Individual exposure dose assessment of residents for lifting of evacuation orders (Contract research)

Sato, Rina; Sanada, Yukihisa; Yoshimura, Kazuya; Nakayama, Mariko*

JAEA-Review 2022-055, 42 Pages, 2023/01

JAEA-Review-2022-055.pdf:1.31MB

The evacuation order zones established after the accident at the Tokyo Electric Power Company's Fukushima Daiichi Nuclear Power Station have been reorganized according to the decrease in ambient dose equivalent rates and the decontamination progress. It has been decided to decontaminate the difficult-to-return zones and lift the evacuation order depending on the evacuee's intention of returning to the areas over the course of the 2020s. In order to consider the future of individual exposure dose assessment for residents for lifting of the evacuation orders, the methods and characteristics of the assessment that have been conducted after the accident using personal dosimeter measurements and simulations were systematically reviewed. This report summarized the results of the review.

A Unique high natural background radiation area; Dose assessment and perspectives

Hosoda, Masahiro*; Nugraha, E. D.*; Akata, Naofumi*; Yamada, Ryohei; Tamakuma, Yuki*; Sasaki, Michiya*; Kelleher, K.*; Yoshinaga, Shinji*; Suzuki, Takahito*; Rattanapongs, C. P.*; et al.

Science of the Total Environment, 750, p.142346_1 - 142346_11, 2021/01

https://doi.org/10.1016/j.scitotenv.2020.142346

The biological effects of low dose-rate radiation exposures on humans remains unknown. In fact, the Japanese nation still struggles with this issue after the Fukushima Dai-ichi Nuclear Power Plant accident. Recently, we have found a unique area in Indonesia where naturally high radiation levels are present, resulting in chronic low dose-rate radiation exposures. We aimed to estimate the comprehensive dose due to internal and external exposures at the particularly high natural radiation area, and to discuss the enhancement mechanism of radon. A car-borne survey was conducted to estimate the external doses from terrestrial radiation. Indoor radon measurements were made in 47 dwellings over three to five months, covering the two typical seasons, to estimate the internal doses. Atmospheric radon gases were simultaneously collected at several heights to evaluate the vertical distribution. The absorbed dose rates in air in the study area vary widely between 50 nGy h and 1109 nGy h. Indoor radon concentrations ranged from 124 Bq m to 1015 Bq m. That is, the indoor radon concentrations measured exceed the reference levels of 100 Bq m recommended by the World Health Organization. Furthermore, the outdoor radon concentrations measured were comparable to the high indoor radon concentrations. The annual effective dose due to external and internal exposures in the study area was estimated to be 27 mSv using the median values. It was found that many residents are receiving radiation exposure from natural radionuclides over the dose limit for occupational exposure to radiation workers. This enhanced outdoor radon concentration might be as a result of the stable atmospheric conditions generated at an exceptionally low altitude. Our findings suggest that this area provides a unique opportunity to conduct an epidemiological study related to health effects due to chronic low dose-rate radiation exposure.

Measurements and evaluations of air dose rates around the Fukushima NPP site, 6; Status and issues on evaluation of individual doses due to external exposures

Saito, Kimiaki; Kurihara, Osamu*; Matsuda, Norihiro; Takahara, Shogo; Sato, Tetsuro*

Radioisotopes, 65(2), p.93 - 112, 2016/02

https://doi.org/10.3769/radioisotopes.65.93

Late information is introduced on dose evaluation due to external exposures which employ an important role in the exposures due to the Fukushima accident. First, merits and demerits of the currently used two methods, that is the estimation based air dose rates and the measurements using personal dosimeters, are discussed indicating some basic data after a fundamental concept of external dose evaluation is provided. Next, main activities are summarized on external dose measurements and evaluations after the accident. Finally, a new trial on dose evaluation in introduced.

Evaluation of -ray dose components in criticality accident situations

Sono, Hiroki; Yanagisawa, Hiroshi*; Ono, Akio*; Kojima, Takuji; Soramasu, Noboru*

Journal of Nuclear Science and Technology, 42(8), p.678 - 687, 2005/08

https://doi.org/10.3327/jnst.42.678

Component analysis of -ray doses in criticality accident situations is indispensable for further understanding on emission behavior of -rays and accurate evaluation of external exposure to human bodies. Such dose components were evaluated, categorizing -rays into four components: prompt, delayed, pseudo components in the period of criticality, and a residual component in the period after the termination of criticality. This evaluation was performed by the combination of dosimetry experiments at the TRACY facility using a thermoluminescent dosimeter (TLD) made of lithium tetra borate and computational analyses using a Monte Carlo code. The evaluation confirmed that the dose proportions of the above components varied with the distance from the TRACY core tank. This variation was due to the difference in attenuation of the individual components with the distance from the core tank. The evaluated dose proportions quantitatively clarified the contribution of the pseudo and the residual components to be excluded for accurate evaluation of -ray exposure.

Development and assessment of new radioactive decay database used for dosimetry calculation

Endo, Akira; Yamaguchi, Yasuhiro; Eckerman, K. F.*

Radiation Protection Dosimetry, 105(1-4), p.565 - 569, 2003/09

https://doi.org/10.1093/oxfordjournals.rpd.a006304

The present paper discusses a strategy for the development of a new radioactive decay database, which will succeed ICRP Publ.38 used for dosimetry calculations. The development of the database requires 1) Consistency checking of the ENSDF used for compilation of the decay data, 2) Improvement of the computer code EDISTR for processing the ENSDF, and 3) Comparison with other decay data prepared from the different computer codes and libraries for the verification of the compiled data. This paper identifies several technical issues that need to be addressed for the development of the new radioactive decay database.

Reassessment and reinforcement of nuclear decay database used for dose calculations

Endo, Akira; Yamaguchi, Yasuhiro

Proceedings of 10th International Congress of the International Radiation Protection Association (IRPA-10) (CD-ROM), 8 Pages, 2000/05

no abstracts in English

Compilation of nuclear decay data used for dose calculations; Data for radionuclides not listed in ICRP Publication 38

Endo, Akira; *; Yamaguchi, Yasuhiro

JAERI-Data/Code 99-035, 355 Pages, 1999/07

JAERI-Data-Code-99-035.pdf:14.77MB

no abstracts in English

Health physics in JAERI, No.39; April 1, 1996 - March 31, 1997

Department of Health Physics; Safety Division, Naka; Safety Division, Takasaki; ; ; Operation Safety Administration Division, Mutsu

JAERI-Review 97-016, 248 Pages, 1997/12

JAERI-Review-97-016.pdf:7.82MB

no abstracts in English

Health physics in JAERI, No.38; April 1, 1995 - March 31, 1996

Department of Health Physics; Safety Division, Naka; Safety Division, Takasaki; ;

JAERI-Review 96-014, 236 Pages, 1996/10

JAERI-Review-96-014.pdf:7.25MB

no abstracts in English

Health physics in JAERI, No.36; April 1,1993 - March 31,1994

Department of Health Physics; Safety Division, Naka; Safety Division, Takasaki; ; Operation Safety Administration Division, Mutsu;

JAERI-Review 94-007, 262 Pages, 1994/11

JAERI-Review-94-007.pdf:7.85MB

no abstracts in English