Increasing Analytical Quality by Designing a Thin-Layer Chromatography Scanner Method for the Determination of the Radiochemical Purity of Radiopharmaceutical Sodium Iodide 131I Oral Solution

The goal of this study was to apply the principles of analytical quality by design (AQbD) to the analytical method for determining the radiochemical purity (PQR) of the radiopharmaceutical sodium iodide 131I oral solution, utilizing thin-layer chromatography (TLC) with a radio-TLC scanner, which also enables the evaluation of product quality. For AQbD, the analytical target profile (ATP), critical quality attributes (CQA), risk management, and the method operable design region (MODR) were defined through response surface methodology to optimize the method using MINITAB® 19 software. This study encompassed the establishment of a control strategy and the validation of the method, including the assessment of selectivity, linearity, precision, robustness, detection limit, quantification limit, range, and the stability of the sample solution. Under the experimental conditions, the method parameters of the TLC scanner were experimentally demonstrated and optimized with an injection volume of 3 µL, a radioactive concentration of 10 mCi/mL, and a carrier volume of 40 µL. Statistical analysis confirmed the method's selectivity for the 131I iodide band Rf of 0.8, a radiochemical impurity IO3- Rf of 0.6, a linearity from 6.0 to 22.0 mCi/mL, and an intermediate precision with a global relative standard deviation (RSD) of 0.624%. The method also exhibited robustness, with a global RSD of 0.101%, a detection limit of 0.09 mCi/mL, and a quantification limit of 0.53 Ci/mL, meeting the prescribed range and displaying stability over time (at 0, 2, and 20 h) with a global RSD of 0.362%, resulting in consistent outcomes. The development of a method based on AQbD facilitated the creation of a design space and an operational space, with comprehensive knowledge of the method's characteristics and limitations. Additionally, throughout all operations, compliance with the acceptance criteria was verified. The method's validity was confirmed under the established conditions, making it suitable for use in the manufacturing process of sodium iodide 131I and application in nuclear medicine services.

Influence of short-lived radioiodines other than 131I on screening direct thyroid measurements with TCS-172 NAI(TL) survey meters

In a nuclear emergency, one of the actions taken for the sake of public is to monitor thyroid exposure to radioiodines. Japan's Nuclear Regulation Authority recently published a report on such monitoring and proposed direct thyroid measurements with conventional NaI(Tl) survey meters (e.g. Hitachi model TCS-172) as a primary screening method. A previous study proposed screening levels (SLs) used in these simplified measurements as the net reading values of the TCS-172 device. Age-specific SLs were derived from a thyroid equivalent dose of 100 mSv due to the inhalation intake of 131I. This study addressed the possible influence of short-lived iodine isotopes other than 131I on the simplified measurements. In preparation for such measurements, the responses of the device for 132I as an ingrowth component from 132Te, 133I, 134I and 135I in the thyroid were evaluated by numerical simulations using age-specific stylized phantoms in addition to those obtained for 131I in the previous study. The radioactivity ratios of the relevant isotopes were taken from the inventory data of the Fukushima Daiichi Nuclear Power Plant. The results were used to predict the net readings of the device when 132Te-132I and 133I as well as 131I were inhaled at 24 or 72 h after the shutdown of a nuclear power plant. In these cases, the signals from 132Te-132I and 133I become undetectable a couple of days after intake, which could lead to underestimations of the thyroid dose. To estimate the thyroid dose accurately from the simplified measurements, it is necessary to identify the exact time of intake after the shutdown and the actual physiochemical property of 132Te that affects the thyroid uptake of 132I.

THYROID CANCER INCIDENCE IN THE POPULATION OF UKRAINE AND ITS EPIDEMIOLOGICAL DETERMINANTS: IONIZING RADIATION AND ENDOCRINE DISRUPTORS

OBJECTIVE

to estimate the risk of thyroid cancer incidence in the population of Ukraine in connection with its exposure to radioactive iodine fallout of Chornobyl origin and the use of pesticides in agricultural production in the country.

OBJECT OF STUDY

Incidence rates of thyroid cancer in the population of Ukraine in 2001-2019, average regional radiation doses absorbed by the thyroid because of the Chornobyl accident, the volume of use of various groups of pesticides in the regions of Ukraine.

RESEARCH METHODS

statistical, mathematical and cartographic.

RESULTS

The study covering the period of 2001-2019, revealed significant temporal and regional differences in the thyroid cancer incidence in the population of the Ukraine regions in 2001-2019. The existence of a significant correlation between the thyroid cancer incidence and the amount of radiation exposure to the thyroid associated with the Chornobyl accident was established. The existence of a significant correlation between the thyroid cancer incidence and the degree of pesticide use intensity in agriculture in the Ukraine regions was established. A significant value of multiple correlation r = 0.5866 (p < 0.05) was found between the thyroid cancer incidence in Ukraine andthe average regional radiation doses and the pesticide use intensity in agricultural production in the country.

CONCLUSIONS

A reliable value of the multiple correlation between the value of the average regional radiation exposure doses to the thyroid associated with the Chornobyl accident and the degree of pesticide use intensity in the national economy of Ukraine and the thyroid cancer incidence in the population was determined.

TIME PATTERN OF RADIONUCLIDE EMISSIONS AND DISCHARGES INTO THE NATURAL ENVIRONMENT OF THE PIVDENNOUKRAINSKA NPP SURVEILLANCE ZONE

OBJECTIVE

assessment of impact of operation of the Pivdennoukrainska Nuclear Power Plant (PUNPP) on the environment of surveillance zone (SZ) based on parameters of radiation monitoring within 2015-2021 period.

METHODS

socio-hygienic (analysis of the radiation monitoring parameters), analytical, statistical.

RESULTS

The environmental radiation impact associated with emissions and discharges of radioactive substances originated in the production cycle of the PUNPP in everyday conditions was found as insignificant. The gas-aerosol atmospheric emissions of inert radioactive gases, long-lived nuclides, and 131I did not exceed the established permissible levels (PL) and amounted to a hundredth of a percent of the emission limit (EL) for the inert radioactive gases and long-lived nuclides, and a thousandth of a percent for radioactive iodine. Total atmospheric emissions of the 51Cr, 54Mn, 59Fe, 58Co, 60Co, 90Sr, 95Zr, 95Nb, 134Cs, 137Cs, and 3Н radionuclides by the PUNPP power units (actual and % of EL) did not exceed the established PL. Maximum average values of atmospheric air concentration of 137Cs in SZ forthe 2015-2021 period ranged from 2.858 μBq/m3 (PUNPP industrial site) to 1.986 μBq/m3 (Riabokoneve village, 33.5 km distance), and maximum average values of the 90Sr air concentration were from 1.310 μBq/m3 to 0.566 μBq/m3, respectively. According to radionuclide monitoring no significant change of the quality of surface water occurred upon the PUNPP discharges to the Pivdennyi Bug River. Specific activity of the 137Сs in agricultural products in the PUNPP SZ was insignificant and not exceeding the PL of the content in food products. Content of 137Cs in the samples from the PUNPP SZ did not exceed 1.0 % of the total activity.

CONCLUSION

Average concentration of radionuclides in atmospheric air of the settlements in the PUNPP SZ was several orders of magnitude lower than that established by regulatory documents. The PUNPP discharges to the Pivdennyi Bug River, according to radionuclide parameters that are monitored, have not significantly changed the quality of surface water. The content of 90Sr and 137Cs was uniform in all observation radii of distance from the NPP, confirming the very low level of 90Sr and 137Cs environmental emission by the PUNPP. The content of 137Cs in agricultural products within the PUNPP SZ was significantly lower than PL.

Evaluation of internal exposure of nuclear medicine staff working with radioiodine in Poland

The iodine-131 (I-131) content in the thyroid of staff members working with this radionuclides has been measured with about 500 employees in about 25 hospital's departments of nuclear medicine performing therapy and diagnosis of thyroid disease in Poland. The measurements were performed with portable detection unit for in situ measurements of radioiodine. This is consist with scintillation detector sodium iodine activated by thallium (NaI(Tl)) - battery-powered and portable tube base Multichannel Analyzer Canberra UniSPEC. Based on direct measurements of the iodine content, the effective dose equivalent for workers due to inhalation of I-131 was estimated. All individuals actively working with iodine show measurable amounts of this isotopes in their thyroids. The average measured activity in the thyroid of the nuclear medicine staff was found to be equal at average 550 Bq within the range 70 Bq-2.5 kBq. There is no apparent correlation between the measured I-131 levels and risk categories. Nevertheless the technical and nuclear medicine staff show higher I-131 thyroid level comparing to hospital services staff. Calculated maximum committed effective dose for particular exposed person is <10% of 20 mSv/year. Int J Occup Med Environ Health. 2023;36(5):587-95.

131I dose coefficients for a reference population using age-specific models

Age-specific dose coefficients are required to assess internal exposure to the general public. This study utilizes reference age-specific biokinetic models of iodine to estimate the total number of nuclear disintegrations ã(rS,τ) occurring in source regions (rS) during the commitment time (τ). Age-specific S values are estimated for 35 target regions due to131I present in 22rSusing data from 10 paediatric reference computational phantoms (representing five ages for both sexes) published recently by the International Commission of Radiation Protection (ICRP). Monte Carlo transport simulations are performed in FLUKA code. The estimated ã(rS,τ) and S values are then used to compute the committed tissue equivalent dose HT(τ) for 27 radiosensitive tissues and dose coefficients e(τ) for all five ages due to inhalation and ingestion of131I. The derived ã(rS,τ) values in the thyroid source are observed to increase with age due to the increased retention of iodine in the thyroid. S values are found to decrease with age, mainly due to an increase in target masses. Generally, HT(τ) values are observed to decrease with age, indicating the predominant behaviour of S values over ã(rS,τ). On average, ingestion dose coefficients are 63% higher than for inhalation in all ages. The maximum contribution to dose coefficients is from the thyroid, accounting for 96% in the case of newborns and 98%-99% for all other ages. Furthermore, the estimated e(τ) values for the reference population are observed to be lower than previously published reference values from the ICRP. The estimated S, HT(τ) and e(τ) values can be used to improve estimations of internal doses to organs/whole body for members of the public in cases of131I exposure. The estimated dose coefficients can also be interpolated for other ages to accurately evaluate the doses received by the general public during131I therapy or during a radiological emergency.

Screening levels of TCS-172 NaI(Tl) survey meters used for direct thyroid measurements in nuclear disasters

It is a challenging task to establish a feasible and robust method for the population monitoring of individuals' thyroid exposure following an accidental intake of radioiodines in a nuclear emergency, because of the time restriction. The authors previously proposed a method for such monitoring to obtain as many reliable human data as possible and one of the components is simplified measurements by conventional NaI(Tl) survey meters that are intended to be used for the initial triage to identify significantly exposed individuals and get an overall picture of the exposure levels in a target population in a timely manner. This study determined screening levels (SLs) for a conventional NaI(Tl) survey meter (model TCS-172, Hitachi, Japan) using the conversion factor (131I kBq in the thyroid per μSv h-1) that were obtained from experiments and simulations with age-specific phantoms. The results demonstrated that the derived SLs for 100 mSv thyroid equivalent dose were as follows: 0.2 μSv h-1 (SL1) for the age group ≤ 5-y-olds, 0.5 μSv h-1 (SL2) for the 10- and 15-y-old age groups and 1.0 μSv h-1 (SL3) for adults. These SLs would be reasonably available within 1 week after the intake of 131I on the safe side.

Uncertainties associated with direct thyroid measurements using an NaI(Tl) survey meter: the effect of anatomical differences among individuals

Photon detectors utilised for direct thyroid measurements to determine the radioiodine content in the thyroid are normally calibrated using a phantom that mimics the human neck, including the thyroid. However, such measurements are necessarily subject to uncertainty because of the difference between the phantom and the real human subject and also the morphological differences among individuals. In this study, personal voxel phantoms were created from magnetic resonance images of the necks of 24 adult volunteers (15 males and 9 females), and numerical simulations using these phantoms were performed to examine the variation in a conversion factor (131I kBq in the thyroid per μSv h-1) for a conventional NaI(Tl) survey meter among the individuals and also to confirm the suitability of reference Japanese voxel phantoms as a calibration standard for such measurements. As a result, it was found that the conversion factor obtained from the reference Japanese male (female) phantom was 1.29 (1.18) times larger than the average conversion factor for the male (female) subjects, suggesting that the conversion factors of the reference Japanese adult male and female phantoms would generally overestimate the 131I thyroidal contents and that the thyroid volume would be one of the factors influencing the conversion factor. This study also revealed a wide difference in the thyroid volume among individuals, which would be of concern when performing specific dose assessments for heavily exposed persons.

Internal organ dose rate conversion coefficients of Japanese macaques to 134Cs,137Cs and 131I†

The purpose of this study was to estimate the internal dose of radiation in Japanese macaques (aka Nihonzaru or snow monkey) due to the Fukushima nuclear power plant accident. Images of a male Japanese macaque weighing ~10 kg were acquired using a multi-slice computed tomography (CT) scan with a 64-row segment detector. The CT images were used to create voxel phantoms of the bones, bone marrow, brain, eyes, heart, lungs, stomach, liver, spleen, pancreas, kidneys, intestines, bladder, testes, thyroid and miscellaneous tissue. The Particle and Heavy Ion Transport System (PHITS) Monte Carlo code was used to calculate the internal exposure rate conversion factors for 134Cs, 137Cs and 131I isotopes for the created voxel phantoms with a statistical precision higher than 1%. The PHITS-calculated energy deposits were compared with those for rhesus monkeys. The results showed that the fractions of energy deposits for β-radiation in different organs were almost identical between the two species. For γ-radiation, there was excellent agreement in the self-absorption rate with the approximate curve of the Japanese macaque, with an average deviation of 2%. The maximum deviation of 12% was for the kidney, which has two organs, so the error with the approximate curve is slightly larger due to the energy loss created between organs.

Determination of Radiation Exposure of Individuals in the Population by Patients after Radioiodine Therapy - Comparison of two Measurement Systems

According to the requirements of radiation protection legislation, patients may only be discharged from the nuclear medicine therapy ward if it is ensured that the cumulative radiation exposure of the population is below 1 mSv per year. In the present study, dose measurements of patients after radioiodine therapy (RIT) and their relatives are to be used to prove that the radiation exposure resulting from the medical application is low and that the legal framework conditions are complied with. Furthermore, the results allow conclusions to be drawn about the measurement accuracy of the dosimeters used.

METHODS

In 147 patients after RIT and their relatives, the dosage was measured over 14 days with different measuring systems. Finger ring dosimeters (FRD) were worn during the whole day, furthermore the dose was determined by non-official OSL and TLD dosimeters during the sleep phase.

RESULTS

88 data sets were used for the final analysis. With the FRD, dose values between 0.1-50 mSv were determined for the patients. As expected, the finger ring dose of the relatives was significantly lower, averaging 0.75 mSv compared to 10 mSv for the patient. For the TLD and OSL used in the sleep phase, the measured values were in the same range. The reproducibility of the measurement results was significantly better for the OSL than for the TLD.

CONCLUSION

Despite method-related measurement uncertainties, it can be concluded that the exposure dose of patients' relatives after radioiodine therapy is low and that the legal requirements are met. Moreover, the now official OSL dosimeters represent a more accurate and for the chosen measurement task better suited measurement system than the TLD.

KEY POINTS

· The exposure dose of patients' relatives after radioiodine therapy is low.. · The requirements of radiation protection legislation after discharge from the nuclear medicine therapy ward are complied with. · OSL dosimeters are a accurate and for the measurement task suited system.

CITATION FORMAT

· Hartmann H, Andreeff M, Claußnitzer J et al. Determination of Radiation Exposure of Individuals in the Population by Patients after Radioiodine Therapy - Comparison of two Measurement Systems. Fortschr Röntgenstr 2023; 195: 605 - 612.

No evidence of thyroid consequences in seven nuclear workers at the Tokyo Electric Power Company Fukushima Daiichi Nuclear Power Plant accident: 10-year follow-up results of thyroid status

Seven emergency nuclear workers, who had internal exposure due to an intake of radionuclides, mainly I-131, during the emergency response operation in March 2011, after the accident at the Tokyo Electric Power Company (TEPCO) Fukushima Daiichi Nuclear Power Plant (FDNPP), visited the National Institute of Radiological Sciences (NIRS) outpatient clinic for medical evaluation. They were followed up after their first visit for 10 years. The estimated committed equivalent doses to the thyroid were distributed between 3.2 to 1.2 × 10 Sv. This group thought to be received highest exposure at the accident. None of the workers had symptoms related to abnormal thyroid function. The examinations, including thyroid function tests and ultrasound, detected no abnormalities related to radiation exposure. However, there is a need for continuous monitoring of their thyroid status for longer periods in the future.

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.

In-situ Field Gamma Spectrometry in a Radionuclide Air Sampler

The work being presented is on the development of a system to measure the speciation of airborne radionuclide emissions from the environment during a nuclear emergency. On-site air sampling measurements that were conducted during the Fukushima Daiichi accident were limited because field teams had to be sent out to run the sampling systems and retrieve the filters for gamma spectrometry analysis in a separate laboratory. The start of air sampling was delayed, and it was impossible for emergency responders to use the information about the airborne radionuclide composition in a timely way. The goal of the current study is to develop a system that could provide live, near real-time information about the concentrations of different radionuclides in the air without having to rely on human intervention. The development of the prototype in the current work is largely being enabled by Cd-Zn-Te spectrometers, which provide reasonably high-resolution spectrometry given that it is a room temperature sensor, and allow the measurements to be conducted in the field. A custom filter cartridge has been designed to hold a pair of aerosol and iodine filters in place while keeping the gamma spectrometers as close as possible in order to obtain high count rate efficiencies. A single cartridge holds both filters and has an internal flow channel directing the air flow between them. The cartridge design also facilitates replacing the filters as the accumulated radioactivity on the filters becomes too high. An automation system can move a filter cartridge from the fresh cartridge storage bank to the sampling location (filtration and gamma spectrometry) and return the used filter cartridge to the used cartridge storage bank. The radionuclide air sampling system prototype has been designed and constructed. It has been tested with fixed sources located on the respective aerosol and iodine filters. The real-time data capture aspects of the system were also demonstrated with a live 131I capture experiment. The projected performance of the system during a reactor accident was also simulated, emulating the characteristic detector efficiencies and projecting how the airborne concentrations could be reconstructed. The study has designed and constructed a radionuclide air sampler that could be used for measuring airborne radioactivity in emissions from a nuclear accident. Because the gamma spectrometry measurements are done in situ with good resolution and the system is automated, it would allow data to be transmitted back to an emergency operations center immediately rather than having to wait for additional laboratory analysis.

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 (>1.1 μm) and fine (<1.1 μm) 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.

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.

VARIATION IN RADIATION DOSE RATES FROM RADIONUCLIDES DISCHARGED BY THE SPENT NUCLEAR FUEL REPROCESSING PLANT IN ROKKASHO UNDER DIFFERENT YEARLY WEATHER CONDITIONS

The radiation dose rate from radionuclides released by the spent nuclear fuel reprocessing plant in Rokkasho, Japan, was assessed for a year specified in the safety review during which the weather conditions were not significantly different from those of the other 10 y. However, the actual year-by-year variation in annual radiation dose rate was not examined. A model system for evaluating the dose rate from the radionuclides released into the atmosphere was constructed. In this study, the radiation dose rate in the weather conditions of 24 weather bins was estimated for a standard year by the model. The annual maximum dose rate from 1959 to 2012 was estimated using a simplified method that integrated the dose rates of each weather bin in the standard year by estimating the annual frequency of the bin in the target year. We obtained ~1.3 as the maximum/minimum ratio of the annual maximum dose rate.

IODINE ABSORPTION BY APPLE LEAF SURFACES

Apple is an important agricultural product in Aomori Prefecture, Japan, where the first commercial nuclear fuel reprocessing plant is currently under construction. As the behavior of radioiodine deposited on the surface of apple leaves is not well known, we studied the absorption and transfer to fruit of stable iodine applied onto the leaf surface. Droplets of NaI solution were applied to the leaf surface $\sim$86-89 days after flowering. The leaves were collected periodically and washed with detergent solution, followed by determination of iodine amounts absorbed or remaining on the leaf surface. Subsequently, iodine levels were determined separately for each part of the apple tree. Our results indicated that iodine applied on the surface of the leaf was absorbed and accumulated inside the leaf, but the transfer of absorbed iodine to the fruit was negligible; hence, iodine was less likely to accumulate in the fruit.

SOIL-SOIL SOLUTION DISTRIBUTION COEFFICIENT OF RADIOIODINE IN SURFACE SOILS AROUND SPENT NUCLEAR FUEL REPROCESSING PLANT IN ROKKASHO, JAPAN

The soil-soil solution distribution coefficient (Kd) of radioiodine in soil samples with various total carbon (TC) contents was measured in a batch sorption experiment using 125I tracer spiked as I-. The log values of Kd-125I and TC concentration in low-TC soils (< 10g kg-1) were positively correlated, whereas those of Kd-125I in TC rich soils (> 10 g kg-1) and dissolved organic carbon (DOC) in liquid phase were negatively correlated. The proportion of 125I in the < 3 kDa fraction in the liquid phase is negatively correlated with the log of DOC, implying that 125I is primarily combined with high-molecular-weight organic matter in soil solutions rich in DOC. The results suggest that Kd-125I in soil with high soil organic material (SOM) content is governed by DOC via the combination of 125I and DOC. In contrast, Kd-125I in soils with a low SOM content was governed by SOM because the anion exchange capacity of SOM was vital for the sorption of 125I-.

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.

Distribution of Anthropogenic 129I in the Western South China Sea and Its Application for Tracing the Sources and Movement of Pollution

Anthropogenic ¹²⁹I has been dispersed all over the world and could be utilized as an oceanographic tracer based on its conservative nature in the ocean. The first datasets of ¹²⁹I and ¹²⁷I were obtained by analysis of seawater of 36 water columns collected in the western South China Sea during August-September 2018. The measured ¹²⁹I concentrations decreased with depth from (0.93-1.61) × 10⁷ atoms/L in the upper 200 m to (0.04-0.14) × 10⁷ atoms/L at 1500 m, indicating a clear anthropogenic source in the upper layer, mainly originated from the global fallout. The riverine input of the deposited ¹²⁹I on the catchment area of the Mekong River is an important source besides the direct deposition in the seas. The water mass with high ¹²⁹I from the Mekong River water moves to the east at 11°N by the North Nansha Current in the surface layer (2-25 m). The exponentially decreasing ¹²⁹I level with depth indicates that the vertical dispersion of ¹²⁹I from the upper to the lower layer was mainly through slow diffusion, and the deep water at more than 1500 m was not significantly contaminated by the upper layer water at least in the past 70 years.

Time-series variations in 129I concentrations and 129I/137Cs ratios in suspended particulate matter collected in eastern Japan immediately after the 2011 nuclear accident in Fukushima, Japan

We have determined the hourly atmospheric concentrations of ¹²⁹I in aerosols dispersed into the atmosphere by the nuclear accident at the Fukushima Daiichi Nuclear Power Plant (FD1NPP) on March 11, 2011. Data were obtained by measuring the quantity of ¹²⁹I in suspended particulate matter (SPM) collected on filter tapes at 41 SPM monitoring stations in Fukushima and other prefectures in eastern Japan, including the metropolitan area of Tokyo and the surrounding area. After scrutiny, 500 out of 920 hourly SPM samples were determined to be reliable (i.e., devoid of cross-contamination), and these were subjected to further analysis and discussion. Based on the data from these samples, especially data from the four SPM sampling sites located close to the FD1NPP (Futaba, Naraha, Haramachi and Nihonmatsu), the time-series variations in the atmospheric concentration of ¹²⁹I and the activity ratio of ¹²⁹I/¹³⁷Cs were reconstructed by using ¹³⁷Cs concentration data in the literature. ¹²⁹I and ¹³⁷Cs were observed to be continuously and sometimes explosively dispersed into the atmosphere in aerosols transported by radioactive plumes from the FD1NPP. The highest activity concentrations of ¹²⁹I and ¹³⁷Cs were observed in the SPM sample at the Futaba SPM station (3.2 km west-northwest of the FD1NPP) at 14:00-15:00 on March 12 after the venting of Unit 1. Systematically high ¹²⁹I/¹³⁷Cs activity ratios were observed at the Futaba and Haramachi stations from March 12 to 14, suggesting that radioactive masses released from the FD1NPP during the first few days after the nuclear accident were relatively enriched in radioiodine. High activity ratios of ¹²⁹I/¹³⁷Cs were also measured starting on March 21 at Naraha (17.5 km south of FD1NPP) and from March 22-23 in the metropolitan area which must have been caused by a different type of emission event(s) on those days at the FD1NPP, as previously reported. The ¹²⁹I data from this study are highly effective in the validation and elaboration of the modelling of the atmospheric dispersion of radioiodine. They further contribute to assessing the internal exposure due to inhalation of ¹³¹I estimated by means of such elaborate atmospheric diffusion models.

Analysis of volatile nuclides' behavior in the atmosphere released due to the FDNPP accident

The volatile nuclides, 131I, 132I, and 132Te, which were released in large quantities during the early stage of the Fukushima Dai-ichi Nuclear Power Plant accident, are the most dominant ones in determining the impact on the public and the environment. Since the behavior of these nuclides in the environment and their effects on human health differ depending on their physicochemical forms, it is necessary to understand more about the release fraction and the deposition process of each form. In this study, a behavior model was developed to calculate physical and chemical processes of organic, inorganic, and particulate 131I and 132I, and gaseous and particulate 132Te. This behavior model was used to estimate the physicochemical composition of iodine at the time of release, the 132Te/132I activity ratio at the time of release, and the dry deposition velocity of 132Te. The estimation was performed for five plumes transported during the period from March 14 to 21, 2011, and the estimated values were obtained by comparing with the values measured in previous studies. As a result of the estimation, the organic iodine fraction at the time of release was estimated to be 0.1 or less for most plumes, while a significantly higher value of 0.3 was estimated for the plume released in the night of March 14. This result implied that the possibility of formation and release of organic iodine in the liquid phase in Unit 3, which was considered to be the source of this plume. As for the 132Te/132I ratio at the time of release, it was estimated to be about 0.3-0.4 for most plumes, while it was about 1 in the plume released in the early morning of March 15, which is consistent with the release process in Unit 2 on the night of 14 and early morning of the 15. In addition, a remarkably high dry deposition velocity of 132Te was estimated in this plume, which was consistent with the existence of radiocaesium-bearing microparticles (CsMP) with a particle size of a few micrometers that had been found to be specific to this plume.

129I in rainwater across Argentina

Concentrations of ¹²⁷I and ¹²⁹I in rainwater samples from several stations across Argentina (latitudes between 25° S and 55° S) were measured and analyzed for the assessment of distribution patterns and potential sources of ¹²⁹I in the Southern Hemisphere. Measured ¹²⁹I levels, clearly above those explainable by natural background and atmospheric nuclear weapons tests, can be understood by the injection into the Southern Hemisphere of ¹²⁹I that had been discharged from nuclear fuel reprocessing plants in the Northern Hemisphere.

Assessment of internal exposure to 131I and short-lived radioiodine isotopes and associated uncertainties in the Ukrainian cohort of persons exposed in utero

This study revised the thyroid doses for 2582 Ukrainian in utero cohort members exposed to Chornobyl fallout (the Ukrainian in utero cohort) based on revision of: (i) 131I thyroid activity measured in the Ukrainian population, (ii) thyroid dosimetry system for entire Ukraine, and (iii) 131I ground deposition densities in Ukraine. Other major improvements included: (i) assessment of uncertainties in the thyroid doses considering shared and unshared error, and (ii) accounting for intake of short-lived radioisotopes of tellurium and iodine (132Te+132I and 133I). Intake of 131I was the major pathway for thyroid exposure, its median contribution to the thyroid dose was 97.4%. The mean prenatal and postnatal thyroid dose from 131I was 87 mGy (median = 17 mGy), higher than previous deterministic dose of 72 mGy (median = 12 mGy). For 39 individuals (1.5%) the dose exceeded 1.0 Gy, while the highest dose among the cohort members was 2.7 Gy. The geometric standard deviation (GSD) of 1000 individual stochastic doses varied from 1.9 to 5.2 with a mean of 3.1 and a median of 3.2. The lowest uncertainty (mean GSD = 2.3, median GSD = 2.2) was found for the subjects whose mothers were measured for 131I thyroid activity, while for individuals, whose mothers were not measured, the mean and median GSDs were 3.4. Uncertainties in thyroid doses were driven by shared errors associated with the parameters of the ecological model.

Large seasonal fluctuations of groundwater radioiodine speciation and concentrations in a riparian wetland in South Carolina

Recent studies evaluating multiple years of groundwater radioiodine (¹²⁹I) concentration in a riparian wetland located in South Carolina, USA identified strong seasonal concentration fluctuations, such that summer concentrations were much greater than winter concentrations. These fluctuations were observed only in the wetlands but not in the upland portion of the plume and only with ¹²⁹I, and not with other contaminants of anthropogenic origin: nitrate/nitrite, strontium-90, technecium-99, tritium, or uranium. This unexplained observation was hypothesized to be the result of strongly coupled processes involving hydrology, water temperature, microbiology, and chemistry. To test this hypothesis, an extensive historical groundwater database was evaluated, and additional measurements of total iodine and iodine speciation were made from recently collected samples. During the summer, the water table decreased by as much as 0.7 m, surface water temperature increased by as much as 15 °C, and total iodine concentrations were consistently greater (up to 680%) than the following winter months. Most of the additional iodine observed in the summer could be attributed to proportional gains in organo-iodine, and not iodide or iodate. Furthermore, ¹²⁹I concentrations were observed to be two-orders-of-magnitude greater at the bottom of the upland aquifer than at the top. A coupled hydrological and biogeochemical conceptual model is proposed to tie these observations together. First, as the surface water temperature increased during the summer, microbial activity was enhanced, which in turn stimulated the formation of mobile organo-I. Hydrological processes were also likely involved in the observed iodine seasonal changes: (1) as the water table decreased in summer, the remaining upland water entering the wetland was comprised of a greater proportion of water containing elevated iodine concentrations from the low depths, and (2) water flow paths in summer changed such that the wells intercepted more of the contaminant plume and less of the diluting rainwater (due to evapotranspiration) and streamwater (as the lower levels promote a predominantly recharging system). These results underscore the importance of coupled processes influencing contaminant concentrations, and the need to assess seasonal contaminant variations to optimize long-term monitoring programs of wetlands.

Radiation Dose to Veterinarians and Veterinary Technicians During Radioiodine Treatment of Felis Catus

The uptake of radioiodine in veterinarians or veterinary staff when 131I is administered via injection to domesticated cats (Felis catus) with hyperthyroidism has not been well studied. Veterinarians and staff undergo specific training for the handling of radioiodine injection of cats to minimize and prevent an inhalation intake. An in-vivo bioassay is performed post cat injection to determine if 131I was inhaled or absorbed. The frequency of in-vivo bioassays requires dedicated time of the veterinarians and those who must perform the bioassay. Bioassay data from veterinarians and staff at the Colorado State University Veterinary Teaching Hospital administering 131I from the past 20 years were analyzed (n = 168) to ascertain if there is a correlation between the amount of time elapsed between the 131I administration, the bioassay, and the net counts resulting from the bioassay. The amount of 131I administration and the bioassay net counts were also analyzed to determine if there was a correlation. No correlations were found, and out of 168 131I administrations over 20 years, only 3 bioassays resulted in measurable doses of 131I with a committed dose equivalent (CDE) of 0.19 mSv, 0.77 mSv, and 1.6 mSv. The current precautions taken to prevent the inhalation intake of 131I appear sufficient to consider changing the requirements for veterinary bioassay after routine administration of 131I to cats.

DESIGN AND FABRICATION OF A PEDIATRIC THYROID PHANTOM FOR USE IN RADIO-IODINE UPTAKE MEASUREMENT, IMAGE QUALITY CONTROL AND DOSIMETRY

Estimating internal contamination from 131I for children in nuclear accidents is a crucial subject in the radiation protection field. Throughout this paper, an urgent and simple method was proposed for measuring 131I inside the pediatric thyroid gland by constructing a neck and thyroid phantom. For this purpose, CT scan images of healthy child's thyroids were obtained, and the sizes of different parts were determined by a 3D slicer image processing software. Girls with the body surface area between 0.95 and 1.05 were involved in this study. The fabricated phantom is composed of 5 cylindrical slabs of 2-cm thickness, and several small holes were constructed for TLD dosemeters near the thyroid gland and all other parts of the neck. The phantom was constructed utilizing a 3D printer with acrylonitrile butadiene styrene plastic. The thyroid phantom was filled with radioiodine-131, and calibration curves were plotted for contamination estimation. A nodular thyroid phantom was also constructed. The nodular phantom or the resolution phantom has 4 removable parts containing cylindrical holes with diameters of 3, 6, 9 and 12 mm. These holes on the thyroid glands can be filled with different activities of radionuclides to serve as hot and cold spots for quality control of nuclear medicine images. The results show that the designed phantom is applicable in different fields such as nuclear image quality and resolution tests, dosimetry and iodine thyroid uptake estimation in nuclear medicine departments, and nuclear emergency monitoring.

Mathematical simulation of the Pacific Proving Grounds 129I/127I nuclear bomb peaks in coral cores from the Philippines

One recent way of reconstructing the historical impact of aboveground nuclear weapons testing (ANWT) in places lacking historical data is by measuring ¹²⁹I in natural archives such as coral cores. However, discussions arising from ¹²⁹I in corals remain qualitative or semi-quantitative, which do not maximize the potential information derivable from the data. In this study, we construct a mathematical model that simulates the ¹²⁹I bomb peaks from the Pacific Proving Grounds (PPG) tests, as observed in available coral core data from the east (Baler) and west (Parola) sides of the Philippines. Results show that the model can determine the expected increase in ¹²⁹I/¹²⁷I ratio in the Philippines per megaton of ANWT detonated in the PPG; confirm time lags for each major transport pathway from the PPG to the Philippines, indicating when to expect the radioactivity spike after detonation; and determine the most significant transport pathway from the PPG to each coral location. This work increases the application and significance of ¹²⁹I/¹²⁷I coral core data by deriving quantitative information about the magnitude, timing, and transport pathways of radioactivity from the ANWT site to the coral location. In the future, the model can be expanded to simulate other ¹²⁹I sources besides ANWT.

Estimation of the Thyroid Equivalent Doses to Residents in Areas Affected by the 2011 Fukushima Nuclear Disaster Due to Inhalation of 131I Based on Their Behavioral Data and the Latest Atmospheric Transport and Dispersion Model Simulation

ABSTRACT

It has been challenging to obtain reliable estimates of thyroid equivalent doses (TEDs) to residents involved in the 11 March 2011 Fukushima Daiichi Nuclear Power Plant (FDNPP) accident because of the shortage of direct human measurements associated with 131I, the largest contributor to the dose of concern. The present study attempted to perform the estimation of the TEDs by inhalation of 131I to residents from Namie-town, one of the most radiologically-affected municipalities, by means of the latest atmospheric transport and dispersion model (ATDM) simulations with the Worldwide version of System for Prediction of Environmental Emergency Dose Information (WSPEEDI) ver. 2, coupled with personal behavioral data containing the history of the whereabouts of individuals shortly after the accident. We analyzed 1,637 residents who underwent direct measurements with whole-body counters several months after the accident and provided their personal behavioral data. We divided the subjects into two groups based on whether the distances between their locations and the FDNPP were >20 km as of 15:00 on 12 March in relation to the timepoint of the hydrogen explosion at the Unit 1 Reactor building. As a result, the 90th percentile TEDs of the 1,249 prompt evacuees and 388 late evacuees were 3.9 mSv (adult)-6.8 mSv (10-y-old) and 24.1 mSv (adult)-35.6 mSv (5-y-old), respectively, excluding 16 persons whose TEDs exceeded 50 mSv. The 90th percentile (median) TEDs to 1-y-old children (not included in the subjects) for the prompt and late evacuation groups were 8.1 (1.0) mSv and 36.3 (19.7) mSv, respectively. Additionally, this study provided the evidence to support the view that the explosive event at the Unit 1 Reactor building on the afternoon of 12 March 2011 could have caused the critical group among Namie-town's residents, whereas the largest release event on 15 March gave relatively small doses to the residents because their exposure took place mostly at sites that were distant from the FDNPP. However, the present dose estimation has potentially large uncertainty at the individual level; further validations are thus necessary.

Backward Estimation of Atmospheric Release of 137Cs and 131I Using Total Cumulative Deposition in Terrestrial Areas Following the Fukushima Daiichi Nuclear Power Plant Accident

ABSTRACT

The Fukushima Daiichi Nuclear Power Plant (FDNPP) accident caused a significant release of radionuclides into the environment. It is important to explore the timing and amount of radioactive release to terrestrial areas in order to clarify the consequences of the accident, including the dose received by the population living in the areas affected by the accident. In general, backward estimations are performed using air concentrations of radionuclides, but they are difficult to measure when radioactive plumes are passing through, and only spatially and temporally limited measurements are available. Therefore, a new method of backward estimation was developed based on the total cumulative deposition density, which can provide sufficient data in the environment by combining the atmospheric transport, dispersion, and deposition model calculations. Consequently, our estimations show that a major release of 137Cs and 131I occurred on 15, 20, 21, 22, 25, and 30 March 2011, after the accident. The amounts of release estimated by our new method for 137Cs and 131I were 4.9 × 1015 Bq and 120 × 1015 Bq, respectively. These results have no significant contradiction with the estimated results by the previous studies that were based on air concentrations and air dose rates that were measured in terrestrial areas. It was found that our new method is applicable for backward estimation oriented to the dose assessment for the people living in terrestrial areas.

Assessment of radiological consequence of a hypothetical accident at the Ghana Research Reactor-1 facility based on terrorist attack

The International Atomic Energy Agency defines a nuclear and radiation accident as an occurrence that leads to the release of radiation causing significant consequences to people, the environment, or the facility. During such an event involving a nuclear reactor, the reactor core is a critical component which when damaged, will lead to the release of significant amounts of radionuclides. Assessment of the radiation effect that emanates from reactor accidents is very paramount when it comes to the safety of people and the environment; whether or not the released radiation causes an exposure rate above the recommended threshold nuclear reactor safety. During safety analysis in the nuclear industry, radiological accident analyses are usually carried out based on hypothetical scenarios. Such assessments mostly define the effect associated with the accident and when and how to apply the appropriate safety measures. In this study, a typical radiological assessment was carried out on the Ghana Research Reactor-1. The study considered the available reactor core inventory, released radionuclides, radiation doses and detailed process of achieving all the aforementioned parameters. Oak Ridge isotope generation-2 was used for core inventory calculations and Hotspot 3.01 was also used to model radionuclides dispersion trajectory and calculate the released doses. Some of the radionuclides that were considered include I-131, Sr-90, Cs-137, and Xe-137. Total effective doses equivalent to released radionuclides, the ground deposition activity and the respiratory time-integrated air concentration were estimated. The maximum total effective doses equivalent value of 5.6 × 10-9 Sv was estimated to occur at 0.1 km from the point of release. The maximum ground deposition activity was estimated to be 2.5 × 10-3 kBq/m3 at a distance of 0.1 km from the release point. All the estimated values were found to be far below the annual regulatory limits of 1 mSv for the general public as stated in IAEA BSS GSR part 3.

Intrasubject relationship between striatal 18F-FP-CIT uptake and cardiac 123I-MIBG uptake differs by motor subtype in early Parkinson disease

Parkinson disease (PD) is a heterogeneous neurodegenerative disorder. Dopamine transporter imaging using 123I-2β-carbomethoxy-3β-(4-iodophenyl)-N-(3-fluoropropyl)-nortropane (FP-CIT) and noradrenergic cardiac imaging using 123I-meta-iodobenzylguanidine (MIBG) have been used in combination or separately to study PD patients. Published results regarding uptake of the 2 tracers in each motor subtype are fairly abundant and mostly in agreement. However, data on the intrasubject association between dopaminergic and noradrenergic systems in PD patients are relatively scant and vary. We aimed to assess the intrasubject relationship between striatal dopamine transporter density using a PET tracer and cardiac sympathetic innervation in tremor-dominant subtype (TD) and akinetic-rigid subtype (AR) of PD.This study has a cross-sectional design. Thirty-one patients with early PD (17 TD/14 AR) who underwent both 123I-MIBG cardiac scintigraphy and 18F-FP-CIT PET/CT were retrospectively selected. We assessed the relationship between heart-to-mediastinum ratio (H/M) of 123I-MIBG and specific (striatal)-to-nonspecific (cerebellar) dopamine transporter binding ratio (S/N) measured from 4 separate regions-of-interest (bilateral caudate nuclei and lentiform nuclei) of 18F-FP-CIT in each motor subtype.S/N of all 4 striatal regions were significantly lower in the AR subgroup than in the TD subgroup. H/M was not significantly different. There was a significant intrasubject correlation between H/M and S/N of the lentiform nucleus in AR-PD but no correlation between H/M and any of 4 S/N in TD-PD.Our data suggest a coupled degeneration of nigrostriatal dopaminergic and myocardial sympathetic denervation in AR subtype, but not in TD subtype, of early PD patients. These different results between the 2 motor subtypes likely reflects the heterogeneous pathophysiology of PD.

The course of thyroid nodules and thyroid volume over a time period of up to 10 years: a longitudinal analysis of a population-based cohort

OBJECTIVE

Thyroid disorders are common. Information on the long-term progression of morphologic disorders is scarce. The aim of this study was to describe the course of thyroid nodules and volume over a period of up to 10 years.

DESIGN AND METHODS

Data from the population-based Study of Health in Pomerania were used for longitudinal analysis of 10 years, on average. Billing data from the Association of Statutory Health Insurance Physicians were matched to the data to exclude participants with thyroid surgery, radioiodine therapy and thyroid carcinoma. Changes in the number and size of thyroid nodules and thyroid volume were observed using ultrasound.

RESULTS

A total of 1270 participants were included (53% female, median age at baseline 51 years). The proportion of subjects with at least one thyroid nodule increased from 34.9 to 47.5% after 10 years. The majority of participants had an unchanged or reduced number of nodules. About one-quarter had at least one nodule of size ≥ 1 cm. The proportion of participants with goitre increased from 35 to 37% after 10 years. Nevertheless, individual thyroid volume increased by < 1 mL (95% CI: 0.38-3.66) after adjusting for age and BMI irrespective of thyroid medication.

CONCLUSION

Thyroid nodules and goitre are common. After 10 years, the number of nodules did not increase in about 70% of people. This proportion did not differ substantially when excluding people with thyroid medication. Thyroid volume increased slightly over the follow-up period. These changes do not seem clinically relevant. Our results support a more restrictive approach regarding follow-up diagnostics in asymptomatic patients with thyroid nodules or minimally enlarged thyroid.

PROBABILISTIC ANALYSES OF 131I THYROID ACTIVITY IN PERSONS WITH SURFACE CONTAMINATION IN DIRECT MEASUREMENT WITH A STANDING-TYPE WHOLE-BODY COUNTER AS AN EMERGENCY RESPONSE IN A RADIOLOGICAL INCIDENT

The authors' previous study suggested that a simple standing-type whole-body counter called FASTSCAN (Canberra, Meriden, CT, USA), widely installed throughout Japan after the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident in March 2011, could be used for thyroid measurements in internal dose assessment after a future radiological incident accompanied by the release of 131I into the environment. The present study performed Monte-Carlo simulations using a computational human phantom with several patterns of body surface contamination and used the results to formulate a method for probabilistic analyses of 131I thyroid activity in persons with surface contamination. The major advantage of this method is that the upper limit of the thyroid activity can be determined from the relative frequency distribution without identifying where body surface contamination remains. Therefore, this method is especially effective for use in the early phase of a radiological incident when time and resources are limited, making it difficult to physically remove all body surface contamination for the purpose of gaining more accurate population-wide thyroid screening measurements. As a case study of the FDNPP accident, the proposed method was applied to the results of in vivo measurements for a male subject with body surface contamination. In comparing the probabilistic analyses before and after removal of the subject's contaminated work clothes, the uncertainty of the relative frequency distribution of 131I thyroid activity was reduced by their removal. Therefore, in terms of accurate estimates and avoidance of radiation exposure from their contaminated clothes, efforts to remove body surface contamination still should be made as much as possible in the chaotic situation of the early phase of a radiological incident.

Simultaneous measurements of single gamma ray of 131I and annihilation radiation of 18F with Compton PET hybrid camera

In internal 131I therapy for thyroid cancer, a decision to continue treatment is made by comparing 131I scintigraphy and [18F]FDG-PET. However, with current SPECT and PET systems, simultaneous imaging of diagnostic PET nuclides and therapeutic 131I nuclides has not been achieved so far. Therefore, we demonstrated that the recently developed Compton PET hybrid camera with Ce:Gd3(Al,Ga)5O12 (GAGG)- Silicon Photomultiplier(SiPM) scintillation detectors can be used to simultaneously image 131I Compton image and 18F PET image.

Korean-specific biokinetic model for iodine in radiological protection

The International Commission on Radiological Protection (ICRP) recently adopted a detailed biokinetic model for systemic iodine with reference transfer coefficients based on typical worldwide dietary intakes of stable iodine. The regional data provided demonstrate that the ICRP reference thyroidal biokinetics may differ substantially across regions with atypically low or high dietary intakes of stable iodine. Importantly, the design of the ICRP model facilitates modifications of reference thyroidal kinetics based on regional dietary iodine intake. The present study extended the ICRP model to the South Korean population, whose dietary iodine intake is much higher than the global mean. The following three transfer coefficients were selected as targets for Korean-specific values: thyroidal uptake rate (λ₁), hormonal secretion rate (λ₄) and leakage rate of thyroidal organic iodine as inorganic iodide (λ₅). The Korean-specific values forλ₁,λ₄andλ₅were determined to be 4.48, 0.0086 and 0.0171 d^-1, respectively, to yield the measurements of thyroidal iodine and physiological status of Korean adults. The determinedλ₁andλ₅values differed noticeably from the ICRP values, whereas theλ₄value was comparable to that of the ICRP. Compared with the ICRP reference model, the Korean model, in which the Korean-specific transfer coefficients were adopted, predicted noticeably lower thyroidal uptake and faster decrease of thyroidal iodine. In addition, the predicted cumulative activities of radioiodine in the thyroid were substantially lower (40-80%) than those predicted by the ICRP model. The Korean model developed in this study demonstrates that the iodine biokinetics for Koreans (i.e. a population with a high iodine consumption) obviously differ from the prediction of the ICRP model. Hence, the Korean model may serve to improve the accuracy of thyroid dose estimation for Koreans and will lead to practical changes in matters concerned with radiological protection.

Mass spectrometry - based imaging techniques for iodine-127 and iodine-129 detection and localization in the brown alga Laminaria digitata

129I is one of the main radioisotopes of iodine derived from the nuclear fuel cycle that can be found sustainably in the environment due to its long half-life. In coastal marine environment, brown macroalgae, such laminariales (or kelps), are known to naturally feature highest rates of iodine accumulation, and to be an important source of biogenic volatile iodinated compounds released to the atmosphere. These seaweeds are therefore likely to be significantly marked by but also potential vectors of radioactive iodine. In order to better understand the chemical and isotopic speciation of iodine in brown algal tissues, we combined mass spectrometry-based imaging approaches in natural samples of Laminaria digitata young sporophytes, collected at two different locations along the south coast of the English Channel (Roscoff and Goury). Laser desorption ionization (LDI) and desorption electrospray-ionization techniques (DESI), coupled with mass spectrometry, confirmed the predominance of inorganic I- species on the surface of fresh algae, and a peripheral iodine localization when applied on micro-sections. Moreover, radioactive isotope 129I was not detected on plantlet surface or in stipe sections of algal samples collected near Roscoff but was detected in L. digitata samples collected at Goury, near La Hague, where controlled liquid radioactive discharges from the ORANO La Hague reprocessing plant occur. At the subcellular scale, cryo-fixed micro-sections of algal blade samples from both sites were further analyzed by secondary ion mass spectrometry (nano-SIMS), leading to similar results. Even if the signal detected for 129I was much weaker than for 127I in samples from Goury, the chemical imaging revealed some differences in extracellular distribution between radioactive and stable iodine isotopes. Altogether LDI and nano-SIMS are complementary and powerful techniques for the detection and localization of iodine isotopes in algal samples, and for a better understanding of radioactive and stable iodine uptake mechanisms in the marine environment.

Intake Ratio of 131I to 137CS Derived from Thyroid and Whole-body Doses to Residents of Iwaki City in Japan's Fukushima Prefecture

ABSTRACT

It is very important to determine the precise internal thyroid doses of Fukushima residents involved in the 2011 Fukushima nuclear disaster, particularly for small children. This has been challenging due to the lack of direct human measurements to identify 131I, the biggest contributor to the thyroid doses. We previously used a dataset of late whole-body counter (WBC) measurements targeting 134Cs and 137Cs for the thyroid dose estimation in comparison with the intake ratios of 131I to 137Cs (or 134Cs) derived from thyroid and whole-body doses individually obtained from different subject groups, assuming simultaneous acute intake via inhalation. Herein, we applied the same method to the doses of residents in Iwaki city (located south of the Fukushima Daiichi Nuclear Power Plant) with a relatively high activity ratio (131I/137Cs) for the ground deposition density. Our analyses revealed that the intake ratio (131I/137Cs) for the Iwaki residents was 4.2-4.3, which is relatively consistent with the values obtained in other studies (average 3.0-5.0). No regional difference in the intake ratios from other areas was observed, but further studies are required to determine the accurate intake ratio in the early phase of the accident, in particular focusing on the reasonable interpretation of results of the late WBC measurements to evaluate the actual Cs intake.

A historical record of the impact of nuclear activities based on 129I in coral cores in Baler, Philippines: An update

In a previous study in 2016, we presented how ¹²⁹I in coral cores from the east (Baler) and west (Parola) sides of the Philippines recorded the impacts of human nuclear activities, including nuclear weapons testing, nuclear fuel reprocessing, and nuclear accidents. However, the 2016 Baler dataset only had a two-year time resolution and a crude age model based on growth band counting. Here we present a new 2020 Baler ¹²⁹I/¹²⁷I atomic ratio dataset that features at least annual time resolution and a more accurate age model constructed using 3D X-ray Computed Tomography. Results show that the bomb peaks in Baler primarily came from the Pacific Proving Grounds or PPG with a time lag of about 1.8 years (or more specifically, between 1.3 and 2.4 years). Moreover, a review of the Parola dataset shows that PPG signals may have been transported to Parola in the West Philippine Sea via two pathways: the northward and southward bifurcations of the North Equatorial Current, reaching Parola about 4.5 and 8.5 years after detonation, respectively. Moreover, a prominent peak in the year 2014.7 in Baler possibly came from the 2011 Fukushima Accident, transported by the Kuroshio Recirculation Gyre and the North Pacific Mode Waters with a 3.5-year time lag. This study contributes to the understanding of the impact and transport of human-made radionuclides to the Philippines and the relevant oceanographic processes in the Western Equatorial Pacific region.

Thyroid Doses to French Polynesians Resulting from Atmospheric Nuclear Weapons Tests: Estimates Based on Radiation Measurements and Population Lifestyle Data

Thyroid doses were estimated for the subjects of a population-based case-control study of thyroid cancer in a population exposed to fallout after atmospheric nuclear weapons tests conducted in French Polynesia between 1966 and 1974. Thyroid doses due to (1) intake of I and of short-lived radioiodine isotopes (I, I, I) and Te, (2) external irradiation from gamma-emitting radionuclides deposited on the ground, and (3) ingestion of long-lived Cs with foodstuffs were reconstructed for each study subject. The dosimetry model that had been used in 2008 in Phase I of the study was substantially improved with (1) results of radiation monitoring of the environment and foodstuffs, which became available in 2013 for public access, and (2) historical data on population lifestyle related to the period of the tests, which were collected in 2016-2017 using focus-group discussions and key informant interviews. The mean thyroid dose among the study subjects was found to be around 5 mGy while the highest dose was estimated to be around 36 mGy. Doses from I intake ranged up to 27 mGy, while those from intake of short-lived iodine isotopes (I, I, I) and Te ranged up to 14 mGy. Thyroid doses from external exposure ranged up to 6 mGy, and those from internal exposure due to Cs ingestion did not exceed 1 mGy. Intake of I was found to be the main pathway for thyroid exposure accounting for 72% of the total dose. Results of this study are being used to evaluate the risk of thyroid cancer among the subjects of the epidemiologic study of thyroid cancer among French Polynesians.

Temporal variation of iodine-129 concentrations in kelps (Saccharina) from coastal waters off northern Japan

Concentrations of ¹²⁹I and ¹²⁷I in kelps (Saccharina) collected from coastal waters off northern Japan were monitored from 2007 to 2019. During the 2007-2008 test operation of the Rokkasho nuclear fuel reprocessing plant, ¹²⁹I discharge from the plant increased, and the ¹²⁹I concentration and ¹²⁹I/¹²⁷I atom ratio in the kelps reached maxima of 42 μBq/g-dry and 264 × 10^-11, respectively. By 2009, both had decreased by one order of magnitude. After the Fukushima Dai-ichi Nuclear Power Plant accident in 2011, the ¹²⁹I concentration and ¹²⁹I/¹²⁷I atom ratio in the kelps increased to 2.24 μBq/g-dry and 11.6 × 10^-11, respectively. After 2012, the ratio in kelps decreased to (2.1-8.9) × 10^-11, which is almost the same as the seawater value off Aomori Prefecture before the test operation. The ¹²⁹I/¹²⁷I atom ratio in kelps thus represents the ambient seawater ratio during the growth period of the kelps.

Circulation of Circumpolar Deep Water and marine environment traced by 127I and 129I speciation in the Amundsen Sea Polynya, Antarctica

The long-lived anthropogenic ¹²⁹I released from human nuclear activities has been widely employed as an effective oceanographic tracer to investigate circulation of water masses in marine environment. Depth profiles of seawater collected from the Amundsen Sea Polynya, Antarctica were analyzed for total ¹²⁹I and ¹²⁷I, as well as their species of iodide and iodate. The measured ¹²⁹I concentrations ((1.15-3.43) × 10⁶ atoms/L) and ¹²⁹I/¹²⁷I atomic ratios ((0.53-1.19) × 10^-11) indicate that anthropogenic ¹²⁹I has not only reached the Antarctic surface marine environment but also the deep water due to a strong vertical mixing of water masses. The Circumpolar Deep Water (CDW) flowed southward along continental shelf towards the ice shelf zone (74.25°S) at a depth of 1025 m and then migrated upward and northward to the polynya and finally to the sea ice zone (71.95°S). The maximum upwelling depth of the CDW was around 200 m in the polynya. The source of ¹²⁹I^- in the polynya is predominantly the intrusion of source waters rather than the in-situ reduction of iodate by phytoplankton, implying a considerably slow reduction process of iodate to iodide in this region.

RECONSTRUCTION OF THE RADIOACTIVE CONTAMINATION OF THE TERRITORY OF UKRAINE BY IODINE-131 DURING INITIAL PERIOD OF THE CHORNOBYL ACCIDENT USING THE RESULTS FROM NUMERICAL MODEL WRF

OBJECTIVE

To reconstruct the 131I activity concentrations in air and 131I ground deposition densities from 26 April to7 May 1986 from the radioactivity release after the Chornobyl accident in the settlements of Ukraine using themesoscale radionuclides atmospheric transport model LEDI and meteorological information from the numericalweather forecast model WRF and to compare the obtained results with those calculated previously as well as withavailable measurements of 131I activity in soil.Object of research: the near-ground layer of the atmosphere and the surface of the territory of Ukraine radioactively contaminated as a result of the Chornobyl accident.Materials and methods of research. The dispersion of 131I in the atmosphere and deposition on the ground surfacein Ukraine were calculated using the Lagrangian-Eulerian diffusion model LEDI. The detailed fields of meteorological parameters calculated using the mesoscale weather forecast model WRF, which was adapted for the territory ofUkraine, were used as input data for the LEDI model.

RESULTS

The 131I daily-average activity concentrations in the surface air and 131I daily ground deposition densitiesfrom 26 April to 7 May 1986 were calculated using the up-to-date mesoscale model of numerical weather forecastWRF for 30,352 settlements in entire Ukraine, including 1,263 settlements in Kyiv, 1,717 - in Zhytomyr and 1,570 -in Chernihiv Oblasts.

CONCLUSIONS

The method of mathematical modeling of the atmospheric transport of the radionuclides is combination with the up-to-date mesoscale model of numerical weather forecast WRF is a useful tool for reconstruction ofradioactive contamination of the air and the ground surface after the Chornobyl accident. Calculated in this study131I activity concentrations in air and 131I ground deposition densities were used to reconstruct the thyroid doses dueto 131I intake to the population of Ukraine.

Determination of 131I activity concentration and rate in main inflows and outflows of Salitre wastewater treatment plant (WWTP), Bogota

Samples were collected for several weeks to determine the evolution of the ¹³¹I (Iodine-131) activity concentration in the inflow water processed at the Salitre wastewater treatment plant (WWTP) in Bogota, Colombia, derived from medical facilities for thyroid cancer diagnosis and treatment. Mass balances on ¹³¹I were performed based on the activity rates at the main inflow and outflow of the plant. The ¹³¹I activity concentration in the raw water stream was observed to increase significantly from Monday onwards throughout the week, while the daily activity concentration was highest in the morning and then continuously decreased over the rest of the day. The ¹³¹I activity concentration in the raw water exceeds the reference value for drinking water and is very close to the discharge limit in water bodies in Colombia. A mass balance calculation showed that the activity rate for the inflow and outflow waters of the WWTP is about 15% of the authorized activity to use for facilities discharging water into the basins and the use of bio-sludge stream for organic fertilizer production does not represent a significant risk of external irradiation for the population. The results of this work are the first of its kind in Colombia, which ones contribute significantly to determinate the radiological risk to public health due to utilization of treated water and sludge, know the ¹³¹I behavior in the city sewage systems, and give information for the performance review of regulatory control on ¹³¹I management in the country.

Investigation of the new non-invasive semi-quantitative method of 123I-IMP pediatric cerebral perfusion SPECT

In pediatric cases requiring quantification of cerebral blood flow (CBF) using 123I-N-isopropyl-p-iodoamphetamine (123I-IMP) single-photon emission computed tomography (SPECT), arterial blood sampling is sometimes impossible due to issues such as movement, crying, or body motion. If arterial blood sampling fails, quantitative diagnostic assessment becomes impossible despite radiation exposure. We devised a new easy non-invasive microsphere (e-NIMS) method using whole-body scan data. This method can be used in conjunction with autoradiography (ARG) and can provide supportive data for invasive CBF quantification. In this study, we examined the usefulness of e-NIMS for pediatric cerebral perfusion semi-quantitative SPECT and compared it with the invasive ARG. The e-NIMS estimates cardiac output (CO) using whole-body acquisition data after 123I-IMP injection and the body surface area from calculation formula. A whole-body scan was performed 5 minutes after the 123I-IMP injection and CO was estimated by region of interest (ROI) counts measured for the whole body, lungs, and brain using the whole-body anterior image. The mean CBF (mCBF) was compared with that acquired via ARG in 115 pediatric patients with suspected cerebrovascular disorders (age 0-15 years). Although the mCBF estimated by the e-NIMS indicated a slight deviation in the extremely low- or high-mCBF cases when compared with the values acquired using the invasive ARG, there was a good correlation between the two methods (r = 0.799; p < 0.001). There were no significant differences in the mCBF values based on physical features, such as patients' height, weight, and age. Our findings suggest that 123I-IMP brain perfusion SPECT with e-NIMS is the simplest semi-quantitative method that can provide supportive data for invasive CBF quantification. This method may be useful, especially in pediatric brain perfusion SPECT, when blood sampling or identifying pulmonary arteries for CO estimation using the graph plot method is difficult.

Experience and performance of In Vivo Monitoring Laboratory of NIRP in 2017 thyroid measurement intercomparison

Determination of the ¹³¹I activity in the thyroid of exposed people or workers is one of the major concerns that needs to be addressed following a nuclear or radiological emergency. International intercomparison exercises on bioassay measurements are one of the effective methods to improve the capability and quality of internal dose assessment. In 2017, Working Group 1 (Internal Dosimetry) of the Asian Radiation Dosimetry Group (ARADOS) organized an intercomparison exercise on the thyroid measurement, aiming at enhancing and coordinating the radiation dosimetry capabilities of Asian countries. This paper describes the measurement experience and results of In Vivo Monitoring Laboratory of NIRP in the 2017 intercomparison exercise, which can provide technical reference for laboratories that have not yet participated in such thyroid measurement intercomparsion. It covers technical aspects such as calibration, measurement and data processing. The results presented in this intercomparison are within an acceptable range of performance criteria on the bioassay measurements. In addition, further research work considered in the field of thyroid measurement is described in the discussion section.

Iodine effective diffusion coefficients through volcanic rock: Influence of iodine speciation and rock geochemistry

Accurate prediction of the subsurface transport of iodine species is important for the assessment of long-term nuclear waste repository performance, as well as monitoring compliance with the Comprehensive Nuclear-Test-Ban Treaty, given that radioiodine decays into radioxenon. However, the transport of iodine through intact geologic media is not well understood, compromising our ability to assess risk associated with radioiodine migration. The current study's goal is to quantify the matrix diffusion of iodine species through saturated volcanic rock, with particular attention paid to the redox environment and potential speciation changes. Diffusion experiments were run for iodide through lithophysae-rich lava, lithophysae-poor lava, and welded tuff, whereas iodate diffusion was studied through welded tuff. Iodine transport was compared with a conservative tracer, HDO, and effective diffusion coefficients were calculated. Likely due to a combination of size and anion exclusion effects, iodine species diffused more slowly than the conservative tracer through all rock types tested. Furthermore, oxidation of iodide to iodate was observed in the lithophysae-poor lava, affecting transport. Results provide much needed data for subsurface transport models that predict radioiodine migration from underground sources, and indicate the pressing need for geochemical and redox interactions to be incorporated into these models.

Accounting for Unfissioned Plutonium from the Trinity Atomic Bomb Test

The Trinity test device contained about 6 kg of plutonium as its fission source, resulting in a fission yield of 21 kT. However, only about 15% of the Pu actually underwent fission. The remaining unfissioned plutonium eventually was vaporized in the fireball and after cooling, was deposited downwind from the test site along with the various fission and activation products produced in the explosion. Using data from radiochemical analyses of soil samples collected postshot (most many years later), supplemented by model estimates of plutonium deposition density estimated from reported exposure rates at 12 h postshot, we have estimated the total activity and geographical distribution of the deposition density of this unfissioned plutonium in New Mexico. A majority (about 80%) of the unfissioned plutonium was deposited within the state of New Mexico, most in a relatively small area about 30-100 km downwind (the Chupadera Mesa area). For most of the state, the deposition density was a small fraction of the subsequent deposition density of Pu from Nevada Test Site tests (1951-1958) and later from global fallout from the large US and Russian thermonuclear tests (1952-1962). The fraction of the total unfissioned Pu that was deposited in New Mexico from Trinity was greater than the fraction of fission products deposited. Due to plutonium being highly refractory, a greater fraction of the Pu was incorporated into large particles that fell out closer to the test site as opposed to more volatile fission products (such as Cs and I) that tend to deposit on the surface of smaller particles that travel farther before depositing. The plutonium deposited as a result of the Trinity test was unlikely to have resulted in significant health risks to the downwind population.

Gut Microbiome and Radioiodine-Refractory Papillary Thyroid Carcinoma Pathophysiology

Gut microbiome (GM) might be associated with radioiodine (RAI)-refractory papillary thyroid carcinoma (PTC) through different mechanisms related to sodium/iodide (Na⁺/I^-) symporter (NIS) regulation. However, whether thyroid carcinoma (TC), especially RAI-refractory PTC, causes dysbiosis, or vice versa, is still unknown. Further studies are needed to investigate the mechanism between GM and RAI-refractory PTC.

RADIATION DOSE ASSESSMENT TO FAMILY MEMBERS TAKING CARE OF NON-CANCEROUS THYROID PATIENTS TREATED WITH I-131 THERAPY IN NUCLEAR MEDICINE DEPARTMENT

This study aimed to determine the effective doses of caregivers taking care of non-cancerous patients treated with iodine-131 (I-131). Patients (administered 185-1110 MBq of I-131) were given specific radiation safety instructions (RSI). Afterwards, caregivers were provided with thermoluminescent (TLD) dosimeter badges to be worn for 12-28 days when taking care of the patients. At the end of this period, TLD measurements were obtained. Results showed that caregivers' mean effective dose was 0.15 ± 0.15 mSv, which is far less than the international recommendations of 5 mSv. Furthermore, the effective doses had no significant correlation with administered I-131 activity to the patients, distance from the hospital, caregivers' age, educational level and mode of transport. Our study showed that radiation doses received by caregivers of non-cancerous patients are higher than that of cancerous patients, nevertheless their received doses were within the international limits, thereby indicating good compliance by the caregivers to RSI.