129I Concentrations Research Articles

Changes in 129I concentration of soil samples after thermal drying

Abstract To precisely evaluate the concentration of iodine-129 (129I) in soil samples, changes in this concentration after thermal drying under several temperature conditions were investigated. The soil sample used in this study was collected from a site located near a nuclear fuel reprocessing plant, which atmospherically released 129I in a test operation in 2006–2008, resulting in the soil sample containing higher 129I concentrations than their natural levels. Thermal drying was conducted from 60°C to 110°C and compared with lyophilization result, showing that the 129I concentration in the soil sample was statistically comparable among all the drying treatments.

Riverine 129I dynamics during high-flow events on the Abukuma River in Fukushima

This study presents the riverine 129I concentrations and fluxes during high-flow events. The river water samples obtained by a previous study were subjected to 129I analyses. River water samples were collected at the midstream of the Abukuma River for five and seven times during high-flow events in July 2018 and October 2018, respectively. Suspended solids and filtered water samples were measured for 129I/127I ratios using an accelerator mass spectrometer system and for 127I concentrations using ICP-MS. Aggregated mean values of dissolved 129I concentration and 129I concentrations in suspended solids were 0.11 μBq/L (n = 12) and 0.60 mBq/kg (n = 12), respectively. Corresponding values of 129I/127I ratios were in 2.2 × 10−9 (n = 12) and 3.7 × 10−9 (n = 12), respectively. These concentrations and ratios were comparable to those at the background level before the Fukushima Dai-ichi nuclear power plant accident. Positive correlations with dissolved 137Cs and Cl− concentrations suggested that the dissolved 129I concentration decreased due to dilution of the river water during the events. A positive correlation with total carbon content suggested that organic matter contents determine 129I concentrations in suspended solids. The total 129I fluxes during JUL18 and OCT18 were 9.9 × 103 and 2.2 × 104 Bq, respectively. Although dissolved 129I was predominant under low-flow conditions, the particulate 129I flux increased by one or two orders of magnitude during the peak water discharge phases. These results underline the importance of particulate 129I dynamics during high-flow events for quantitative evaluation of the 129I cycle.

Chemical characteristics, formation mechanisms, and geological evolution processes of high-salinity coal reservoir water in the Binchang area of the southern Ordos Basin, China

The chemical characteristics of coal reservoir water are important for studying the formation and enrichment of biogenic coalbed methane (BCM). Based on geological and sampling test data, this paper studied the geochemical characteristics and formation mechanisms of high-salinity coal reservoir water (CRW) in the Jurassic Yan'an Formation of the Binchang area in the southern Ordos Basin. The results show that the TDS contents of the CRW in the Binchang area are between 7577.38 and 15,138.61 mg/L (av. 13,268.95 mg/L), which is high-salinity brackish water. The ion types of CRW are mainly Na+, Cl− and HCO3−, and the correlations between TDS and Na+ and Cl− are close to 1. The Piper trilinear diagram indicates that the evolution direction of the CRW is deep concentrated brine, and the hydrochemical type is the NaCl type. The 127I concentrations of CRW are between 285 and 484 μg/L, which are much higher than the values of 55.88 μg/L for seawater. The results of 129I dating show that the minimum age of the CRW in the study area is between 6.7 Ma and 39.97 Ma, which is much younger than the actual geological age of the Yan'an Formation. The hydrogen and oxygen isotope results show that the CRW in the study area experiences an apparent oxygen drift, indicating that the coal reservoir of the Yan'an Formation has good sealing and a long retention time for the CRW. The hydrodynamic factors show that the hydrodynamic conditions of the coal reservoir are weak, and the primary ions in the CRW originated from the dissolution of salt rocks. The main ion differentiation indices show that high-salinity coal seam water is mainly formed by evaporation, and the ion exchange between CRW and the surrounding rock and the alternating adsorption of cations in water are very weak. Evaporation and diagenesis lead to an increase in the contents of Na+, Cl− and I+ in coalbed water, which in turn leads to an increase in the total dissolved solids contents of CRW and its evolution toward concentrated brine. The genesis and evolution of the CRW in the study area are affected by the combination of the relationships among the paleoclimate, aquifers and aquifuges, and tectonic evolution processes. The CRW in the study area has experienced five evolution stages, i.e., sedimentary water and diagenetic water, high-salinity infiltration water, primary mixed water, paleoatmospheric precipitation recharge water, and secondary mixed water. The above understanding can provide a basis for studying the formation period and accumulation mechanism of BCM and provide a hydrogeological basis for water resource utilisation and pollution prevention and the control of high-salinity water.

Reconstructing atmospheric 129I deposition over 170 years with the varved sediment in the Sihailongwan Maar Lake, northeast China

Long-term deposition of atmospheric radioactive iodine-129 (129I) is important for assessing the impact of human nuclear activities (HNAs), but still not well understood in East Asia. In this study, we quantitatively reconstructed the deposition history of airborne 129I using varved sediment from Sihailongwan Maar Lake (SHLW) in northeast China. Our results revealed significant increases in 129I concentrations and 129I/127I atomic ratios since the 1950s, indicating the influence of HNAs on the environment and marking the onset of the Anthropocene. The variation of 129I in the investigated site can be primarily attributed to the global fallout of ANWT as well as nuclear fuel reprocessing in Europe, Russia and the USA. Notably, neither the Chernobyl nor the Fukushima nuclear accidents have had any discernable impact on the SHLW Lake. Over the past 170 years (1846–2021), the reconstructed fluxes indicate a rapid increase in 129I deposition from the early 1950s until the 1970s followed by dramatic changes thereafter. The measured 129I fluxes range between (1.26–349) × 109 atoms m−2 yr−1 in the SHLW Lake, which are consistent with similar latitude zones across East Asia, but differ significantly from those observed in high-elevation glaciers within the Northern Hemisphere due to prevailing atmospheric circulation patterns. The total 129I inventory was calculated to be 11.9 × 1012 atoms m−2, with natural and anthropogenic 129I accounting for 2.86 % and 97.1 %, respectively, suggesting an overwhelming artificial contribution. The reconstructed fluxes and inventory of atmospheric 129I deposition quantitatively distinguish the natural and artificial contributions, and provide a novel insight into the historical environmental impact of HNAs in East Asia and the characteristics of the Anthropocene.

Sources of highly regional 129I in soils in northeast China

The transport and deposition pathways of anthropogenic radionuclides at the global scale, particularly volatile 129I, remain somewhat elusive due to a dearth of comprehensive investigations. To gain a better understanding of the transport dynamics and deposition mechanism of anthropogenic 129I in the terrestrial environment, one hundred surface soil samples collected from northeast China were analyzed for 129I and 127I concentrations in this study. Our findings reveal that 129I/127I atomic ratios in the mid-eastern Inner Mongolia (MIM) were approximately an order of magnitude higher than the rest of the investigated area. This is, besides the global fallout and the long-range transport of 129I released from the European nuclear reprocessing plants via westerly winds, possibly attributed to the dust with high 129I levels from the East Asian arid regions. In addition to the significant dust-induced 129I input, the unique meteorological conditions and topographical features in the MIM synergistically contribute to the pronounced accumulation and deposition of 129I in this region. This study will provide novel insights into the transport and deposition mechanism of anthropogenic radionuclides, which is significant for the assessment of anthropogenic nuclear activities on the environment in the future.

Chronological Study of Coal‐seam Water and its Implication on Gas Production in the South Qinshui Basin

AbstractThe knowledge of the residence time of formation water is fundamental to understanding the subsurface flow and hydrological setting. To better identify the origin and evolution of coal seam water and its impact on gas storage and production, this study collected coalbed methane co‐produced water in the southeast Qinshui Basin and detected chemical and isotopic compositions, especially 36Cl and 129I concentrations. The calculated tracer ages of 129I (5.2–50.6 Ma) and 36Cl (0.13–0.76 Ma) are significantly younger than the age of coal‐bearing formation (Pennsylvanian ‐ Cisuralian), indicating freshwater recharge after coal deposition. The model that utilises 129I/I and 36Cl/Cl ratios to constrain the timing of recharge and the proportion of recharge water reveals that over 60% of pre‐anthropogenic meteoric water entered coal seams since 10 Ma and mixed with residue initial deposition water, corresponding to the basin inversion in Cenozoic. The spatial distribution of major ion concentrations reveals the primary recharge pathway for meteoric water from coal outcrops at the eastern margin to the basin center. This study demonstrates the occurrence of higher gas production rates from wells that accept water recharge in recent times and suggests the possible potential of the non‐stagnant zones for high gas production.

Optimal Cumulative I-131 Activity in Metastatic Differentiated Thyroid Cancer: Balancing Efficacy and Adverse Events.

The optimal cumulative activity (CA) of I-131 therapy for patients with metastatic differentiated thyroid cancer (mDTC) remains contentious. This study aimed to determine the maximum CA of I-131 that could be administered without a significant increase in adverse events (AEs) by analyzing a long-term cohort of patients. Data from mDTC patients treated with I-131 therapy and followed for at least two years from 1967 to 2019 were reviewed. Patients were categorized into three groups based on the received CA: Group-A (≤600mCi), Group-B (>600-1000mCi), and Group-C (>1000mCi). The study assessed long-term AEs and survival outcomes. The study included 671 adult mDTC patients (mean age 48 years, range: 19-81) with a median follow-up of 122 months (IQR: 82-180). Group A, Group B, and Group C comprised 269 (40.0%), 212 (31.6%), and 190 (28.4%) patients, respectively. Ten-year survival rates were 72%, 42.7%, and 29% in Groups A, B, and C, respectively. A total of 40/671 (6%) AEs were observed in 38 patients: 3 (1.1%), 12 (5.7%), and 25 (13.2%) in Groups A, B, and C, respectively. Five patients developed second primary malignancy (SPM): 3 in Group A and one each in Group B and C. However, CA >1000mCi of I-131 was associated with significant increase in bone marrow suppression, decreased pulmonary function, and xerostomia (p < 0.001). The study suggests that a maximum CA of up to 1000mCi strikes a favorable balance between keeping AEs low and benefiting a subset of patients with extensive metastases showing intense I-131 concentration.

Modeling and assessment of radioactive iodine dispersion inside Egyptian radioisotope production facility

Indoor Air Quality (IAQ) is very important topic in any radioisotope production facility. It is mandatory for some operators to be available behind hot cell that produce radioisotope to practice some tasks concerning maintenance, dosimetry and operation. One of these tasks is redundant transferring Radioiodine from cell to quality control lab and vice versa for measurements. Contam3.2 is a simulation model from NIST (National Institute of Standards and Technology) is used to study and predict I131 concentration in air in hot cell and area of operator behind the cell in emergency case. Emergency is described by dropping small amount of I131 on cell floor. The model predicts the elapsed time to remove contaminants by extraction ventilation system to deposit these contaminants in the dedicated filters and protect operators from inhalation. An emergency situation is also studied in case of opening I131 cell door hole (20 cm) by operators to pick the sample for quality control tests. Pressure interference occurs in this situation permitting some Iodine traces to be available in the areas under consideration. Ventilation system is responsible for removing all radioactive contaminants to settle it inside dedicated charcoal filters to clean the area and keeps it in permissible safe limits.

Transfer of 129I to freshwater fish species within Fukushima and Chernobyl exclusion zones

Unique data is reported on the transfer of 129I iodine from freshwaters to fish as well as the internal distribution within fish from the Fukushima and Chernobyl exclusion zones (ChEZ). Samples of water, sediments and fish were collected in the contaminated ponds Inkyozaka and Suzuuchi, and in the less contaminated Abukuma river in Fukushima, as well as in the contaminated Glubokoye lake and in the less contaminated Starukha lake in ChEZ. In water, 129I was mainly present as low molecular mass (LMM) and negatively charged species, while a minor fraction was associated with colloidal fraction, most probably organic material in water. The sediment-water 129I apparent distribution coefficients, Kd, ranged from 225 to 329 L/kg, equal that of stable iodine, but did not correlate with 129I/127I ratio or 129I/137Cs ratio as the environmental distribution of radioactive iodine was different from that of stable iodine and radioactive cesium. Concentration ratios (CR) of 129I in muscle of freshwater fish ranged from 85 to 544 across waterbodies with limited water exchange, similar in Fukushima and Chernobyl, but varied with respect to fish species. Thus, this is the first results on the transfer of 129I to freshwater fish, showing that the CR for freshwater fish is higher than CR reported for marine fish. Concentrations of 129I in fish muscle were, however, lower than in the intestinal content, indicating the influence of more contaminated dietary ingredients probably of terrestrial origin based due to δ13C signal on as well as of biodilution. The present results highlighted also that the radiation dose in fish was highly inhomogeneously distributed. Based on the present 129I/127I atomic ratio of 10−5 in the most contaminated fish in the ponds in Fukushima and Glubokoye lake in Chernobyl, however, a radiation dose of 10 μSv/y would not pose any harm to the fish population.

Current 129I concentration levels from the western Black Sea through the Bosporus to the northeastern agean Sea

The level of 129I concentrations in various areas can provide us important information about licit and illicit nuclear activities, or possible environmental nuclear contamination in an incipient and harmless phase. It can be used as a long-term tracer for nuclear pollution if the initial concentration of 129I is known in the investigated geographical region.In this paper we continued our work to determine 129I concentration in water samples from western Black Sea between 2017 and 2022 to establish the level of 129I and whether this changed in time. The average value of 129I concentration obtained is (1.24 ± 0.03) × 108 atoms/L.In this study, the concentrations of 129I determined in waters collected from several points in the Bosporus and Dardanelles straits were found to have values close to those obtained for the Black Sea but slightly lower values were observed in the Aegean Sea water.These AMS studies help to discover the outspread of pollution from sources outside Eastern Europe but also from new unknown sources that may appear in the new geo-political context.

Atmospheric dispersion and dose assessment of 137Cs and 131I from hypothetical incidents of nuclear power plant in Southeast Asia

In the event of radiological incidents, specifically nuclear accidents, a substantial quantity of radionuclides may be distributed, resulting in potential cancer hazards and the possibility of death. Hence, it is imperative for governing bodies to replicate hypothetical accidents that may occur from potential nuclear reactors, with the aim of ascertaining the probable dose exposure that the populace may face. The aim of this study was to evaluate the level of dispersion of 131I and 137Cs that would ensue from a hypothetical incident scenario of a nuclear power plant (NPP) in Ninh Thuan, Vietnam, and Mersing, Malaysia, by utilizing the HYSPLIT model. The model was set up based on the meteorological conditions in the potential site for NPP located in Southeast Asia. Following the study, a comparison was made between the results and the authorized dose limits proposed by the International Atomic Energy Agency to assess the potential mortality risk arising from an accident. The outcomes revealed that the mean activity concentration for both radionuclides was greater in Mersing than in Ninh Thuan on the initial day of the accident. The activity concentration of 137Cs and 131I at Mersing is the highest at 3.34 × 102 kBq/m3 and 2.01 × 104 kBq/m3, respectively. Meanwhile, Ninh Thuan has the highest activity concentration of 137Cs and 131I at 2.37 × 102 kBq/m3 and 1.43 × 104 kBq/m3, respectively. Based on these figures, the release of 137Cs and 131I at Mersing results in an effective dose of approximately 2.58 × 10−4 mSv and 0.71 mSv, respectively. Conversely, the release of 137Cs and 131I at Ninh Thuan results in an effective dose of approximately 8.21 × 10−5 mSv and 0.23 mSv, respectively. According to risk assessment, the inhalation of radionuclides poses the highest mortality risk in Mersing, with a rate of 51 out of 100,000 individuals at altitudes between 0 m and 10 m within 4 h of an accident. Similarly, in Ninh Tuan, the predicted mortality rate due to radionuclide inhalation at the same altitude level is approximately 17 out of 100,000 individuals. To mitigate the radiological consequences on the population, it is crucial to improve emergency protocols in these regions, taking into account their location and geographical features. This can be achieved through measures such as evacuation, sheltering, and resettlement of the population to safer areas.

Study on the Atmospheric Diffusion of Airborne Radionuclide under LOCA of Offshore Floating Nuclear Power Plants Based on CALPUFF

Studying the migration and diffusion of radionuclides plays an important role in emergency decision making and accident mitigation of floating nuclear power plants. Based on the CALPUFF model, this paper simulates the spatial distribution and concentration distribution of airborne radionuclides 131I diffusion under the conditions of sailing and power supply under LOCA (Loss-of-Coolant Accident) of the floating nuclear power plant, and the influence of four meteorological parameters, namely wind speed, cloudiness, temperature and air pressure, on the migration was analyzed using sensitivity analysis. The results show that the wind direction affects the diffusion direction of 131I, and the concentration of 131I decreases with the increase in the diffusion distance; under the same conditions, the radionuclides diffuses farther and the affected area is larger under the sailing condition. Wind speed is the dominant factor affecting the diffusion of radionuclides, followed by the cloud amount parameter, temperature parameter, and air pressure parameter. The research results can provide theoretical support for emergency responses to nuclear accidents in offshore floating nuclear power plants.

Оценка уровней оперативного вмешательства для защиты населения на основе сценариев аварий на российских АЭС

The paper presents a brief analysis of indicators designed to assess the radioecological situation in the acute period after a nuclear accident and to apply protective measures. Authors described an approach to the evaluation of operational intervention levels (OILs) for the protection of the members of the public recommended by the IAEA. The OILs for the indicators “ambient dose rate” and “concentration of I-131 and Cs-137” have been calculated based on the emergency scenarios for Russian NPPs. The input data included the information about the radioactive releases to the atmosphere due to design-based and beyond design-based accidents at NPPs with reactors VVER-1000, VVER-1200, RBMK-1000 and BN-800. The excess in the calculated "monitoring" operational intervention levels means the exceeding the dose criteria for protecting the public, which requires the implementation of protective measures. The generalization of the OILs calculated for each emergency scenario on a conservative basis resulted in an establishment of generalized (unified) OILs. The values of the latter differ from the values of similar indicators recommended by the IAEA, which is due to the specific nature of the radionuclide composition of releases from beyond design basis accidents at sodium-cooled BN-800 reactors. The paper shows the significance of the OILs established in the first period after the accident based on data on actual accidental releases using the appropriate calculation tools. The conclusion is that it is necessary to consider accident scenarios for all types of reactors when calculating generalized OILs for Russian NPPs.

Оценка доз облучения населения от жидких сбросов Белорусской АЭС в режиме нормальной эксплуатации

Radiation safety of the population from liquid discharges of the Belarusian NPP (hereinafter - BelNPP) into surface water bodies is considered to be ensured if the exposure dose to the population due to the discharges does not exceed the value of the Dose Constraint (hereinafter - DC) established by the sanitary norms and rules for ensuring radiation safety: 50 gSv/year. If there are prerequisites for the possibility of reducing the specified DC standard, it can be revised by decision of the state sanitary supervision institutions based on estimates of annual effective doses to the population (hereinafter -referred to as YED) for a certain period of NPP operation. The purpose of the study was to consider the rightfulness of the established value of the DC standard by comparing it with the calculated values of the YED of the population from the design and predictive actual liquid discharges of the BelNPP after the commissioning of the plant. As model parameters for predictive estimates, data on actual liquid discharges from NPP - analogues of the BelNPP with a VVER-1200 reactor were used. The article presents the results of the assessment and analysis of the YED from the design and predictive actual liquid discharges of the BelNPP through all exposure pathways. It is shown that the predictive estimates of the actual YED of the population are comparable with the design YED from BelNPP discharges into the Viliya River and do not exceed 22 % of the corresponding DC standard. The remaining reserve of 78 % is sufficient to reliably ensure compliance with the DC standard for public exposure from liquid radioactive discharges of the BelNPP, including after the commissioning of the second power unit. At least 80 % of the YED of the population from liquid discharges of the BelNPP into the Viliya River will be formed due to internal irradiation, to a large extent from the consumption of fish caught in the river. External exposure of the population from liquid discharges of the BelNPP occurs mainly when staying on the beach, its contribution to the total YED from discharges does not exceed 20 %. The list of the main dose-forming radionuclides was determined and the necessity of mandatory control of the volumetric concentration of radionuclides 131I, 60Co, 58Co, 54Mn, 90Sr in waste waters of the BelNPP was substantiated.

127I and 129I species in the English Channel and its adjacent areas: Uncovering impact on the isotopes marine pathways

Radioactive iodine-129 has been released from the La Hague nuclear fuel reprocessing facility (NRF) into the English Channel, but the distribution and transformation of the isotope species, and environmental consequences have not been fully characterized in the Channel. Here we present data on iodine isotopes (129I and 127I) species in surface water of the English Channel and the southern Celtic Sea. Compared to 127I species, the concentrations of 129I− and 129IO3− show more variations, but iodate is the major species for both 129I and 127I. Our data provide new information regarding iodide-iodate inter-conversion showing that water dilution and mixing are the main factors affecting the 127I and 129I species distribution in the Channel. Some reduction of iodate occurs within the English Channel and mainly in the west part because of biotic processes. The 129I species transformation is overall insignificant, especially in the eastern Channel, where a constant value of 129IO3−/129I is observed, which might characterize the La Hague wastewater signal. In the Celtic Sea, oxidation of iodide can be traced by 127I and 129I species. On a larger scale, 129I generally experienced an oxidation process in the Atlantic Ocean, while in the coast of shallow shelf seas, new produced 129I− can be identified, especially in the German Bight and the Baltic Sea. The data of 129I species in the English Channel can provide estimate of redox rates in a much broader marine areas if the transit time of 129I from La Hague is well-defined. Furthermore, estimate of inventories for 129I and its species in the Channel, and fluxes of 129I species from the English Channel to the North Sea add important information to the geochemical cycle of 129I.

DISTRIBUTION OF IODINE-127 IN MARINE ORGANISMS FROM COASTAL WATERS AROUND AOMORI, JAPAN.

We measured the concentrations and determined the distribution of the stable isotope 127I in the marine organisms. Marine fish were collected from the Pacific Ocean near Aomori, Japan. The mean 127I concentrations in the muscle of marine fish ranged from 0.67μgg-1-wet weight (ww) in cherry salmon to 0.84μgg-1-ww in fat greenling. Among the tissues measured, the muscle showed the lowest levels of 127I in all fish species. The highest 127I concentration in the tissues of marine fish was observed in the ovary of fat greenling. The mean 127I concentration in the of Japanese scallop ranged from 0.06μgg-1-ww in adductor muscle to 5.49μgg-1-ww in mid-gut gland. The 127I concentrations in seaweeds were 67μgg-1-dry weight (dw) in sea lettuce and 1783μgg-1-dw in kombu. Thus, the distribution of 127I concentration in marine organisms varied considerably depending on the tissue.

TRITIUM AND IODINE-129 IN WATER SAMPLES COLLECTED ADJACENT TO A SPENT NUCLEAR FUEL REPROCESSING PLANT IN ROKKASHO, JAPAN.

Between April 2006 and October 2008, tritium ( 3H) and iodine-129 ( 129I) were released into the atmosphere and ocean from a spent nuclear fuel reprocessing plant in Rokkasho, Japan. From 2005 to 2020, water samples were collected from water bodies around the plant, including a river, groundwater wells, a brackish lake, a fishing port and a coastal sea, to measure spatiotemporal changes in 3H and 129I concentrations. Water samples from the brackish lake and the fishing port between 2006 and 2008 occasionally had higher than background levels of 3H and 129I. Batched discharge of waste 3H and 129I was quickly diluted by advection-diffusion processes in the coastal sea, causing 3H and 129I from the plant to be indetectable. By contrast, concentrations of 3H and 129I that flowed into the brackish lake and the fishing port through various routes were high, as these water bodies are mostly closed systems.

TEMPORAL VARIATION OF POST-ACCIDENT 129I IN ATMOSPHERIC PARTICULATE MATTER COLLECTED FROM AN EVACUATED AREA OF FUKUSHIMA PREFECTURE, JAPAN.

To understand the behavior of atmospheric 129I that originated from the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident, activity concentrations of 129I in samples of atmospheric particulate matter (PM), comprising coarse (>1.1μm) and fine (<1.1μm) fractions (separated using a single stage impactor), were measured on a nearly monthly basis from October 2012 to October 2014 at a site in an area evacuated after the FDNPP accident. Total atmospheric 129I activity concentrations in PM at the site ranged between 0.15 and 2.17 nBq m-3. Specific activity concentration of 129I in total atmospheric PM ranged between 40.8 and 336 mBq kg-1, with a mean and standard deviation of 142 and 77.6 mBq kg-1, respectively. The specific activity in PM tended to be higher than not only the background values reported from soil collected before the FDNPP accident but also than those reported from the contaminated soil after the accident (range: 1.6-57 mBq kg-1; mean and standard deviation: 10.6 and 12.3 mBq kg-1, respectively). Total 129I/127I atomic ratios in PM ranged from 2.0×10-8 to 59.8×10-8, with a mean and standard deviation of 15.0×10-8 and 14.4×10-8, respectively. These ratios were generally lower than those of the contaminated soil collected after the FDNPP accident (range: 4.9×10-8-443×10-8; mean and standard deviation: 74.2×10-8 and 85.4×10-8, respectively). The 129I concentration and 129I/127I atomic ratio in atmospheric PM showed different characteristics from that of contaminated soils, suggesting that the presence of other atmospheric PMs plays a more important role as the host for 129I.

RESEARCH ON THE ENVIRONMENTAL EFFECTS OF RADIONUCLIDES AT IES - AN OVERVIEW.

This paper summarises the research works of the Institute for Environmental Sciences on the environmental behaviour of radionuclides related to the first commercial-spent nuclear fuel reprocessing plant at Rokkasho Village, Aomori Prefecture, Japan. The distribution and fluctuation in natural radiation in Aomori Prefecture were estimated as basic data. Radionuclides possibly released from the plant operation have been continuously measured using a variety of samples from different locations in Aomori Prefecture. During the test of cutting and chemical treatment of the spent fuel rods from 2006 to 2008, the concentration of 85Kr, 14C, 3H and 129I in the air increased, whereas that of 3H and 129I increased in several environmental samples. A numerical simulation model consisting of several sub-models was constructed for predicting the behaviour of released radionuclides in the environment and for evaluating the realistic radiation dose of residents around the facility.

ACTIVITY CONCENTRATIONS OF RADIOCAESIUM, 90SR AND 129I IN AGRICULTURAL CROPS COLLECTED FROM FUKUSHIMA AND REFERENCE AREAS IN JAPAN, AND INTERNAL RADIATION DOSES

Abstract Significant quantities of radionuclides were released into the environment due to the 2011 TEPCO’s FDNPS accident. Radiocaesium is the most important radionuclide for assessment of radiation dose, and small amounts of 90Sr and very long-lived radionuclide of 129I were also released into the environment. Spinach, potato and brown rice were collected from Fukushima, neighboring prefectures and reference areas of negligible deposition in 2018 and 2019. The activity concentration of 137Cs in crops in Hamadori (coastal side) was relatively higher than other areas. The activity concentration of 90Sr in the crops showed a similar range among four areas in Fukushima, and they were similar level of those collected throughout Japan. The activity concentration of 129I in the crops collected from Hamadori was higher than other Fukushima areas. However, the activity ratio of 129I/137Cs was lower by five to seven orders of magnitude. Internal radiation doses of radiocaesium for adult males from ingestion of local crops collected from Hamadori were 0.0046 mSv, and that of 129I were 0.00000045 mSv in 2019.