​Fukushima in 2016

The Fukushima and Chernobyl accidents: different impacts on the environment

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Fukushima and Chernobyl accidents:

Different impacts on the environment

​In the contaminated territories of Fukushima, the first results of the ecological studies are often contradictory, and on occasions differ from those observed in the contaminated exclusion zone following the Chernobyl accident (Ukraine).

Different impacts on the environment

Fukushima and Chernobyl accidents:

Different impacts on the environment

​In the contaminated territories of Fukushima, the first results of the ecological studies are often contradictory, and on occasions differ from those observed in the contaminated exclusion zone following the Chernobyl accident (Ukraine).

Effects on fauna and flora

Thirty and five years respectively after the two major nuclear accidents that occurred at the Chernobyl (Ukraine) and Fukushima (Japan) power plants, the ecological studies conducted on the fauna and flora chronically exposed to ionising radiation deliver conclusions that are often contradictory.

Morphological anomalies in pine trees are observed at Chernobyl as well as Fukushima. The frequency of occurrence of these anomalies would appear to be linked to the dose absorbed by the trees. However, the dosimetric estimations in the study carried out at Fukushima are incomplete and therefore do not enable solid dose-effects relationships to be established.The effects observed on the abundance of terrestrial invertebrates depend on the groups of species studied. For certain invertebrates only, the evolution of abundance based on the ambient level of exposure differs between the Chernobyl and Fukushima sites.
According to the studies, differences in radiosensitivity between species and the effects linked to chronic exposure over several generations are the main explanations behind these differences.
A decline in the number of birds has been observed in the Chernobyl exclusion zone and in the contaminated territories of Fukushima - a phenomenon that is correlated with the increase in the ambient dose rate.
According to the IRSN, the effects observed are consistent with a study showing a reduction in reproductive capacity linked to an increase in the doses absorbed.
In Fukushima, a recent IRSN study estimated that the absorbed dose has more impact on the fall in the total number of birds than the evacuation of human populations.
In Chernobyl, the evacuation of human populations is considered by certain authors having published works on the large mammals of the Belarusian reserves, to be the deciding factor concerning the return of animals to the contaminated territories.

Nonetheless, the review of ecological studies highlights shortcomings in cooperation between the basic scientific disciplines; a situation that can lead to biased conclusions. 

Download "Ecological studies carried out over the long term on the fauna and flora of the territories contaminated by the Chernobyl and Fukushima accidents" (PDF, 813 Ko)

 

​Japanese paradise flycatcher in the contaminated area of Fukushima, Japan. © Jean-Marc Bonzom/IRSN.

Effects on fauna and flora

Effects on fauna and flora

​Japanese paradise flycatcher in the contaminated area of Fukushima, Japan. © Jean-Marc Bonzom/IRSN.

Thirty and five years respectively after the two major nuclear accidents that occurred at the Chernobyl (Ukraine) and Fukushima (Japan) power plants, the ecological studies conducted on the fauna and flora chronically exposed to ionising radiation deliver conclusions that are often contradictory.

Morphological anomalies in pine trees are observed at Chernobyl as well as Fukushima. The frequency of occurrence of these anomalies would appear to be linked to the dose absorbed by the trees. However, the dosimetric estimations in the study carried out at Fukushima are incomplete and therefore do not enable solid dose-effects relationships to be established.The effects observed on the abundance of terrestrial invertebrates depend on the groups of species studied. For certain invertebrates only, the evolution of abundance based on the ambient level of exposure differs between the Chernobyl and Fukushima sites.
According to the studies, differences in radiosensitivity between species and the effects linked to chronic exposure over several generations are the main explanations behind these differences.
A decline in the number of birds has been observed in the Chernobyl exclusion zone and in the contaminated territories of Fukushima - a phenomenon that is correlated with the increase in the ambient dose rate.
According to the IRSN, the effects observed are consistent with a study showing a reduction in reproductive capacity linked to an increase in the doses absorbed.
In Fukushima, a recent IRSN study estimated that the absorbed dose has more impact on the fall in the total number of birds than the evacuation of human populations.
In Chernobyl, the evacuation of human populations is considered by certain authors having published works on the large mammals of the Belarusian reserves, to be the deciding factor concerning the return of animals to the contaminated territories.

Nonetheless, the review of ecological studies highlights shortcomings in cooperation between the basic scientific disciplines; a situation that can lead to biased conclusions. 

Download "Ecological studies carried out over the long term on the fauna and flora of the territories contaminated by the Chernobyl and Fukushima accidents" (PDF, 813 Ko)

 

Effects on forest environments

In both Chernobyl and Fukushima, a large proportion of the highly-contaminated territories is covered by forest. Knowledge about the evolution of the radionuclides deposited within these ecosystems following the accidents, as well as differing management practices regarding these environments between the two countries, enable valuable lessons on the post-accident management of forest environments to be learned.

The main characteristics of the forest ecosystems impacted by radioactive fallout differ between the two accidents. In particular, the appearance of the "red forest" is specific to the Chernobyl accident and has not been observed at Fukushima.One of the main characteristics of forest ecosystems is the high remanence of radioactive contamination. There is a very dynamic redistribution of the radionuclides. It is the result of processes that are part of the radionuclides' cycle, which is strongly correlated with that of organic matter, tree type, type of soil, climatic and anthropogenic factors as well as the characteristics of the radionuclides deposited.The interception of radioactive deposits by the canopy and transfers of radionuclides towards the leaf litter and soil are the most important processes in the early phase and first months following the accident. Little knowledge existed for the Chernobyl exclusion zone, but the data collected at Fukushima has enabled a better understanding of this process. After initial interception by the canopy, the transfer of contamination towards the soil is the result of two processes: leaching of the canopy and trunks by the rain, and the fall of biomass to form leaf litter.With the leaching of the canopies and fall of aerial biomass, the soil becomes the preponderant reservoir where radioactive caesiums (caesium-134 and caesium-137) can be found. Five years after the Fukushima accident, between 80% and 90% of these caesiums have been entrained into the top layers of soil or humus, i.e. rates comparable to those observed at Chernobyl.There is a high risk of fire in the Chernobyl exclusion zone where the forest, left to evolve naturally, can be exposed to periods of drought. This risk is lower in Japan since it is limited by the short dry season in the spring. Nonetheless, such fires would constitute catastrophic events, leading to the mass dissemination of radionuclides on a local, and even regional, scale.

In Japan, the management of contaminated forest ecosystems differs from that applied to the forest ecosystem in the Chernobyl exclusion zone. Japan decided upon a strategy of extensive decontamination. Nevertheless, in the end the authorities decided that it was unrealistic to decontaminate the forests in their entirety, due to the volumes of waste generated and the dramatic ecological consequences that could result from mass actions to remove leaf litter or fell trees.

Henceforth, Japan distinguishes between three types of forest surfaces: those located around the residential areas with the removal and disposal of contaminated leaf litter and humus; those visited by workers on a daily basis where decontamination measures are in place and, finally, those of the "deep" forest where measures aim to restrict the dispersion of radionuclides by preventing soil erosion.

Download "Management of forest environments: the lessons learned following the Chernobyl and Fukushima accidents" (PDF, 593 Ko)

​Measurement of ambient radioactivity in contact with soil in a forest © Jean-Marc Bonzom/IRSN

Effects on forest environments

Effects on forest environments

​Measurement of ambient radioactivity in contact with soil in a forest © Jean-Marc Bonzom/IRSN

In both Chernobyl and Fukushima, a large proportion of the highly-contaminated territories is covered by forest. Knowledge about the evolution of the radionuclides deposited within these ecosystems following the accidents, as well as differing management practices regarding these environments between the two countries, enable valuable lessons on the post-accident management of forest environments to be learned.

The main characteristics of the forest ecosystems impacted by radioactive fallout differ between the two accidents. In particular, the appearance of the "red forest" is specific to the Chernobyl accident and has not been observed at Fukushima.One of the main characteristics of forest ecosystems is the high remanence of radioactive contamination. There is a very dynamic redistribution of the radionuclides. It is the result of processes that are part of the radionuclides' cycle, which is strongly correlated with that of organic matter, tree type, type of soil, climatic and anthropogenic factors as well as the characteristics of the radionuclides deposited.The interception of radioactive deposits by the canopy and transfers of radionuclides towards the leaf litter and soil are the most important processes in the early phase and first months following the accident. Little knowledge existed for the Chernobyl exclusion zone, but the data collected at Fukushima has enabled a better understanding of this process. After initial interception by the canopy, the transfer of contamination towards the soil is the result of two processes: leaching of the canopy and trunks by the rain, and the fall of biomass to form leaf litter.With the leaching of the canopies and fall of aerial biomass, the soil becomes the preponderant reservoir where radioactive caesiums (caesium-134 and caesium-137) can be found. Five years after the Fukushima accident, between 80% and 90% of these caesiums have been entrained into the top layers of soil or humus, i.e. rates comparable to those observed at Chernobyl.There is a high risk of fire in the Chernobyl exclusion zone where the forest, left to evolve naturally, can be exposed to periods of drought. This risk is lower in Japan since it is limited by the short dry season in the spring. Nonetheless, such fires would constitute catastrophic events, leading to the mass dissemination of radionuclides on a local, and even regional, scale.

In Japan, the management of contaminated forest ecosystems differs from that applied to the forest ecosystem in the Chernobyl exclusion zone. Japan decided upon a strategy of extensive decontamination. Nevertheless, in the end the authorities decided that it was unrealistic to decontaminate the forests in their entirety, due to the volumes of waste generated and the dramatic ecological consequences that could result from mass actions to remove leaf litter or fell trees.

Henceforth, Japan distinguishes between three types of forest surfaces: those located around the residential areas with the removal and disposal of contaminated leaf litter and humus; those visited by workers on a daily basis where decontamination measures are in place and, finally, those of the "deep" forest where measures aim to restrict the dispersion of radionuclides by preventing soil erosion.

Download "Management of forest environments: the lessons learned following the Chernobyl and Fukushima accidents" (PDF, 593 Ko)

Redistribution of radioactive deposits in a post-accident situation

In the contaminated zones, the redistribution of radioactive caesiums is governed by hydrological processes such as surface runoff or transport into waterways. Knowledge about the dynamics of flows of radionuclides associated with these processes is essential in order to optimise post-accident management strategy, in particular for the exploitation of aquatic resources by man.

The leaching of catchment basins governs the redistribution of the radionuclides deposited on the soils following a nuclear accident. In Chernobyl and Fukushima, this process annually remobilises less than 1% of the radioactive caesiums deposited. These flows are transported towards catchment basins by water and particles.The transport of radioactive caesiums is the result of complex chemical, hydrological and erosive processes that are expressed in two different phases: the rapid leaching phase during the first weeks after the accident, where the flows of caesium-137 are high and export around 1% of the initial deposit onto the catchment basin, and the slow leaching phase, where exported flows are much lower, at around 0.1% per year.The flows of exported radioactive caesiums at Fukushima and Chernobyl differ. This situation is linked to the availability for leaching of the radionuclides deposited on the soils, and to differences in topography and weather patterns. Consequently, the leaching of radioactive caesiums is mainly solid in Fukushima and liquid in Chernobyl. However, in both cases, the majority of annual exports to the sea are caused by rises in the water level.

The strategy applied to the management of aquatic environments in Chernobyl and Fukushima is different. In the Ukraine, the Dniepr river and its reservoirs are the main supply source of water. Countermeasures - such as dykes and dams - have therefore greatly affected the aquatic environments at Chernobyl. In Japan, even though a change in dam management methods is under consideration, countermeasures remain massively focused on the decontamination of the contaminated territories (agricultural areas and around houses).

Download "Redistribution of radioactive deposits in a post-accident situation" (PDF, 375 Ko)

 

Go to the next part  Health impact in 2016

Body of water located in the contaminated and evacuated area of Fukushima, Japan. © Jean-Marc Bonzom/IRSN

Redistribution of radioactive deposits in a post-accident situation

Redistribution of radioactive deposits in a post-accident situation

Body of water located in the contaminated and evacuated area of Fukushima, Japan. © Jean-Marc Bonzom/IRSN

In the contaminated zones, the redistribution of radioactive caesiums is governed by hydrological processes such as surface runoff or transport into waterways. Knowledge about the dynamics of flows of radionuclides associated with these processes is essential in order to optimise post-accident management strategy, in particular for the exploitation of aquatic resources by man.

The leaching of catchment basins governs the redistribution of the radionuclides deposited on the soils following a nuclear accident. In Chernobyl and Fukushima, this process annually remobilises less than 1% of the radioactive caesiums deposited. These flows are transported towards catchment basins by water and particles.The transport of radioactive caesiums is the result of complex chemical, hydrological and erosive processes that are expressed in two different phases: the rapid leaching phase during the first weeks after the accident, where the flows of caesium-137 are high and export around 1% of the initial deposit onto the catchment basin, and the slow leaching phase, where exported flows are much lower, at around 0.1% per year.The flows of exported radioactive caesiums at Fukushima and Chernobyl differ. This situation is linked to the availability for leaching of the radionuclides deposited on the soils, and to differences in topography and weather patterns. Consequently, the leaching of radioactive caesiums is mainly solid in Fukushima and liquid in Chernobyl. However, in both cases, the majority of annual exports to the sea are caused by rises in the water level.

The strategy applied to the management of aquatic environments in Chernobyl and Fukushima is different. In the Ukraine, the Dniepr river and its reservoirs are the main supply source of water. Countermeasures - such as dykes and dams - have therefore greatly affected the aquatic environments at Chernobyl. In Japan, even though a change in dam management methods is under consideration, countermeasures remain massively focused on the decontamination of the contaminated territories (agricultural areas and around houses).

Download "Redistribution of radioactive deposits in a post-accident situation" (PDF, 375 Ko)

 

Go to the next part  Health impact in 2016