Fukushima Daiichi Nuclear Power Plant Accident: Understanding Formation Mechanism of Radioactive Particles through Sr and Pu Quantities.

The Fukushima Daiichi Nuclear Power Plant accident released considerable radionuclides into the environment. Radioactive particles, composed mainly of SiO, emerged as distinctive features, revealing insights into the accident's dynamics. While studies extensively focused on high-volatile radionuclides like Cs, investigations into low-volatile nuclides such as Sr and Pu remain limited.

Status of the transfer state of Cs in zooplankton and surface water fish off Fukushima during 2018-2021.

Radiocaesium introduced to coastal waters by the accident at the Fukushima Dai-ichi Nuclear Power Station (F1NPS) elevated the radioactivity level in biota. The radionuclide level in zooplankton, concentration of Cs radioactivity in surface water fish decreased rapidly, which was the primary food source for planktivorous fish, was recognized as not to be depurated at the same level prior to the accident. To evaluate the possible cause of this phenomenon, zooplankton and surface water fish were collected off Fukushima during 2018-2021, and the presence of radioactive particles was also examined.

Natural radionuclides and radiological risk assessment in the stream and river sediments of a high background natural radiation area Kanyakumari, India.

The Kanyakumari coast is known to be a high background natural radiation area due to the placer deposits of heavy minerals such as ilmenite, monazite, and rutile. The Kanyakumari river sediments that could be the source of the elevated amounts of natural radionuclides in the coastal sands have been studied in this paper. The activity concentrations of primordial radionuclides Ra, Th, and K were determined using high-purity germanium (HPGe) gamma-ray spectrometry.

Rapid Method To Determine Cs, Np, and Pu Isotopes in Seawater by SF-ICP-MS.

Neptunium-237, owing to its long half-life ( = 2.14 × 10 year) and similar conservatism to Cs, has the potential to replace Cs for water mass circulation studies on decades and even longer time scales. A new method for the determination of Cs, Np, and Pu isotopes in seawater samples was proposed to solve the difficulty of Np analysis in seawater.

Development of a dose estimation system for external exposure assessment at the late phase for individuals living in areas affected by the Fukushima nuclear accident.

Although the elevated ambient dose equivalent (ADE) rates in areas radiologically affected by the 2011 Fukushima nuclear plant accident decreased as time passed, the assessment of Fukushima residents' external dose is still important. A dose estimation system for external exposure assessment at the late phase for individuals living in Fukushima Prefecture was developed for this purpose. The developed system enables the estimations of external doses over the future based on an individual behavioral pattern and ADE-rate distributions from aerial monitoring data and its predicted ADE rate.

Distribution of strontium-90 in soils affected by Fukushima dai-ichi nuclear power station accident in the context of cesium-137 contamination.

Sr and Cs activity concentrations were determined by radiometric methods in 76 soil samples (soil, litter, rain gutter deposit, and roadside sediment samples) affected by the Fukushima Dai-ichi Nuclear Power Station (FDNPS) accident and collected from the Fukushima exclusion zone. The Sr and Cs activity concentrations were in the range of 3 to 1050 Bq kg (median 82 Bq·kg) and 0.7 to 6770 kBq·kg (median 890 kBq·kg), respectively (decay correction date: March 15, 2011).

ACTIVITY RATIO OF URANIUM IN FUKUSHIMA SOIL SAMPLES USING MULTI-COLLECTOR INDUCTIVELY COUPLED PLASMA MASS SPECTROMETRY.

The Fukushima soils have been collected from Namie and Futaba areas for the radiocaesium and uranium isotope ratio studies. The 137Cs activity concentration of soil samples ranged from 6 ± 1 to 756 ± 14 kBq/kg. The uranium isotope ratios are measured using multi collector inductively coupled plasma mass spectrometry.

Distributions and impacts of plutonium in the environment originating from the Fukushima Daiichi Nuclear Power Plant accident: An overview of a decade of studies.

This paper reviews the current knowledge on plutonium (Pu) isotopic composition (the atom or activity ratios) and activity concentrations of Pu, Pu, Pu, and Pu resulting from the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident in 2011. In this critical review, we document the characteristic values of Pu atom or activity ratios (fingerprints) and present their spatial distributions around the FDNPP site. Based on multiple Pu fingerprints (Pu/Pu activity ratio, Pu/Pu atom ratio, and Pu/Pu atom ratio), we clarify that Pu contamination from the FDNPP accident occurred in a restricted terrestrial area, while Pu in the Northwest Pacific Ocean is still predominately sourced from the Pacific Proving Grounds (PPG) and global fallout.

Source and distribution characteristics of Pu, Np and Cs in sediments in the Northwest and Central Equatorial Pacific after the Fukushima nuclear accident.

To understand the possible influence of the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident on the deep sea, as well as the geochemical behavior and transport of radionuclides, Cs, Cs, Pu, Pu, and Np were measured in the abyssal sediments of the Northwest Pacific (NWP) and Central Equatorial Pacific (CEP) Ocean. Data on the characteristics of these sediments obtained after the FDNPP accident are extremely rare, especially in the NWP subtropical gyre (NPSG) region. FDNPP-derived radio-Cs (Cs, Cs) arrived at the open sea floor of the NWP before 2018 but was only found in the Kuroshio-Oyashio Extension (KOE) region.

Factors controlling dissolved Cs activities in coastal waters on the eastern and western sides of Honshu, Japan.

The distributions of dissolved Cs in river, nearshore, and offshore waters on the east and west coasts of the Japanese island of Honshu were studied in 2018-2021, 7-10 years after the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident. On the east side along the north western North Pacific (Fukushima Prefecture), estuarine processes, including desorption from riverine particles and dissolution into pore water from riverine particles that had settled to the seafloor, contributed to the maintenance of high dissolved Cs activities in nearshore and offshore waters. A survey and mass-balance calculation in a semi-enclosed estuarine area, the Matsukawa-ura, in the northern part of Fukushima, provided convincing evidence that rivers contributed to the influx of Cs to coastal waters.

Rapid analysis of Np and Pu isotopes in small volume urine by SF-ICP-MS and ICP-MS/MS.

Internal contamination with alpha-particle emitting actinides, such as Np, Pu, Pu, is likely to bring a large amount of dose to the tissues of persons even if the intake amount is small. To provide timely information for prompt decision-making in radiation emergency therapy, we developed a simple and rapid method for urinary bioassay to determine ultra-trace Np and Pu isotopes using SF-ICP-MS and ICP-MS/MS. To avoid polyatomic interferences and tailing effects from U, Np and Pu isotopes were collected after removing U effectively using a simple single chromatographic column packed with 2 mL AG MP-1M anion exchange resin, exhibiting a high decontamination factor of 10 for U.

A Microwave Digestion Technique for the Analysis of Rare Earth Elements, Thorium and Uranium in Geochemical Certified Reference Materials and Soils by Inductively Coupled Plasma Mass Spectrometry.

Two different digestion methods-microwave digestion (Mw) and Savillex digestion (Sx)-were used to evaluate the best quality control for analysis of the rare earth elements, Th and U in the geochemical certified reference material JSd-2, supplied by the Geological Survey of Japan (GSJ). The analysis of trace elements was carried out using inductively coupled plasma mass spectrometry (ICP-MS). The digestion recovery was > 90% for almost all elements by both methods.

Behavior of Radiocesium in Sediments in Fukushima Coastal Waters: Verification of Desorption Potential through Pore Water.

Concentrations of Cs in seawater, seabed sediment, and pore water collected from the area around Fukushima were investigated from 2015 to 2018, and the potential of coastal sediments to supply radiocesium to the bottom environment was evaluated. The Cs concentration in the pore water ranged from 33 to 1934 mBq L and was 10-40 times higher than that in the overlying water (seawater overlying within 30 cm on the seabed). At most stations, the Cs concentrations in the overlying water and the pore water were approximately proportional to those in the sediment.

Changing Emotions About Fukushima Related to the Fukushima Nuclear Power Station Accident-How Rumors Determined People's Attitudes: Social Media Sentiment Analysis.

Background: Public interest in radiation rose after the Tokyo Electric Power Company (TEPCO) Fukushima Daiichi Nuclear Power Station accident was caused by an earthquake off the Pacific coast of Tohoku on March 11, 2011. Various reports on the accident and radiation were spread by the mass media, and people displayed their emotional reactions, which were thought to be related to information about the Fukushima accident, on Twitter, Facebook, and other social networking sites. Fears about radiation were spread as well, leading to harmful rumors about Fukushima and the refusal to test children for radiation.

Suspended Particle-Water Interactions Increase Dissolved Cs Activities in the Nearshore Seawater during Typhoon Hagibis.

Distributions of Cs in dissolved and particulate phases of the downstream reaches of seven rivers and adjacent nearshore and offshore waters as far as ∼60 km south of the Fukushima Dai-ichi nuclear power plant (FDNPP) were studied during the high-river-flow period (June-September 2019) and during the period of October 2019 after typhoon Hagibis. Dissolved Cs activities in nearshore water were higher than those in rivers and offshore waters, and this distribution was more intensified after the typhoon, indicating the desorption of Cs from riverine suspended particles in addition to the ongoing release of contaminated water from the FDNPP and re-entry of radiocesium via submarine groundwater discharge. This scenario is also supported by the reduction of distribution coefficient () from a geometric mean value of 5.

Chemical Separation of Uranium and Precise Measurement of U/U and U/U Ratios in Soil Samples Using Multi Collector Inductively Coupled Plasma Mass Spectrometry.

A new chemical separation has been developed to isolate uranium (U) using two UTEVA columns to minimize iron and thorium interferences from high background area soil samples containing minerals like monazites and ilmenite. The separation method was successfully verified in some certified reference materials (CRMs), for example, JSd-2, JLk-1, JB-1 and JB-3. The same method was applied for purification of U in Fukushima soil samples affected by the Fukushima dai-ichi nuclear power station (FDNPS) accident.

Precise Measurement of Tellurium Isotope Ratios in Terrestrial Standards Using a Multiple Collector Inductively Coupled Plasma Mass Spectrometry.

Precise tellurium (Te) isotope ratio measurement using mass spectrometry is a challenging task for many decades. In this paper, Te isotope ratio measurements using multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) in terrestrial Te standards have been reported. Newly developed Faraday cup with 10 Ω resistor is used to measure low abundance Te, whereas the 10 Ω resistor is used to measure other Te isotopes.

I in a sediment core offshore Fukushima: Distribution, source and its implication.

I released from the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident has been observed in the atmospheric, terrestrial and oceanic environments, and it also entered the marine sediments via dispersion by sea water movement and deposition around Japan. However, there have been few studies of marine sediment cores in contrast to the large number of studies on seawater. In this work, a sediment core collected near FDNPP was analyzed for I.

Reconstruction of radiocesium levels in sediment off Fukushima: Simulation analysis of bioavailability using parameters derived from observed Cs concentrations.

Radiocesium was released to the North Pacific coastal waters by the accident at the Fukushima Dai-ichi Nuclear Power Plant (1FNPP) of the Tokyo Electric Power Company (TEPCO) in March 2011. Since the radiocesium in the sediment off Fukushima was suggested as a possible source for the transfer of this radionuclide through the benthic food chain, we conducted numerical simulations of Cs in sediments off the Fukushima coast by using a model which incorporates dynamic transfer processes between seawater and the labile and refractory fractions in sediment particles. This model reproduced the measured temporal changes of Cs concentration in seabed surface sediment off Fukusima coasts, by normalizing the radiocsium transfer between seawater and sediment according to the particle diameter sizes.

Accurate and precise determination of Sr at femtogram level in IAEA proficiency test using Thermal Ionization Mass Spectrometry.

A novel method for the determination of ultra-trace level Sr has been recently developed applying thermal ionization mass spectrometry (TIMS). The method includes the chemical separation of Zr (isobaric interference of Zr) from the samples followed by determination of Sr/Sr abundance  sensitivity (2.1 × 10).

First determination of Pu isotopes (Pu, Pu and Pu) in radioactive particles derived from Fukushima Daiichi Nuclear Power Plant accident.

Radioactive particles were released into the environment during the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident. Many studies have been conducted to elucidate the chemical composition of released radioactive particles in order to understand their formation process. However, whether radioactive particles contain nuclear fuel radionuclides remains to be investigated.

Dose rate estimation of freshwater wildlife inhabiting irrigation ponds in the exclusion zone of the Fukushima Dai-ichi Nuclear Power Plant accident.

To assess the risks of ionising radiation to freshwater environments in the exclusion zone of the Fukushima Dai-ichi Nuclear Power Plant accident, the absorbed dose rates to aquatic organisms possibly inhabiting the irrigation ponds were estimated using the ERICA Assessment Tool from Cs and Cs radioactivity monitoring data for the period 2013 to 2017. In each year, the total dose rates to benthic organisms were in the same or higher levels compared with those to pelagic organisms. Among pelagic organisms, the total dose rates to amphibians, birds, and pelagic fish were two orders of magnitude higher than those to plankton.

Low-temperature fusion using NHHSO and NHHF for rapid determination of Pu in soil and sediment samples.

Two fusion methods were established for rapid determination of Pu in soil and sediment samples. The methods consisted of NHHSO or NHHF fusion procedures incorporated with procedures for CaF/LaF co-precipitation, extraction chromatography and SF-ICP-MS measurement. The fusion procedures were done on a portable hot plate instead of in a cumbersome muffle furnace and took only 15 min heating-up time from room temperature to 250 °C and 15 min fusion time at 250 °C.

Effects of chronic γ-irradiation on growth and sexual maturation of the Tohoku hynobiid salamander, Hynobius lichenatus.

There are still considerable gaps in knowledge regarding the biological effects of chronic ionising radiation exposure in amphibians. To fill these gaps, Tohoku hynobiid salamanders, Hynobius lichenatus (Amphibia, Caudata), were chronically irradiated with Cs γ-rays from embryonic to adult stages over 1954 days, and the effects on their growth and sexual maturation were examined under laboratory conditions. Irradiation at a dose rate of 33 μGy h had some stimulatory effects on growth (body weight increase) of H.

Establishing rapid analysis of Pu isotopes in seawater to study the impact of Fukushima nuclear accident in the Northwest Pacific.

In order to assess the impact of the Fukushima derived Pu isotopes on seawater, a new analytical method to rapidly determine Pu isotopes in seawater by SF-ICP-MS including Fe(OH) primary co-precipitation, CaF/LaF secondary co-precipitation and TEVA+UTEVA+DGA extraction chromatographic separation was established. High concentration efficiency (~100%) and high U decontamination factor (~10) were achieved. The plutonium chemical recoveries were 74-88% with the mean of 83 ± 5%.