Time Trend Change of Air Dose Rate on Paved Areas in Fukushima City After the Fukushima Daiichi NPP Accident

Abstract A car-borne survey of air dose rate measurements was performed yearly from 2011 to 2013 to determine the levels of environmental radiation in Gunma prefecture after the Fukushima Daiichi Nuclear Power Plant accident in 2011. The results revealed that the average ambient doses in each year were 85.3 ± 34.1 nGy/h in 2011, 60.3 ± 19.9 nGy/h in 2012, and 43.5 ± 15.1 nGy/h in 2013. The ambient dose rate in 2011, which was about three times higher than the average of 27.0 ± 7.1 nGy/h in 1998, was still in safety level considering the public health, and the ambient dose rate subsequently decreased in 2013 to approximately half the 2011 level. A contour map of the ambient dose rate showed relatively higher levels in the northern and western parts of the prefecture, with relatively lower levels toward the eastern and southern parts.

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Impact on ambient dose rate in metropolitan Tokyo from the Fukushima Daiichi Nuclear Power Plant accident

Journal of Environmental Radioactivity ◽

10.1016/j.jenvrad.2016.03.022 ◽

2016 ◽

Vol 158-159 ◽

pp. 1-8 ◽

Cited By ~ 12

Author(s):

Kazumasa Inoue ◽

Hiroshi Tsuruoka ◽

Tan Van Le ◽

Moeko Arai ◽

Kyoko Saito ◽

...

Keyword(s):

Power Plant ◽

Nuclear Power Plant ◽

Dose Rate ◽

Nuclear Power ◽

Nuclear Power Plant Accident ◽

Fukushima Daiichi ◽

Ambient Dose

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Radiation dose rates now and in the future for residents neighboring restricted areas of the Fukushima Daiichi Nuclear Power Plant

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1315684111 ◽

2014 ◽

Vol 111 (10) ◽

pp. E914-E923 ◽

Cited By ~ 71

Author(s):

Kouji H. Harada ◽

Tamon Niisoe ◽

Mie Imanaka ◽

Tomoyuki Takahashi ◽

Katsumi Amako ◽

...

Keyword(s):

Power Plant ◽

Nuclear Power Plant ◽

Radiation Dose ◽

Radiation Exposure ◽

Dose Rate ◽

Nuclear Power ◽

Solid Cancer ◽

External Dose ◽

Dose Rates ◽

Fukushima Daiichi

Radiation dose rates were evaluated in three areas neighboring a restricted area within a 20- to 50-km radius of the Fukushima Daiichi Nuclear Power Plant in August–September 2012 and projected to 2022 and 2062. Study participants wore personal dosimeters measuring external dose equivalents, almost entirely from deposited radionuclides (groundshine). External dose rate equivalents owing to the accident averaged 1.03, 2.75, and 1.66 mSv/y in the village of Kawauchi, the Tamano area of Soma, and the Haramachi area of Minamisoma, respectively. Internal dose rates estimated from dietary intake of radiocesium averaged 0.0058, 0.019, and 0.0088 mSv/y in Kawauchi, Tamano, and Haramachi, respectively. Dose rates from inhalation of resuspended radiocesium were lower than 0.001 mSv/y. In 2012, the average annual doses from radiocesium were close to the average background radiation exposure (2 mSv/y) in Japan. Accounting only for the physical decay of radiocesium, mean annual dose rates in 2022 were estimated as 0.31, 0.87, and 0.53 mSv/y in Kawauchi, Tamano, and Haramachi, respectively. The simple and conservative estimates are comparable with variations in the background dose, and unlikely to exceed the ordinary permissible dose rate (1 mSv/y) for the majority of the Fukushima population. Health risk assessment indicates that post-2012 doses will increase lifetime solid cancer, leukemia, and breast cancer incidences by 1.06%, 0.03% and 0.28% respectively, in Tamano. This assessment was derived from short-term observation with uncertainties and did not evaluate the first-year dose and radioiodine exposure. Nevertheless, this estimate provides perspective on the long-term radiation exposure levels in the three regions.

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Detailed source term estimation of the atmospheric release for the Fukushima Daiichi Nuclear Power Station accident by coupling simulations of an atmospheric dispersion model with an improved deposition scheme and oceanic dispersion model

Atmospheric Chemistry and Physics ◽

10.5194/acp-15-1029-2015 ◽

2015 ◽

Vol 15 (2) ◽

pp. 1029-1070 ◽

Cited By ~ 154

Author(s):

G. Katata ◽

M. Chino ◽

T. Kobayashi ◽

H. Terada ◽

M. Ota ◽

...

Keyword(s):

Dose Rate ◽

Nuclear Power ◽

Source Term ◽

Dispersion Model ◽

Atmospheric Dispersion ◽

Air Concentration ◽

Power Station ◽

Release Rates ◽

Surface Deposition ◽

Fukushima Daiichi

Abstract. Temporal variations in the amount of radionuclides released into the atmosphere during the Fukushima Daiichi Nuclear Power Station (FNPS1) accident and their atmospheric and marine dispersion are essential to evaluate the environmental impacts and resultant radiological doses to the public. In this paper, we estimate the detailed atmospheric releases during the accident using a reverse estimation method which calculates the release rates of radionuclides by comparing measurements of air concentration of a radionuclide or its dose rate in the environment with the ones calculated by atmospheric and oceanic transport, dispersion and deposition models. The atmospheric and oceanic models used are WSPEEDI-II (Worldwide version of System for Prediction of Environmental Emergency Dose Information) and SEA-GEARN-FDM (Finite difference oceanic dispersion model), both developed by the authors. A sophisticated deposition scheme, which deals with dry and fog-water depositions, cloud condensation nuclei (CCN) activation, and subsequent wet scavenging due to mixed-phase cloud microphysics (in-cloud scavenging) for radioactive iodine gas (I2 and CH3I) and other particles (CsI, Cs, and Te), was incorporated into WSPEEDI-II to improve the surface deposition calculations. The results revealed that the major releases of radionuclides due to the FNPS1 accident occurred in the following periods during March 2011: the afternoon of 12 March due to the wet venting and hydrogen explosion at Unit 1, midnight of 14 March when the SRV (safety relief valve) was opened three times at Unit 2, the morning and night of 15 March, and the morning of 16 March. According to the simulation results, the highest radioactive contamination areas around FNPS1 were created from 15 to 16 March by complicated interactions among rainfall, plume movements, and the temporal variation of release rates. The simulation by WSPEEDI-II using the new source term reproduced the local and regional patterns of cumulative surface deposition of total 131I and 137Cs and air dose rate obtained by airborne surveys. The new source term was also tested using three atmospheric dispersion models (Modèle Lagrangien de Dispersion de Particules d'ordre zéro: MLDP0, Hybrid Single Particle Lagrangian Integrated Trajectory Model: HYSPLIT, and Met Office's Numerical Atmospheric-dispersion Modelling Environment: NAME) for regional and global calculations, and the calculated results showed good agreement with observed air concentration and surface deposition of 137Cs in eastern Japan.

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CHANGES OF ABSORBED DOSE RATE IN AIR BY CAR-BORNE SURVEY IN NAMIE TOWN, FUKUSHIMA PREFECTURE AFTER THE FUKUSHIMA DAIICHI NUCLEAR POWER PLANT ACCIDENT

Radiation Protection Dosimetry ◽

10.1093/rpd/ncz096 ◽

2019 ◽

Vol 184 (3-4) ◽

pp. 527-530 ◽

Cited By ~ 2

Author(s):

Y Shiroma ◽

M Hosoda ◽

K Iwaoka ◽

M Hegedűs ◽

H Kudo ◽

...

Keyword(s):

Power Plant ◽

Dose Rate ◽

Nuclear Power ◽

Absorbed Dose ◽

Local Distribution ◽

Absorbed Dose Rate ◽

Distribution Maps ◽

Dose Rates ◽

Fdnpp Accident ◽

Fukushima Daiichi

Abstract The latest car-borne survey was carried out by Hirosaki University in order to grasp the local distribution of the absorbed dose rate in air after the evacuation order was lifted on Namie Town in 2017. The car-borne survey of absorbed dose rate in air was carried out on most of the roads which were accessible by car in Namie Town using a 3-in × 3-in NaI(Tl) scintillation spectrometer. The range of the absorbed dose rate in air was calculated to be 0.041–11 μGy h−1. The distribution maps of the absorbed dose rate in air were drawn based on the data obtained during the surveys in 2011, 2015 and 2017. The comparison of these absorbed dose rates in air suggests that the elevated absorbed dose rate in air in Namie Town caused by the FDNPP accident may be decreasing faster than natural decline which includes weathering effect and physical decay due to the artificial decontamination.

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