Pre- and post-accident environmental transfer of radionuclides in Japan: lessons learned in the IAEA MODARIA II programme.

An international review of radioecological data derived after the accident at the Fukushima Daiichi nuclear power plant was an important component of activities in working group 4 of the IAEA Models and data for radiological impact assessment, phase II (MODARIA II) programme. Japanese and international scientists reviewed radioecological data in the terrestrial and aquatic environments in Japan reported both before and after the accident. The environmental transfer processes considered included: (a) interception and retention radionuclides by plants, (b) loss of radionuclides from plant and systemic transport of radionuclides in plants (translocation), (c) behaviour of radiocaesium in soil, (d) uptake of radionuclides from soil by agricultural crops and wild plants, (e) transfer of radionuclides from feedstuffs to domestic and wild animals, (f) behaviour of radiocaesium in forest trees and forest systems, (g) behaviour of radiocaesium in freshwater systems, coastal areas and in the ocean, (h) transport of radiocaesium from catchments through rivers, streams and lakes to the ocean, (i) uptake of radiocaesium by aquatic organisms, and (j) modification of radionuclide concentrations in food products during food processing and culinary preparation. These data were compared with relevant global data within IAEA TECDOC-1927 'Environmental transfer of radionuclides in Japan following the accident at the Fukushima Daiichi Nuclear Power Plant'. This paper summarises the outcomes of the data collation and analysis within MODARIA II work group 4 and compares the Japan-specific data with existing radioecological knowledge acquired from past and contemporary radioecological studies. The key radioecological lessons learned are outlined and discussed.

Whole-body to tissue concentration ratios for use in biota dose assessments for animals.

Environmental monitoring programs often measure contaminant concentrations in animal tissues consumed by humans (e.g., muscle). By comparison, demonstration of the protection of biota from the potential effects of radionuclides involves a comparison of whole-body doses to radiological dose benchmarks. Consequently, methods for deriving whole-body concentration ratios based on tissue-specific data are required to make best use of the available information. This paper provides a series of look-up tables with whole-body:tissue-specific concentration ratios for non-human biota. Focus was placed on relatively broad animal categories (including molluscs, crustaceans, freshwater fishes, marine fishes, amphibians, reptiles, birds and mammals) and commonly measured tissues (specifically, bone, muscle, liver and kidney). Depending upon organism, whole-body to tissue concentration ratios were derived for between 12 and 47 elements. The whole-body to tissue concentration ratios can be used to estimate whole-body concentrations from tissue-specific measurements. However, we recommend that any given whole-body to tissue concentration ratio should not be used if the value falls between 0.75 and 1.5. Instead, a value of one should be assumed.

Dynamics of radionuclide activity concentrations in weed leaves, crops and of air dose rate after the Fukushima Daiichi Nuclear Power Plant accident.

Data on reduction of radioactivity in plants are highly important for making decision on emergency response and remediation of contaminated areas. Dynamics of the 131I and 137Cs concentrations in the weed leaves sampled in the areas affected by the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident in Japan was assessed for the period March-December 2011. The effective half-lives for 131I and 137Cs of 3.8-4.2 days and 7.1-13.3 days in the weed leaves were calculated for the first two months after the deposition. The approach for assessment of the aggregated transfer factors based on the ambient dose equivalent rate was suggested and validated. The geometric means of the soil to the weed leaves aggregated transfer factors were estimated for June-December 2011. Soil to crop 137Cs- concentration ratios (buckwheat, brown rice and soybean) were estimated for 2011-2016. Soil to crop concentration ratios were found to decrease in the order of soybean > buckwheat > brown rice. The effective half-lives for 137Cs in these crops were estimated to be between 1 and 2.5 years for the period 2011 2016, and longer than 5-7 years after 2016. It was found that these data comply with the Chernobyl related data obtained for similar conditions and complement of international documents on radionuclide transfer in agricultural environment such as the IAEA TRS 472.

Relationships between air dose rates and radionuclide concentrations in agricultural plants observed in areas affected by the Fukushima Dai-ichi accident.

Most of environmental monitoring programs include measurements of the air dose rates and the radionuclides activity concentration in plants. Both these parameters depend on deposition density of radionuclides. Therefore, measurements of one parameter can (with some supplementary information) be used as an indicator for the other parameter. After the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident, the Emergency Operation Centre (EOC) operated by the Environmental Radioactivity Monitoring centre of Fukushima and Ministry of Agriculture, Forestry and Fisheries (MAFF) of Japan carried out large sampling programme over different distances from the NPP. The sampling programme was focused on the usage of the weed leaves as a proxy for the prediction of radionuclide transfer to some cultivated plants. The MAFF monitoring programme in 2011-2016 was addressed mainly to agricultural crops. In both cases, the air dose rates were measured at the sites of the sampling. The paper addresses the assessments of relationship between radionuclide activities concentrations in plants and ambient dose rates. The time-dependent relationships were quantified based on weed, buckwheat, brown rice and soybean data obtained in 2011-2016. The recommendations on optimizing emergency sampling programmes based on use of the data of ambient dose rates are also presented.

An extended critical review of twenty years of countermeasures used in agriculture after the Chernobyl accident.

A wide range of different countermeasures has been used to mitigate the consequences of the Chernobyl accident for agriculture in affected regions in Belarus, Russia and Ukraine. The paper comprehensively brings together key data on countermeasure application over twenty years for all three countries and critically evaluates the response to the accident with respect to agriculture. The extents of countermeasures implementation in various periods following the ChNPP accident are documented. Examples of best practices and drawbacks in remediation of affected areas are identified. Data on the effectiveness of agricultural countermeasures have been evaluated and the impact of countermeasures implementation to mitigate consequences of the accident has been assessed for the period 1986-2006. Implementation of agricultural countermeasures averted 30-40% of the internal collective dose that would have been received by the residents of affected regions without the use of countermeasures. The current situation in agriculture of areas subjected to contamination following the Chernobyl accident is described. Current and future needs for remediation, including a consideration of various strategies of rehabilitation of affected areas are presented.

A Comparison of Remediation After The Chernobyl and Fukushima Daiichi Accidents.

Extensive remediation was conducted on contaminated landscapes after the Chernobyl accident in 1986 and the Fukushima Daiichi accident in 2011. A comparison is made of a range of different features relevant to each accident including the characteristics of the contamination and the landscapes affected, the radiological criteria, the designation of areas to be remediated and the remediation measures adopted.

Bioaccumulation and biological effects in the earthworm Eisenia fetida exposed to natural and depleted uranium.

The accumulations of both natural (U) and depleted (DU) uranium in the earthworms (Eisenia fetida) were studied to evaluate corresponding biological effects. Concentrations of metals in the experimental soil ranged from 1.86 to 600 mg kg(-1). Five biological endpoints: mortality, animals' weight increasing, lysosomal membrane stability by measuring the neutral red retention time (the NRRT), histological changes and genetic effects (Comet assay) were used to evaluate biological effects in the earthworms after 7 and 28 days of exposure. No effects have been observed in terms of mortality or weight reduction. Cytotoxic and genetic effects were identified at quite low U concentrations. For some of these endpoints, in particular for genetic effects, the dose (U concentration)-effect relationships have been found to be non-linear. The results have also shown a statistically significant higher level of impact on the earthworms exposed to natural U compared to depleted U.

Density-functional theory with effective potential expressed as a direct mapping of the external potential: applications to atomization energies and ionization potentials.

In this paper the authors further develop and apply the direct-mapping density functional theory to calculations of the atomization energies and ionization potentials. Single-particle orbitals are determined by solving the Kohn-Sham [Phys. Rev. A. 140, 1133 (1965)] equations with a local effective potential expressed in terms of the external potential. A two-parametric form of the effective potential for molecules is proposed and equations for optimization of the parameters are derived using the exchange-only approximation. Orbital-dependent correlation functional is derived from the second-order perturbation theory in its Moller-Plesset-type zeroth-order approximation based on the Kohn-Sham orbitals and orbital energies. The total atomization energies and ionization potentials computed with the second-order perturbation theory were found to be in agreement with experimental values and benchmark results obtained with ab initio wave mechanics methods.