Nobuaki Yoshizawa

JENDL High Energy File

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.

Development of heavy ion transport Monte Carlo code

Abstract 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.

Fluence to Dose Conversion Coefficients for High-Energy Neutron, Proton and Alpha Particles

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.

Development of Heavy Ion Transport Monte Carlo Code

We are developing a heavy ion transport Monte Carlo code which can treat the fragments produced by heavy ion reactions. For this purpose, we planned to combine the two codes, the one is the HIC or ISABEL code, to calculate the heavy ion nuclear reaction cross section and the other is the hadron transport Monte Carlo code, HETC-3STEP. First, we investigated the calculational accuracy of the HIC and ISABEL codes by comparing the calculated results with the experimental data. The ISABEL gives better agreement with the experimental data than the HIC. For easier handling we first coupled the HIC code with the HETC-3STEP code for developing the heavy ion transport Monte Carlo code. We also made a simple version of a heavy ion transport Monte Carlo code for limited geometry using the HIC code. The results calculated with this version of the code were compared with the experimental data. We are trying to couple the ISABEL code with the HETC-3STEP code.

Overview of Fluence to Dose Conversion Coefficients for High Energy Radiations

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 Russian group (HADRON). This overview also summarized the calculational conditions and data such as computer codes, data libraries, mathematical phantoms and energy range of each particle for estimating dose conversion coefficient for each particle. Comparison of effective dose conversion coefficients of neutron, photon and proton in five groups were performed up to 10 GeV. These results will be helpful to establish an authoritative dose equivalent conversion coefficient for high energy radiation up to 10 GeV.

Calculations of Effective Dose and Ambient Dose Equivalent Conversion Coefficients for High Energy Photons

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.

Surveys of Food Intake Just after the Nuclear Accident at the Fukushima Daiichi Nuclear Power Station.

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.

ESTIMATION OF EFFECTIVE DOSE FROM EXTERNAL EXPOSURE DUE TO SHORT-LIVED NUCLIDES IN THE PREFECTURES SURROUNDING FUKUSHIMA

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.

131I DOSE ESTIMATION FROM INTAKE OF TAP WATER IN THE EARLY PHASE AFTER FUKUSHIMA DAIICHI NUCLEAR POWER PLANT ACCIDENT

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.

Evaluations of Neutron and Proton Cross Sections on Fe up to 3 GeV

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.