Comparison of codes for calculation of projocted radiation-induced cancer risks.

The lifetime attributable risk (LAR) of cancer caused by radiation exposure is crucial when deciding on radiological protection measures or protective actions for nuclear emergency preparedness and response. Although a model for estimating LAR among the Japanese population has been developed based on epidemiological data from A-bomb survivors, a flexible projection code implementing this model must be developed. This study investigated existing codes to contribute to the development of a projection code.

Biofilm Formation on Excavation Damaged Zone Fractures in Deep Neogene Sedimentary Rock.

Deep underground galleries are used to access the deep biosphere in addition to mining and other engineering applications, such as geological disposal of radioactive waste. Fracture networks developed in the excavation damaged zone (EDZ) are concerned with accelerating mass transport, where microbial colonization might be possible due to the availability of space and nutrients. In this study, microbial biofilms at EDZ fractures were investigated by drilling from a 350-m-deep gallery and subsequent borehole logging at the Horonobe Underground Research Laboratory (URL).

Soil dust and bioaerosols as potential sources for resuspended Cs occurring near the Fukushima Dai-ichi nuclear power plant.

One of the current pathways to radiation exposure, caused by the radionuclides discharged during the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident, is the inhalation of resuspended Cs present in the air. Although wind-induced soil particle resuspension is recognized as a primary resuspension mechanism, studies regarding the aftermath of the FDNPP accident have suggested that bioaerosols can also be a potential source of atmospheric Cs in rural areas, although the quantitative impact on the atmospheric Cs concentration is still largely unknown. We propose a model for simulating the Cs resuspension as soil particles and bioaerosols in the form of fungal spores, which are regarded as a potential candidate for the source of Cs-bearing bioaerosol emission into the air.

Occurrence of radioactive cesium-rich micro-particles (CsMPs) in a school building located 2.8 km south-west of the Fukushima Daiichi Nuclear Power Plant.

Radioactive Cs-rich microparticles (CsMPs) released from the Fukushima Daiichi Nuclear Power Plant (FDNPP) are a potential health risk through inhalation. Little has been documented on the occurrence of CsMPs, particularly their occurrence inside buildings. In this study, we quantitatively analyze the distribution and number of CsMPs in indoor dust samples collected from an elementary school located 2.

Evaluating the effectiveness of a geostatistical approach with groundwater flow modeling for three-dimensional estimation of a contaminant plume.

When assessing the risk from an underground environment that is contaminated by radioactive nuclides and hazardous chemicals and planning for remediation, the contaminant plume distribution and the associated uncertainty from measured data should be estimated accurately. While the release history of the contaminant plume may be unknown, the extent of the plume caused by a known source and the associated uncertainty can be calculated inversely from the concentration data using a geostatistical method that accounts for the temporal correlation of its release history and groundwater flow modeling. However, the preceding geostatistical approaches have three drawbacks: (1) no applications of the three-dimensional plume estimation using concentration data from multiple depths in real situations, (2) no constraints for the estimation of the plume distribution, which can yield negative concentration and large uncertainties, and (3) few applications to actual cases with multiple contaminants.

Conformation, hydration, and ligand exchange process of ruthenium nitrosyl complexes in aqueous solution: Free-energy calculations by a combination of molecular-orbital theories and different solvent models.

Distribution of solvent molecules near transition-metal complex is key information to comprehend the functionality, reactivity, and so forth. However, polarizable continuum solvent models still are the standard and conventional partner of molecular-orbital (MO) calculations in the solution system including transition-metal complex. In this study, we investigate the conformation, hydration, and ligand substitution reaction between NO and H O in aqueous solution for [Ru(NO)(OH)(NO ) ] (A), [Ru(NO)(OH)(NO ) (ONO)] (B), and [Ru(NO)(OH)(NO ) (H O)] (C) using a combination method of MO theories and a state-of-the-art molecular solvation technique (NI-MC-MOZ-SCF).

Assessment of doses in contaminated urban areas: modelling exercise based on Fukushima data.

State-of-the-art dose assessment models were applied to estimate doses to the population in urban areas contaminated by the Fukushima Daiichi Nuclear Power Plant accident. Assessment results were compared among five models, and comparisons of model predictions with actual measurements were also made. Assessments were performed using both probabilistic and deterministic approaches.

Urban working groups in the IAEA's model testing programmes: overview from the MODARIA I and MODARIA II programmes.

The IAEA's model testing programmes have included a series of Working Groups concerned with modelling radioactive contamination in urban environments. These have included the Urban Working Group of Validation of Environmental Model Predictions (1988-1994), the Urban Remediation Working Group of Environmental Modelling for Radiation Safety (EMRAS) (2003-2007), the Urban Areas Working Group of EMRAS II (2009-2011), the Urban Environments Working Group of (Modelling and Data for Radiological Impact Assessments) MODARIA I (2013-2015), and most recently, the Urban Exposures Working Group of MODARIA II (2016-2019). The overarching objective of these Working Groups has been to test and improve the capabilities of computer models used to assess radioactive contamination in urban environments, including dispersion and deposition processes, short-term and long-term redistribution of contaminants following deposition events, and the effectiveness of various countermeasures and other protective actions, including remedial actions, in reducing contamination levels, human exposures, and doses to humans.

Radiochemical analysis of the drain water sampled at the exhaust stack shared by Units 1 and 2 of the Fukushima Daiichi Nuclear Power Station.

Radioactive gas of Unit 1 of the Fukushima Daiichi Nuclear Power Station was released from the exhaust stack shared by Units 1 and 2 through the venting line on March 12th, 2011. In the present study, radiochemical analysis of drain water sampled at the drain pit of the exhaust stack was conducted to study radionuclides released during venting of the Unit 1. Not only volatile I, Cs and Cs but also Co, Sr, Sb and Unit 1-originated stable Mo isotopes were detected.

Volatilization of BC control rods in Fukushima Daiichi nuclear reactors during meltdown: B-Li isotopic signatures in cesium-rich microparticles.

Boron carbide control rods remain in the fuel debris of the damaged reactors in the Fukushima Daiichi Nuclear Power Plant, potentially preventing re-criticality; however, the state and stability of the control rods remain unknown. Sensitive high-resolution ion microprobe analyses have revealed B-Li isotopic signatures in radioactive Cs-rich microparticles (CsMPs) that formed by volatilization and condensation of Si-oxides during the meltdowns. The CsMPs contain 1518-6733 mg kg of B and 11.

Dose Estimation of Landfill Disposal of Removed Soil Generated Outside Fukushima Prefecture.

Dose estimation was conducted by assuming landfill disposal of removed soil generated outside the Fukushima Prefecture by each local town and in a lump sum. Because the radioactivity of removed soil is lower than that of specified waste that was generated at Fukushima Prefecture and the radioactivity concentration is 100,000 Bq kg-1 or less, simple landfill covered with 30 cm of non-contaminated soil was used. The exposure doses of loading/unloading, transportation, and landfill workers and the public residing near the repository site were estimated.

Development of an External Radiation Dose Estimation Model for Children Returning to Their Homes in Areas Affected by the Fukushima Nuclear Accident.

On 1 April 2017, around 6 y after the Fukushima Daiichi nuclear power station accident, evacuation orders for large affected areas were lifted, and areas to which people could return were expanded. In the current study, a dose estimation model based on a probabilistic approach has been developed to estimate the external radiation doses children would receive after returning to these areas. The target groups are children from infants to high school students, and the target areas are nine municipalities including evacuation areas as of 5 September 2015.

A noniterative mean-field QM/MM-type approach with a linear response approximation toward an efficient free-energy evaluation.

Mean-field treatment of solvent provides an efficient technique to investigate chemical processes in solution in quantum mechanics/molecular mechanics (QM/MM) framework. In the algorithm, an iterative calculation is required to obtain the self-consistency between QM and MM regions, which is a time-consuming step. In the present study, we have proposed a noniterative approach by introducing a linear response approximation (LRA) into the solvation term in the one-electron part of Fock matrix in a hybrid approach between molecular-orbital calculations and a three-dimensional (3D) integral equation theory for molecular liquids (multicenter molecular Ornstein-Zernike self-consistent field [MC-MOZ-SCF]; Kido et al.

Development and application of a method for discriminating the influence of radon progenies in air from aerial radiation monitoring data.

The influence of gamma-rays from natural nuclides (particularly the radon progenies, Pb and Bi) must be excluded from aerial radiation monitoring (ARM) data to accurately estimate the deposition of artificial radionuclides. A method for discriminating the influence of the radon progenies in air from the ARM data was developed. Two types of detectors with different crystal sizes were installed in a helicopter.

Dose Estimation in Recycling of Decontamination Soil Resulting From The Fukushima NPS Accident For Road Embankments.

Since the Fukushima nuclear power station accident, large quantities of radiocesium-contaminated soil generated from decontamination activities have been stored in Fukushima prefecture. To complete the final disposal of decontamination soil, reducing the disposal volume through recycling can prove effective. The Ministry of the Environment of Japan has developed a policy of handling low-activity decontamination soil as recycled materials under the management of public authority.

Dose-reduction Effects of Vehicles against Gamma Radiation in the Case of a Nuclear Accident.

Self-evacuation by a private vehicle is one of the most commonly used methods of public evacuation in the case of a nuclear accident. The aim of this paper is to evaluate the dose-reduction effects of vehicles. To achieve this aim, a model for calculating the dose reduction factor was developed based on the actual shape and weight of Japanese vehicles.

Estimation of radiocesium dietary intake from time series data of radiocesium concentrations in sewer sludge.

After the Fukushima accident, it became important to determine the quantity of radionuclide ingested by inhabitants. The most common methods currently used to obtain such data are the "market basket" (MB) and "duplicate" (DP) methods. However, it is difficult to conduct monitorings using these methods with sufficient frequency as they are high cost and time-consuming.

Application of topographical source model for air dose rates conversions in aerial radiation monitoring.

After the Fukushima Daiichi Nuclear Power Station (FDNPS) accident in 2011, aerial radiation monitoring (ARM) using a manned helicopter was conducted to rapidly measure air dose rates and the deposition of radioactive nuclides over a large area. Typically, the air dose rate is obtained by conversion from the count rate using conventional flat source model (FSM). The converted dose rate obtained via aerial monitoring poorly matches the results of ground measurement in the mountain and forest areas because FSM does not consider topographical effects.

A Probabilistic Approach to Assess External Doses to the Public Considering Spatial Variability of Radioactive Contamination and Interpopulation Differences in Behavior Pattern.

Dose assessment is an important issue from the viewpoints of protecting people from radiation exposure and managing postaccident situations adequately. However, the radiation doses received by people cannot be determined with complete accuracy because of the uncertainties and the variability associated with any process of defining individual characteristics and in the dose assessment process itself. In this study, a dose assessment model was developed based on measurements and surveys of individual doses and relevant contributors (i.

Bioaccessibility of Fukushima-Accident-Derived Cs in Soils and the Contribution of Soil Ingestion to Radiation Doses in Children.

Ingestion of contaminated soil is one potential internal exposure pathway in areas contaminated by the Fukushima Daiichi Nuclear Power Plant accident. Doses from this pathway can be overestimated if the availability of radioactive nuclides in soils for the gastrointestinal tract is not considered. The concept of bioaccessibility has been adopted to evaluate this availability based on in vitro tests.

Assessment of residual doses to population after decontamination in Fukushima Prefecture.

Large quantities of radioactive materials were released into the environment as a result of the Fukushima Daiichi Nuclear Power Station accident. Many inhabitants residing in the affected areas are now exposed to radiation in their daily lives. In an attempt to manage this radiation dose, an additional radiation dose of 1 mSv/y was adopted as a long-term dosimetric target.

A hybrid framework of first principles molecular orbital calculations and a three-dimensional integral equation theory for molecular liquids: multi-center molecular Ornstein-Zernike self-consistent field approach.

In this study, we reported the development of a new quantum mechanics/molecular mechanics (QM/MM)-type framework to describe chemical processes in solution by combining standard molecular-orbital calculations with a three-dimensional formalism of integral equation theory for molecular liquids (multi-center molecular Ornstein-Zernike (MC-MOZ) method). The theoretical procedure is very similar to the 3D-reference interaction site model self-consistent field (RISM-SCF) approach. Since the MC-MOZ method is highly parallelized for computation, the present approach has the potential to be one of the most efficient procedures to treat chemical processes in solution.

Statistical characterization of radiation doses from external exposures and relevant contributors in Fukushima prefecture.

In areas contaminated by radioactive materials, well designed dose assessment is necessary in order to protect people from radiation exposure and manage the exposure situation appropriately. Probabilistic dose assessment is a useful method for providing a more complete characterization of information on dose distributions in the population and requires statistically characterized data on pathway-relevant contributors. The objective of this paper is to determine statistical features of contributors to external exposures, as well as to identify causes of variabilities of individual doses to the populations living in areas contaminated by the Fukushima Daiichi Nuclear Power Plant accident.