccurate; complexities were resolved using a manual radioisotope identification procedure. The impact of target composition, integrated beam current and duration of target irradiation on the waste produced was studied. Results indicate that an average of 0.059 ± 0.003 GBq of waste is generated per 1 GBq of 99mTc produced. Two-thirds of the total waste activity produced was attributed to 99Mo (T 1/2 = 66 h) alone, while a total of fifty radioisotopes were found in the waste. Long-lived isotopes (T 1/2 > 2 months) constituted only 1% of the total waste activity at end of beam (EOB). In conclusion, it was determined that the waste generated during cyclotron-based 99mTc production was acceptably low for routine clinical production.


Assuntos
Ciclotrons , Resíduos Radioativos/análise , Radioquímica/instrumentação , Tecnécio/química , Raios gama , Isótopos/química , Molibdênio/química , Segurança
16.
J Environ Radioact ; 199-200: 45-57, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30685638

RESUMO

Stand-off, in-situ, laser induced breakdown spectroscopy (LIBS) offers a rapid, safe, and cost-effective method for discrimination of radioactive waste materials arising during the operation of nuclear plants and from decommissioning activities. Characterisation of waste materials is a critical activity in understanding the nature of the waste, ensuring hazardous material is managed safely and that waste can be segregated for reuse, recycle or sentenced for appropriate disposal. Characterisation of materials, often in hostile environments, requires the ability to remotely differentiate between materials in terms of their chemical composition and radioactivity. This proposition was tested using a case study on nuclear grade graphite. Graphite has been used extensively as a moderator material in many nuclear reactors. Internationally, over 250,000 tons of various nuclear-grade graphite, and graphite-bearing, materials exist. These are a major issue for nuclear decommissioning and radioactive waste management, due to the long half-lives of the associated 14C and 36Cl isotopes. LIBS offers a method for discrimination of nuclear grade graphites and other carbon and non-carbon-bearing wastes. This paper describes the development of a workflow method, including LIBS measurement analysis, for the discrimination of pre-irradiated nuclear 'Pile Grade A' (PGA) graphite moderator rod and domestic lumpwood charcoal, which act as surrogates for nuclear grade graphite and other carbon-bearing wastes. A new analysis workflow comprising the examination of spectral characteristics, multivariate analysis and molecular isotopic spectroscopy is proposed to enable rapid segregation of graphite from a heterogeneous waste stream. Enhanced characterisation techniques have the potential to significantly reduce the cost of decommissioning large parts of legacy nuclear generation plants.


Assuntos
Monitoramento de Radiação/métodos , Resíduos Radioativos/análise , Gerenciamento de Resíduos/métodos , Grafite/química , Reatores Nucleares , Reciclagem , Fluxo de Trabalho
17.
J Environ Radioact ; 196: 164-170, 2019 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-27887973

RESUMO

The Techa Cascade of water reservoirs (TCR) is one of the most environmentally challenging facilities resulted from FSUE "PA "Mayak" operations. Its reservoirs hold over 360 mln m3 of liquid radioactive waste with a total activity of some 5 × 1015 Bq. A set of actions implemented under a special State program involving the development of a strategic plan aimed at complete elimination of TCR challenges (Strategic Master-Plan for the Techa Cascade of water reservoirs) resulted in considerable reduction of potential hazards associated with this facility. The paper summarizes the key elements of this master-plan: defining TCR final state, feasibility study of the main strategies aimed at its attainment, evaluation of relevant long-term decommissioning strategy, development of computational tools enabling the long-term forecast of TCR behavior depending on various engineering solutions and different weather conditions.


Assuntos
Centrais Nucleares , Resíduos Radioativos/análise , Instalações de Eliminação de Resíduos , Recuperação e Remediação Ambiental
18.
Environ Sci Pollut Res Int ; 25(30): 29996-30008, 2018 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-30187403

RESUMO

Radiostrontium is a common product of nuclear fission and was emitted into the environment in the course of nuclear weapon tests as well as from nuclear reactor accidents. The release of 90Sr and 89Sr into the environment can pose health threats due to their characteristics such as high specific activities and easy access in human body due to its chemical analogy to calcium. Radiostrontium enters the human food chain by the consumption of plants grown on sites comprising fission-derived radionuclides. For humans, Sr is not an essential element, but, due to solubility in water and homology with calcium, once interred in the body, it gets deposited in bones and in teeth. This concern has drawn the attention of researchers throughout the globe to develop sustainable treatment processes to remediate soil and water resources. Nowadays, phytoremediation has become a promising approach for the remediation of large extents of toxic heavy metals. Some of the plants have been reported to accumulate Sr inside their biomass but detailed mechanisms at genetic level are still to be uncovered. However, there is inadequate information offered to assess the possibility of this remediation approach. This review highlights phytoremediation approach for Sr and explains in detail the uptake mechanism inside plants.


Assuntos
Recuperação e Remediação Ambiental/métodos , Plantas/metabolismo , Radioisótopos de Estrôncio/metabolismo , Biodegradação Ambiental , Plantas/química , Resíduos Radioativos/análise , Poluentes do Solo/análise , Poluentes do Solo/metabolismo , Radioisótopos de Estrôncio/análise
19.
Health Phys ; 115(4): 539-544, 2018 10.
Artigo em Inglês | MEDLINE | ID: mdl-30148819

RESUMO

The dose rate profile at different heights above the ground and as a function of distance from the north, west, and south walls of an above-ground waste storage facility was analyzed using the Monte Carlo n-Particle Transport eXtended (MCNPX) radiation transport code. The waste storage facility houses 9,996 waste barrels of conditioned waste. The facility has concrete shielding added to the building walls on the north, west, and east sides, with no such additional shielding towards the roof or the south side wall; instead, the distance from the first row of barrels to the wall is extended to allow for maneuverability of a crane on the south side. The dose rate is computed as a function of distance using MCNPX and assuming a homogeneous Co distribution in each waste barrel. Different dose regions are identified and analyzed based on graphical features and best-fit functions. The dose rates were expected to be largest at the wall of the facility and subsequently decrease continuously with distance from the repository; however, our analysis indicates a peak in dose rate observed for all heights on the north and west sides of the facility. This peak is likely due to scattering in the shielding material and atmosphere, and possibly could be ascribed to skyshine. The difference between the dose rate at 1 m outside the wall and the peak dose rate is significant, and indicates that the dose rate measured close to the wall may not always be conservative for extended sources, such as an above-ground waste storage facility.


Assuntos
Arquitetura de Instituições de Saúde , Modelos Estatísticos , Monitoramento de Radiação/métodos , Proteção Radiológica , Resíduos Radioativos/análise , Eliminação de Resíduos/métodos , Simulação por Computador , Humanos , Método de Monte Carlo , Doses de Radiação
20.
J Environ Radioact ; 192: 513-523, 2018 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-30114622

RESUMO

The study demonstrates the effect of sorption properties of fractured host rocks from the Yeniseysky site (Nizhne-Kansky rock massif, Krasnoyarsk region) on the migration of dissolved radioactive components (137Cs, 90Sr, 79Se, 99Tc, 152(154)Eu, 239(240)Pu) in the deep geological conditions of a high-level radioactive waste repository. Estimates of radionuclide distribution coefficients between the aqueous solution and fractured rocks obtained from sorption experiments were used to study the influence of various petrographic types and fracture-filling substances on the retardation of radioactive components by different fractured rock units of Nizhne-Kansky rock massif. Based on the results of sorption experiments, we concluded that the type and attributes of rock discontinuities, as well as the mineral composition of the material in fractures, are crucial for the immobilization of radionuclides during their migration through a geological environment.


Assuntos
Absorção Fisico-Química , Modelos Químicos , Resíduos Radioativos/análise , Radioisótopos de Césio/análise , Eliminação de Resíduos , Federação Russa , Radioisótopos de Estrôncio/análise , Tecnécio/análise
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