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1.
J Environ Radioact ; 208-209: 106030, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31476610

RESUMO

The Comprehensive Nuclear-Test-Ban Treaty (CTBT) bans all nuclear explosions, including those detonated from an underwater nuclear explosion. To improve the understanding of the radionuclide signatures of such an event, and whether it would be detectable under the verification regime of the CTBT, the 1955 Wigwam underwater nuclear explosive test has been modelled. Inventory calculations and atmospheric transport modelling has been performed to estimate the activity at the radionuclide stations (RN) of the International Monitoring System (IMS). This has utilized reported release values (0.92%) and meteorological data from the event. The research shows that there is a high probability that Wigwam would have been detectable at U.S. IMS stations at Wake Island (RN77) at 8.4 d, Upi, Guam (RN80) at 10.7 d and Sand Point, AK (RN71) at 13.7 d. At these locations, the majority of IMS relevant radionuclides were fission products, such that additional radionuclides from the seawater activation had largely decayed before reaching the stations.


Assuntos
Armas Nucleares , Monitoramento de Radiação , Poluentes Radioativos da Água/análise , Explosões , Polinésia , Água do Mar , Radioisótopos de Xenônio/análise
2.
J Environ Radioact ; 208-209: 106037, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31476609

RESUMO

Pacific Northwest National Laboratory (PNNL) staff developed the Radionuclide Aerosol Sampler Analyzer (RASA) for worldwide aerosol monitoring in the 1990s. Recently, researchers at PNNL and Creare, LLC, have investigated possibilities for how RASA could be improved, based on lessons learned from more than 15 years of continuous operation, including during the Fukushima Daiichi Nuclear Power Plant disaster. Key themes addressed in upgrade possibilities include having a modular approach to additional radionuclide measurements, optimizing the sampling/analyzing times to improve detection location capabilities, and reducing power consumption by using electrostatic collection versus classic filtration collection. These individual efforts have been made in a modular context that might constitute retrofits to the existing RASA, modular components that could improve a manual monitoring approach, or a completely new RASA. Substantial optimization of the detection and location capabilities of an aerosol network is possible and new missions could be addressed by including additional measurements.


Assuntos
Aerossóis/análise , Poluentes Radioativos do Ar/análise , Monitoramento de Radiação , Acidente Nuclear de Fukushima
3.
J Environ Radioact ; 208-209: 106039, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31491585

RESUMO

An alpine ice core, extracted from the Adamello glacier (Central Italian Alps), was analyzed in its entire length through low background γ-spectroscopy, for the detection of 137Cs. Our results show that in glacier ice 137Cs is tightly bound to insoluble particulate matter inside the ice core, and it is therefore possible to restrict γ-spectroscopy analysis to particulate matter only. We show how the sensibility of the detection limit can be improved by almost one order of magnitude by using a well-type detector instead of a coaxial one. Hypothesis on the dating of some radioactive layers are also hereby presented.


Assuntos
Radioisótopos de Césio/análise , Camada de Gelo/química , Monitoramento de Radiação , Poluentes Radioativos/análise , Itália
4.
J Environ Radioact ; 208-209: 106029, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31491586

RESUMO

Long term radioactivity monitoring programs contribute to the understanding of the behavior of radionuclides in the environment. This work aims to investigate the long term behavior of Cesium-137 in pasture ecosystem (root soil, grass and cow's milk) by using of more than twenty five years monitoring data collected at ten of French pasture sites contaminated by atmospheric fallouts from Chernobyl and nuclear atmospheric tests. We estimated with a simple exponential model the long term effective half-lives of radiocesium in root soil, grass vegetation and cow's milk along with their associated uncertainties. The average values of the effective half-lives over all the investigated sites were determined as 17, 11 and 9 years for soil, grass and milk respectively. Those values compare favorably to those estimated in previous studies in literature. These findings further enable us to quantify the decrease of 137Cs bioavailability which ranges from 0.008 to 0.044 year-1 with an average value of 0.026 year-1 (i.e. effective half lives ranging from 16 to 87 years with an average value of 26 years in soil).


Assuntos
Radioisótopos de Césio/análise , Monitoramento de Radiação , Cinza Radioativa/análise , Poluentes Radioativos do Solo/análise , França , Pradaria
5.
J Environ Radioact ; 208-209: 106038, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31494388

RESUMO

Aerial Gamma-Ray Surveys (GRS) are ideal for tracking anthropogenic gamma radiation releases and transport. The interpretation of a GRS can be complicated by natural gamma-ray sources such as atmospheric radon, cosmic rays, geologic materials, and even the survey equipment itself. Some of these complicating factors can be accounted for or corrected by calibration or mathematic techniques. Real-time algorithms that attempt to enhance potential radiogenic anomalies over background are also in use. However, natural geology is a source of significant background gamma-ray production and neither mathematical corrections nor real-time algorithmic approaches directly account for geology and geochemistry. In this study, we advance techniques to predict geologic background exposure rates using rapid and practical methods which can be achieved in the field. In addition we generate models that focus specifically on highlighting radiogenic anomalies for emergency response or further investigation. Predictive models developed in this study were generally able to predict background with medians of ± 1.0 µR/h compared to measured data, and were also able to highlight anomalous areas even where radiation exposure rates were within the range of natural background.


Assuntos
Exposição à Radiação/estatística & dados numéricos , Monitoramento de Radiação , Tecnologia de Sensoriamento Remoto , Radiação de Fundo , Raios gama
6.
J Environ Radioact ; 208-209: 106041, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31494389

RESUMO

We developed a simple model to evaluate and predict the 137Cs discharge from catchments using a tank model and the L-Q equation. Using this model, the 137Cs discharge and discharge ratio from the Abukuma River and 13 other rivers in the Fukushima coastal region were estimated from immediately after the Fukushima accident up to 2017. The 137Cs discharge (and discharge ratio to the deposition inventory in the catchment) of the Abukuma River and 13 other rivers in the Fukushima coastal region during the initial six months after the accident were estimated to be 18 TBq (3.1%) and 11 TBq (0.79%), respectively. These values of 137Cs discharge ratio were 1-2 orders of magnitude higher than those observed after June 2011 in previous studies (Ueda et al., 2013; Tsuji et al., 2016; Iwagami et al., 2017a), indicating that the initial 137Cs discharge from the catchments through the rivers was significant. The simulated initial 137Cs discharge rates for the initial six months after the Fukushima accident were about 9-30 times larger in each catchment than those after that point until 2017, though initial 137Cs concentration in river water was derived from an extrapolation of data based on a two exponentially decreasing fitting. However, it was found that the impact on the ocean from the initial 137Cs discharge through the rivers can be limited because the 137Cs discharge from the Abukuma River and the 13 other rivers in the Fukushima coastal region (29 TBq) was two orders of magnitude smaller than the direct release from Fukushima Dai-ichi Nuclear Power Plant (FDNPP) into the ocean (3.5 PBq) and from atmospheric deposition into the ocean (7.6 PBq) (Kobayashi et al., 2013). This model is expected to be useful to evaluate and predict 137Cs discharge from catchments in future water management and in the estimation of 137Cs discharge into reservoirs and the ocean.


Assuntos
Radioisótopos de Césio/análise , Monitoramento de Radiação , Poluentes Radioativos da Água/análise , Poluição Radioativa da Água/estatística & dados numéricos , Acidente Nuclear de Fukushima , Japão , Rios
7.
J Environ Radioact ; 208-209: 106040, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31518883

RESUMO

Because of the Fukushima Dai-ichi Nuclear Power Plant accident, forest ecosystems in wide areas were contaminated with 137Cs. It is important to characterize the behavior of 137Cs after its deposition onto forest surface environments for evaluating and preventing long-term radiation risks. In the present study, 137Cs vertical distributions in the soil profile were observed repeatedly at five forest sites with different vegetation types for 4.4 years after the accident in 2011, and 137Cs migration in the organic layer and mineral soil was analyzed based on a comparison of models and observations. Cesium-137 migration from the organic layer to the underlying mineral soil was represented by a two-component exponential model. Cesium-137 migration from the organic layer was faster than that observed in European forests, suggesting that the mobility and bioavailability of 137Cs could be suppressed rapidly in Japanese forests. At all sites, 137Cs transfer in mineral soil could be reproduced by a simple diffusion equation model with continuous 137Cs supply from the organic layer. The diffusion coefficients of 137Cs in the mineral soil were estimated to be 0.042-0.55 cm2 y-1, which were roughly comparable with those of European forest soils affected by the Chernobyl Nuclear Power Plant accident. Model predictions using the determined model parameters indicated that 10 years after the accident, more than 70% of the deposited 137Cs will migrate to the mineral soil but only less than 10% of the total 137Cs inventory will penetrate deeper than 10 cm in the mineral soil across all sites. The results of the present study suggest that the 137Cs deposited onto Japanese forest ecosystems will be retained in the surface layers of mineral soil for a long time.


Assuntos
Radioisótopos de Césio/análise , Florestas , Acidente Nuclear de Fukushima , Monitoramento de Radiação , Poluentes Radioativos do Solo/análise , Japão , Modelos Químicos , Solo
8.
J Environ Radioact ; 208-209: 106044, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31521882

RESUMO

This paper presents a geostatistical simulation approach to not only map the county-level indoor radon concentration (IRC) distributions in South Korea, but also quantify the uncertainty that can be used as decision-supporting information. For county-level IRC mapping in South Korea, environmental factors including geology, radium concentration in surface soil, gravel content in subsoil, and fault line density, which are known to be associated with the source and migration of radon gas, were incorporated into IRC measurements using multi-Gaussian kriging with local means. These four environmental factors could account for about 36% of the variability of noise-filtered IRCs, implying that regional variations of IRCs were affected by these factors. Sequential Gaussian simulation was then applied to generate alternative realizations of county-level IRC distributions. By summarizing the multiple simulation results, we identified some counties that lay on the great limestone series showed elevated IRCs. In addition, there were some counties in which the proportion of grids exceeding the recommended level was high but the uncertainty was also large according to the analysis of several uncertainty measures, which indicates that additional sampling is required for these counties. From the local cluster analysis in conjunction with simulation results, we found that the counties with higher levels of IRC belonged to the statistically significant clusters of high values, and these counties should be the prime targets for radon management and in-depth survey. The geographical distributions of IRC and uncertainty measures presented in this study provide guidance for effective radon management if they are consistently combined with both future IRC measurements and a geogenic radon potential map.


Assuntos
Poluentes Radioativos do Ar/análise , Poluição do Ar em Ambientes Fechados/estatística & dados numéricos , Monitoramento de Radiação , Radônio/análise , Poluição do Ar em Ambientes Fechados/análise , Contaminação Radioativa do Ar/estatística & dados numéricos , Análise por Conglomerados , República da Coreia , Análise Espacial
9.
J Environ Radioact ; 208-209: 106047, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31526956

RESUMO

As part of an underground gas migration study, two radioactive noble gases (37Ar and 127Xe) and two stable tracer gases (SF6 and PFDMCH) were injected into a historic nuclear explosion test chimney and allowed to migrate naturally. The purpose of this experiment was to provide a bounding case (natural transport) for the flow of radioactive noble gases following an underground nuclear explosion. To accomplish this, soil gas samples were collected from a series of boreholes and a range of depths from the shallow subsurface (3 m) to deeper levels (~160 m) over a period of eleven months. These samples have provided insights into the development and evolution of the subsurface plume and constrained the relative migration rates of the radioactive and stable gas species in the case when the driving pressure from the cavity is low. Analysis of the samples concluded that the stable tracer SF6 was consistently enriched in the subsurface samples relative to the radiotracer 127Xe, but the ratios of SF6 and 37Ar remained similar throughout the samples.


Assuntos
Gases Nobres/análise , Armas Nucleares , Monitoramento de Radiação , Radioatividade , Explosões , Nevada , Medidas de Segurança
11.
Mar Pollut Bull ; 146: 645-652, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31426204

RESUMO

90Sr and 137Cs activity concentrations in surface waters of the Sea of Japan (SOJ) decreased during the period of 1993-2010 with effective half-lives of 18 and 15 y, respectively. The longer effective half-life of 90Sr in the SOJ may suggest a surplus of 90Sr to SOJ surface waters, however, no clear evidence of possible 90Sr source has been found. After the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident, temporal variations of 137Cs in the surface water of the SOJ have changed, while 90Sr variations followed the pre-accident trends. The 90Sr/137Cs ratios reveal that increases of 137Cs due to the FDNPP accident continued in surface waters of the SOJ until 2016.


Assuntos
Radioisótopos de Césio/análise , Radioisótopos de Estrôncio/análise , Poluentes Radioativos da Água/análise , Acidente Nuclear de Fukushima , Japão , Centrais Nucleares , Monitoramento de Radiação , Água do Mar
12.
Isotopes Environ Health Stud ; 55(5): 499-510, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31394926

RESUMO

Radon, thoron and associated progeny measurements have been carried out in 71 dwellings of Douala city, Cameroon. The radon-thoron discriminative detectors (RADUET) were used to estimate the radon and thoron concentration, while thoron progeny monitors measured equilibrium equivalent thoron concentration (EETC). Radon, thoron and thoron progeny concentrations vary from 31 ± 1 to 436 ± 12 Bq m-3, 4 ± 7 to 246 ± 5 Bq m-3, and 1.5 ± 0.9 to 13.1 ± 9.4 Bq m-3. The mean value of the equilibrium factor for thoron is estimated at 0.11 ± 0.16. The annual effective dose due to exposure to indoor radon and progeny ranges from 0.6 to 9 mSv a-1 with an average value of 2.6 ± 0.1 mSv a-1. The effective dose due to the exposure to thoron and progeny vary from 0.3 to 2.9 mSv a-1 with an average value of 1.0 ± 0.4 mSv a-1. The contribution of thoron and its progeny to the total inhalation dose ranges from 7 to 60 % with an average value of 26 %; thus their contributions should not be neglected in the inhalation dose assessment.


Assuntos
Poluentes Radioativos do Ar/análise , Poluição do Ar em Ambientes Fechados/análise , Exposição por Inalação/análise , Produtos de Decaimento de Radônio/análise , Radônio/análise , Camarões , Habitação , Humanos , Monitoramento de Radiação/instrumentação , Monitoramento de Radiação/métodos
13.
J Environ Radioact ; 208-209: 106024, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31376730

RESUMO

The disequilibrium of the grandparent-daughter pair 210Pb (t1/2=22.3 years)-210Po (t1/2=138 days) has been used to estimate the export fluxes of particulate organic carbon in the ocean using particulate-matter-associated 210Po. 210Po is produced from 210Bi, not from 210Pb. The half-life of 210Bi (t1/2=5.01 days) is sufficiently long compared to the rates of biological particle formation and decomposition or dissolution occurring at sea. The role of 210Bi has not yet been assessed quantitatively in the apparent disequilibrium between 210Pb and 210Po, partly due to the non-existence of 210Bi depth profile measurements at sea up to now. However, greater affinity of 210Bi over 210Po and 210Pb was found recently in coastal waters and phytoplankton 207Bi uptake experiments. Build upon these findings, we developed a primitive and simple analytical approach to elucidate the role of 210Bi in the 210Po-210Pb pair in the ocean using a simplified two-box irreversible steady-state ocean model. We assumed that the activity concentrations in the dissolved and particulate phases of 210Pb, 210Bi, and 210Po in a given water column are solely determined by the concentration of the particles, their input and output, the distribution coefficients between dissolved and particulate phases, and decay constants of these radionuclides in the steady-state ocean. The 210Bi contribution to the 210Pb-210Po activity difference in seawater is found to be significant, therefore, it needs to be considered in estimating particle fluxes using 210Pb-210Po secular equilibrium at sea.


Assuntos
Bismuto/química , Radioisótopos de Chumbo/química , Polônio/química , Monitoramento de Radiação , Poluentes Radioativos da Água/química , Radioisótopos de Chumbo/análise , Polônio/análise
14.
J Environ Radioact ; 208-209: 106008, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31419761

RESUMO

Channelization significantly affects soil erosion in river floodplains. The object of this study was to use 137Cs as a tracer to determine the 137Cs inventory and derived soil erosion rates under various land use types in a catchment on channelized river floodplain in the lower reaches of Yangtze River, China. Sampling was carried out to establish a137Cs reference inventory in a 70-year old paddy field located on the shoulder-slope of a local hill. The mean reference inventory of 137Cs was 1275 Bq m-2, whereas the 137Cs inventory within the catchment ranged from 284 to 1150 Bq m-2 and the soil erosion rates from -33.3 to -2.4 t ha-1 yr-1, respectively. The dominated land use of paddy in cultivated soils contributed relative low soil erosion. Bamboo and castanea mollissima were preferential for local land uses in uncultivated soils in comparison with woodland and Pinnus massoniana. The rates of soil erosion rates in old tea garden were higher than that in new tea garden. Overall, severe soil erosion and no deposition in the entire catchment occurred in the entire catchment due to the human-induced channelization in the 1970s. Our results suggest that restricting farmland being returned to tea plantations, thereby maintaining the current land use types would reduce soil erosion in river floodplain in the future.


Assuntos
Monitoramento de Radiação , Poluentes Radioativos do Solo/análise , Radioisótopos de Césio/análise , China , Fenômenos Geológicos , Rios/química
15.
J Environ Radioact ; 208-209: 106025, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31419762

RESUMO

Long-term environmental behaviour of radioactive particles released during the Chernobyl accident and deposited in sandy topsoil in Ivankiv district of Kyiv Region (Ukraine), in radioactive trench waste materials from the Red forest, and in bottom sediments from the Cooling pond has been assessed. The efficiency of the models describing the dissolution/weathering rates of U fuel particles developed 15-20 years ago was tested, and their predictions for the dynamics of remobilization, mobility and plants uptake of 90Sr were confirmed. It was found that at present in the topsoil and in radioactive trench waste material, total dissolution of fuel particles of low chemical stability (UO2+x) has occurred and about half of the non-oxidized chemically stable fuel particles (UO2) has also dissolved, indicating radiological stabilization of the environment and that the mobile fraction of radionuclides would be reduced in the future. The biological availability of 90Sr in topsoil due to fuel particles dissolution has reached maximum values and further decrease is expected. The presence of chemically extra-stable fuel particles (U-Zry-Ox) in environments should be taken into account when the total radionuclides activity concentrations are assessed during radioactive materials management. It was shown that nearly half of the 90Sr activity remained as part of the non-dissolved UO2 fuel particles at the time of the study. Taking into consideration that 31 ±â€¯4% of the radionuclide activities were still associated with non-dissolved chemically extra-stable particles (U-Zry-Ox) in radioactive trench waste materials from the Red forest, increased dissolution should not be expected in the near future. The physico-chemical form of radionuclides in air exposed sediments from the Cooling pond were determined, and results showed that about 70-80% of total 90Sr, 241Am and plutonium isotopes activity were associated with U fuel particles. The low dissolution rate of radionuclides from the pond sediments is attributed to prolonged slightly alkaline pH in the medium due to zebra mussel residues. According to new data, the emission value of 238Pu associated with fuel particles released during the Chernobyl accident amounted to 1.8 × 1013Bq (1.2% of the activity in the reactor) and 90Sr amounted to 2.6 × 1015Bq (1.5% of the activity in the reactor).


Assuntos
Acidente Nuclear de Chernobyl , Monitoramento de Radiação , Cinza Radioativa/análise , Poluentes Radioativos do Solo/análise
16.
J Environ Radioact ; 208-209: 106028, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31421312

RESUMO

We investigated time-dependent trends of artificial radionuclides in aquatic moss, zoobenthos (amphipods and caddisfly larvae), and three abundant wild fish species (Northern pike, Arctic grayling, and Siberian dace) inhabiting the Yenisei River in the vicinity of the radioactive discharge site in 2007-2015, in a period before and after the shutdown of the last nuclear reactor plant at the Mining-and-Chemical Combine (MCC), which occurred in 2010. From our research, we learned that concentrations of short-lived radionuclides, whose discharges to the Yenisei either stopped or declined after the shutdown of the reactor plant at the MCC (24Na, 46Sc,51Cr, 54Mn, 58Co, 59Fe, 60Co, 65Zn, 103Ru, 141,144Ce, 152,154Eu, 239Np), decreased in biota samples as well. The ecological half-life (EHL) of 65Zn (0.4-0.7 y) was similar to the physical half-life of this isotope, the EHLs of 60Co (1.2-2.1 y) and 152Eu (1.8 y) were shorter than the physical half-lives of these isotopes. Concentration of 137Cs did not decrease significantly in biota of the Yenisei after the shutdown of the last reactor plant because the discharges of this radionuclide to the Yenisei continued at the same level. On a longer-term scale (since 1973 and since 1991), concentration of 137Cs in fish muscle had significantly decreased, following the decrease in annual discharges of this radionuclide to the Yenisei, and the EHL of 137Cs was estimated as 6.5-12.8 y. Statistically significant correlation with annual discharges of 137Cs was revealed for the concentration of this radionuclide in grayling (whole bodies and muscle); dace (muscle), and amphipods. Despite their ability to accumulate high concentrations of 137Cs, aquatic moss and caddisfly larvae (analyzed together with their stony casings) were not sensitive to interannual fluctuations in the releases of this radionuclide to the Yenisei. Among the analyzed fish species of the Yenisei, the highest activity concentration of 137Cs was revealed in pike (body and muscle), indicating biomagnification of this radionuclide in the top level of the trophic chain.


Assuntos
Organismos Aquáticos/química , Monitoramento de Radiação , Poluentes Radioativos da Água/análise , Biota , Rios , Sibéria
17.
J Environ Radioact ; 208-209: 106026, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31437807

RESUMO

Increased uranium (U) concentrations are found in certain ground and surface waters of the Swiss Plateau. Analysis of more than 100 public fountains revealed that increased 238U concentrations frequently occur close to the interface between the Lower Freshwater Molasse and the Upper Marine Molasse, cropping out in the western part of the Swiss Molasse Basin. Out of these locations, Mont Vully, situated ca. 20 km west of Berne, was studied in detail. As this hill consists of the two aforementioned stratigraphic Molasse units, it represents an ideal case study. Two springs at the northern slopes of Mont Vully exhibit the highest 238U concentrations with more than 300 mBq/L and were thus monitored for almost two years in order to screen possible seasonal variations. Further water samples were collected from spring captures, creeks and drainage pipes. The pipes drain the farmland north of Mont Vully showing 238U concentrations with more than 600 mBq/L. In order to discover the reason for the duplication in concentration, gamma dose rate measurements were accomplished on the farmland, revealing elevated dose rates of up to 160 nSv/h. These are located above ancient pathways of creeks that originated from Mont Vully. At these locations with elevated dose rates, three shallow sediment drill cores were taken and analyzed for their U content. The sediment cores can essentially be divided into three parts: (i) an upper soil with common U concentrations of about 30 Bq/kg 238U, (ii) an U-rich peat horizon with concentrations of up to 500 Bq/kg 238U, and (iii) an impermeable clay unit that acts as an aquitard with again minor 238U concentrations. Radiocarbon dating of the U-rich peat horizon reveals ages younger than 8.1 kyrs. This study suggests that a wetland was formed on top of the impermeable clay layer after the last glaciation during the Holocene. The stream waters with 238U concentrations of more than 300 mBq/L originating from Mont Vully contributed significantly to the water supply for the development of the wetland. Due to the reducing conditions that are present in wetlands, the dissolved U in the incoming streams was reduced and adsorbed onto organic matter. Accordingly, an entrapment for U was generated, persisting for at least 6 kyrs - a sufficient time to accumulate up to 500 Bq/kg. In the course of the last century, numerous wetlands in Switzerland were drained by capturing streams and installing drainage pipes to make the land suitable for agriculture. This kind of melioration was also done at the wetlands north of Mont Vully resulting in a subsequent change in redox conditions within the soil. The solubility of U depends on its oxidation state and U can be oxidized by oxygen-rich rainwater. The rainwater leached the U adsorbed on the peat yielding 238U concentrations of more than 600 mBq/L. Consequently, the duplication of 238U concentrations in the drainage water as compared to the original concentration that creeks brought into the ancient wetlands has been clarified during this study. Twenty of the analyzed public fountains in the Swiss Plateau exhibited a 238U concentration of more than 50 mBq/L. All of them could have contributed to the formation of a wetland after the last glaciation, which leads to the assumption that the situation at Mont Vully is not a singularity in the Swiss Plateau.


Assuntos
Monitoramento de Radiação , Poluentes Radioativos/análise , Agricultura , Solo , Suíça , Áreas Alagadas
18.
J Environ Radioact ; 208-209: 106031, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31450017

RESUMO

The rapid monitoring of radioactive gas is one of the most direct and sensitive methods used to characterize the leakage of nuclear installations, and its technical difficulty lies in achieving the goals of rapid and high sensitivity as much as possible. Several techniques, including adsorption at ultralow temperatures, impurity removal with hollow fiber membranes, and on-site measurements with low background, were used to develop a rapid and highly sensitive monitoring system for radioxenon isotope. This system could simultaneously separate xenon from air and measure radioxenon isotopes in a rapid and efficient way. The technical specifications of this system are as follows: the recovery of stable xenon is greater than 70%; and the MDCs of 133Xe and 135Xe are 4.3 Bq/m3 and 0.4 Bq/m3 within a 30 min cycle of sampling and testing, respectively. It is worth noting that the MDC of 133Xe here is only approximately 1/18000 to 1/800 of those obtained with other similar equipment, and the monitoring period of this system is one fortieth of that of noble gas equipment for OSI, for example, XESPM-III. As a result, the standard uncertainties are less than 16%. The system developed in this paper can be applied in leakage monitoring of nuclear facilities and can also provide instructive technical support for other tests, such as nuclear safety monitoring and evaluation.


Assuntos
Poluentes Radioativos do Ar/análise , Monitoramento de Radiação/métodos , Radioisótopos de Xenônio/análise , Armas Nucleares
19.
J Environ Radioact ; 208-209: 106034, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31454588

RESUMO

A radiological dispersal device (RDD) is built using an explosive device laced with radioactive materials. The RDD appears as a speculative radiological weapon with the aim of spreading radioactive material across an inhabited area. This study seeks to evaluate how the official decision-making process is influenced by the radiation vertical profile dose, using the hypothetical scenario of a simulated RDD detonation in a densely populated urban area. A simulated plume of strong radiation was generated from the explosion site, contaminating the surrounding area. Several atmospheric conditions impact on the contamination. However, this study focusses on the following main variables considered by HotSpot for a conservative simulation: (a) the atmospheric stability conditions (Pasquill-Gifford - PG classes); (b) the explosive power, and (c) the source-term. Gaussian modeling was used for its speed, and for its capacity to estimate the time-integrated atmospheric concentration of an aerosol at any point in 3D space. The simulation provided information about four main outcomes: (a) contamination plume area; (b) radiological risk dependency on PG classes; (c) total effective dose equivalent (TEDE) with a possible dependence on receptor height; and (d) potentially affected population's size. The findings suggest that a protocolled response from authorities should be implemented in order to effectively follow possible changes in the PG class. Which, in turn, may negatively impact the decision-making process.


Assuntos
Doses de Radiação , Liberação Nociva de Radioativos , Aerossóis , Tomada de Decisões , Explosões , Armas Nucleares , Monitoramento de Radiação , Medição de Risco
20.
J Environ Radioact ; 208-209: 106032, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31466011

RESUMO

Radiocesium contamination of forests has been a severe problem after the Fukushima Daiichi Nuclear Power Plant accident in 2011. Bed logs of Konara oak (Quercus serrata Murray), used for mushroom cultivation, were an economically important product from the forests prior to their contamination. One of the potential countermeasures to reduce radiocesium content in trees is potassium fertilization, but the evidence for the effect of K+ in reducing Cs+ uptake has not been obtained yet in the woody plant. Therefore, we investigated the ability of rhizospheric K+ to suppress uptake and translocation of Cs+ in Konara oak seedlings through hydroponic experiments in order to clarify the effect of K+. Elemental analysis showed that the seedlings cultivated for 4 weeks under low-K (K+ = 50 µM) contained higher amount of Cs comparing to the seedlings cultivated under high-K (K+ = 3 mM). Then, the uptake rate of Cs+ and K+ in the seedlings from the solution having 50 µM K+ and 0.1 µM Cs+ was calculated using radioactive 137Cs+ and 42K+ to evaluate the effect of growth condition on the ion uptake mechanism. The interference between Cs+ and K+ at the site of root uptake was also evaluated based on the Cs+ and K+ uptake rates at K+ concentrations of 50 µM, 200 µM, and 3 mM in the seedlings grown under the medium-K (K+ = 200 µM) condition. As a result, the Cs+ uptake rate at 50 µM K+ was not influenced by the growth condition, whereas Cs+ uptake decreased when the uptake solution itself was supplemented with 3 mM K+. In addition, the Cs/K ratio in the seedlings was found to rise to exceed the Cs/K ratio in the culture solution as the rhizospheric K+ concentration increased, which was in contrast with previous findings in herbaceous plants. Our experiments demonstrated the first direct evidence for woody plants that a high K+ concentration can suppress Cs accumulation in Konara oak and that it was derived from competition for uptake between K+ and Cs+ in the rhizosphere, not from the growth K+ condition.


Assuntos
Radioisótopos de Césio/metabolismo , Potássio/metabolismo , Quercus/metabolismo , Poluentes Radioativos do Solo/metabolismo , Acidente Nuclear de Fukushima , Potássio/análise , Monitoramento de Radiação , Poluentes Radioativos do Solo/análise
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