Transport and dispersion of tritium from the radioactive water of the Fukushima Daiichi nuclear plant

Determination and human health risk assessment of TFWT, OBT and carbon-14 in seafood around Qinshan Nuclear Power Plant

This work aims to evaluate the effects of the operation of Qinshan nuclear Power Plant (QNPP) on tritium (3H) and carbon-14 (14C) levels in seafood and assess the health risks caused by seafood consumption. Five kinds of seafood, including marine fish, prawn, razor clam, crabs, and seaweed, were collected from QNPP and the sea around Hangzhou Bay. The activity concentrations of tissue free water tritium (TFWT), organically bound tritium (OBT) and 14C were determined, respectively, and the annual intake and annual effective dose (AED) were calculated. The results showed that the TFWT, OBT, and 14C activity concentrations of the seafood in the surrounding area of QNPP ranged from 2.00 to 74.75 Bq/L, <1.04 to 19.68 Bq/L and 0.09 to 0.17 Bq/g·C, respectively. The TFWT, OBT, and 14C activity concentrations of the seafood in Hangzhou Bay ranged from 1.36 to 10.55 Bq/L, 1.08 to 6.78 Bq/L and 0.07 to 0.13 Bq/g·C, respectively. The differences were not statistically significant. The total AED from 3H and 14C due to the seafood consumption for the residents in the surrounding of QNPP and Hangzhou Bay were 1.96 × 10-4 and 1.61 × 10-4 mSv/year, respectively. The results showed that the operation of QNPP had no obvious effect on 3H and 14C accumulation in seafood, and the dose burden of population was low.

Three-Dimensional Printed Filters Based on Poly(ethylene glycol) Diacrylate Hydrogels Doped with Silver Nanoparticles for Removing Hg(II) Ions from Water

Nowadays, due to water pollution, more and more living beings are exposed to dangerous compounds, which can lead to them contracting diseases. The removal of contaminants (including heavy metals) from water is, therefore, a necessary aspect to guarantee the well-being of living beings. Among the most used techniques, the employment of adsorbent materials is certainly advantageous, as they are easy to synthesize and are cheap. In this work, poly(ethylene glycol) diacrylate (PEGDA) hydrogels doped with silver nanoparticles (AgNPs) for removing Hg(II) ions from water are presented. AgNPs were embedded in PEGDA-based matrices by using a photo-polymerizable solution. By exploiting a custom-made 3D printer, the filters were synthesized. The kinetics of interaction was studied, revealing that the adsorption equilibrium is achieved in 8 h. Subsequently, the adsorption isotherms of PEGDA doped with AgNPs towards Hg(II) ions were studied at different temperatures (4 °C, 25 °C, and 50 °C). In all cases, the best isotherm model was the Langmuir one (revealing that the chemisorption is the driving process and the most favorable one), with maximum adsorption capacities equal to 0.55, 0.57, and 0.61 mg/g, respectively. Finally, the removal efficiency was evaluated for the three temperatures, obtaining for 4 °C, 25 °C, and 50 °C the values 94%, 94%, and 86%, respectively.

Surface and subsurface dispersal of radioactive materials from Fukushima by subpolar gyre and intermediate waters in the North Pacific

Radioactive materials were released into the ocean following the Fukushima Daiichi Nuclear Power Plant accident in 2011. Six years after the accident, the radioactive material concentration was markedly increased in the Okhotsk Intermediate Water (OIW) of the Sea of Okhotsk. This material may have been subjected to southward subsurface dispersal by the North Pacific Intermediate Water (NPIW), which originates from the OIW. The spatiotemporal limitations of available methods have made it challenging to track the dispersal paths of radioactive materials in the North Pacific Subpolar region. Here, we performed a tracer experiment using a three-dimensional numerical model to determine the path of 137Cs from Fukushima to the Sea of Okhotsk via surface subpolar gyre currents and subsurface dispersion by OIW and NPIW. The results showed that the 137Cs concentration in the Sea of Okhotsk increased via the surface current and moved progressively southward via OIW six years after the accident and eastward via OIW and NPIW nine years after the accident, indicating that 137Cs transported by NPIW entered the subtropical region. Based on experiments, this temporal change was mainly caused by ocean currents. Thus, subsurface recirculation of radioactive material via the OIW and NPIW should be considered based on the predicted path and travel time of additional materials released from the power plant.

A critical review and update of modelling of treated water discharging from Fukushima Daiichi NPP

Since the accident at the Fukushima Daiichi nuclear power plant (FDNPP) in March 2011 seawater is still needed to cool the reactor cores. This water, contaminated with radionuclides, has been collected in tanks and treated on the site of the FDNPP. In 2021, the Japanese government decided to gradually discharge treated water into the ocean, which started on the 24th of August 2023 and will continue for the next 30 years. This paper provides a critical analysis of the models that were used in the different radiological impact studies. Based on the analysis, a hydrodynamic and a compartment models with a harmonized setup were used to estimate the impact of the discharge on humans and biota. Doses obtained with these two models were within one order of magnitude for humans (<0.1 μSv/year) and for biota (<10-6 mGy/d) indicating that harmonization of the model parameters improved the reliability of the simulation results.

Advanced porous materials and emerging technologies for radionuclides removal from Fukushima radioactive water

Japan recently announced the plan to discharge over 1.2 million tons of radioactive water into the Pacific Ocean, which contained hazardous radionuclides such as 60Co, 90Sr, 125Sb, 129I, 3H, 137Cs, and 99TcO4-, etc. The contaminated water will pose an enormous threat to global ecosystems and human health. Developing materials and technologies for efficient radionuclide removal is highly desirable and arduous because of the extreme conditions, including super acidity or alkalinity, high ionic strength, and strong ionizing radiation. Recently, advanced porous material, such as porous POPs, MOFs, COFs, PAFs, etc., has shown promise of improved separation of radionuclides due to their intrinsic structural advantages. Furthermore, emerging technologies applied to radionuclide removal have also been summarized. In order to better deal with radionuclide contamination, higher requirements for the design of nanomaterials and technologies applied to practical radionuclide removal are proposed. Finally, we call for comprehensive implementation of strategies and strengthened cooperation to mitigate the harm caused by radioactive contamination to oceans, atmosphere, soil, and human health.

The application of compulsory conciliation in the settlement of disputes over Fukushima contaminated water discharge

The imminent discharge of Fukushima-contaminated water into the ocean would result in severe controversies and disputes concerning marine environment pollution in Japan and the neighboring countries. This paper argues that high similarities can be found between the disputes arising from the imminent discharge and those subject to compulsory conciliation under the dispute settlement mechanism of the law of the sea. Together with the advantages of compulsory conciliation in settling disputes related to the exercise of discretion by states, it is asserted that compulsory conciliation could become the best choice to settle the potential disputes arising from the imminent discharge between Japan and the neighboring countries. This article also draws attention to some essential issues related to the application of compulsory conciliation, including the establishment of jurisdiction and authorities of the conciliation commission, and the implementation of the conciliation report.

Origin and pathway of a subsurface maximum of 137Cs detected in the winter of 2012 after the Fukushima accident

This study investigates the dispersion behavior of 137Cs and evaluates its origin (atmospheric deposition or direct ocean release) from the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident using a Lagrangian particle tracking model. The ocean circulation fields based on the Modular Ocean Model Version 5 (MOM5) were adopted for the simulation. The MOM5 results represented the formation and migration of subtropical mode water (STMW) comparable with observations and reanalysis data. Particularly, anticyclonic eddies south of the Kuroshio extension promoted surface mixing over 300 m in the cooling season. The particle tracking simulation reproduced well the maximum subsurface activity between 142 and 146°E, where STMW is deep owing to anticyclonic eddies, compared to the activity found via measurements conducted around 149°E in the winter of 2012. It also demonstrated that the 137Cs of the tropical and subtropical regions (10-35°N, 142-146°E) in the winter of 2012 almost entirely originated from atmospheric deposition.

Tritium: Its relevance, sources and impacts on non-human biota

Tritium (³H) is a radioactive isotope of hydrogen that is abundantly released from nuclear industries. It is extremely mobile in the environment and in all biological systems, representing an increasing concern for the health of both humans and non-human biota (NHB). The present review examines the sources and characteristics of tritium in the environment, and evaluates available information pertaining to its biological effects at different levels of biological organisation in NHB. Despite an increasing number of publications in the tritium radiobiology field, there exists a significant disparity between data available for the different taxonomic groups and species, and observations are heavily biased towards marine bivalves, fish and mammals (rodents). Further limitations relate to the scarcity of information in the field relative to the laboratory, and lack of studies that employ forms of tritium other than tritiated water (HTO). Within these constraints, different responses to HTO exposure, from molecular to behavioural, have been reported during early life stages, but the potential transgenerational effects are unclear. The application of rapidly developing "omics" techniques could help to fill these knowledge gaps and further elucidate the relationships between molecular and organismal level responses through the development of radiation specific adverse outcome pathways (AOPs). The use of a greater diversity of keystone species and exposures to multiple stressors, elucidating other novel effects (e.g., by-stander, germ-line, transgenerational and epigenetic effects) offers opportunities to improve environmental risk assessments for the radionuclide. These could be combined with artificial intelligence (AI) including machine learning (ML) and ecosystem-based approaches.

Simulation study on 3H behavior in the Fukushima coastal region: Comparison of influences of discharges from the Fukushima Daiichi and rivers

The release of tritium (³H) to the ocean is planned on the coastal environment in the Fukushima coastal region from Spring or Summer of 2023. Before its release, we evaluate the effect of ³H discharges from the port of Fukushima Daiichi and rivers in the Fukushima coastal region using a three-dimensional hydrodynamic model (3D-Sea-SPEC). The simulation results showed that discharges from the port of Fukushima Daiichi dominantly affected the ³H concentrations in monitoring points within approximately 1 km. Moreover, the results indicate that the effect of riverine ³H discharge was limited around the river mouth under base flow conditions. However, its impact on the Fukushima coastal regions under storm flow conditions was found, and the ³H concentrations in seawater in the Fukushima coastal region were formed around 0.1 Bq/L (mean ³H concentrations in seawater in the Fukushima coastal region) in the near shore.

The impact of Japanese nuclear wastewater discharge into the sea on the global economy: Input-output model approach

As the division of work within the world economic system becomes increasingly complex, the impact of disturbing events on the economic system is expanding. Recently, Japan proposed to discharge nuclear wastewater into the Pacific Ocean, which will cause damage to marine fisheries, thereby seriously affecting fisheries and other industries in Japan and other countries and regions around the world. Considering different scenarios of final and intermediate demand shifting, this paper uses the Inoperability Input-Output Model (IIM) and Multi-Region Input-Output Model (MRIO) to simulate the economic consequences of nuclear wastewater discharge in Japan and calculate the economic changes of each industry and country (region). The results show that: In the short term, when only the final demand for Japanese fishery products decreases. (1) The ten countries (regions) with significant economic losses are Japan, the United States, Chinese Taipei, Canada, Chile, South Africa, Mexico, Peru, the United Kingdom, and Ireland. (2) The ten countries (regions) with a significant increase in total output due to demand shift are China (People's Republic of), the Rest of the World, India, Indonesia, Viet Nam, the Philippines, Brazil, Myanmar, the Russian Federation, and Malaysia. (3) A ranking of changes in the total output of different industries. In the long term, when both intermediate and final demand for Japanese fishery products decrease. (4) The change in value added in Japan. (5) The change in value added of 67 countries (regions) worldwide. The ten countries (regions) with the most significant increase in value-added are the Russian Federation, China (People's Republic of), the Rest of the World, the United States, Indonesia, Australia, Norway, Korea, Viet Nam, and Myanmar. The ten countries (regions) with the most significant decrease in value-added are Japan, Chinese Taipei, Chile, South Africa, Peru, Thailand, Mexico, Cambodia, Costa Rica, and Morocco. Changes in value added of 45 industrial sectors worldwide.

Impact of the Fukushima Accident on 3H and 14C Environmental Levels: A Review of Ten Years of Investigation

The investigation of the impact of the Fukushima accident is still going on although more than ten years have passed since the disaster. The main goal of this paper was to summarize the results of tritium and radiocarbon determinations in different environmental samples, possibly connected with the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident. A document containing compiled data may serve as a solid basis for further research in the selected fields. To accomplish such effort, we went through dozens of relevant published papers, reporting 3H and 14C activity concentrations in precipitations, groundwater, seawater, river systems, tree rings, and, in some more extraordinary samples, such as herbaceous plants or debris from the damaged reactor buildings. As the referenced results would not be obtainable without adequate analytical techniques, the most common methods for routine measurement of tritium and radiocarbon concentrations are discussed as well. We believe that the correct identification of the affected environmental compartments could help quantify the released 3H and 14C activities and track their following fate, which could be especially important for plans to discharge contaminated water from the FDNPP in the upcoming years.

Flux of tritium from the sea to the atmosphere around a nuclear reprocessing plant: Experimental measurements and modelling for the Western English channel

Tritium is released to the environment by nuclear industries in various forms, mainly HTO. In impact studies leading to estimated doses for the population, atmospheric discharges are mainly taken into consideration because they generally lead to values higher than those related to liquid discharges. However, the tritium released in liquid environments can be transferred to the atmosphere by evaporation and then be transported to terrestrial ecosystems by wind. This study was carried out in France near a fuel reprocessing plant (RP) which discharges tritium into the western English Channel. We highlighted the influence of a mass of water enriched with tritium on the HTO levels in atmospheric water vapour downwind through 18 field campaigns. A hydrodynamic model able to simulate tritium activity in the water was coupled with an evaporation an atmospheric transport model. It allows to reconstitute variations in atmospheric tritium on the coast, depending on liquid discharges of tritium from the reprocessing plant. On this basis, when seawater containing 20-100 Bq.L^-1 of tritium flows between 0 and 10 km off the coast, variations in atmospheric activity onshore can increase of 2-15 Bq.L^-1. Mean tritium quantities released by the sea into the atmosphere in the Western English Channel reached 130 TBq.y^-1 over the 2017-2020 period. Emissions were estimated at 0.9-11.3 GBq km^-2.y^-1 and depends principally on the distance from the liquid discharge point. If we compare the "marine" source term, in HTO form, with the direct source term for gaseous discharges, the marine source term is one order of magnitude greater for the marine region affected by liquid discharges. Finally, we estimate that approximately 1.1% of tritium stock discharged at sea (regulated and controlled) return to the atmosphere each year at the scale of the Western English Channel.

Traffic light-type ratiometric fluorescence visual sensing of Cs+ in soybean oil based on dimension regulation of 2D perovskite nanosheets

Determination of cesium ion in soybean oil is of high importance since the increasing risk from releasing of main component of nuclear waste cesium 137. The complex composition and high viscosity of soybean oil make it necessary to convert it into water phase by nitration before detection, so developing a simple, accurate and sensitive method for on-site sensing of Cs⁺ in soybean oil is still a big challenge. In this work, we report a traffic light-type ratiometric fluorescence strategy for the visual sensing of Cs⁺ in soybean oil based on dimensional regulation of two dimensional (PEA)₂PbI₄ perovskite nanosheets (NSs). The PEA⁺ in (PEA)₂PbI₄ NSs exchanged with Cs⁺ and lead to dimension of partial (PEA)₂PbI₄ NSs progressively increase from 2D to 3D CsPbI₃ NCs. Resultantly, the fluorescence of (PEA)₂PbI₄ NSs decreases with a concomitant fluorescence enhancement of CsPbI₃ NCs upon increasing the concentrations of Cs⁺, and the emission accordingly change from green, yellow to red with a high fluorescence colorimetric resolution up to 5.0 μM, make it successful to achieve on-site sensing of Cs⁺ in soybean oil just with naked eye in 5 min without any nitration, demonstrating a bright application future for determination of Cs⁺ in the soybean oil.

Development and calibration of a modifiable passive sampler for monitoring atmospheric tritiated water vapor in different environments

Anthropogenic release of tritium from nuclear facilities is expected to increase significantly in the coming decades, which may cause radiation exposure to humans through the contamination of water and food chains. It is necessary and urgent to acquire detailed information about tritium in various environments for studying its behavior and assessing the potential radiation risk. In the atmosphere, although the passive sampling technique provides a low-cost and convenient way to characterize the dynamics of tritiated water vapor (HTO), a single, simple sampler configuration makes it difficult to collect sufficient and representative samples within the expected period from different environments. In this study, we systematically studied the impacts of sampler configurations on sampling performance and proposed a modifiable sampler design by scaling sampler geometry and adjusting absorbent to achieve different monitoring demands. The samplers were subsequently deployed at five sites in China and Germany for the field calibration and the measured results exhibited a good agreement between the adsorption process obtained in sites corrected with diffusion coefficient and the one calibrated in Shanghai. This suggests the feasibility of predicting sampling performance in the field based on known data. Finally, we developed a strategy for sampler modification and selection in different environments and demonstrated that using easily obtainable environmental data, our sampler can be optimized for any area without any time-consuming preliminary experiments. This work provides a scientific basis for establishing high-resolution atmospheric HTO database and expands the conventional empirical sampler design paradigm by demonstrating the feasibility of using quantitative indices for sampler performance customization.

Tritium transport in non-saturated concrete under temperature fluctuations

This work studies the effect of the environmental conditions on tritium transport in concrete cells storing radioactive waste. Water with high concentration of tritium was leaking from drains situated in these concrete cells, which indicates flow of water and tritium transport in these cells. 2D numerical models together with temperature and humidity measurements suggested that this leak of tritiated water is caused by a combination of thermo-hydraulic processes occurring in the unsaturated concrete, that comprise capillary rise from the groundwater, evaporation and condensation due to temperature gradients caused by seasonal temperature fluctuations outside. Following this conceptual model, numerical models have been developed to study the tritium transport in the concrete. Model results show that tritium concentration varies according to evaporation and condensation processes inside the concrete cell. An analysis of tritium fluxes revealed that differences in transport mechanisms in liquid and gas can cause concentration gradients of tritium in zones of high water content very different or even opposite to those in zones with low water content. From our numerical calculations, we conclude that there is no release of tritiated water to the groundwater.

Viewpoint on the Integration of Geochemical Processes into Tracer Transport Models for the Marine Environment

Two types of models are used to describe the interactions of tracers dissolved in the ocean with marine sediments: equilibrium and dynamic models. A brief description of these models is given in this opinion paper, and some examples are presented to show that preference should be given to the dynamic descriptions in modern pollutant transport models to be used in emergencies as well as in the case of chronic tracer releases to the sea.

Establishing historical 90Sr activity in seawater of the China seas from 1963 to 2018

Historical ⁹⁰Sr activity in seawater was established in the China seas from 1963 to 2018. Based on the exponential decrease in ⁹⁰Sr activity in seawater, the effective half-life (EHL) of ⁹⁰Sr was quantified to be 11.5 ± 1.6 a, 16.5 ± 2.4 a, 27.2 ± 6.2 a, and 26.7 ± 4.3 a in the Bohai Sea, Yellow Sea, East China Sea, and South China Sea, respectively. We found contrasting patterns in the EHL of ⁹⁰Sr and ¹³⁷Cs in the marginal seas and open oceans that were closely related to the subtly different pathways of ⁹⁰Sr and ¹³⁷Cs in marine environment. Additionally, we demonstrated that Fukushima-derived ⁹⁰Sr (<0.01 Bq/m³) would be difficult to identify in the China seas. Our study not only provided the key parameter of the EHL in marine models for predicting the ⁹⁰Sr activity in the China seas in the post-Fukushima era but also enhanced our understanding of ⁹⁰Sr behavior and its fate in marine environments.

Planned release of contaminated water from the Fukushima storage tanks into the ocean: Simulation scenarios of radiological impact for aquatic biota and human from seafood consumption

The radiological impact for human and aquatic biota as a result of a planned release of contaminated water stored in tanks near the Fukushima Dai-ichi Nuclear Power Plant to the Pacific Ocean is assessed. The total activity for 10 dominant radionuclides (³H, ¹⁴C, ⁶⁰Co, ⁹⁰Sr, ⁹⁹Tc, ¹⁰⁶Ru, ¹²⁵Sb, ¹²⁹I, ¹³⁴Cs, ¹³⁷Cs) in tanks is estimated. The compartment model POSEIDON-R is applied to compute the concentration of activity for each radionuclide in water, bottom sediments, and biota, and corresponding doses to marine organisms and humans from seafood consumption. Predicted concentrations of activity in marine products in future will not exceed food safety limits in Japan. The computed maximum committed effective dose to humans is less than 1 μSv per year with the highest contribution from ¹²⁹I and ¹⁴C. Maximum absorbed doses to non-human biota are in the order of 0.05 to 20 μGy per year, meaning that no deleterious effects are expected.

Opening Fukushima floodgates: Modelling 137Cs impact in marine biota

A numerical model was applied to simulate the transport of ¹³⁷Cs released with the waters which were used to cool Fukushima reactors. These stored waters will be released to the Pacific Ocean according to Japanese government plans. The radionuclide transport model is Lagrangian and includes radionuclide interactions with sediments and an integrated dynamic foodweb model for biota uptake. Calculations made from a conservative approach indicate that expected concentrations in sediments and marine fish would be orders of magnitude below those detected after Fukushima accident and also lower than those resulting from global fallout background.