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Massive release of radioactive materials into the atmosphere occurred due to the Fukushima Daiichi Nuclear Power Station (FDNPS) accident in March 2011. The World Health Organization (WHO) and the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) reported the results of dose estimation to assess the health effect of the accident and both reports state that their assessments of internal and external exposure doses contain certain uncertainties due to uncertainties inherent to the basic data. Therefore, estimation of the internal dose from tap water was conducted in this study by utilizing a database of deposition calculated by an atmospheric transfer, dispersion and deposition model (ATDM) in conjunction with the newly obtained data on the volume of daily water intake obtained by a web-based survey. The median mean and 95-percentile of thyroid equivalent doses were estimated for 1-year and 10-year children and adults in 12 municipalities in the evacuation area in Fukushima prefecture. The present mean thyroid dose estimations for 1-year children (0.4–16.2 mSv) are smaller than the corresponding values in the UNSCEAR 2013 report (1.9–49 mGy). Dose-modifying factors in the Japanese or local community are discussed.

As a result of the nuclear accident at the Fukushima Daiichi nuclear power station (FDNPS) after the Great East Japan Earthquake on March 11, 2011, volatile radionuclides including iodine-131 were released into the environment and contaminated open-field vegetables, raw milk, tap water, etc. It is important for the health care of residents to correctly comprehend the level of their exposure to radioactive substances released following the accident. However, an evaluation of the internal exposure doses of residents of Fukushima Prefecture as a result of the ingestion of foods, which is indicated in the report issued by United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR)1 is based on a number of assumptions. For instance, the estimation assumes that foods were ingested as usual, without regard to the places to which residents were evacuated after the accident, the places where food shipment restrictions were imposed, and so forth. The present report aims to improve the accuracy of estimation of the amount of food actually ingested at evacuation areas, in order to reduce as much as possible the level of uncertainty in conventional values estimated directly after the accident, which were in fact values based on conservative assumptions. More concretely, as basic source material to more accurately estimate internal exposure doses from food ingestion, various patterns of evacuation and dietary habits at the time of the accident of the residents of 13 municipalities in Fukushima Prefecture who were evacuated during the period from directly after the accident of March 11, 2011 until the end of March are clarified in this report. From survey results, most of the food that evacuees took immediately after the accident was confirmed to have been sourced from either stockpiles prepared before the accident, or relief supplies from outside of the affected areas. The restriction orders of food supplies such as contaminated vegetables and milk, and tap water intake were implemented within several days after the major release of radionuclides on March 15, 2011. In addition, collapse in supply chains, i.e., damage to distribution facilities, lack of transportation vehicles or electricity, and the closure of retail stores, contributed to a situation where food or supplies contaminated with iodine -131 were not consumed in large quantities in general, even before the food restriction order. Since people consumed tap water and water from other sources before the implementation of restriction orders in affected areas, we surveyed the status of water as a potential route of internal exposure.

The Fukushima Daiichi Nuclear Power Plant (FDNPP) accident resulted in a release of radionuclides into the environment. Since the accident, measurements of radiation in the environment such as air dose rate and deposition density of radionuclides have been performed by various organizations and universities. In particular, Japan Atomic Energy Agency (JAEA) has been performing observations of air dose rate using a car-borne survey system continuously over widespread areas. Based on the data measured by JAEA, we estimated effective dose from external exposure in the prefectures surrounding Fukushima. Since car-borne survey started a few months after the accident, the main contribution to measured data comes from 137Cs and 134Cs whose half-lives are relatively long. Using air dose rate of 137Cs and 134Cs and the ratio of deposition density of short-lived nuclides to that of 137Cs and 134Cs, we also estimated contributions to the effective dose from other short-lived nuclides.

In March 2011, the Fukushima Daiichi Nuclear Power Plant Accident occurred and a large amount of radionuclides was released. To study its effect, we estimated the internal exposure due to intake of tap water in the early phase after the accident. As the number of measured values of tap water following the accident was limited, 131I concentration in tap water was estimated by 1-compartment model using the deposition amount of radionuclides calculated by an atmospheric transport, dispersion and deposition simulation. The internal doses for the evacuees were estimated by assuming representative evacuation patterns, and the internal doses for the non-evacuees were estimated for each municipal government. In the evacuation areas, the maximum of thyroid equivalent dose of 1- and 10-year-old children and adults were 22, 11 and 4.7 mSv, respectively. The maximum of thyroid equivalent dose of those three groups in the non-evacuation areas were 9.5, 4.7 and 2.0 mSv, respectively.

The Fukushima Daiichi Nuclear Power Plant accident caused a release of radionuclides. Radionuclides were deposited on the ground not only in Fukushima prefecture but also in nearby prefectures. Since the accident, measurement of radiation in environment such as air dose rate and deposition density of radionuclides has been performed by many organizations and universities. In particular, Japan Atomic Energy Agency (JAEA) has been performing observations of air dose rate using a car-borne survey system continuously and over wide areas. In our study, using the data measured by JAEA, we estimated effective dose from external exposure in the six prefectures adjacent to Fukushima prefecture. Since car-borne survey was started a few months later after the accident, measured air dose rate in this method is mainly contributed by 137 Cs and 134 Cs whose half-lives are relatively long. Therefore, based on air dose rate of 137 Cs and 134 Cs and the ratio of deposition density of short-half-life nuclides to that of 137 Cs and 134 Cs, we also estimated effective dose contributed from not only 137 Cs and 134 Cs but also other short-half-life nuclides. We compared the effective dose estimated by the method above with that of UNSCEAR and measured data using personal dosimeters in some areas.

Reconstruction has progressed steadily since the 2011 TEPCO's Fukushima Daiichi Nuclear Power Station accident. However, some people still hesitate to eat foods from Fukushima or to travel there, and there are concerns about the health risks of radiation. We investigated the relationships among reconstruction-related behavior, risk perception, types of information, and information sources, in order to consider appropriate measures for providing information and promoting reconstruction-related behavior a number of years after the accident. We conducted an online questionnaire survey (n = 1000) of Tokyo residents. First, a factor analysis was conducted on knowledge associated with radiation. Two factors were extracted; namely, "physical knowledge" and "health/social knowledge." We conducted structural equation modeling to construct a model of "knowledge," "radiation risk perception," and "intention concerning reconstruction-related behavior." "Intention concerning reconstruction-related behavior" decreased with "radiation risk perception" and increased with "health/social knowledge." In addition, "health/social knowledge" negatively affected "radiation risk perception;" this effect was not large, but it was significant. Second, respondents were clarified by information sources using a cluster analysis. Clusters that included respondents who got information from public relations materials issued by municipalities and websites of administrative agencies had a higher factor score for "health/social knowledge" than other clusters. The cluster of respondents who did not get any particular knowledge had the lowest factor score, which was significant, and also had a low "perception of reconstruction."

Nuclear Data Center at Japan Atomic Energy Research Institute is developing the JENDL High Energy File in cooperating with Japanese Nuclear Data Committee. The JENDL High Energy File includes neutron and proton nuclear data 20 MeV to 3 GeV. In this report, reported are evaluation methods and results of the evaluation and benchmark tests for the JENDL High Energy File.

The neutron and proton cross sections of 54,56,37,58Fe were evaluated up to 3 GeV. JENDL High Energy Files of 54,56, 57,58Fe were also developed. ECISPLOT and Quick-GNASH programs were used for cross section calculations up to 250 MeV. In the energy region from 250 MeV to 3 GeV, TOTELA and JQMD were mainly used. For neutrons, the high-energy data above 20 MeV are merged in JENDL-3.3. Evaluated data were compared with several experimental data. There are acceptable agreements between evaluated data and experiment.

Activity concentrations in food and drink, represented by water and vegetables, have been monitored continuously since the Fukushima Daiichi Nuclear Power Plant accident, with a focus on radioactive cesium. On the other hand, iodine-131 was not measured systematically in the early phase after the accident. The activity concentrations of iodine-131 in food and drink are important to estimate internal exposure due to ingestion pathway. When the internal dose from ingestion in the evacuation areas is estimated, water is considered as the main ingestion pathway. In this study, we estimated the values of activity concentrations in water in the early phase after the accident, using a compartment model as an estimation method. The model uses measurement values of activity concentration and deposition rate of iodine-131 onto the ground, which is calculated from an atmospheric dispersion simulation. The model considers how drinking water would be affected by radionuclides deposited into water. We estimated the activity concentrations of water on Kawamata town and Minamisouma city during March of 2011 and the committed effective doses were 0.08 mSv and 0.06 mSv. We calculated the transfer parameters in the model for estimating the activity concentrations in the areas with a small amount of measurement data. In addition, we estimated the committed effective doses from vegetables using atmospheric dispersion simulation and FARMLAND model in case of eating certain vegetables as option information.

The dose contributions due to photo nuclear reactions were estimated for photons from 20MeV to 10GeV considering the secondary particles emitted from (γ,n), (γ,p), (γd), (g,t) (γ,3He) and (γ,α) reactions and recoil nuclei. A 30cm-thick semi-infinite slab phantom was used to calculate the photonuclear reaction rate in human body tissues. Averaged photon fluences in the phantom were calculated by using EGS4 Monte Calro code. The photonuclear reaction cross sections and the secondary particle energy spectra were obtained from JENDL Photonuclear Data File. The kinetic energy of recoil nuclei was calculated assuming energy and momentum conservation in the photonuclear reactions. The transports and intra-nuclear cascade processes of secondary neutrons in the phantom were calculated using HETC-3STEP code for neutrons above 20MeV and MORSE-CG/KFA with a coupled neutron-gamma cross section set based on JENDL-3.2 for the energy below 20MeV. The calculated contribution of photonuclear reactions was about 0.7% to the...

We developed a heavy ion transport Monte Carlo code HETC-CYRIC which can treat the fragments produced by heavy ion reactions. The HETC-CYRIC code is made by incorporating a heavy ion reaction calculation routine, which consists of the HIC code, the SPAR code, and the Shen formula, into the hadron transport Monte Carlo code HETC-3-STEP. The results calculated with the HETC-CYRIC were compared with the experimental data, and the HETC-CYRIC gave good agreement with the experiment.

In and around high energy accelerator facilities, high energy radiation dose estimation is important to the radiological protection of workers. The contribution of high energy protons and neutrons to the radiation exposure of astronauts can not also be disregarded inside a spacecraft. Effective doses are adequate radiological quantities to evaluate radiation risks of individuals, exposed to radiation not only of low and intermediate energy but also of high energy. The conversion coefficients of fluence to effective doses have not been specified for all kinds of radiation in any publications of ICRP or ICRU, except the data up to 180 MeV of neutron in the ICRP74.This report provides an overview of calculational methodologies and estimated results of dose conversion coefficient of effective doses for high energy radiation such as photon, neutron, proton, alpha particle, electron, muon and pion in five groups: USA group (LAHET code), German group (LAHET), Japanese group (HERMES), Italian group (FLUKA) and Ru...

Fluence to effective dose coefficients for neutron, proton, and alpha particles are calculated in the energy range from 20 MeV/nucleon to 10 GeV/nucleon. Two different versions of effective dose are treated, respectively calculated using: (a) the radiation weighting factor wR, and (b) the Q-L relationship given in ICRP 60. Organ doses per unit fluence related to deterministic effects are also reported. Monte Carlo calculations are performed applying the HETC-3STEP and the MORSE-CG/KFA in the HERMES code system. For alpha particles, the effective dose derived using wR proved to overestimate that obtained with the Q-L relationship by about factor of 10.

The conversion coefficients from photon fluence to ambient dose equivalent, H* (10) and effective doses were calculated for photons up to 10 GeV. A Monte Carlo code EGS4 was used for these calculations and secondary particle transports were considered. The calculated ambient dose equivalents were compared to the calculated effective doses. The comparison shows that the ambient dose equivalents at 1 cm depth, H* (10) underestimate the effective doses at the energy above 5MeV. H* (10) is not suitable operational quantity since it does not provide reasonable estimation of effective dose. It is difficult to define the operational quantity which can be consistently used for photons from low energy to high energy above 10 MeV. Instead of operational quantities, the maximum effective dose in various irradiation geometries can be used for shielding design calculations.

A calculational method is presented to evaluate equivalent doses of tissues or organs and effective dose for high energy radiations, where the radiation weighting factor given in ICRP 60 was replaced by an average quality factor estimated from the Q-L relationship in ICRP 60. The equivalent doses of tissues or organs and fluence to effective dose conversion coefficients are calculated for photons up to 10GeV with a Monte Carlo code EGS4 in which a mathematical model of an anthropomorphic phantom is included. The equivalent doses for 24 tissue and organs have been calculated for AP and PA incidence of aligned and expanded photons from I MeV to 10 GeV. The effective doses were obtained by summing the equivalent doses with tissue weighting factors from ICRP 60. It is also demonstrated that the kerma approximation overestimates significantly the effective dose for photons above 10 MeV.

In Greater Tokyo, many people commute by train between the suburbs and downtown Tokyo for 1 to 2 h per day. The spread of influenza in the suburbs of Tokyo should be studied, including the role of commuters and the effect of government policies on the spread of disease. We analyzed the simulated spread of influenza in commuter towns along a suburban railroad, using the individual-based Monte Carlo method, and validated this analysis using surveillance data of the infection in the Tokyo suburbs. This simulation reflects the mechanism of the real spread of influenza in commuter towns. Three measures against the spread of influenza were analyzed: prohibition of traffic, school closure, and vaccination of school children. Prohibition of traffic was not effective after the introduction of influenza into the commuter towns, but, if implemented early, it was somewhat effective in delaying the epidemic. School closure delayed the epidemic and reduced the peak of the disease, but it was not as effective in decreasing the number of infected people. Vaccination of school children decreased the numbers not only of infected children but also of infected adults in the regional communities.

The NCRP has recently defined RBE values and a new quantity (Gy-Eq) for use in estimation of deterministic effects in space shielding and operations. The NCRP's RBE for neutrons is left ambiguous and not fully defined. In the present report we will suggest a complete definition of neutron RBE consistent with the NCRP recommendations and evaluate attenuation properties of deterministic effects (Gy-Eq) in comparison with other dosimetric quantities.

We developed a heavy ion transport Monte Carlo code HETC-CYRIC which can treat the fragments produced by heavy ion reactions. The HETC-CYRIC code is made by incorporating a heavy ion reaction calculation routine, which consists of the HIC, the SPAR, and the Shen’s formula, into the hadron transport Monte Carlo code HETC-3STEP. The results calculated with the HETC-CYRIC were compared with the experimental data, and the HETC-CYRIC gave rather good agreement with the experiment.