Search

Arrays of small reaction containers, ranging from 624 femtoliters (10-15 L) to 270 attoliters (10-18 L), for capturing a single enzyme molecule and measuring the activity were developed together with a new reversible sealing system based on a pneumatic valve actuator made of polydimethylsiloxane (PDMS). The valve was actuated by PBS solution, effectively preventing evaporation of the solution from the micro- and nanochambers and allowing the assay to be carried out over a long period of time. The hydrolysis rates of β-D-galactosidase (β-gal), kcat, were decreased according to the chamber size decrease, and the overall tendency seems to be symmetrical relationship to the specific surface area of the chambers even under the prevented condition of non-specific adsorption. The spatial localisation of the protons in the chambers, which might could affect the dissociation state of the proteins, was also investigated to explain the decrease in the hydrolysis rate. The developed chamber system developed here may be useful for artificially reproducing the confined intracellular environments and molecular crowding conditions.

The radioactivity concentrations for 90Sr and 137Cs in soil samples collected near Fukushima Daiichi nuclear power station were investigated. The depth profile of 137Cs from the surface soil to 20 cm showed a typical decreasing tendency, that is, high radioactivity from the surface down to 5 cm due to the strong sorption of specific minerals. After deposition of 90Sr, 90Sr has migrated to deeper soil layers in the past 5 years compared to 137Cs. This tendency was supported by the results of sequential extraction to identify the predominant sorption species, and by the sorption coefficients determined by batch-wise sorption experiments.

Estimation of

Aggregating welfare across individuals to reach collective decisions is one of the most fundamental problems in our society. Interpersonal comparison of utility is pivotal and inevitable for welfare aggregation, because if each person’s utility is not interpersonally comparable, there is no rational aggregation procedure that simultaneously satisfies even some very mild conditions for validity1–3 (Arrow’s impossibility theorem). However, scientific methods for interpersonal comparison of utility have thus far not been available1, 2, 4, 5. Here, we have developed a method for interpersonal comparison of utility based on brain signals, by measuring the neural activity of participants performing gambling tasks. We found that activity in the medial frontal region was correlated with changes in expected utility, and that, for the same amount of money, the activity evoked was larger for participants with lower household incomes than for those with higher household incomes. Furthermore, we found that the ratio of neural signals from lower- income participants to those of higher-income participants coincided with estimates of their psychological pleasure by “impartial spectators”, i.e. disinterested third-party participants satisfying specific conditions6, 7. Finally, we derived a decision rule based on aggregated welfare from our experimental data, and confirmed that it was applicable to a distribution problem. These findings suggest that our proposed method for interpersonal comparison of utility enables scientifically reasonable welfare aggregation by escaping from Arrow’s impossibility and has implications for the fair distribution of economic goods. Our method can be further applied for evidence-based policy making in nations that use cost-benefit analyses or optimal taxation theory for policy evaluation8, 9.

We investigated the radiocaesium content of nine epiphytic foliose lichens species and the adjacent barks of Zelkova serrata (Ulmaceae, "Japanese elm") and Cerasus sp. (Rosaceae, "Cherry tree") at the boundary of the Fukushima Dai-ichi Nuclear Power Station six years after the accident in 2011. Caesium-137 activities per unit area (the 137Cs-inventory) were determined to compare radiocaesium retentions of lichens (65 specimens) and barks (44 specimens) under the same growth conditions. The 137Cs-inventory of lichens collected from Zelkova serrata and Cerasus sp. were respectively 7.9- and 3.8-times greater than the adjacent barks. Furthermore, we examined the radiocaesium distribution within these samples using autoradiography and on the surfaces with an electron probe micro analyzer (EPMA). Autoradiographic results showed strong local spotting and heterogeneous distributions of radioactivity in both the lichen and bark samples, although the intensities were lower in the barks. The electron microscopy analysis demonstrated that particulates with similar sizes and compositions were distributed on the surfaces of the samples. We therefore concluded that the lichens and barks could capture fine particles, including radiocaesium particles. In addition, radioactivity was distributed more towards the inwards of the lichen samples than the peripheries. This suggests that lichen can retain 137Cs that is chemically immobilised in particulates intracellularly, unlike bark.

Many lichens are well known to accumulate radiocaesium and, thus acting as biomonitors of contamination levels. However, the actual localisation and chemical forms of radiocaesium in contaminated lichens have not yet been elucidated because, despite their high radioactivity, these forms are present in trace amounts as chemical entities. Here, we use autoradiography and demonstrate for the first time in situ microscale localisation of radiocaesium within thallus tissues to investigate the radiocaesium forms and their accumulation mechanism. Radiocaesium distributions showed similar trends in lichen tissues collected two and six years after the Fukushima nuclear accident. The radiocaesium was localised in the brown pigmented parts i.e., melanin-like substances, in the lower cortex of lichen thallus. Quantum chemical calculations showed that functional group of melanin-like substances can chelate Cs+ ion, which indicates that the Cs+ ions form complexes with the substances. Based on these findings, we suggest that radiocaesium ions may be retained stably in melanin-like substances for long periods (two to six years) due to steric factors, such as those seen in porphyrin-like structures and via multimer formation in the lower cortex. In addition, electron microscopy and autoradiography were used to observe radiocaesium-bearing microparticles (CsMPs) on/in the upper cortex and around the medullary layer. Micron-sized particles appeared to adhere to the surface tissue of the thallus, as shown by electron microscopy, suggesting that the particles were trapped by development of an adhesive layer; that is, CsMPs were trapped both physically and physiologically. These findings provide information on in situ localisation of two chemical forms of radiocaesium, cations and particles, in lichen thallus tissues and their accumulation mechanisms.

Nine years after the Fukushima Dai-ichi Nuclear Power Plant accident, in line with the strong efforts to devise ever more effective methods to monitor airborne radioactive dusts, in the present study we proposed for the first time the use of mosses transplanted in bags as biointerceptors of 134Cs and 137Cs in the evacuated zone of the Fukushima territory and according to a standardised protocol. The work aimed to investigate the ability of the moss transplants to accumulate radiocaesium and therefore to act as radiocaesium biointerceptors. To this purpose, the activity concentrations of radiocaesium were measured in moss bags filled with 3 widely studied moss species (Sphagnum palustre, Hypnum cupressiforme, Hypnum plumaeforme) and exposed for 3, 6 and 9 weeks at 5 residential sites within Fukushima area. The levels of radiocaesium found in moss bags were evaluated as function of different parameters (e.g. exposure time, site conditions, moss species). The moss bags were able to accumulate 137Cs in all exposure sites and periods, with Sphagnum palustre acting as the most performant moss species. The 137Cs activity concentrations (from 28 to 4700 Bq kg-1), could be explained by the Cs deposition levels and decontamination status of each exposure site, highlighting the sensitivity of the moss bags to discriminate among exposure sites according to their contamination level. Autoradiography and electron microscopy analysis of the distribution and the chemical composition of the particles entrapped by moss surfaces revealed a prevalence soil-derived radiocaesium. The linear dependency of Cs accumulation with the exposure time allowed a radiocaesium quantitative assessment by using location-specific (LF) and species-specific (SF) factors, with the latter susceptible to an “universal” applicability in future biomonitoring studies with the same experimental design.

Contamination of agricultural products by resuspended matter remains a concern in the highly contaminated areas. Radiocesium concentration of spinach cultivated with non-contaminated soil was low in the decontaminated areas, but high in the contaminated areas. The washed plants had relatively lower radiocesium concentration than the unwashed plants. Furthermore, the plants cultivated closer to the ground surface tended to have a higher radiocesium concentration than those cultivated farther from the ground. Therefore, it can be concluded that radiocesium found in the spinach leaves derived from resuspended matter in the air. With further analysis, radiocesium in the resuspended matter was confirmed to be present as particles.

A study is presented on the applicability of the distribution coefficient (Kd) absorption/desorption model to simulate dissolved 137Cs concentrations in Fukushima river water. The upstream Ota River basin was simulated using GEneral-purpose Terrestrial Fluid-flow Simulator (GETFLOWS) for the period 1 January 2014 to 31 December 2015. Good agreement was obtained between the simulations and observations on water and suspended sediment fluxes, and on particulate bound 137Cs concentrations under both base and high flow conditions. By contrast the measured concentrations of dissolved 137Cs in the river water were much harder to reproduce with the simulations. By tuning the Kd values for large particles, it was possible to reproduce the mean dissolved 137Cs concentrations during base flow periods (observation: 0.32 Bq/L, simulation: 0.36 Bq/L). However neither the seasonal variability in the base flow dissolved 137Cs concentrations (0.14-0.53 Bq/L), nor the peaks in concentration that occurred during storms (0.18-0.88 Bq/L, mean: 0.55 Bq/L), could be reproduced with realistic simulation parameters. These discrepancies may be explained by microbial action and leaching from organic matter in forest litter providing an additional input of dissolved 137Cs to rivers, particularly over summer, and limitations of the Kd absorption/desorption model. It is recommended that future studies investigate these issues in order to improve simulations of dissolved 137Cs concentrations in Fukushima rivers.

Estimation of 3H discharge from river catchments is important to evaluate the effect of Fukushima Dai-ichi discharge and future planned 3H release to the ocean on the coastal environment. Using a previously developed model based on the tank model and observed 3H concentration in river water, the 3H discharge from the Abukuma River and 13 other rivers in the Fukushima coastal region were estimated from June 2013 to March 2020. The 3H discharge from catchments of the Abukuma River and 13 other rivers in the Fukushima coastal region during 2014–2019 were estimated to be 1.2–4.0 TBq/y. These values were approximately 2–22 times larger than the annual 3H discharge from the Fukushima Dai-ichi after 2016, indicating the significance of 3H discharge from the catchments through the rivers. This estimation is expected to be useful to evaluate and predict 3H concentrations and inventories in the Fukushima coastal region for consideration of planned 3H release to the ocean.

Radiocesium is an important environmental contaminant in fallout from nuclear reactor accidents and atomic weapons testing. A modified Diffusion-Sorption-Fixation (mDSF) model, based on the advection-dispersion equation, is proposed to describe the vertical migration of radiocesium in soils following fallout. The model introduces kinetics for the reversible binding of radiocesium. We test the model by comparing its results to depth profiles measured in Fukushima Prefecture, Japan, since 2011. The results from the mDSF model are a better fit to the measurement data (as quantified by R2) than results from a simple diffusion model and the original DSF model. The introduction of reversible sorption kinetics means that the exponential-shape depth distribution can be reproduced immediately following fallout. The initial relaxation mass depth of the distribution is determined by the diffusion length, which depends on the distribution coefficient, sorption rate and dispersion coefficient. The mDSF model captures the long tails of the radiocesium distribution at large depths, which are caused by different rates for kinetic sorption and desorption. The mDSF model indicates that depth distributions displaying a peak in activity below the surface are possible for soils with high organic matter content at the surface. The mDSF equations thus offers a physical basis for various types of radiocesium depth profiles observed in contaminated environments.

In order to elucidate the radiocesium transport behaviors in natural environment, we systematically investigated sediments from the highly contaminated rivers of Ukedo and Odaka around the Fukushima Daiichi Nuclear Power Plant. We focused on determining the key factors controlling the radiocesium sorption and fixation, such as variations in the particle size, clay mineralogy, and organic matter (OM). The distribution patterns of the 137Cs concentration and particle size fractions were found to be similar for the two rivers, indicating that both clay and silt fractions contributed almost equally to the Cs sorption. The clay mineralogical composition evaluated using X-ray diffraction analysis showed that the relative contents of micaceous minerals were higher in the Ukedo River samples, whereas the relative contents of smectite and kaolinite were higher in the Odaka River samples. This implies that the sediments in both rivers were likely at different weathering stages due to the different geological settings in both catchments. The effects of OM on the sediment properties were also investigated by comparing the cation exchange capacity (CEC) and the radiocesium interception potential (RIP) of the two samples both with and without OM present. The CEC values were controlled by both the clay minerals and OM, and the RIP values increased significantly in the absence of OM. Such trends were correlated to the total organic carbon values, which may be used to understand the direct and indirect roles of OM in the sorption and fixation of Cs. These key differences in river sediment were attributed to the differences in the geological settings and weathering stages. These properties may contribute to the different sorption and fixation behaviors of radiocesium. In the second part paper, we further examined these behaviors and identified key factors by investigating their relationship to the sediment properties of both rivers.

We systematically investigated the sorption and fixation behaviors of radiocesium (137Cs) for sediments taken from the rivers of Ukedo and Odaka around the Fukushima Daiichi Nuclear Power Plant. By comparing the Cs sorption and sequential desorption results at various Cs concentrations, across a range of sediment properties, we were able to understand the different contributions at frayed edge sites (FESs) and regular exchange sites (RESs) of the clay minerals, and their relationships with the Cs concentrations and the contents of organic matter (OM). The Cs sorption and fixation were dominated by FESs at trace Cs concentrations, and by ion exchange at RES and the collapse of interlayers at higher Cs concentrations. The Cs sorption at lower Cs concentration was strongly related to radiocesium interception potential (RIP); however, Cs fixation was more related to clay mineralogy (i.e. contents of mica, vermiculite and hydroxy-interlayered vermiculite) rather than the RIP. The first-order kinetic constants for time-dependent Cs sorption at low Cs concentrations were correlated negatively to the ratio between the total organic carbon and RIP values. This implies that Cs access to FESs requires a relatively long duration that is dependent on the contents of the OM. From these results, the sorption and fixation mechanisms were confirmed to be significantly different at different Cs concentrations. Then, the prediction of Cs transport should be based on the key mechanisms that are dominant at the actual trace levels of Cs. A significant difference between the Cs fixation behaviors at the Ukedo River and Odaka River may be understood by considering the differences in their clay mineralogy, due to the different geological settings and weathering stages of both catchments.

In order to evaluate the migration and transfer of radionuclides in the environment, not only Strontium-90 (Sr-90) in water but also those in soil and biological samples should be measured. For rapid quantification of Sr-90, a new method by means of online solid phase extraction coupled with inductively coupled plasma mass spectrometry (SPE-ICP-MS) has been developed. In this method, it is unavoidable to eliminate the interference by polyatomic ion induced by isotopes and matrices in fishes. In this study, SPE-ICP-MS method was applied to the measurement of Sr-90 in fishes, and the influence of the Sr isotopes and coexisting ions such as Ca element was evaluated. The detection limit (3σ) was evaluated as 0.35Bq/L (740Bq/kg), which was applicable level to WHO guidelines for drinking water quality.

In order to investigate statistically the physicochemical properties of the radiocaesium-bearing microparticles (CsMPs) emitted from the Fukushima Daiichi Nuclear Power Plant, an efficient method for collecting and separating the microparticles is required. In this study we established a separation method for CsMPs from lichens using electron microscopic analysis. Lichens were first digested within hydrogen peroxide and then an automatic particle analyser system based on FE-EPMA was used for detecting CsMPs within lots of mineral-like and metalic particles quickly. The elemental composition and radiocaesium activities of the separated CsMPs were measured, and the results suggest that the digestion treatment did not influence the CsMPs characteristics. An inhomogeneous elemental distribution was found in some CsMPs by two-dimensional elemental analysis using FE-EMPA. Our methods for separation of CsMPs and analysing their elemental composition are expected to be useful for grasping the chemical composition trends of CsMPs statistically as first step before more detailed analyses such as TEM analysis.

Schizophrenia and bipolar disorder overlap considerably in terms of symptoms, familial patterns, risk genes, outcome, and treatment response. This article provides an overview of the specificity and continuity of schizophrenia and mood disorders on the basis of biomarkers, such as genes, molecules, cells, circuits, physiology and clinical phenomenology. Overall, the discussions herein provided support for the view that schizophrenia, schizoaffective disorder and bipolar disorder are in the continuum of severity of impairment, with bipolar disorder closer to normality and schizophrenia at the most severe end. This approach is based on the concept that examining biomarkers in several modalities across these diseases from the dimensional perspective would be meaningful. These considerations are expected to help develop new treatments for unmet needs, such as cognitive dysfunction, in psychiatric conditions.

Undesirable habitual or addictive behaviors are often difficult to change. The issue of “behavior change” has long been studied in various research fields. Several models for behavior change have converged to the hypothesis that attitudes, norms, and self-efficacy are important determinants of intentions and behavior. To improve the accuracy of behavior-change models, some researchers have tried to combine behavioral economics models with existing models for behavior change. However, these attempts have failed because the existing models [e.g., Theory of Planned Behavior (TPB)] are not consistent with Expected Utility Theory (EUT), which underlies various behavioral economics models. In the present paper, we clarify the corresponding components between existing models for behavior change and EUT, and propose a new model, the Decision-Theoretic Model of behavior change (DTM), which is a natural extension of ordinary EUT.

A mixture of acetylacetone and water was condensed in low-temperature Ar matrices at 5 K, and infrared spectra were observed. It was found that the H2O molecules formed hydrogen bonds with the acetylacetone. The structure of the H2O-C5H8O2 complex was estimated with the aid of a density functional calculation. A similar sample was prepared using deuterium-substituted water to confirm the structure of the complex. Upon annealing the matrix-isolated sample, aggregation of H2O molecules was observed and the amount of the complex remained unchanged.

The environment in the area around Fukushima Daiichi Nuclear Power Plant has been contaminated by widely deposited significant amount of radioactive materials, which were released to the atmosphere caused by the Fukushima Daiichi Nuclear Power Plant accident due to the Great East Japan Earthquake, which occurred on March 11, 2011. The radiocesium released in the accident mainly affects radiation dose in the environment. Decontamination work in the contaminated area except a mountain forests has been conducted to decrease the radiation dose. However, there are concerns that the redistribution of this radiation due to water discharge will occur due to the resulting transport of radiocesium. In particular, the deposition of soil particles containing radiocesium on the flood plains in the downstream areas of Fukushima's rivers can potentially increase the local radiation dose. Therefore, it is important to understand the influence of the deposition behavior of radiocesium on the radiation dose. Investigations of rivers have been performed to enhance the understanding of the mechanisms by which radiocesium is deposited on these flood plains. It was found that the spatial distribution of the radiocesium concentration on the flood plain along the river is heterogeneous with a dependence on the depositional condition and that the number of points with high air dose rates is limited. In detail, the radiocesium concentration and air dose rates in flood channels are higher than those at the edges of the river channels. Based on these heterogeneity and hydrological events, the deposition and transport mechanisms of the radiocesium due to water discharge at rivers were also interpreted, and a conceptual model was constructed.

The deposited radiocesium in the Fukushima river basin is transported in the river systems by soil particles and redistributed in the downstream areas. Although predicting the behaviors of minerals that adsorb radiocesium and of radiocesium dissolved in river water within the river systems is essential, the dominant mineral species that adsorb radiocesium have not yet been comprehensively identified. We identify herein such mineral species by investigating the 137Cs distribution and the mineral species in each size fraction that are found in the bedload sediments from an upstream reservoir to an estuary within the Tomioka river basin located east of Fukushima Prefecture in Japan. In the fine sand sediment, which is the dominant fraction in terms of the 137Cs quantity in the river bedload, the 137Cs concentrations of the felsic and mafic minerals are comparable to that of micas. The mafic minerals contain 62% of the 137Cs in the fine sand fraction in the upstream area, while the felsic minerals contain the highest quantities of 137Cs in the downstream area. These results suggest that the quantification of the mineral species and the 137Cs concentration of each size fraction are critically important in predicting the behaviors of the minerals and radiocesium within the Fukushima river basin in the future.

Radiocaesium-bearing microparticles (CsMPs) composed of silicate glass were released by the Fukushima Daiichi Nuclear Power Plant accident in March 2011. Since CsMPs contain a high concentration of radiocaesium, their dynamics and fate in the environment are urgent issues to be investigated. Here, we show that CsMPs are dissolved by weathering in the environment and that their radioactivity is more rapidly decreased by dissolution than the physical decay of radiocaesium. We conducted dissolution experiments with CsMPs in pure water that absorbed CO2 from the atmosphere and in artificial seawater at several temperatures. The dissolution progress was monitored by the decrease in the 137Cs radioactivity in CsMPs, and the dissolution rate was estimated. The activation energy for the dissolution of CsMPs was estimated to be 65 and 88 kJ/mol and the dissolution rate at 13 °C (approximate annual mean temperature in Fukushima City) was 0.014 and 0.140 μm/y for pure water and seawater, respectively, assuming that radiocaesium is uniformly distributed in spherical CsMPs. The shapes of the CsMPs dissolved in pure water were considerably altered, suggesting that the dissolution proceeded without maintaining the geometry. Tin oxide and iron oxide nanoparticulates formed on the surfaces. Such features were similar to those observed in CsMPs recently collected in Fukushima Prefecture, indicating that weathering dissolution of CsMPs is also occurring in the environment. For the CsMPs dissolved in seawater, a crust of secondary Mg- and Fe-rich minerals was formed, and the glass matrix inside the crust decreased, creating space between the crust and the glass matrix.

Radiocesium-bearing microparticles (CsMPs), consisting substantially of silicate glass, were released to the environment during the Fukushima Daiichi Nuclear Power Plant accident in March 2011. Since the CsMPs were formed inside the damaged reactors during the accident, we investigate the inner structures of several CsMPs by transmission electron microscopy to understand the events within the reactors. Elemental mapping of the CsMPs shows a distinct radial distribution of Cs with a higher concentration near the surface of the CsMPs, implying that Cs was in a gaseous state in the reactor atmosphere and diffused into the glass matrix after formation of the glass particles. In some CsMPs, Zn and Fe also showed a similar radial distribution to Cs, suggesting that those elements may have diffused outward where Cs was abundant. In addition, submicron crystals were present as inclusions in several of the CsMPs and were identified as chromium spinels ((Fe2+,Zn)(Cr,Fe3+)2O4), acanthite (Ag2S), molybdenite (MoS2) and hessite (Ag2Te). The spinels contained ferrous iron (Fe2+), suggesting that the atmosphere inside the reactors was reductive to some extent. Also, boron was not detected in the glass matrix of the CsMPs despite using electron energy-loss spectroscopy, indicating that most of the control rods made of B4C might have created a eutectic alloy without vaporization. These detailed investigations of the inner structures in the CsMPs may offer information on the damaged reactors that are difficult to access because of the high radiation fields.

Radiocesium-bearing microparticles (CsPs) substantially made of silicate glass are a novel form of radiocesium emitted from the broken containment vessel of Fukushima Dai-ichi nuclear power plant. CsPs have a potential risk of internal radiation exposure caused by inhalation. Radiation-contaminated waste including CsPs is being burned in incinerators; therefore, this study has investigated the responses of CsPs to heating in air. The radioactivity of CsPs gradually decreased from 600 °C and was almost lost when the temperature reached 1000 °C. The size and spherical morphology of CsPs were almost unchanged after heating, but cesium including radiocesium, potassium and chlorine were lost, probably diffused away from the CsPs. Iron, zinc and tin originally dissolved in the glass matrix were crystallized to oxide nanoparticles inside the CsPs. When the CsPs were heated together with weathered granitic soil that is common in Fukushima, the radiocesium released from CsPs was sorbed by the surrounding soil. From these results, it is expected that the radioactivity of CsPs will be lost when radiation-contaminated waste including CsPs is burned in incinerators.

Approximately two months after the Fukushima nuclear accident, the Japan Atomic Energy Agency (JAEA) led off a series of demonstration tests to develop effective but easily applicable decontamination methods for various school facilities in Fukushima. This effort included (1) dose reduction measures in schoolyards, (2) purification of swimming pool water, and (3) removal of surface contamination from playground equipment. Through these demonstration tests, they established practical methods suitable for each situation: (1) In schoolyards, dose rates were drastically reduced by removing topsoil, which was then placed in 1-m-deep trenches at a corner of the schoolyard. (2) For the purification of pool water, the flocculation coagulation treatment was found to be effective for collecting radiocesium dissolved in the water. (3) Demonstration tests for playground equipment, such as horizontal bars and a sandbox wood frame indicated that the decontamination effectiveness considerably varied depending on the material, paint or coating condition of each equipment piece. These findings were summarized in reports, some of which were compiled in local/national guidelines or handbooks for decontaminating the living environment in Fukushima.

A study is presented on the applicability of the distribution coefficient (K

A study is presented on the applicability of the distribution coefficient (K

Trends of air dose rate decrease after decontamination works and factors which affect them constitute essential information for radiation protection, such as prediction of external exposure to the public and implementation of measures to reduce such exposure. This study investigated the decrease of air dose rate (ambient dose rate at 1 m above the ground) at 163 points across sub-urban areas in the evacuation zone around the Fukushima Dai-ichi Nuclear Power Plant over the period of four years following the decontamination works carried out in November 2012. The air dose rate on the asphalt pavement decreased faster than on soil surfaces. In addition, air dose rates near the forest decreased at a slower pace than in open fields. These results suggest that the air dose rate in urbanized areas can decrease faster than in other types of land, even after decontamination. Based on comparisons with decrease rates obtained in other studies, the air dose rate tends to decrease faster outside the evacuation zone than inside it. The decrease in air dose rate after decontamination was slower than before decontamination. The contribution of the weathering effect and human activity was estimated to be about 80% and 20% of the ecological decrease rate, respectively.

Following the release of radionuclides into the environment as a result of the accident at Fukushima Daiichi nuclear power plant, Japan Atomic Energy Agency (JAEA) had to develop an immediate and effective method of reducing the dose rate received by students in school facilities. A demonstration of a reducing method was carried out by JAEA at a junior high school ground and kindergarten yard in the center of Fukushima-city. Dose rates of the released radionuclides are largely controlled by the ground level contamination and accumulation of mainly Cesium137 (Cs-137) and Cesium 134 (Cs-134) in populated areas. An effective means of reducing dose rate was to remove the surface soil and to bury it on-site under fresh uncontaminated soil or soil collected under deep depth at the site for shielding. The dose rate at1 m above ground level was reduced from 2.5 µSv/h to 0.15 µSv/h.

The diffusion behavior of HA and Nd in the presence of HA in compacted bentonite was investigated experimentally by means of the through-diffusion method. Breakthrough of HA is observed in 1 and 0.1 mol dm −3 NaCl solution and is more significant with a lower dry density such as 1.2 Mg m −3 . The one dimensional diffusion model taking parallel complexation equilibrium into account was fitted to the experimentally obtained breakthrough curves and concentration profiles, and the diffusion parameters, such as effective diffusivity and rock capacity factor, were evaluated. The obtained effective diffusivity, around 10 −11 m 2 s −1 , for HA and Nd–HA is comparable to the previously reported value. Using these parameters, predictive calculations were performed to evaluate the effect of HA concentration and sorption distribution coefficient. It is indicated that the effect of sorption distribution coefficient is significant only for a short period and that relatively low HA concentrations might bring higher diffused mass depending on the diffusion behavior of dominant species.

The binding of europium to dissolved humic substances (HSs), isolated from deep groundwater in the Horonobe area, Hokkaido, Japan, was evaluated by means of a three-dimensional fluorescence quenching technique. The Ryan and Weber model, extended by the charge neutralization model, was applied to the fluorescence quenching profiles to evaluate the conditional binding constants (K) at pH 5.0 and an ionic strength of 0.1. The K values for fulvic (FA) and humic acids (HA) in the Horonobe groundwater were comparable with each other regardless of the position of the fluorescence peaks. As compared with HSs from Lake Biwa, Aldrich, and Dando soil, the K values of the Horonobe groundwater HSs were the smallest, indicating that the Horonobe groundwater HSs have a lower affinity for the binding of europium compared to the HSs from surface environments. In addition, the results of the Aldrich-based comparison indicate that the Horonobe groundwater HSs have a lower binding affinity for trivalent lanthanides/actinides...

Sorption and diffusion behaviors of Eu in sedimentary rock in the presence of humic substance were investigated. The sedimentary rock collected from 500 m depth of HDB-6 bore hole at horonobe URL site of Japan and Aldrich humic acid (HA) were used in the present study. Sorption behaviors of Eu and the HA on the sedimentary rocks with and without the rock organic matter (ROM) were elucidated as a function of HA concentration. The HA reduced the sorption of Eu on the rock with the increase of HA. Eu and HA sorption on the rock with the ROM was larger than on the rock after removing the ROM, indicating that the ROM plays an important role on the sorption of Eu and HA. The diffusion of Eu in the presence of HA was examined as a function of HA concentration and molecular weight of the HA (∼150 kDa or below 10 kDa) by means of a reservoir depletion test method with the intact rock core of the sedimentary rock. Depletion of Eu concentration in the reservoir was reduced with the increase of HA concentration. On the other hand, slight depletion of HA concentration in the reservoir was observed, indicating that the larger HA molecule diffused less into the rock. From the depletion curve and in-diffusion profile of Eu in the rock, the effective diffusion coefficient, D e, and distribution coefficient, K d, in the intact system were estimated based on the profile fitting of the diffusion data with the conventional simple diffusion-sorption model. It was elucidated that the HA reduced the K d and D e of Eu in the intact system with the increase of HA. The contribution of the HA with smaller molecular weight to both the Eu sorption and diffusion was examined.

Bentonite colloids may be generated from bentonite in the geological disposal system planned in Japan, and sorb radionuclides (RNs) thus facilitating migration. In this context, distribution coefficients and reversibility of the sorption of RNs onto colloids are sensitive factors in safety assessment. In this study, distribution behavior of Cs and Am in the synthetic groundwater-bentonite colloids-granite ternary system was investigated by batch methods. To evaluate the sorption reversibility, three series with different addition order of components were prepared, such as CR+G corresponding to the series beginning with a colloid (C)–RN (R) solution binary system followed by addition of granite (G) after around 100 d, GR+C and CG+R. Distribution coefficients for the bentonite colloids (R d,col) interaction with Cs obtained in CR+G and CG+R are similar to calculated value (6.7–15 m3 kg−1) based on a previously reported sorption model, while that of GR+C is higher. Considering the contribution of micaceous colloids generated from granite, high R d,col in GR+C can be explained. The experimental R d,col data for Am in each series show similar values and agree well with calculation results (7.6×103–8.7×103 m3 kg−1) by applying the sorption models. Therefore, it is concluded that the sorption behavior of Cs and Am onto the bentonite colloids are reversible and the sorption models developed in the binary system are applicable to the ternary system. Interaction of Cs with granite shows slow kinetics both in sorption and desorption process. The K d,gra values for Am in CR+G are lower than those of other series just after addition of granite, however, they gradually increase with time and finally congruent values are attained. The concentration of free Am in CR+G is one order of magnitude higher than that in GR+C in spite of the ternary system under similar chemical conditions of the solution, suggesting temporal generation of species such as colloidal Am which is not sorbed on granite in CR+G.

In the geological disposal system with stable colloidal particles, the influence of the colloidal particles on the migration of radionuclides has to be evaluated. Not only the distribution coefficient, which is a measure for adsorption of radionuclides on colloidal particles, but also the reversibility of adsorption should be determined. In this study, adsorption and desorption of Cs + ions on colloidal montmorillonite particles were investigated in the wide range of the initial Cs + concentrations. A rapid, almost linear and reversible adsorption of Cs + on montmorillonite was observed at basic condition, indicating that the adsorption of Cs + on montmorillonite was mostly dominated by ion exchange. The size of the montmorillonite particles slightly affected the distribution coefficients at lower Cs + concentrations, suggesting the contribution of surface complexation. The ion exchange and surface complexation model reproduced the adsorption and desorption behavior of Cs + . To explain the fixation of Cs + , montmorillonite was conditioned with the solutions of various Cs + concentrations and the basal spacing was measured by X-ray diffraction (XRD). Conditioning montmorillonite at higher Cs + concentrations > 5 × 10 − 3 M decreased the basal spacing which may result in the fixation of Cs + in the interlayer space. Since the adsorption experiments were carried out at lower Cs + concentration − 4 M, Cs + adsorption was reversible.

High-purity synthetic barite powder was added to pure water or aqueous solutions of soluble salts (BaCl2, Na2SO4, NaCl and NaHCO3) at 23 ± 2 °C and atmospheric pressure. After a short pre-equilibration time (4 h) the suspensions were spiked either with 133Ba or 226Ra and reacted under constant agitation during 120–406 days. The pH values ranged from 4 to 8 and solid to liquid (S/L) ratios varied from 0.01 to 5 g/l. The uptake of the radiotracers by barite was monitored through repeated sampling of the aqueous solutions and radiometric analysis. For both 133Ba and 226Ra, our data consistently showed a continuous, slow decrease of radioactivity in the aqueous phase. Mass balance calculations indicated that the removal of 133Ba activity from aqueous solution cannot be explained by surface adsorption only, as it largely exceeded the 100% monolayer coverage limit. This result was a strong argument in favor of recrystallization (driven by a dissolution–precipitation mechanism) as the main uptake mechanism. Because complete isotopic equilibration between aqueous solution and barite was approached or even reached in some experiments, we concluded that during the reaction all or substantial fractions of the initial solid had been replaced by newly formed barite. The 133Ba data could be successfully fitted assuming constant recrystallization rates and homogeneous distribution of the tracer into the newly formed barite. An alternative model based on partial equilibrium of 133Ba with the mineral surface (without internal isotopic equilibration of the solid) could not reproduce the measured activity data, unless multistage recrystallization kinetics was assumed. Calculated recrystallization rates in the salt solutions ranged from 2.8 × 10−11 to 1.9 × 10−10 mol m−2 s−1 (2.4–16 μmol m−2 d−1), with no specific trend related to solution composition. For the suspensions prepared in pure water, significantly higher rates (∼5.7 × 10−10 mol m−2 s−1 or ∼49 μmol m−2 d−1) were determined. Radium uptake by barite was determined by monitoring the decrease of 226Ra activity in the aqueous solution with alpha spectrometry, after filtration of the suspensions and sintering. The evaluation of the Ra uptake experiments, in conjunction with the recrystallization data, consistently indicated formation of non-ideal solid solutions, with moderately high Margules parameters (WAB = 3720–6200 J/mol, a0 = 1.5–2.5). These parameters are significantly larger than an estimated value from the literature (WAB = 1240 J/mol, a0 = 0.5). In conclusion, our results confirm that radium forms solid solutions with barite at fast kinetic rates and in complete thermodynamic equilibrium with the aqueous solutions. Moreover, this study provides quantitative thermodynamic data that can be used for the calculation of radium concentration limits in environmentally relevant systems, such as radioactive waste repositories and uranium mill tailings.

In the geological disposal system, if colloids can stably exist in groundwater, radionuclides (RNs) might be sorbed onto the colloids and migrate long distance without retardation such as the sorption onto minerals and the matrix diffusion. The distribution coefficient (Rd), which is a measure for sorption onto colloids, is one of the sensitive parameters in evaluation of the effect of colloids on the RN migration. In this study, theRds of Am onto bentonite colloids were evaluated by batch sorption experiments under weakly basic and low ionic strength conditions. Colloidal species of Am seems to be generated even in the absence of bentonite colloids, however, it has less contribution toRd. The obtainedRdvalues are larger than those obtained for larger montmorillonite particles reported in literatures. The difference ofRdis considered to be due to a difference of composition of experimental solution and a difference of reactive site capacity affected by particle size. Site capacities of bentonite colloids are evaluated by acid titration and it is observed that bentonite colloids have about 8 times larger site capacities than bentonite sediments. A relatively simple and generalized mechanistic sorption model, 2SPNE SC/CE model, is applied to estimate theRdfor Am sorption onto bentonite colloids using reaction constants reported in literatures and site capacities obtained in this study. CalculatedRds mostly agree well with corresponding experimental data at pH 8, while,Rds are underestimated at pH 10. Based on the speciation plots, it is probably due to the underestimation of surface complexation reaction.

For establishing a reliable safety assessment methodology for high-level radioactive waste (HLW) geological disposal, it is essential to clarify the applicability of sorption data determined with a conventional batch sorption method to an actual repository environment. In the present study, sorption data represented as distribution coefficients (K d) were compared experimentally by applying a batch method with crushed sedimentary rock samples and a dynamic circulation method with intact sedimentary rock samples. The K d values for cesium (Cs) determined with the dynamic circulation method are around one order of magnitude lower than those obtained using the batch method, depending on Cs concentration at sorption equilibrium. This disagreement was discussed considering permeability, specific surface area, solid/liquid ratio (S/L) and solution chemistry. The K d values determined with the dynamic circulation method were corrected for different specific surface areas. As a consequence, the K d values determined with the two methods are then comparable within an order of magnitude. The K d values become even more comparable when taking into account that they decrease with increasing the S/L ratio as it is the case when going from batch to column experiments. The results basically suggest that the K d determined with the batch method are reasonably applicable to describe sorption in the actual environment in a given nuclear waste repository after appropriate corrections.

In the present study the interaction of Ra(II) with calcium silicate hydrates (C-S-H) as well as with fresh and degraded hardened cement pastes (HCP) has been investigated using batch-type sorption tests. Synthetic C-S-H phases with varying CaO:SiO2 (C:S)mol ratios, relevant to non-degraded HCP and degraded HCP, were prepared in the absence of alkalis (Na(I), K(I)) and in an alkali-rich artificial cement pore water (ACW). The Ra(II) sorption kinetics, the effect of the solid to liquid ratio and the C:S mol ratio on the Ra(II) uptake were investigated. In addition, the reversibility of Ra(II) sorption was tested using dilution tests. Comparison with data on the uptake of Sr(II) by C-S-H phases obtained from previous in-house studies showed that the same model concept could be applied to interpret the immobilization of Sr(II) and Ra(II) in these systems. Ra(II) sorption on C-S-H in the absence of alkalis could be interpreted in terms of a Ra2+-Ca2+ cation exchange model. The Ra2+-Ca2+ exchange selectivity coefficient, Ra CaKC, was determined to be (6±4). There are indications that, in the presence of alkalis, the Ra(II) sorption by C-S-H phases can only be described with the help of an ion-exchange model involving Ra2+, Ca2+ and the monovalent alkalis. The cation exchange model developed for C-S-H phases in the absence of alkalis was successfully applied to predict the sorption of Ra(II) on degraded HCP, assuming that the Ra(II) sorbs solely on the C-S-H fraction of the HCP. Model predictions and experimental data were found to agree well in view of the simplified sorption model used.

The corrosion of carbon steel and its effect on neptunium diffusion were studied by corrosion tests of carbon steel and neptunium diffusion tests under conditions designed with consideration of constituents of a repository for High-level Radioactive Waste disposal. The major constituents of the conditions were carbon steel, corrosion products pre-formed under aerobic conditions, compacted bentonite, reductant and a low-oxygen glove box. The corrosion tests were performed in the presence of water-saturated compacted bentonite. The neptunium diffusion tests were performed with and without carbon steel. The carbon steel and the bentonite were observed by taking photographs and analyzed by X-ray diffraction. The color of the corroded surface of the carbon steel changed from red/orange/black under aerobic conditions to a dark-green under reducing conditions. Portions of the bentonite changed their original color, pale-gray, to a brownish color after the test. Gas-induced cracks were also observed in some bentonite specimens. These changes were discussed combining thermodynamic predictions under the present experimental conditions. The results revealed that anaerobic corrosion of carbon steel occurred in the bentonite. The corrosion processes were also discussed. The corrosion rate of carbon steel was estimated to be ∼0.1 μm/year from iron profiles in the bentonite. This value was much lower than the conservative setting value 20 μm/year in the current performance assessment. The significant restriction in corrosion could be attributed to the presence of bentonite and corrosion products. Oxidation states of neptunium in the bentonite were investigated by thenoyltrifluoroacetone in xylene extraction technique. It was found that tetravalent neptunium accounted for 99% of the total neptunium in the presence of carbon steel and only 63% without. The results revealed that anaerobic corrosion of carbon steel could maintain strong reducing conditions to keep most tetravalent neptunium from being oxidized to pentavalent neptunium, thus effectively restraining migration of neptunium in the bentonite. The apparent diffusions were estimated to be in the order of 10−15–10−14 m2/s for tetravalent neptunium and 10−13–10−12 m2/s for the pentavalent. No significant effect of the corrosion products on neptunium sorption was found through comparing the apparent diffusion coefficients obtained in the diffusion with and without carbon steel. Corrosion of carbon steel under conditions relevant to the repository is essential for further studies, providing a confident and defensible value of corrosion rate for repository design. The effects of corrosion on radionuclide migration, especially redox-sensitive radionuclides in the buffer, should be considered for a reliable safety assessment of geological disposal.

Predictive syntactic processing plays an essential role in language comprehension. In our previous study using Japanese object-verb (OV) sentences, we showed that the left inferior frontal gyrus (IFG) responses to a verb increased at 120-140 ms after the verb onset, indicating predictive effects caused by a preceding object. To further elucidate the automaticity of the predictive effects in the present magnetoencephalography study, we examined whether a subliminally presented verb (“subliminal verb”) enhanced the predictive effects on the sentence-final verb (“target verb”) unconsciously, i.e., without awareness. By presenting a subliminal verb after the object, enhanced predictive effects on the target verb would be detected in the OV sentences when the transitivity of the target verb matched with that of the subliminal verb (“congruent condition”), because the subliminal verb just after the object could determine the grammaticality of the sentence. For the OV sentences under the congruent condition, we observed significantly increased left IFG responses at 140-160 ms after the target verb onset. In contrast, responses in the precuneus and midcingulate cortex (MCC) were significantly reduced for the OV sentences under the congruent condition at 110-140 and 280-300 ms, respectively. By using partial Granger causality analyses for the OV sentences under the congruent condition, we revealed a bidirectional interaction between the left IFG and MCC at 60-160 ms, as well as a significant influence from the MCC to the precuneus. These results indicate that a top-down influence from the left IFG to the MCC, and then to the precuneus, is critical in syntactic decisions, whereas the MCC shares its task-set information with the left IFG to achieve automatic and predictive processes of syntax.

Radiocaesium activity concentrations ((134)Cs and (137)Cs) were measured in parmelioid lichens collected within the Fukushima Prefecture approximately 2 y after the Fukushima Dai-ichi Nuclear Power Plant accident. A total of 44 samples consisting of nine species were collected at 16 points within a 60 km radius of the Fukushima Dai-ichi Nuclear Power Plant. The activity concentration of (134)Cs ranged from 4.6 to 1000 kBq kg(-1) and for (137)Cs ranged from 7.6 to 1740 kBq kg(-1). A significant positive correlation was found between the (137)Cs activity concentration in lichens and the (137)Cs deposition density on soil (n = 44), based on the calculated Spearman's rank correlation coefficients as r = 0.90 (P

Philosophers have often appealed to intuitive judgments in various thought experiments to support or reject particular theses. Experimental philosophy is an emerging discipline that examines the cognitive nature of such intuitive judgments. In this paper, we assess the methodological and epistemological status of experimental philosophy. We focus on the Knobe effect, in which our intuitive judgment of the intentionality of an action seems to depend on the perceived moral status of that action. The debate on the philosophical implications of the Knobe effect has been framed in terms of the distinction between the competence and performance of the concept of intentionality. Some scholars seem to suggest that the Knobe effect reflects the competence (or otherwise, the performance error) of the concept of intentionality. However, we argue that these notions are purely functional and thus do not have philosophical implications, without assuming normativism, which we see as problematic in a psychological methodology. Finally, focusing on the gap between competence and rationality, we suggest future directions for experimental philosophy.