March 2016

Updating of the knowledge relating to
the dispersion and deposition of atmospheric releases
from the Fukushima Daiichi nuclear accident in March 2011
Since 2011, IRSN has been working on improving the understanding of the Fukushima accident and of its
environmental consequences, by coupling the analysis of the measurements in the environment withthe modelling of the atmospheric dispersion. This work has been largely carried out as part of1
international collaborations. For example, the SAKURA project, a bilateral collaboration between IRSN
2
and the MRI , gave IRSN access to numerous data (radiological and meteorological measurements,
meteorological models) that proved to be decisive. IRSN also participated in the UNSCEAR expert group3
for the assessment of population exposure levels due to the Fukushima accident [UNSCEAR (2013)] .
Finally, the Institute participates in international comparison exercises of atmospheric dispersion model
4
regarding the Fukushima accident, coordinated by the Science Council of Japan [SCJ (2014)] .
Five years after the accident at the Fukushima Daiichi nuclear site, IRSN evaluated the understanding of
the behaviour of atmospheric releases and of the main contamination sequences of the terrestrial
environment. Many radiological measurements in the environment have made it possible to reconstruct
to a great extent the various contamination sequences, to identify the likely trajectories of radioactive
5
plumes and to link them to rain events to explain deposition zones . However, many uncertainties
remain, and measurements alone do not allow satisfactorily reconstructing of all of the contamination
sequences.
The remainder of this paper outlines the various measurements in the environment. A second part isdevoted to the current understanding of contamination events, provided by the cross analysis ofradiological and meteorological observation data. In the third part, additional insight provided bymodelling is presented. Two additional notes discuss these last two topics in detail:

Note on the contamination events;
Note on the modelling of the atmospheric transport and fallout of the releases.

1

This Hubert Curien partnership (PHC) is funded by the Foreign Ministry.
The MRI is the research unit of the Japanese meteorological forecasting centre (JMA).
3
The UNSCEAR (United Nations Scientific Committee on the Effects of Atomic Radiation) posted the report online.
4
The first exercise resulted in a report in September 2014. The second was launched in early 2016.
5
The term "deposition" means the fallout that has been deposited on the ground, buildings and plants during thepassage of the radioactive plume through the atmosphere. When the deposition is made without rain, it is called a"dry deposition". When radionuclides have been dragged down to the ground by rain, it is called a "wetdeposition". This process is generally considered to be the most effective.
2

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March 2016

Measurements in the environment
Many radiological measurements were made public, some as early as March 2011 and others very
recently. These are of three types:
1. Dose rate measurements 6 are those that were available more quickly during the accident.
Fixed measurement stations are well distributed throughout Japan (Figure 1) and give theevolution over time of the contamination. However, the signal is difficult to interpret because
it corresponds to radiation emitted by all radionuclides, whether on the ground or airborne,
without it being possible to distinguish them. Thus, in locations highly contaminated bydeposits, the signal remains very high after the passage of the plume, possibly masking thedetection of subsequent events. The dose rate measurements give no information on theisotopic composition of the contamination.
2. Measurements of the deposits on the ground enable precise mapping of the contamination.
They come from airborne measurement campaigns 7 [Sanada et al (2014)] and soil samples[Endo et al (2012; Saito et al (2015)] taken after the main atmospheric releases. These
measurements therefore concern mainly caesium isotopes, 134Cs and 137Cs, with long half-life.
Some studies evaluate, from samples, the deposition of radioactive iodine including 131I
[Kinoshita et al (2011)], whose half-life is short, but these assessments are more uncertain. In
addition, the mapping carried out a posteriori does not allow distinguishing the periods during
which the various deposition zones were formed.
3. Activity concentration measurements give direct concentration in the air of an isotope over agiven period (in Bq/m3). These measurements, invaluable for the reconstitution of the plume
trajectory in the atmosphere, were scarce until recently, and integrated over long periods oftime, making them of little use. In 2015, activity concentration measurements of 137Cs
estimated from particulate filters of air quality monitoring stations in Japan were made public[Tsuruta et al (2014)]. These measurements, numerous and well distributed throughout Japan,
have hourly time increments. Access to these data enabled real progress in the understandingof the sequence of events. However, since the air samples were taken at ground level, they
only indicate the presence of plumes that touch the ground; however, it can be located at ahigh level. In the event of rain, this can lead to soil contamination by wet deposition (leachingof the plume at high altitude), while the activity concentration measurements are very low.
Furthermore, these measurements may be underestimated if there is fog. Finally, given thatthe filter measurements are relatively recent, there is no available information regarding shortlived radionuclides. The location of the activity concentration stations is shown in Figure 1.

6

The dose rate is the gamma radiation emitted by all radioactive isotopes at a given point per unit time. Its unit is
Gy/h.
7
The results of the campaigns are listed on the NRA (Nuclear Regulation Agency) website.

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March 2016

Nakadori valley, with Fukushimabasin to the north.
Nikko mountains and mountains of
the Gunma Prefecture
Greater Tokyo
Oshika peninsula
Tokai region
Idate
North of the Miyagi Prefecture andsouth of the Iwate Prefecture

Figure 1: locations of the dose rate (red) and activity concentration (yellow) beacons are represented on arelief map of Japan. Regions whose importance is mentioned in the text are also located on the map.

With regard to meteorological observations, IRSN had access, as part of the SAKURA project, to the JMA
AMEDAS measurement network data8.These include:Wind observations (speed and direction) at 10 meters (around 1,200 stations)
Rain observations given by pluviometers. These give the amount of rainfall in mm/h in discrete
0.5 mm/h increments. Light rain (less than 0.5 mm/h) was thus not measured. However, somemore sophisticated pluviometers indicate the occurrence of light rain without giving theamount;Temperature, humidity, visibility and snow depth observations, which were used for example todetermine the possible presence of snow or fog. This information is important for estimating
depositions.

In addition to the AMEDAS data, rainfall observations made by radar 9 (corrected by the pluviometers)
were used. These give spatial information at a very fine resolution (1km), but do not allow light rain tobe identified either.

8
9

Automated Meteorological Data Acquisition System (http://www.jma.go.jp/en/amedas/)
http://www.jma.go.jp/en/radnowc/

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March 2016

Contamination of Honshu Island
The major releases into the atmosphere took place over three weeks between 11 March and 31 March
2011. During this period, part of the Japanese territory was contaminated. Several studies based onmodelling estimate that around 80% of the releases into the atmosphere were deposited over the
Pacific Ocean and approximately 15-20% on Honshu, the main island of Japan [Morino et al (2011),
Morino et al (2013), Yasunari et al (2011)]. Assessments by IRSN corroborate these estimates[Korsakissok et al (2013) ; Groëll et al (2014)]. The observations indicate that the surface area of Japan
contaminated with more than 185 kBq/m² of 137 Cs 10 covers about 1700 km² [Steinhauser et al (2014)]
and the surface area contaminated with over 10 kBq/m² covers about 24,000 km [Champion et al(2013)]In 2012, IRSN presented a description of the main atmospheric release events and their future [IRSN(2012)]. In light of the new measurements available, particularly as part of the SAKURA project, theInstitute has re-analysed the various sequences.
Deposits measured (kBq/m2)

20-21 March

12 and 18
March

14-16 March

20-21 March
14-16 March

Figure 2: Regions affected by the fallout of the main contamination episodes are indicated in colour andsuperimposed on the map of measured deposits of 137 Cs. The episodes of 12 and 18 March are in green, theepisode of 14-16 March is in pink and that of 20-21 March is in blue.

10

The value of 185 kBq/m² corresponds to 5 Ci/km², which was the threshold value defining the evacuated areas
following the Chernobyl accident. After Chernobyl, the surface area contaminated with more than 185 kBq/m² of137
Cs was approximately 29,400 km².

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March 2016
The ground contamination of the Japanese territory primarily occurred in four time slots: that of 12
March, that of 14-16 March, that of 18 March and that of 20-21 March (Figure 2).
The 12 and 18 March episodes did not lead to significant depositions (Figure 2), but the activity
concentration measurements at stations H, I and J show that they were significant from the point ofview of the population exposure to radioactive plumes in the area located to the north of the power
plant, along the coast of the Fukushima Prefecture (Figure 3). Farther north, the Oshika Peninsula(Zone 4 Figure 1) shows 137 Cs deposits that formed during these episodes. These are dry depositions.
The 14 to 16 March episode is the most studied event of the accident sequence because it was
responsible for the main depositions on the island of Honshu. During this event, the winds shifted
gradually pushing the contamination to the Southwest, West, Northwest and then the South along thecoast. As from 6:00 am on 15 March11, the plumes present in the Nakadori valley (Zone 1 Figure 1,
Stations A to G) and between the power plant and the Fukushima basin (Station A), were leached,causing most of the deposits observed in these areas. The analysis of the observations tends to reject
the hypothesis, long raised by several Japanese teams, of depositions by the fog in the valley Nakadori.
The most significant deposits occurred with the early rainfall, some of which were too weak to bemeasured in some locations. The analysis of the observations seems to suggest that a significant part of
the activity in the air was located at a high altitude, probably because of the relief of the regions
crossed. Figure 3 shows that the portion of the activity measured in the air from 14 th to the 16th Marchin the Fukushima Basin (Station A) is lower than for the 20-21 March episode. However, deposits weremainly formed on the 15th of March. Further south, the deposits on the side of the Nikko Mountains andon the mountains of Gunma Prefecture (Zone 2 Figure 1) probably occurred during this episode. The
measurements are too incomplete to study the sequence of contamination, but the assumption of adeposition caused by a locally created fog or by clouds caught in the mountains is very likely [Kaneyasu
et al (2012) ; Hososhima et Kaneyasu (2015)].
The 20 to 21 March episode is the main contamination episode of the Kanto plain, the Tokai region
and the area between the north of the Miyagi Prefecture and south of the Iwate prefecture.
Between the 20th and the 21st of March, several plumes were detected to the North West of the power
plant (the area of Stations J, I, H and beyond), in the Nakadori Valley (Stations A to G) and in Greater
Tokyo. Light winds favoured their stagnation, which led, overall, to a high 137Cs activity concentration,over the period between the 20th and the 21st of March. Based on soil contamination and dose rates, theevent of the period between the 14th and the 16th of March has been up until now considered to be theepisode that led to one of the greatest exposures of the population of the Fukushima basin, theNakadori valley and Greater Tokyo. Measurements of the activity concentration in 137 Cs challenge thisidea by indicating a non-negligible exposure to the plume during the episode of the 20-21 March (Figure3). However, measurements by radionuclide indicate that the proportion of iodine, tellurium and ofrare gases contained in the plume was lower on those dates than during previous episodes. Yet it isthese elements (especially iodine and tellurium) that are the most critical regarding health impact
during the passage of the plume.

11

All times are given in Universal Time (UTC). 9 hours must be added to obtain the local Japanese time.

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March 2016

Total
deposits(kBq/m²)

Integrated
activity
concentration(Bq/m3)11 March
14-16 March
18 March
20-21 March
Figure 3: The coloured dots represent the values of the 137 Cs activity concentrations at the stations
integrated between 11 March and 24 March. They are superimposed on the map of total 137 Cs deposits. The
pie charts show the distribution of the activity concentrations observed for each of the main contamination
periods.

To summarize, the joint analysis of the radiological measurements in the environment and themeteorological observations have made it possible to determine the path of the plume through theatmosphere and the periods of leaching by rain, leading to the main soil contamination episodes. The
analysis of the activity concentrations revealed areas that were subjected to a significant atmosphericcontamination by 137Cs, while the deposits measured are low and the dose rates show no significant
increase (Figure 3).
The analysis of the measurements highlighted the main challenges limiting the understanding of theevents.


The complex orography (influence of the coast and reliefs) played a crucial role in the pathtaken by the plume, but also in its vertical rising. It also affected the distribution of thedepositions. When the plume was at a high altitude, no measurement could detect it (thestations are on the ground). However, several plumes were probably carried by high altitude
winds, to be subsequently leached by rain and form contamination patches that cannot be
explained otherwise.

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March 2016
The deposition cannot be satisfactorily explained by taking into account only rain observations(pluviometers or radars). Indeed, light rain (less than 0.5 mm/h) is not measured. Analysis of
the measurements shows that the main ground contamination, on 15-16 March, is linked toplume leaching having started earlier than the first rain observations, thus consequent to light
rain.



No measurement provides access to the isotopic composition of the plumes and deposits.
Measurements of 129I have started to be published and make it possible to deduce the 131I
content [Muramatsu et al (2015)].

Transport and fallout modelling
Since 2011, the international community of atmospheric dispersion modelling has been working on
simulating as closely as possible the environmental consequences of the Fukushima accident. The
motivation is twofold. The first objective is, of course, to achieve a better understanding of theaccident. The second is to improve dispersion models and the representation of physical processes. IRSN
extends this second objective to the operational tools that it develops for the assessment ofradiological consequences. This objective responds to the need to improve the relevance of theInstitute’s expertise, in the event of a nuclear accident.
First objective: to precisely simulate and better understand the accident
Fairly quickly after the accident, the main release events were identified and their consequences wereroughly assessed. Since then, the understanding of the various episodes has been greatly improved, theprocesses responsible for the depositions have been determined, and simulations have become more
realistic. The most significant progress has been the result of efforts focused on improving the main
input data of dispersion models. These are the weather conditions and the quantification of thereleases to the atmosphere.
The weather conditions are provided by forecasting models. They determine the transport of theradioactive plume through the atmosphere. Rainfall is responsible for soil contamination, due toleaching of the plume. Spatial or temporal shifts in the forecast, such as a delay of a few hours in thechange of wind direction, or the onset of precipitation, can strongly penalise the reproduction of somecontamination episodes. After the accident, simulations were made using weather forecasts with too
low resolution as shown, in 2012, by IRSN [Mathieu et al (2012), Korsakissok et al (2013)]. Forecastswith a finer resolution [WMO (2011), Sekiyama et al (2015)] were thus produced, to significantly
improve the Fukushima accident simulations. IRSN had access to many forecast sources, especially as
part of its participation in the UNSCEAR and SAKURA project work. Radar rainfall observations were also
used in the simulations, replacing the precipitations forecast by the models.
The source term, that is to say, the temporal evolution of the rate of each radionuclide released into
the atmosphere, is the other essential input data of atmospheric dispersion models. Currently, there isno detailed source term estimated only through modelling the changes in the state of the reactors. The
existing ones were all assessed based on methods using environmental measurements and atmosphericdispersion simulations. Several source terms have been published. The first were relatively rough. They
have since been extensively refined. However, there is no consensus on a source term considered to be
more realistic than the other. The contribution of IRSN to the detailed assessment of the accident
releases is significant and original [Winiarek et al (2012) ; Saunier et al (2013) ; Winiarek et al (2014)].

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March 2016
IRSN was the first team to develop an automatic method for reconstructing the source term frommeasurements of the dose rates in the environment.
The detailed source terms and fine scale weather forecasts have made it possible to realisticallysimulate the transport and fallout of the plumes. The comparison with observations was significantly
improved. However, some episodes remain difficult to simulate. For example, simulations of thesequence between the 14 th and 16th of March are still unable to reproduce the various deposition
events. This fact reflects the remaining uncertainties and the complexity of the situation encountered.
These difficulties have oriented the progress areas that should be favoured to improve dispersion
models.
Second objective: to improve the dispersion models and crisis management tools
The improvements of the atmospheric dispersion models favoured by the community working on the
Fukushima accident relate to the representation of the deposition process. Indeed, regarding
population exposure, modelling the deposition is a major challenge, both due to the doses induced bydeposits and to the depletion of the plume that it generates. The studies carried out, in particular by
IRSN [Quérel et al (2016)], show that the remaining uncertainties with regard to the input data in thecase of Fukushima are still too large to study the deposition process. Their precise modelling therefore
does not provide, at this stage, any real added value to improve the realism of the simulations. The
subjects of the vertical distribution of plumes and the deposition during light rain episodes are
considered to be a prior necessity before a better simulation of soil contamination can be envisaged.
Further analysis of the accident from the perspective of environmental measurements and intercomparisons of models such as those organised by the SCJ are two means available to the community tocontinue to make progress on these issues and improve the simulation of the accident.
Beyond working on dispersion models, modelling the Fukushima accident has demonstrated the value of
having operational tools to estimate detailed source terms from environmental measurements. IRSN has
been quite innovative in this regard. Now, all operating-oriented teams are seeking to develop such atool (European Project PREPARE, PHE and Met Office12 teams for England, ZAMG13 for Austria).
The great lesson learned from the Fukushima accident concerns the uncertainties related to theweather data and releases. These are inevitable and the major challenge for the consequencemodelling community is to successfully take them into account in the management of an accident
situation. Assessing their impact on the simulations and modelling them for more relevant decision
making in view of the risk of exposure constitutes an important challenge. Since 2011, IRSN initiated a
project on this theme [Girard et al (2014) ; Girard et al (2015)]. At the European level, other teams arealso moving in this direction [Sørensen et al (2015)].

1213

PHE is Public Health England and MetOffice is the English weather centre.
The ZAMG is the Central Institute for Meteorology and Geodynamics.

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March 2016

Champion, D., Korsakissok, I., Didier, D., Mathieu, A., Quélo, D., Groell, J., Quentric, E., Tombette,
M., Benoit, J.-P., Saunier, O., Parache, V., Simon-Cornu, M., Gonze, M. A., Renaud, P., Cessac,
B., Navarro, E. et Servant-Perrier, A.-C. (2013). "The IRSN's earliest assessments of the
Fukushima accident's consequences for the terrestrial environment in Japan." Radioprotection
48(01): 11-37.
Endo, S., Kimura, S., Takatsuji, T., Nanasawa, K., Imanaka, T. et Shizuma, K. (2012). "Measurement ofsoil contamination by radionuclides due to the Fukushima Dai-ichi Nuclear Power Plant accident
and associated estimated cumulative external dose estimation." Journal of Environmental
Radioactivity 111: 18-27.
Girard, S., Korsakissok, I. et Mallet, V. (2014). "Screening sensitivity analysis of a radionuclides
atmospheric dispersion model applied to the Fukushima disaster." Atmospheric Environment95(0): 490-500.
Girard, S., Korsakissok, I., Mallet, V. et Mathieu, A. (2015). "Emulation and Sobol’ sensitivity analysis of
an atmospheric dispersion model applied to the Fukushima nuclear accident." Journal ofGeophysical Research Accepted for publication.
Groëll, J., Quélo, D. et Mathieu, A. (2014). "Sensitivity analysis of the modelled deposition of 137Cs on
the Japanese land following the Fukushima accident." Int. J. of Environment and Pollution
55(1/2/3/4): 67-75.
Hososhima, M. et Kaneyasu, N. (2015). "Altitude-Dependent Distribution of Ambient Gamma Dose Rates
in a Mountainous Area of Japan Caused by the Fukushima Nuclear Accident." Environmental
Science & Technology 49(6): 3341-3348.
IRSN (2012). Fukushima, one year later: initial analyses of the accident and its consequences. IRSN.
Rapport n°IRSN/DG/2012-003.
Kaneyasu, N., Ohashi, H., Suzuki, F., Okuda, T. et Ikemori, F. (2012). "Sulfate Aerosol as a Potential
Transport Medium of Radiocesium from the Fukushima Nuclear Accident." Environmental
Science & Technology 46(11): 5720-5726.
Kinoshita, N., Sueki, K., Sasa, K., Kitagawa, J.-i., Ikarashi, S., Nishimura, T., Wong, Y.-S., Satou, Y.,
Handa, K., Takahashi, T., Sato, M. et Yamagata, T. (2011). "Assessment of individual
radionuclide distributions from the Fukushima nuclear accident covering central-east Japan."
Proceedings of the National Academy of Sciences.
Korsakissok, I., Mathieu, A. et Didier, D. (2013). "Atmospheric dispersion and ground deposition inducedby the Fukushima Nuclear power plant accident : a local-scale simulation and sensitivity study."
Atmospheric Environment 70: 267-279.
Mathieu, A., Korsakissok, I., Quélo, D., Groëll, J., Tombette, M., Didier, D., Quentric, E., Saunier, O.,
Benoit, J.-P. et Isnard, O. (2012). "Atmospheric dispersion and deposition of radionuclides fromthe Fukushima Daiichi nuclear power plant accident." Elements 8: 195-200.
Morino, Y., Ohara, T. et Nishizawa, M. (2011). "Atmospheric behavior, deposition, and budget ofradioactive materials from the Fukushima Daiichi nuclear power plant in March 2011."
Geophysical Research Letters 38: L00G11.
Morino, Y., Ohara, T., Watanabe, M., Hayashi, S. et Nishizawa, M. (2013). "Episode Analysis of
Deposition of Radiocesium from the Fukushima Daiichi Nuclear Power Plant Accident."
Environmental Science & Technology 47(5): 2314-2322.
Muramatsu, Y., Matsuzaki, H., Toyama, C. et Ohno, T. (2015). "Analysis of 129I in the soils of Fukushima
Prefecture: preliminary reconstruction of 131I deposition related to the accident at Fukushima
Daiichi Nuclear Power Plant (FDNPP)." Journal of Environmental Radioactivity 139: 344-350.
Quérel, A., Roustan, Y., Quélo, D. et Benoit, J.-P. (2016). "Hints to discriminate the choice of wet
depostion models applied to an accidental radioactive release." Int. J. of Environment and
Pollution Accepted for publication.
Saito, K., Tanihata, I., Fujiwara, M., Saito, T., Shimoura, S., Otsuka, T., Onda, Y., Hoshi, M., Ikeuchi,Y., Takahashi, F., Kinouchi, N., Saegusa, J., Seki, A., Takemiya, H. et Shibata, T. (2015).
"Detailed deposition density maps constructed by large-scale soil sampling for gamma-ray
emitting radioactive nuclides from the Fukushima Dai-ichi Nuclear Power Plant accident."
Journal of Environmental Radioactivity 139: 308-319.

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Sanada, Y., Sugita, T., Nishizawa, Y., Kondo, A. et Torii, T. (2014). "The aerial radiation monitoring inJapan after the Fukushima Daiichi nuclear power plant accident." Progress in Nuclear Scienceand Technology 4: 76-80.
Saunier, O., Mathieu, A., Didier, D., Tombette, M., Quélo, D., Winiarek, V. et Bocquet, M. (2013). "An
inverse modelling method to assess the source term of the Fukushima Nuclear Power Plant
accident using gamma dose rate observations." Atmos. Chem. Phys. 13(22): 11403-11421.
SCJ (2014). A review of the model comparison of transportation and deposition of radioactive materials
released to the environment as a result of the Tokyo Electric Power Company’s Fukushima
Daiichi Nuclear Power Plant accident. Science Council of Japan. Rapport.
Sekiyama, T. T., Kunii, M., Kajino, M. et Shimbori, T. (2015). "Horizontal Resolution Dependence ofAtmospheric Simulations of the Fukushima Nuclear Accident Using 15-km, 3-km, and 500-m Grid
Models." Journal of the Meteorological Society of Japan. Ser. II 93(1): 49-64.
Sørensen, J. H., Amstrup, B., Feddersen, H., Korsholm, U. S., Bartnicki, J., Klein, H., Simonsen, M.,
Lauritzen, B., Hoe, S. C., Israelson, C. et Lindgren, J. (2015). Fukushima Accident: UNcertaintyof Atmospheric dispersion modelling (FAUNA). Nordic Nuclear Safety Research. Rapport n°NKS339 (ISBN 978-87-7893-421-5).
Steinhauser, G., Brandl, A. et Johnson, T. E. (2014). "Comparison of the Chernobyl and Fukushima
nuclear accidents: A review of the environmental impacts." Science of The Total Environment
470–471: 800-817.
Tsuruta, H., Oura, Y., Ebihara, M., Ohara, T. et Nakajima, T. (2014). "First retrieval of hourly
atmospheric radionuclides just after the Fukushima accident by analyzing filter-tapes ofoperational air pollution monitoring stations." Sci. Rep. 4.
UNSCEAR (2013). Report of the United Nations Scientific Committee on the Effects of Atomic Radiation
to the General Assembly. Scientific Annex A: Levels and effects of radiation exposure due to the
nuclear accident after the 2011 great east-Japan earthquake and tsunami. UNSCEAR. Rapport.
Winiarek, V., Bocquet, M., Duhanyan, N., Roustan, Y., Saunier, O. et Mathieu, A. (2014). "Estimation of
the caesium-137 source term from the Fukushima Daiichi nuclear power plant using a consistent
joint assimilation of air concentration and deposition observations." Atmospheric Environment
82(0): 268-279.
Winiarek, V., Bocquet, M., Saunier, O. et Mathieu, A. (2012). "Estimation of errors in the inverse
modelling of accidental release of atmospheric pollutant: Application to the reconstruction of
the cesium-137 and iodine-131 source terms from the Fukushima Daiichi power plant." J.
Geophys. Res. 117(D5): D05122.
WMO (2011). Meeting of the WMO task team on meteorological analyses for Fukushima Daiichi nuclear
power plant accident. World Meteorological Organization Rapport n°TT-MA-NPP-Accident
Report.
Yasunari, T. J., Stohl, A., Hayano, R. S., Burkhart, J. F., Eckhardt, S. et Yasunari, T. (2011). "Cesium137 deposition and contamination of Japanese soils due to the Fukushima nuclear accident."
Proceedings of the National Academy of Sciences.

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