The rapid growth of nuclear energy technology, along with the expansion of global nuclear power projects, has led to a significant increase in high-level radioactive wastes (HLWs), particularly spent fuel from nuclear power plants. The disposal of HLWs remains a major challenge due to its high radioactivity, long half-lives, and complex management requirements. Ensuring the long-term safety of HLW disposal is critical for the sustainable development of nuclear energy. Currently, deep geological disposal is considered the most effective and secure method for isolating HLW. This method relies on a multi-barrier system that combines natural geological barriers with artificial engineering barriers to achieve the long-term isolation of radioactive wastes. Engineering barriers, including waste containers, buffering materials, and backfill materials, are essential for preventing radioactive leakage and maintaining isolation in the face of geological and environmental changes. Recent studies have focused on the design and optimization of these barriers, particularly their impact on the migration of key radioactive nuclides. Insights from international practices and technological advancements have highlighted the importance of materials like bentonite, disposal containers, and other engineering barriers in optimizing multi-barrier systems for HLW disposal. Bentonite, a widely used buffering material, is known for its excellent adsorption properties and low permeability. Recent modifications to bentonite have enhanced its ability to adsorb radioactive nuclides such as cesium (Cs) and plutonium (Pu), significantly improving the safety and long-term stability of disposal facilities. Additionally, the migration mechanisms of radioactive nuclides have been examined, with particular attention to the influence of hydrochemical conditions-such as hydration, ion concentration, and pH-on bentonite's adsorption capabilities. This study sheds light on the migration pathways and rates of these nuclides in HLW disposal systems. Another key area of focus is the materials used for disposal containers, particularly cement-based and metal materials, which play a critical role in mitigating corrosion risks during long-term storage. While experimental data show promising corrosion resistance under specific conditions, continued researches are necessary to evaluate the long-term durability of these materials. These findings provide valuable theoretical insights for the engineering design of HLW geological disposal, offering references for the site selection, design, and material optimization of disposal facilities, particularly in China. As experimental data and theoretical models continue to evolve, future safety assessments and long-term behavior predictions will become more accurate. By promoting international collaboration and interdisciplinary research, these efforts contribute to the development of a scientific foundation for the safe and sustainable disposal of HLWs, ensuring environmental safety and the long-term effectiveness of waste management strategies.

In this study, we explore the application of unmanned aerial vehicle (UAV) gamma spectrometry in terrestrial radiometric surveys, with a particular focus on the impact of UAV flight altitudes and rough terrain on measurement. Through field experiments conducted at a rare earth deposit in Sichuan, China, radioactive data were obtained from 509 UAV survey points and 585 ground measurement points. A physical model for measuring ground radioactivity using UAVs is established, and the digital elevation model (DEM) in the survey area is used to correct the height and terrain of radioactivity at the measurement points. By qualitatively and quantitatively analyzing the differences between UAV and ground measurement systems in height and terrain, it concludes that the use of height and terrain correction method can utilize UAV measurement data to indicate ground air absorption dose rates, and the indication of corrected UAV-measured data is enhanced as the correction range expands. The results of this study not only confirm the effectiveness of UAV measurement technology in radiometric surveys, but also provide a new method for radiometric surveys under large-scale and complex terrain conditions, which has significant practical application value in fields such as environmental monitoring, resource exploration, and nuclear security.

The accuracy of indirect measurements of Ra using gamma spectrometry critically depends on sealing techniques that prevent the escape of Rn (radon) generated within the sample. This study introduces a novel sealing method designed to overcome the limitations of conventional Rn sealing techniques. The Rn sealing performance of five sealing materials-silicone sealant, modified silicone sealant, butyl sealant, polyurethane sealant, and epoxy adhesive-was evaluated by sealing sample containers filled with Rn-containing water samples using each of the five materials, measuring Rn over time, and comparing experimentally estimated half-life of Rn for each sealed container with its physical half-life. Among the five sealing materials evaluated, the experimentally estimated half-life of Rn in samples sealed with modified silicone sealant, butyl sealant, polyurethane sealant, and epoxy adhesive, excluding silicone sealant, closely matched the physical half-life of Rn, demonstrating their reliable sealing performance. To verify the validity of the sealing method, the activity concentration of Ra was estimated in IAEA-434 phosphogypsum, a certified reference material, sealed with five different sealing materials. The results showed that for the four sealing materials, excluding silicone sealant, the measured values were statistically consistent with the certified value of IAEA-434, confirming the validity of the sealing method using these materials. The proposed sealing method enables accurate analytical results without requiring the complete filling of the measurement container, allows for visual inspection of the sample's filling state, and facilitates sample reuse for further analyses. These advantages make it a practical approach for the routine analysis of NORM and environmental samples.

The Radiological and environmental impact assessment models are used for evaluating the radiological impact of actual and potential releases of radionuclides into the environment. For tritium, a special radionuclide that readily enters into many organic forms, the processes involved in its interception and uptake by plant leaves during a tritiated rain are complex and not yet well understood. When rain containing tritiated water (HTO) starts, water is retained progressively on leaves up to a maximum storage capacity and also evaporates from the wet canopy part. The dynamics of leaf HTO concentration depends also on rain intensity and duration. In the absence of experimental data for leaf HTO concentration due to tritiated rain, various processes of potential importance are presented. Processes such as: leaf interception during rain event, interaction between drops and leaf surface, and extension of water layer (adhesion fraction) are described in the present study. Recent results on pesticide spray and sprinkler irrigation experiments and modelling approaches are used, because they provide useful information for the interaction between water droplets and the leaf surface. The rain drop diameter distribution and the associated drop falling velocity are linked with the washout studies and past results for tritium are used. The main crops (i.e. wheat, maize, barley, soybean, oilseed rape, and grape) around Cernavoda Nuclear Power Plant (Romania), operating two CANDU 6 units with high tritium loads are considered. For radiological impact assessment of tritium, the tritiated rain on crops at harvest for normal and/or short term and intense tritium release are presented.

Accurate measurement of the amounts of radiocesium (Cs) that transfer from the canopy to the forest floor at the recent quasi-equilibrium state is crucial for improving the accuracy of long-term predictions of Cs distribution in forests. This study is the first to detail the Cs flux via throughfall, stemflow, and litterfall processes in two Japanese cedar forests (KU1-S and KU2-S) and one deciduous broad-leaved forest (KU1-Q) in the Fukushima Prefecture during the quasi-equilibrium state. From 2020 to 2023, the annual transfer of Cs from the canopy to the forest floor, relative to the initial deposition, varied among the study plots but never exceeded 2% (0.433-0.564% in KU1-S, 1.06-1.62% in KU2-S, and 0.421-0.461% in KU1-Q). Since the transfer of Cs from trees to soil is balanced with the transfer from soil to trees at the quasi-equilibrium state, these percentages can be interpreted as the root uptake of Cs from the soil, which is difficult to observe directly. Analysis of the contributions of litterfall, throughfall, and stemflow to the total transfer of Cs revealed that litterfall accounted for more than 50% in both Japanese cedar and deciduous broad-leaved forests. We also found that the proportion of Cs flux via litterfall was higher in Japanese cedar forests compared to the deciduous broad-leaved forest (KU1-S:91-92%; KU2-S:74-77%; KU1-Q:57-60%). These findings regarding the Cs fluxes at the quasi-equilibrium state will enhance our understanding of the future dynamics of Cs within forest ecosystems and improve the accuracy of long-term predictions of Cs activity concentration in forests.

Tritium is an ubiquitous radioactive hydrogen isotope. It is found in all environmental compartments, in three different forms: tritiated water (HTO), gaseous tritium (HT) and organically bound tritium (OBT). Once internalized in the organism, it can either be found free in the tissues (TFWT) or bound to organic matter (OBT). This study aims to assess if tritiated thymidine, an organic form of tritium, induces DNA breaks once internalized in a model organism and its DNA. To do so, both experimental procedures and nanodosimetry simulations have been used. Zebrafish embryos (3.5 hpf, hours post fertilization) were exposed to three tritiated thymidine activity concentrations (7.5, 40, 110 kBq/mL, leading to internal dose rates of 22, 170 and 270 μGy/h) for four days. Individuals were sampled after 1 and 4 days of exposure and DNA break levels were assessed by the comet assay. Results showed that, even at the lowest activity concentration, tritiated thymidine induced DNA breaks in both embryos (1 dpf) and larvae (4 dpf). It was also highlighted that there was no increase nor decrease in DNA break level between 1 and 4 dpf, except in the case of the exposure to 170 μGy/h, where a slight decrease was observed. Geant4-DNA Monte Carlo simulations, performed on two spherical zebrafish nuclei of two different radii (2.5 and 5 μm), highlighted that organic tritium mainly induced single strand breaks (SSB). The results also showed that most of the damage was indirectly induced. Those results, combined with various experimentations, expose tritiated thymidine genotoxic pathways that could lead to both short- and long-term health effects.

Cementitious materials are commonly used for the long-term disposal of low-level radioactive waste (LLW) in subsurface engineered disposal facilities. Iodine-129 is a key-risk driver, along with Tc and Cs, in proposed low- and high-level waste disposal facilities in the United States. The distribution coefficient (K concentration ratio of I/I) is one of the key parameters used for risk assessments to estimate the risk posed by radioactive waste disposal facilities. The objective of this study is to examine iodine (I) K values in sandy and clayey sediment environments impacted by cementitious leachate. Batch sorption experiments were conducted using subsurface sediments from Savannah River Site (SRS) for three iodine species (iodide (I), iodate (IO) and organo-iodine (org-I)). Besides the SRS groundwater (pH = 5.5), three background solutions were used to simulate the cementitious leachate in different stages of cement aging, including cementitious leachate from a freshly prepared grout (Stage I of cement aging), Ca(OH)-saturated solutions (Stage II, moderately aged grout leachate), and CaCO-saturated solutions (Stage III, aged grout leachate). Sorption of iodide (the most common iodine species) to the sandy and clayey sediments was generally undetected in most solutions, except in groundwater (0.9-5.6 L/kg). Iodate K values ranged from 2.1 to 14 L/kg with sandy sediment and from 3.9 to 54 L/kg with clayey sediment, with the same background solution rankings for both sediments: Stage I < Stage III < Stage II < groundwater. Org-I demonstrated the strongest sorption to both sediments, varying from 20 to 149 L/kg to sandy sediments and from 17 to 117 L/kg on clayey sediments. Compared to groundwater conditions, the three iodine species generally demonstrated decreased sorption in the presence of cementitious leachate-impacted sediments. An important exception was org-I, which had previously been shown to comprise 45 % of the total iodine released from grout waste forms. It generally had enhanced sediment sorption in the presence of Stage II Ca(OH) and Stage III CaCO simulant. The fraction of iodine sorbed in the presence of cementitious leachate simulant with respect to the concentration sorbed under background groundwater conditions (calculated as K-CementLeach/K-GW) was 0.02-0.23 for iodide, 0.07-0.88 for iodate, and 0.14-5.29 for org-I. These results provided novel insight into the importance of accounting for the change in water chemistry in nuclear waste disposal systems containing cementitious engineered barriers. Neglecting to do so may result in the underestimation of the long-term risk posed by radioiodine to the environment and human health. Additionally, these results underscored the divergent geochemical behavior of the three dominant iodine species in waste disposal environments.

Soil erosion represents a critical ecological and environmental challenge on a global scale. In this study, the Baiyang River sub-watershed, located in the eastern Tianshan Mountains of Xinjiang, China, was selected as a representative area for the quantitative analysis of soil erosion. The dual isotope tracer technique, utilizing Cs and Pb, was employed to investigate the distribution patterns of these isotopes within soil profiles and to assess soil erosion dynamics under varying land-use types. This approach aimed to elucidate the influence of different land-use practices on soil erosion rates and nutrient contents to support sustainable land management strategies. The results indicated that the distribution of Cs and Pb followed an exponential pattern in woodland and grassland, whereas in cropland, these isotopes exhibited a relatively uniform distribution. The average soil erosion rate in the study area followed the pattern: cropland (20.39 t ha·yr) > grassland (13.21 t ha·yr) > woodland (1.86 t ha·yr). The contents of soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP) exhibited the opposite trend, with woodland > grassland > cropland. Furthermore, nutrient loss was lowest in woodland, highlighting its superior capacity to retain nutrients. SOC and TN demonstrated stronger correlations with soil particle size and isotopic composition, whereas phosphorus showed weaker correlations, suggesting that the distribution and transport processes of phosphorus differ significantly from those of carbon and nitrogen. The application of the Cs and Pb dual isotope tracer technique offers a novel approach and valuable data for the quantitative assessment of soil erosion in arid regions, contributing significantly to ecological conservation and sustainable land management.

In environmental impact assessments the biota-to-water concentration ratio (CR) is needed for calculating the transfer of radionuclides from water to aquatic organisms. Data are frequently missing, especially for rare elements, and various approaches are used for extrapolation of missing values. In this study we have analysed elemental concentrations in fish based on previously published data for brackish and freshwater. We grouped the fish according to their species and used a mixed linear model to calculate site- and ecosystem-specific CR values. These values were compared with values from different extrapolation methods (site, literature, element and ecosystem analogues). We also calculated edible versus whole body conversion factors. The site-specific CR values frequently differed by an order of magnitude or more between the brackish and freshwater ecosystems. For most elements the value was affected by site, locality (within site) and fish type. Also the inclusion of bones affected some CR values. Literature analogues diverged more from the site data than site analogues, but these both performed better than element and ecosystem analogues. The ratio between edible and whole-body concentrations was typically similar in brackish and freshwater environments. We conclude that a joint analysis of different aquatic ecosystems at similar sites allows for robust estimates of systematic and random variation associated with CR. We suggest that there are more possible analogues than the ones considered in the international recommendations, and that the choice of analogue should be based on the available data and the performance of the analogues in the specific assessment at hand.

This paper describes the creation of a voxel-based dosimetric model of a toadfish (Halobatrachus didactylus) from available CT images in which 29 organs are identified and segmented using 3D Slicer software. To validate the present dosimetric model Specific Absorbed Fractions (SAFs) were calculated for ten vital organs as sources and all targets, for discrete energies of electrons and photons. Then, the obtained dosimetric coefficients were compared to those calculated in similar organs in a voxel-based phantom of a trout fish (Oncorhynchus mykiss). The results showed a general agreement between the comparative dosimetric data, highlighting the validity of our dosimetric model for Halobatrachus didactylus. We conclude that the current dosimetric fish model can be applied in future research to evaluate dosimetry calculations related to radiation exposure in regions surrounding the Fukushima accident site.

Freeze-thaw (F-T) climate causes cracking in the soil cover of uranium tailing ponds, and the exhalation of the carcinogenic gas radon needs to be monitored under the phenomenon. In laboratory experiment, cracking tests under 5 F-T cycles were carried out on 3 soil uranium tailing pond models, including Gansu loess (GS-L), Hengyang laterite (HY-L), and Hebei loess (HB-L). Each cycle consisted of -15 °C, 12 h of freezing and 15 °C, 12 h of thawing. The area, length, mean width and fractal dimension of the cracks on the soil surface were quantified using digital imaging techniques, the correlation of parameters with the radon exhalation was compared. Finally, the qualitative explanation was provided from the perspectives of visual and scanning electron microscopy (SEM). The results showed that: Fine, short and irregular cracks developed to penetrating wide cracks after the 3rd cycle. The radon barrier capacity of the soil was negatively correlated with the number of F-T cycles. After 5th cycles, the radon exhalation rates of GS-L, HY-L, and HB-L were 0.675 Bq/(m·s), 0.555 Bq/(m·s), and 0.462 Bq/(m·s), which increased by 63.8 %, 43.1 %, and 39.6 %, respectively. The mean width of cracks showed the highest correlation with radon exhalation rate: HY-L (0.91), GS-L (0.89), and HB-L (0.87). SEM results showed fewer soil internal pores mean harder radon migration. The findings are relevant to the monitoring of radioactive gas in uranium tailing ponds.

This position paper deals with the critical analysis of the existing European regulation of indoor radon and NORM in building materials. It represents an opinion of the initiative group of experts created during the Workshop of European NORM Association (ENA) held in Rome, 15-17 May 2024. The main conclusions and propositions of the experts have been also discussed at the round table during the IX Terrestrial Radioisotopes in Environment International Conference on Environmental Protection, 19-22 November 2024, Vonyarcvashegy, Hungary. The current paper lists and discusses several missing points and challenges within the European regulatory system in the field of NORM in building materials and indoor radon, consisting of three interconnecting functional levels: Legislative, Normative, and Methodological. It also serves as a Road Map for the regulatory development in the next decade. Our analysis identifies areas for improvement. While the normative guidance (mid-tier of the hierarchical regulatory pyramid) is robust, the legislative framework has gaps, and methodological support remains underdeveloped with several serious deficiencies. These issues significantly hinder the global implementation of GRPs. To address these gaps, new harmonized standards and guidelines are necessary. It is concluded that enhancing radon and NORM regulations can be achieved by developing and globally implementing several relevant European (international) standards and guidelines within rational ISO/IEC concepts. From a legal-philosophical perspective, these findings are intended as an invitation to dialogue, not merely a critique.

Recent global radiological incidents have heightened attention to environmental radioactivity. Although analytical methods for anthropogenic radionuclides in environmental samples and background research are relatively well-established on a global scale, systematic research data are still lacking in the Northwest China region. This region is not only affected by global fallout caused by nuclear weapons tests in the last century, but also the regional fallout -the Lop Nor nuclear test site, China's only nuclear testing base. The various sources, complicated climate and terrain results in the unique distribution of radionuclides. Therefore, systematically summarizing the spatial distribution characteristics of artificial radionuclides in the northwest region serves as a scientific foundation for assessing the environmental risks associated with historical nuclear test legacies. It also represents a critical component in building a global nuclear safety monitoring network. Simultaneously, it provides essential data support for regional ecological environmental protection and the development of green industries. This study reviews anthropogenic radionuclide distribution in Northwest China's environment, highlighting uneven spatial coverage, incomplete nuclide inclusion, and insufficient databases. The paper proposes future directions for systematic and long-term comprehensive research, emphasizing the need to strengthen the investigation of the links between artificial radionuclides and ecological effects as well as health risks. This paper summarizes research to enhance monitoring and improve anthropogenic radionuclide background data, offering a scientific basis for policy-making and environmental protection. The review presented in this paper offers an important reference for further exploring solutions to environmental radioactivity issues in Northwest China.

To establish causal relationships between radiation exposure and tissue effects, it is necessary to calculate the doses to critical organs and tissues and to evaluate the dose-effect relationship. The tools of non-human biota dosimetry that exist nowadays do not take into account the heterogeneous radionuclide distribution between organs and tissues. In the current study, a computational phantom of the roach body segment was developed based on the assessment of the morphometric parameters of target organs. The spine, ribs and head kidney were considered as target organs for bone and hematological effects of radiation exposure. The dose factors to convert specific activity of incorporated Sr and Cs to dose rates in target organs were calculated based on Monte Carlo simulation of electron and photon transport. One Bq/g of Sr in bone tissue lead to dose rates equal to 1.98, 3.38 and 7.49 μGy/day in the head kidney, ribs and spine, respectively. The accumulation of Cs in the bones results in bone-specific dose rates that are 3-4 times lower than those at the same concentration of Sr. The obtained results were used to calculate doses to the roach from two radioactively contaminated waterbodies of Ural region. Maximum doses were typical of vertebra (1.4 ± 0.2 and 27.0 ± 8.3 mGy/day). They were 1.4-3 times higher than doses head kidney and ribs. One can expect more pronounced bone effects of radiation exposure in the vertebral bodies than in the ribs of fish, and they should be considered as separate target organs in the presence of Strontium isotopes in the environment.

Monitoring environmental radiation around nuclear facilities is critical for safety and regulatory compliance. Traditional methods, such as environmental radiation monitoring using high-pressure ion chambers and thermoluminescent dosimeters, have limitations with regard to cost, complexity, and response time. To address these issues, we developed a compact Geiger-Müller (GM) counter-based detector network for real-time radiation monitoring at the Korea Atomic Energy Research Institute (KAERI). The developed GM detector module is operated using a battery and a solar panel to ensure maintenance-free operation and is equipped with LTE wireless communication. The Daejeon KAERI site spans approximately 1.42 km, where a total of 50 GM modules were installed, forming a high-resolution radiation monitoring network. In addition, convolutional neural network-based radiation anomaly detection and source-tracking models were developed to enhance the monitoring capabilities. The anomaly-detection model achieved an accuracy of 0.9999 and an area under the receiver operating characteristic curve of 0.9999, effectively distinguishing between normal and anomalous radiation. The source-tracking model predicted source locations with an average error of 3.44 m for the test set. In field experiments using a low-intensity Cs source, the average error was 54.73 m. The proposed cost-effective, high-resolution radiation mapping solution can be easily deployed and maintained, ensuring comprehensive coverage and timely detection of radiation anomalies.

The CR-39 solid-state nuclear track detector is a commonly used instrument for passively measuring radon. When using CR-39 to measure the radon exhalation rate from the surface of a medium, the effects of leakage are often overlooked. However, to a certain extent, system leakage can affect the accuracy of the measurement results. Therefore, the effect of different effective decay constants (including leakage) on the radon exhalation rate is worth studying. In this study, both theoretical and experimental validation methods were used to verify the effect of the uncertainty of the effective decay constant on the results of CR-39 measurements of radon exhalation rate from the medium surface. In the theoretical validation, different values of radon exhalation rate can be obtained by substituting different effective decay constants into the CR-39 formula for measuring radon exhalation rate while keeping the other variables constant. In the experimental validation, the radon exhalation rate in the same medium was measured using both CR-39 and RAD7. Since the traditional passive method (CR-39 solid-state nuclear track detector) cannot directly obtain the effective decay constant, the effective decay constant in the CR-39 measurement experiment was replaced by the effective decay constant value fitted from the RAD7 experimental data. The results showed that the radon exhalation rate value measured by CR-39 was much larger than that measured by RAD7. From the theoretical and experimental validation, it is concluded that the uncertainty of the effective decay constant has a significant effect on the radon exhalation rate measured by CR-39.

Lacustrine groundwater discharge (LGD) is a crucial component of lake hydrological budgets and serves as a significant source such as nutrients and pollutants. Naturally occurring radioactive radium isotopes (Ra, Ra, Ra, Ra) have emerged as valuable tracers for studying lacustrine groundwater discharge due to their distinctive geochemical properties. While radium isotopes were primarily utilized in studies of submarine groundwater discharge in the past, their "salt effect" characteristics have increasingly established them as essential tools for identifying and quantifying LGD. This review focuses on the application and research advancements of radium isotopes in tracing LGD, encompassing concepts and methodologies related to lacustrine groundwater discharge, the geochemical characteristics of radium isotopes, the development of radium isotope tracing techniques for LGD, and strategies for source identification and quantification of radium in the groundwater discharge process. Furthermore, this review addresses several limitations and challenges encountered in the application of radium isotope tracing techniques for LGD research and outlines future research directions that could enhance the quantitative study of radium isotopes.

This study investigates plutonium (Pu) isotopes preserved in nebkhas--aeolian dunes formed by shrubs intercepting wind-blown sands to reconstruct environmental changes in the semi-arid Mu Us dune field, northern China. Analysis results of two nebkha profiles reveal that the Pu/Pu atom ratios consistently approximate 0.18, indicating a dominant source from global fallout, with no significant local contributions from the Lop Nor or Semipalatinsk nuclear tests or the Chernobyl accident. Total Pu inventories (308 ± 3 Bq/m and 402 ± 3 Bq/m) highly exceed the direct atmospheric fallout value (66 Bq/m), suggesting accumulation of both distant and proximal Pu-bearing sediments transported by wind. Depth distributions of Pu activities (0.005-0.387 mBq/g) show a single-peak corresponding to 1963 and an onset around 1952, consistent with previous Cs and optically stimulated luminescence (OSL) dating results, validating Pu isotopes as reliable chronostratigraphic markers. Sediment deposition rates have declined over the past 20 years compared to the 1960s-1970s, likely due to reduced sandstorm activity and wind speed, potentially linked to regional afforestation and land-use changes. This study demonstrates the widespread nature of global Pu contamination-even in remote deserts, and highlights nebkhas as a novel geological archive for reconstructing atmospheric deposition and environmental changes. By providing a direct record of Pu deposition, this work advances understanding of Pu sources, transport, and behavior in arid regions, with broader implications for using radionuclides to study aeolian processes and environmental evolution.

Remediation of land and groundwater that are contaminated with high-risk driving anionic-radionuclides, such as iodine-129 (I-129) and technetium-99 (Tc-99), remains an intractable problem. The objective of this study was to evaluate biochar materials as a low-cost and effective sorbent for Tc-99 and three iodine species, iodide/iodate/organo-iodine (org-I). Sorption studies were conducted with biochar derived from pecan shells (Carya illinoinensis), that underwent two pyrolysis temperatures (500 °C and 700 °C) and two types of acid-activation (HPO and HCl). Acid-activated biochar had much higher sorption capacities (in terms of distribution coefficient, K, the concentration ratio of solid:liquid) for Tc-99 and different iodine species, than non-acid-activated biochar. The HPO-activated biochar (500 °C) was the most effective sorbent with Tc-99 K of 49,390 ± 14,268 mL/g, iodide K of 2433 ± 312 mL/g, iodate K of 410 ± 168 mL/g, and org-I K of 857 ± 181 mL/g. The HCl-activated biochar (700 °C) was also effective at sequestering Tc-99 (K of 7864 ± 5,585 mL/g) and iodide (K of 2481 ± 237 mL/g) but not for iodate/org-I. Solid-state C-nuclear magnetic resonance (NMR) analysis suggested the strong sorption capacity related to the formation of abundant alkene, aromatic and heteroaromatic functional groups, which was also supported by the Fourier-transform infrared spectroscopy (FTIR) analysis. Additionally, the FTIR suggested the possible electrophilic substitution of C-H by iodine to form C-I bond. Surface area measurements and SEM images indicated the HPO-activated biochar (500 °C) had especially high surfaces areas. Functionalized biochar may provide a cost effective and efficient sorbent for sequestering I-129 and Tc-99 from the biosphere, thereby reducing human risk.

Building materials are one of the main sources of indoor radon, study of radon exhalation from building walls is of great reference significance for indoor radiation protection. Radon exhalation from building walls is comprehensively affected by environmental factors. A radon migration and exhalation model of building walls under the influence of coupled heat-moisture-air transfer was established. The radon exhalation mechanism of an aerated concrete wall under the influence of different relative humidity, temperature, relative humidity difference, temperature difference, air pressure difference and solar radiation was studied. The sensitivity of these factors to radon exhalation rate was analyzed. The results showed that the radon exhalation rate was positively correlated with relative humidity, but not with temperature; The radon exhalation rate was positively correlated with the relative humidity difference, and the temperature affected the correlation degree; The radon exhalation rate was positively correlated with the absolute temperature difference, and the relative humidity affected the correlation degree; The exhalation rate of radon was approximately linearly positive correlated with the pressure difference; Under the influence of solar radiation, the radon exhalation rate decreased; Radon parameters of material, relative humidity and solar radiation were more sensitive to radon exhalation rate than temperature, air pressure and radon concentration in air. For reducing radon exhalation rate of building walls and indoor radon concentration, we propose to use building wall materials with low radium content, keep indoor relative humidity and indoor and outdoor temperature difference low, and strengthen indoor ventilation at night, cloudy and rainy days.

Atmospheric Be activity concentration was continuously measured in Dazaifu (33°30'N, 130°30'E), western Japan, from 1999 to 2020, and its variation was analyzed. Aerosol samples were collected using quartz fiber filters. The filtered samples were punched into circles, pressed, and molded into a 2-mm-thick disk for accurate Be quantification. Daily Be data analysis, encompassing an analysis for 7765 days over 22 years, revealed a concentration range of not detected-18 mBq/m, characterized by substantial monthly variation and smoothed annual variation. An average daily Be activity concentration of 5.0 ± 2.6mBq/m was considered to be representative at the ground-surface-level in 30-40°N. Results from a two-way Analysis of variance (ANOVA) indicated statistical significance in monthly and annual Be variabilities. The monthly variability of Be activity concentration was approximately four times greater than the annual variability. Frequency analysis revealed that the monthly variability comprised major 12-month and minor 6-month periodicities. The substantial decrease in Be activity concentration during summer, a primary driver of monthly variation, was also observed at other locations in Japan, attributed to a stable high-pressure system in the Pacific Ocean that stalled over Japan's southern seas, followed by the inflow of air masses containing low Be activity concentrations. The annual variation was primarily influenced by the 11-year solar activity cycle, which affects the intensity of cosmic rays that produce Be.