A Gaussian-plume based Monte Carlo method for calculating radiation dose in the near field of buildings.

A Monte Carlo (MC) programme was written using the dose point kernel method to calculate doses in the roof zone of a building from nearby releases of radioactive gases. A Gaussian Plume Model (GPM) was parameterised to account for near-field building effects on plume spread and reflection from the roof. Rooftop recirculation zones and building-generated plume spread effects were accounted in a novel Dual Gaussian Plume (DGP) formulation used with the MC model, which allowed for the selection of angle of approach flow, plume release height in relation to the building and position of the release point in relation to the leading edge of the building. Three-dimensional wind tunnel concentration field data were used for the parameterisation. The MC code used the parameterised concentration field to calculate the contributions to effective dose from inhalation, cloud immersion from positron/beta particles, and gamma-ray dose for a wide range of receptor dose positions in the roof zone, including receptor positions at different heights above the roof. Broad trends in predicted radiation dose with angle of approach flow, release position in relation to the building and release height are shown. Alternative approaches for the derivation of the concentration field are discussed.

Review of the sources and behaviors of plutonium isotopes in the atmosphere and ocean.

Plutonium, as well as fission products such as 137Cs, had been released into the earth environment in 1945 after the first atmospheric nuclear explosion of plutonium bomb in the desert of New Mexico (USA, July 16) and later over Nagasaki (August 9), followed then by many other explosions. Thus, plutonium cycling in the atmosphere and ocean has become a major public concern as a result of the radiological and chemical toxicity of plutonium. However, plutonium isotopes and 137Cs are important transient tracers of biogeochemical and physical processes in the environment, respectively. In this review, we show that both physical and chemical approaches are needed to comprehensively understand the behaviors of plutonium in the atmosphere and ocean. In the atmosphere, plutonium and 137Cs attach with aerosols; thus, plutonium moves according to physical and chemical processes in connection with aerosols; however, since plutonium is a chemically reactive element, its behavior in an aqueous environment is more complicated, because biogeochemical regulatory factors, in addition to geophysical regulatory factors, must be considered. Meanwhile, 137Cs is chemically inert in aqueous environments. Therefore, the biogeochemical characteristics of plutonium can be elucidated through a comparison with those of 137Cs, which show conservative properties and moves according to physical processes. Finally, we suggest that monitoring of both plutonium and 137Cs can help elucidate geophysical and biogeochemical changes from climate changes.

Long-term monitoring of outdoor natural gamma absorbed dose rate in air in Bengaluru, Karnataka, India.

This research forms a part of the comprehensive Indian Environmental Radiation Monitoring Network program, focusing on the continuous measurement of absorbed dose rate in outdoor air due to natural gamma radiation (cosmic and terrestrial) in Bengaluru, Karnataka, India. Over the course of a decade (2013-2023), data were collected from 41 monitoring locations in the city using permanently field-installed Geiger-Mueller detector-based environmental radiation monitors. This paper presents an analysis of the extensive long-term monitoring results. The mean absorbed gamma dose rate in outdoor air across the monitoring locations ranged from 84 ± 9 to 156 ± 4 nGy.h-1, with a calculated mean value of 124 ± 15 nGy.h-1. The estimated mean annual effective dose due to outdoor natural gamma radiation varied from 0.10 ± 0.01 to 0.19 ± 0.01 mSv.y-1, with an overall mean of 0.15 ± 0.02 mSv.y-1.

Variation analysis of atmospheric 7Be activity concentrations with respect to precipitation.

Beryllium-7 activity concentrations in the atmosphere and precipitation were continuously measured every day between April 2011 and December 2015 in Dazaifu, western Japan. The measured data were quantitatively analyzed to determine the precipitation-induced variation in 7Be activity concentrations. The average concentrations on nonprecipitation and precipitation days were 5.5 and 3.8 mBq/m3, respectively. This difference of 31% (1.7 mBq/m3) on average, was attributable to the washout effect, which was more significant in the summer. Regarding the association between 7Be activity concentration and precipitation, the concentration remained at a similar level for the small precipitation amount of <5.0 mm/day and showed a decreasing trend (but was insignificant) for the precipitation of 5.0-10.0 mm/day. A significant decrease in the concentration was observed for ≥10 mm/day. Furthermore, when precipitation occurred on two successive days, the 7Be activity concentrations on the second day significantly decreased regardless of precipitation.

Indoor concentrations of radioactive aerosols from nuclear accidents.

In previous studies, some of the important factors that affect the spread of radioactive aerosols into indoors were considered. The studies were based on a new CFD approach and provided good descriptions for the deposition of aerosol particles inside small spaces and the penetration of aerosols into buildings through wall cracks. In this article, an application of those studies is implemented, where all the graphical relations that are required to estimate the indoor concentrations of radioactive aerosols from nuclear accidents are provided. This includes the deposition velocities, deposition rate, and the penetration factor. Particular interest is in the Fukushima-Daiichi nuclear power plant accident that took place in Japan in 2011. The aerosols carrying the radioiodine iodine-131 and the radiocesium cesium-134 and cesium-137 are studied. Based on the model's assumptions, and assuming steady-state air concentrations, the radioactive aerosols' concentrations in indoor air are about 97% of the concentrations in outdoor air. The applications demonstrate the model to be convenient and practical.

Evaluation of the environmental and structural impacts on urban expansion using airborne geophysical data at Hurghada city, Northern Eastern Desert, Egypt.

Airborne gamma-ray spectrometric and magnetic data were processed and interpreted aiming to evaluate the environmental and structural impacts on urban expansion, Hurghada City, Northern Eastern Desert, Egypt. The eastern (coastal area), northern, and southeastern parts of the study area possess the lowest level of absorbed dose rate (ADR) and annual effective dose equivalent (AEDE), which were estimated from the airborne gamma-ray spectral data of this area. Consequently, these parts are considered as suitable sites for urban expansion from the radioactivity point of view. The relatively high level of ADR and AEDE is associated with granitic rocks, some parts of Gabir formation and recent Wadi sediments, situated at southwestern, central, and eastern parts of the study area. The ADR and AEDE of these parts are considered harmful to individuals. Airborne magnetic data were also used to detect major structures that may affect various construction projects in the study area in the future. The NNW-SSE, NW-SE, N-S, and NE-SW trends represent the common structures in the study area. The obtained results of airborne gamma-ray spectrometric and magnetic data illustrated that the urban expansion should not be constructed to the west of the ring road. However, site investigations must be carried out on this part of the study area before starting any construction projects there. The present study proved the important role of airborne gamma-ray spectrometric and magnetic surveys as useful tools to delineate the environmental and structural impacts on urban expansion.

Neighborhood-level socioeconomic disparities in Radon testing in North Carolina from 2010 to 2020.

Radon is a naturally occurring radioactive gas that poses significant health risks to humans, including increased risk of lung cancer. This study investigates the association of neighborhood-level socioeconomic variables with radon testing and radon exposure levels in North Carolina between 2010 and 2020. Our analysis of the two largest commercial household radon tests reveals that 67% of census tracts had testing rates below 10 tests per 1000 population, indicating low testing prevalence. Low radon levels (<2 pCi/L) were detected in 74.1% of the tracts (n = 1626), while medium levels of 2-4 pCi/L and ≥4 pCi/L were observed in 17.2% (n = 378) and 1.6% (n = 36) of the tracts. A generalized spatial regression model was employed to analyze the association between neighborhood-level socioeconomic variables and radon testing rates (per 1000 households), controlling for median radon testing results. The results show a positive correlation (P-value <0.001) of testing rate with various indicators of neighborhood affluence including education level, income, and occupation. In contrast, neighborhood disadvantage, including poverty, unemployment, and public assistance, was associated with a lower radon-testing rate (P-value <0.001). These findings highlight the need for targeted interventions to address socioeconomic disparities in radon testing and promote awareness and access to testing resources in lower socio-economic neighborhoods. Improving testing rates can effectively address radon-related health risks in North Carolina and across the U.S.

The sensitivity of innovative techniques for measuring low levels of radon in the environment using passive detectors.

In recent years, there has been a significant surge in interest in measuring low radon levels in the environment. These measurements are valuable, particularly for identifying radon priority areas as required by the European Council Directive 2013/59/EURATOM and for research related to climate change. Due to the limited sensitivity of existing radon detectors/monitors in addressing these challenges, substantial efforts have been devoted to developing new designs. This report compares the sensitivity of several innovative designs with that of existing passive radon monitors. These novel designs incorporate alpha track detectors, including large area low background detectors, with activated carbon fabric used as an efficient radon adsorber/radiator. Recent innovative solutions to mitigate the impact of temperature and humidity on detectors using adsorbers are also discussed. The background signal of detectors intended for use in these novel designs is examined, and their sensitivity is evaluated. The findings demonstrate that these novel designs have the potential to significantly enhance the sensitivity of long-term radon measurements, surpassing the detectors currently in widespread use by more than an order of magnitude.

Parameter uncertainty analysis of the equivalent lung dose coefficient for the intake of radon in mines: A review.

Radon presents significant health risks due to its short-lived progeny. The evaluation of the equivalent lung dose coefficient is crucial for assessing the potential health effects of radon exposure. This review focuses on the uncertainty analysis of the parameters associated with the calculation of the equivalent lung dose coefficient attributed to radon inhalation in mines. This analysis is complex due to various factors, such as geological conditions, ventilation rates, and occupational practices. The literature review systematically examines the sources of radon and its health effects among underground miners. It also discusses the human respiratory tract model used to calculate the equivalent lung dose coefficient and the associated parameters leading to uncertainties in the calculated lung dose. Additionally, the review covers the different methodologies employed for uncertainty quantification and their implications on dose assessment. The text discusses challenges and limitations in current research practices and provides recommendations for future studies. Accurate risk assessment and effective safety measures in mining environments require understanding and mitigating parameter uncertainties.

Statistical evaluation of individual external exposure dose of outdoor worker and ambient dose rate at evacuation ordered zones after the Fukushima Daiichi Nuclear Power Station accident.

Following the accident at the Fukushima Daiichi Nuclear Power Station, evacuation orders were issued for the surrounding communities. In order to lift the evacuation order, it is necessary to determine individual external doses in the evacuated areas. The purpose of this study was to determine the quantitative relationship between individual external doses and ambient dose rates per hour as conversion coefficients. More specifically, individual external doses of Tokyo Electric Power Company Holdings employees in difficult-to-return zone were measured broadly over a long period (fiscal year 2020 to fiscal year 2022). To obtain highly accurate estimates, we used not only ambient dose rates based on airborne radiological monitoring data, but also Integrated dose rate map data that had been statistically corrected to correspond to local ambient dose rate gradients on the ground. As a result, the conversion coefficients based on the ambient dose rate map measured by airborne radiological monitoring were 0.42 for the Evacuation-Order Lifted Zones (ELZs), 0.37 for the Special Zones for Reconstruction and Rehabilitation (SZRRs), and 0.47 for the Difficult-to-Return Zones without SZRRs (DRZs). On the other hand, the conversion coefficients based on the Integrated dose rate map which is a highly accurate dose rate map based on statistical analysis of various types of monitoring that have been studied in government projects in recent years, were 0.78 for the ELZs, 0.72 for the SZRRs and 0.82 for the DRZs. Using these conversion coefficients, the individual external dose can be estimated from two representative ambient dose rate maps provided by the government.

Evaluation of consumer digital radon measurement devices: a comparative analysis.

Kansas State University (KSU) Engineering Extension conducted an abridged evaluation of eight consumer grade digital radon monitors. Using the KSU secondary radon chamber, these devices were exposed to three different radon concentrations for 7 d in average household temperature and relative humidity conditions. The three different radon concentration ranges used were: 12.8 pCi L-1to 15.5 pCi L-1(473.6 Bq m-3-573.5 Bq m-3), 27.7 pCi L-1to 29.4 pCi L-1(1024.9-10 857.8 Bq m-3), and ambient room level average radon concentration of 0.6 pCi L-1(22.2 Bq m-3). The American National Standards Institute/American Academy of Radon Scientists and Technologists Performance Specifications for Instrumentation Systems Designed to Measure Radon Gas in Air (ANSI/AARST MS-PC) (ANSI/AARST MS-PC 2022Performance Specifications for Instrumentation Systems Designed to Measure Radon Gas in Air(AARST Radon Standards)) minimum performance metrics were used to evaluate the accuracy and precision of each model type for each radon concentration tested. The eight different device models performed within the 0 ± 25% requirement for the individual percent error (IPE) for radon concentrations between 27.7 pCi L-1and 29.4 pCi L-1(1024.9-10 857.8 Bq m-3). For radon concentrations between 12.8 pCi L-1and 15.5 pCi L-1(444-592 Bq m-3) seven of the eight monitors fell within the IPE requirement and for ambient room radon concentrations six of the eight monitors fell within the IPE requirement for the ANSI/AARST MS-PC minimum performance requirement (ANSI/AARST MS-PC 2022Performance Specifications for Instrumentation Systems Designed to Measure Radon Gas in Air(AARST Radon Standards)) ranges. All eight device models fell within the ± 15% ANSI/AARST MS-PC minimum performance requirement (ANSI/AARST MS-PC 2022Performance Specifications for Instrumentation Systems Designed to Measure Radon Gas in Air(AARST Radon Standards)) coefficient of variation (CV) range for radon concentrations between 12.8 pCi L-1and 15.5 pCi L-1(444-592 Bq m-3) and for radon concentrations between 27.7 pCi L-1and 29.4 pCi L-1(1024.9-10 857.8 Bq m-3). In the future, evaluating the performance of these models over time to observe their long term accuracy and precision is anticipated.

Radioactivity of the atmospheric aerosols detected by CTBTO stations in Africa following the accident at the Fukushima Daiichi nuclear power plant.

Radionuclides from the reactor accident Fukushima Daiichi nuclear power plant were observed in the airborne aerosols at CTBT International Monitoring System (IMS) stations (MRP43, CMP13) in Africa. The maximum activity concentrations in the air measured in Mauritania were 186.44 10-6 Bq.m-3, 264.16 10-6 Bq.m-3 and 1269.94 10-6 Bq.m-3 for 134Cs, 137Cs and 131I respectively, and in Cameroon 16.42 10-6 Bq.m-3, 25.53 10-6 and 37.58 10-6 Bq.m-3 respectively for 134Cs, 137Cs and 131I. The activity ratio of 134Cs/137Cs is almost constant throughout the period of time relevant to this study due to their long half-lives of 30.2 years for 137Cs and 2.06 years for 134Cs. Whereas the 131I/137Cs activity ratio varies in time according to the radioactive decay with a half-live of 8.06 days for 131I and different removal rates of both radionuclides from the atmosphere during transport. The EMAC atmospheric chemistry-general circulation was used to simulate the emission and transport of the isotope 137Cs and map the deposition of the 137Cs deposition over Africa.

Radon Exposure Assessment in Occupational and Environmental Settings: An Overview of Instruments and Methods.

Radon is a naturally occurring noble radioactive gas that poses significant health risks, particularly lung cancer, due to its colorless, odorless, and tasteless nature, which makes detection challenging without formal testing. It is found in soil, rock, and water, and it infiltrates indoor environments, necessitating regulatory standards and guidelines from organizations such as the Environmental Protection Agency, the World Health Organization, and the Occupational Health and Safety Agency to mitigate exposure. In this paper, we present various methods and instruments for radon assessment in occupational and environmental settings. Discussion on long- and short-term monitoring, including grab sampling, radon dosimetry, and continuous real-time monitoring, is provided. The comparative analysis of detection techniques-active versus passive-is highlighted from real-time data and long-term exposure assessment, including advances in sensor technology, data processing, and public awareness, to improve radon exposure evaluation techniques.

Relevance of radon progeny measurements for the assessment of inhalation doses in groundwater utilities.

The high radon concentrations measured in the indoor air of groundwater facilities and the prevalence of the problem have been known for several years. Unlike in other workplaces, in groundwater plants, radon is released into the air from the water treatment processes. During the measurements of this study, the average radon concentrations varied from 500 to 8800 Bq m-3. In addition, the indoor air of the treatment plants is filtered and there are no significant internal aerosol sources. However, only a few published studies on groundwater plants have investigated the properties of the radon progeny aerosol, such as the equilibrium factor (F) or the size distribution of the aerosol, which are important for assessing the dose received by workers. Moreover, the International Commission on Radiological Protection has not provided generic aerosol parameter values for dose assessment in groundwater treatment facilities. In this study, radon and radon progeny measurements were carried out at three groundwater plants. The results indicate surprisingly high unattached fractions (fp= 0.27-0.58), suggesting a low aerosol concentration in indoor air. The correspondingFvalues were 0.09-0.42, well below those measured in previous studies. Based on a comparison of the effective dose rate calculations, either the determination of thefpor, with certain limitations, the measurement of radon is recommended. Dose rate calculation based on the potential alpha energy concentration alone proved unreliable.

Quantitative estimation of dust transport in the desert region of northwest China by plutonium isotopes.

Dust is an important source of atmospheric pollution, and quantitative estimation of desert dust transport is crucial for air pollution control. In this study, five typical sandy soil profiles in the Tengger Desert were collected and analyzed for 239,240Pu concentration and 240Pu/239Pu atomic ratios in order to identify the source of 239,240Pu in this area and explore the sedimentary characteristics of dust in different profiles. The results revealed that the concentrations of 239,240Pu in the soil profiles were between 0.002 and 0.443 mBq/g with an exception of the deep layer soil at one site. The measured atomic ratios of 240Pu/239Pu are at the global atmospheric fallout level with a mean of 0.184 ± 0.020, indicating that global fallout is the dominant source of plutonium in this region. The total inventories of 239,240Pu in the reference sites in this area were estimated to be 39.2-44.6 Bq/m2, this is in agreement with the value from the global fallout of atmospheric nuclear weapon tests at the similar latitude (30-40 °N: 42 Bq/m2). The estimated erosion rate in the erosion profile utilizing soil erosion intensity mode is 2491 t/km2/yr and the soil erosion depth is 9.86 cm, While, the stacking rate of the accumulation profile is 1383 t/km2/yr, and the depth of accumulation is estimated to be 5.48 cm. The difference between the erosion and accumulation profiles indicated that approximately 1107 t/km2/yr of dust was exported from the Gobi landform area of the Tengger Desert, which might be transported long distance in the downwind direction.

Theoretical model for calculating and adjusting radon activity concentration in ventilation networks of uranium mines considering pressure drop effect.

The radiation dose of workers in underground uranium mines mainly comes from radon and radon progeny. To ensure a healthy and safe work environment, it is necessary and urgent to optimize the design of ventilation systems. As such, based on the simplified radon diffusion-advection migration model of the rocks, this paper proposes 1) two methods for determining the radon exhalation rate modified by pressure drop, 2) three methods for calculating radon activity concentration of single-branch, and 3) the novel adjustment algorithm and solving procedures for calculating and adjusting the radon activity concentration in ventilation networks by modifying the radon exhalation rate, demonstrated on a specific ventilation network in a simulated underground uranium mine with calculation and analysis via MATLAB. The results show that 1) the radon exhalation rate of different branches can be modified by their pressure drop, and 2) the proposed method can be used to reveal the influences of different ventilation methods and fan pressures on the radon activity concentration in the ventilation network and the radon release rate to the atmosphere.

Radioprotection issues in uraniferous minerals collections with reference to an actual case.

Our work investigated the radioprotection implications associated with the possession of a collection of uraniferous minerals. Considering different scenarios, we developed (and applied to an actual collection) specific formulas for radiation doses evaluation. We discussed the shielding necessary to reduce the gamma irradiation down to the required values. A mathematical model was developed to estimate the minimum air flow rate to reduce the radon air concentration below the reference values. The radiation risks associated to the handling of single specimens was also addressed, including hand skin irradiation and shielding capabilities of surgical lead gloves. Finally, we discussed the radiation risks associated to the exhibition of a single specimen. The results, compared to the safety standards of the EU Directive 13/59, show that the exhibition of uraniferous samples with activity of a few MBq do not need specific radioprotection requirements nor for the involved personnel nor for visitors.

Are solid state nuclear track detectors truly integrated devices?-experimental evidence in radon measurements.

Passive diffusion radon monitoring devices were exposed to a range of radon concentrations and their variations. The experimental results, backed up by the statistical analysis, showed that the radon concentration had virtually no effect on the final integrated exposure results, with the exception for the very low concentration. Therefore, it was proven that such devices are truly integrated exposure devices.

Lagrangian and Eulerian modelling of 106Ru atmospheric transport in 2017 over northern hemisphere.

In September 2017, numerous measurement stations recorded large surface concentrations of Ru106 in Europe. This event was well recorded by various monitoring stations worldwide and offer a valuable framework to compare the modelling strategies deployed to quickly evaluate where the plume goes and with what concentrations. In general, the source and its intensity are not known and hypotheses have to be done. Models have to be fast and accurate: Lagrangian and Eulerian are often used but rarely compared. In this study, the FLEXPART Lagrangian model and the WRF-CHIMERE Eulerian models are used to simulate the emissions, transport and deposition of this source of Ru106. First, it is shown that the hypothesis of location, timing and intensity of the source is realistic, by comparison to surface measurements. Second, sensitivity analysis performed with the Eulerian model and several transport scheme showed that this model may provide better results than the Lagrangian one. It opens the door to further development, including chemistry and mixing with other pollutants during these specific events.

Gamma-spectrometry measurements of filtration media from an Advanced Gas-cooled Reactor.

Filtration media used to quantify particulate and gaseous releases have been collected from Hartlepool Power Station in the United Kingdom and measured using high-sensitivity gamma-spectrometry systems. Radionuclides that are relevant to the monitoring regime of the Comprehensive Nuclear-Test-Ban Treaty (CTBT) have been detected. Results are reported and compared to detections recorded on the International Monitoring System (IMS). Time series activity plots have been produced and results interpreted with respect to known plant activities. The reported results improve the understanding of trace-level radionuclide emissions from Advanced Gas-cooled Reactors (AGRs) and aid interpretation of IMS measurements. This work is being performed as part of the Xenon Environmental Nuclide Analysis at Hartlepool (XENAH) collaboration between the Atomic Weapons Establishment (AWE, UK), EDF Energy (UK), Pacific Northwest National Laboratory (PNNL, US) and the Swedish Defence Agency (FOI, Sweden).