Assessment of individual external exposure doses based on environmental radiation in areas affected by the Fukushima Daiichi Nuclear Power Station accident

Sato, Rina; Yoshimura, Kazuya; Sanada, Yukihisa; Mikami, Satoshi; Yamada, Tsutomu*; Nakasone, Takamasa*; Kanaizuka, Seiichi*; Sato, Tetsuro*; Mori, Tsubasa*; Takagi, Marie*

Environment International, 194, p.109148_1 - 109148_8, 2024/12

https://doi.org/10.1016/j.envint.2024.109148

Assessment of individual external doses from ambient dose equivalents is used for predictive and retrospective assessments where personal dosimeters are not applicable. However, it tends to contain more errors than assessment by personal dosimetry due to various parameters. Therefore, in order to accurately assess the individual dose from ambient dose equivalents, a model that estimates effective doses considering life patterns and the shielding effects by buildings and vehicles, were developed in this study. The model parameters were examined using robust datasets of environmental radiation measured in the areas affected by the Fukushima Daiichi Nuclear Power Station accident in 2020 to 2021. The accuracy of the model was validated by comparison with 106 daily personal doses measured in Fukushima Prefecture in 2020. The measured personal dose was well reproduced by the model-estimated effective dose, showing that the model can be used to assess the individual exposure dose, similar to personal dosimetry. Furthermore, this model is an effective tool for radiation protection, as it can estimate the individual dose predictively and retrospectively by using environmental radiation data.

Analysis of the relationship between operational quantity used for area monitoring and protection quantity for external exposure

Endo, Akira

JAEA-Research 2024-002, 90 Pages, 2024/05

JAEA-Research-2024-002.pdf:4.22MB

This report presents a comprehensive analysis of the relationship between three quantities used for area monitoring - ambient dose equivalent , maximum dose equivalent , and ambient dose - and effective dose for external irradiation by photons, neutrons, electrons, positrons, protons, muons, pions, and helium ions. For the analysis, calculations were performed using PHITS (Particle and Heavy Ion Transport code System) and the ICRU sphere. The analysis result shows that and can induce large differences in the estimation of effective dose over a wide energy range for various particle types covered by ICRP Publication 116 while can conservatively estimate effective dose within the acceptable range for area monitoring. In other words, and have limitations in estimating effective dose, and using is recommended as a more appropriate quantity for the purpose. This conclusion supports the proposal of ICRU Report 95 to use for estimating effective dose in various external exposure situations. The use of ambient dose is particularly important in situations where various types of radiation are encountered, such as the use of radiation in the medical and academic fields and exposure in aviation and can meet the evolving requirements of radiation monitoring for the expansion of the field of radiological protection.

Estimation of radioactivity and dose equivalent rate by combining Compton imaging and Monte Carlo radiation transport code

Sato, Yuki

Applied Radiation and Isotopes, 185, p.110254_1 - 110254_7, 2022/07

https://doi.org/10.1016/j.apradiso.2022.110254

Determination of parameters for an equation to obtain natural background radiation using KURAMA-II loaded with C12137-01 type CsI(Tl) detector

Ando, Masaki; Matsuda, Norihiro; Saito, Kimiaki

Nihon Genshiryoku Gakkai Wabun Rombunshi, 20(1), p.34 - 39, 2021/03

https://doi.org/10.3327/taesj.J20.007

We measured count rates and air dose rates at 11 measurement points where the influence of the Fukushima Dai-ichi Nuclear Power Plant accident could be ignored to obtain parameters for a background equation applying to KURAMA-II loaded with the high sensitivity CsI(Tl) detector, C12137-01. It was found that the sensitivity of KURAMA-II (C12137-01) was about 10 times or more for background measurement, compared with KURAMA-II loaded with the standard type CsI(Tl) detector, C12137. A background equation for the energy range of 1400-2000 keV was determined as, y (Sv/h)=0.062 x (cps). We evaluated background air dose rates using KURAMA-II (C12137-01) for 71 municipalities and compared them with the previous study using KURAMA-II (C12137). Evaluated background air dose rates in this study were almost equal to those in the previous study. We confirmed that the background equation evaluated in this study was applicable for the KURAMA-II (C12137-01).

Initial decrease in the ambient dose equivalent rate after the Fukushima accident and its difference from Chernobyl

Yoshimura, Kazuya; Saegusa, Jun; Sanada, Yukihisa

Scientific Reports (Internet), 10(1), p.3859_1 - 3859_9, 2020/03

https://doi.org/10.1038/s41598-020-60847-0

Measurement of ambient dose equivalent rates by walk survey around Fukushima Dai-ichi Nuclear Power Plant using KURAMA-II until 2016

Ando, Masaki; Yamamoto, Hideaki*; Kanno, Takashi*; Saito, Kimiaki

Journal of Environmental Radioactivity, 190-191, p.111 - 121, 2018/10

https://doi.org/10.1016/j.jenvrad.2018.04.025

Ambient dose equivalent rates in various environments related to human lives were measured by walk surveys using the KURAMA-II systems from 2013 to 2016 around the Fukushima Dai-ichi Nuclear Power Plant. The dose rate of the locations where the walk survey was performed decreased to about 38% of its initial value in the 42 months, which was beyond that attributable to the physical decay. The air dose rates decreased depending on the level of the evacuation areas, and the decrease was slightly larger in populated areas where humans are active. The comparison of walk survey data with car-borne survey data indicated that the air dose rate varies largely even within a 100 m square area. The dose rates measured by the walk surveys were estimated to be medial of those along roads and those of undisturbed flat ground. The air dose rates measured by the walk surveys decreased quickly compared with the air dose rate from the flat ground measurement.

The Evaluation of the 0.07 mm and 3 mm dose equivalent with a portable beta spectrometer

Hoshi, Katsuya; Yoshida, Tadayoshi; Tsujimura, Norio; Okada, Kazuhiko

JPS Conference Proceedings (Internet), 11, p.070009_1 - 070009_6, 2016/11

https://doi.org/10.7566/JPSCP.11.070009

Beta spectra of various nuclide species were measured by commercially available compact spectrometer. The shape of spectra obtained from the spectrometer approximately agreed with that of theoretical spectra. The beta dose equivalent at any depths has been able to be obtained as a product of measured pulse height spectra and appropriate conversion coefficients of ICRP Publ. 74. The dose rates evaluated from the spectra were comparable to the reference dose rates of standard beta calibration sources. And, we were able to determine the dose equivalent with relative error of indication of 10% without the complicated correction.

Measurements and evaluations of air dose rates around Fukushima, 2; Meanings and features of dose quantities used in radiation protection

Saito, Kimiaki; Yamamoto, Hideaki

Radioisotopes, 63(11), p.519 - 530, 2014/11

https://doi.org/10.3769/radioisotopes.63.519

This article aims to provide the basic meanings and features of the doses frequently used in the measurements and evaluations of environmental radiation due to the Fukushima Dai-ichi Nuclear Power Plant accident. The following doses are explained and compared: absorbed dose as basic physical quantity; effective dose and equivalent dose for judgment in radiation protection; and ambient dose equivalent (10) and individual dose equivalent p(10) for radiation measurements.

Dose evaluation in criticality accident conditions using transient critical facilities fueled with a fissile solution

Nakamura, Takemi*; Tonoike, Kotaro; Miyoshi, Yoshinori

Radiation Protection Dosimetry, 110(1-4), p.483 - 486, 2004/09

https://doi.org/10.1093/rpd/nch348

Dose measurement and evaluation technique in criticality accident conditions with a thermo luminescence dosimeter (TLD) was studied at the Transient Experiment Critical Facility (TRACY) of Japan Atomic Energy Research Institute (JAERI). The tissue absorbed dose can be derived from the ambient dose equivalent given by measurement with a TLD using the conversion factor given by computation. Using this technique, the neutron dose around the SILENE reactor of the Institute for Radioprotection and Nuclear Safety (IRSN) of France was measured in the Accident Dosimetry Intercomparison Exercise (June 10-21, 2002) organized by OECD/NEA and IRSN. In this exercise, the dose was also measured with a TLD. In this report, measurements and evaluation results at TRACY and SILENE are presented.

Conceptual design of spectrum changeable neutron calibration fields in JAERI/FRS

Saegusa, Jun; Tanimura, Yoshihiko; Yoshizawa, Michio; Yoshida, Makoto

Radiation Protection Dosimetry, 110(1-4), p.91 - 95, 2004/09

https://doi.org/10.1093/rpd/nch196

For the accurate estimation of neutron dose equivalents, it is important to calibrate dosemeters in the field whose energy spectrum is similar to that in the workplace. For the purpose, studies are made toward the built of the spectrum changeable neutron calibration fields with the Van-de-Graff accelerator in the FRS in JAERI. The fields are produced by bombarding proton or deuteron beam from the accelerator to suitable targets surrounded by quasi-cylindrical moderators and absorbers of various materials. In the fields, neutron spectra with wide range energy index should be provided with sufficient fluence rate for the calibration of dosemeters. The objectives and conceptual design of the fields are discussed here, followed by the test simulation results of neutron spectra produced by various arrangements of a target and moderators.