Mark Horstman travels to Fukushima Prefecture in Japan to investigate where the radioactive fallout has travelled since the Daichi nuclear power plant accident over three years ago.



Please click on the link below for a map of radiation levels from Catalyst’s journey through Fukushima, created by data from a Safecast bGeigie attached to the crew car and carried off road. Radiation levels are in CPM (ionisation counts per minute) and µSv/h (microsieverts per hour) at the left of the map. The colour range of green to brown to red to black corresponds with increasing radiation levels.The highest level recorded is a hotspot of 7 µSv/h in forest at the edge of the exclusion zone around the Daichi nuclear power plant.
https://api.safecast.org/en-US/bgeigie_imports/15354

NARRATION
Fukushima prefecture in northern Japan has long been famous for the beauty of its environment. Snow-capped mountains surround bustling cities. Rushing rivers feed productive agriculture. But the earthquake and tsunami of 2011 has left Fukushima more famous for fallout. Explosions and meltdowns at the Daiichi Nuclear Power Plant released dangerous amounts of radioactive waste. The fallout contained a cocktail of isotopes - some, like iodine, decayed within a few days, but not cesium-137. It has a half-life of 30 years.

Mark Horstman
These mountains of Fukushima prefecture look picture perfect but it's worth remembering that, while 80% of the radioactive plume from the nuclear reactor disaster blew out to sea, 20% of it settled on the rivers and forests of inland Japan.

NARRATION
So, what's happened to that inland contamination since? Japanese people are anxious to know.

Munemitsu Kikuchi
We have to face radiation calmly,with a clear head, without being emotional.

NARRATION
I'm on a radiation road trip through the fallout zone, looking for answers in unexpected places. My journey starts in the mountains with this team of French and Canadian sediment scientists.

Olivier Evrard
We use cesium as a tracer, a specific tracer to track the dispersion of material from the hill slope to the rivers and then to the ocean.

NARRATION
A landscape dusted with cesium is an ideal place for their study of sediment transport.

Mark Horstman
This is the edge of the 20km exclusion zone that surrounds the stricken Daiichi Nuclear Power Plant. The land behind me here is so contaminated with radiation that access for everyone is prohibited.

NARRATION
Just outside the exclusion zone, Olivier Evrard's team compare radiation dose rates from newly deposited sediment with those of the surrounding soil. Cesium-137 is a worry for human health and safety because it dissolves in water, making it hard to clean up and easy to enter the body.

Olivier Evrard
We sample twice a year so after the typhoons and after the snow melts because they are just triggering the main erosion phenomena in the region.

Mark Horstman
When the snow melts in the spring, torrents of water rush down here and deposit new layers of sediment, and that's why we're here. This team has been studying these river and creek sediments for three years and the levels of radiation are still high. In fact, the readings they've got here are the highest for any river sediments in the area.

NARRATION
This soil, washed into the stream by the snow melt, is emitting about 5 microsieverts an hour. That's about 50 times the maximum dose rate considered safe for the general public. And just a few metres away on the forest floor, the levels are even higher - up to 7 microsieverts.

Olivier's colleague
6 to 7.

Olivier Evrard
Ah, it's much higher than on the river.

Mark Horstman
Why is that?

Olivier Evrard
In the forest, you have a lot of vegetation, a lot of litter, which is protecting the soil against erosion. And so it means that there is still a huge stock of contamination in the forest.

Mark Horstman
It sits here for longer?

Olivier Evrard
Yep, that's it.

NARRATION
With more radiation on the forest floor, we don't stay for long. Further downstream, this dam is now empty because the earthquake ruptured the dam wall. But with the dam bed radiating a dose of about 6 microsieverts an hour the problem for future water storage is clear.

Olivier Evrard
There is still a lot of storage of contaminated material here and we can imagine when the water level increases again, it could be flushed much later towards the ocean.

NARRATION
That could mean a succession of radioactive pulses whenever water is released for decades after the original fallout. And that's particularly important for the more densely populated areas downstream, where the chances of exposure to radiation are higher.

Mark Horstman
This is the Abukuma River. It runs right through Fukushima city. It's the largest river basin in the contaminated zone. So, understanding where the radiation is and how it moves through this environment is crucial to understanding how it gets to people through the food chain.

Professor Kenji Nanba
The cesium flowing in the river is almost all affixed to the clay or individual particles. That doesn't really get into living organisms. But cesium that has attached to organic materials or dissolved into water can easily get into living organisms.

NARRATION
Over the last two years, Professor Kenji Nanba and his students have been investigating the link between the organic material in this monsoonal river and the amount of cesium it carries. They collect the suspended particles with a centrifuge, pumping and spinning tons of river water for five hours. The samples are analysed in a gamma-ray spectrometer to identify what's emitting the radiation. The particles of soil or plant material in the river water may be small but their size matters.

Professor Kenji Nanba
Smaller particle have more potential to attach radiocesium on the surface.

Mark Horstman
So it has a greater surface area...

Professor Kenji Nanba
Yes.

Mark Horstman
..in relation to its volume.

Professor Kenji Nanba
Yes.

Mark Horstman
So, therefore, more capacity for the radiocesium to bind onto it.

Professor Kenji Nanba
Yes.

NARRATION
It means that the smallest of these particles can end up being the most radioactive.

Professor Kenji Nanba
These organic particle, if it contains radiocesium, it can be digested and transferred to the body of fish.

NARRATION
That's a concern for human consumption, and fishing in the river had been banned as a precaution. Radiation and its perceived threat loom so large in Japan that monitoring is no longer just left to scientists. From downtown Tokyo a unique citizen science project is going global.

Joe Moross
Basically you can use this as an example if you're unsure how things go together, OK?

NARRATION
Safecast shows volunteers who may have never held a soldering-iron how to build devices that detect and record radiation.

Azby Brown
I hope we can be a model for effective citizens' action in this sort of situation - teaching people, one, how to find out what's happening, two, use that information in an effective way, to lobby their governments and say 'We checked it and this is what we found. You said it's X, we found Y. What's the reason?'

Asako Okazaki
We tend to rely too much on others for data about radiation and other environmental problems. Each of us should be involved in producing our own raw data to know from the ground up. That's why I'm involved.

NARRATION
Engineer and long-term resident Joe Moross has helped develop their cheap, portable Geiger counter, known as the 'bGeigie', that you can clip on your belt, your bike or your car.

Joe Moross
Well, we have here the main component obviously is the sensor. This is a Geiger-Muller tube. It's a 2-inch pancake which gives it a large sensitivity, which helps for the low levels that we're finding in most places in Japan. Then on the top we have a GPS receiver which gives the location and the time of day, a data logger which writes the data onto an SD card, a display, and of course a micro controller that has the firmware that controls the whole system.

NARRATION
That's what's special about this DIY detector. It enables anyone to map radiation by automatically taking thousands of measurements a day for uploading to a website. Through crowd-sourcing, Safecast is building the world's largest public database about radiation, with several hundred detectors in use.

Pieter Franken
Today we measure about a million locations per month and we have collected close to 70 million locations in Japan and now actually also outside of Japan.

NARRATION
Safecast is also working with city governments in Fukushima prefecture.

Munemitsu Kikuchi
Koriyama is co-operating with Safecast. We put dosimeters onto the mail delivery motorbikes - they measure radiation throughout the city from small, narrow roads to the main streets. That data is mapped out and provided to us.

NARRATION
These days, fixed radiation monitors are part of the urban landscape, like bus stops or public toilets. With their quasi-official status, Safecast lets the public know how the government readings of radiation dose compare with their own. No other Safecast volunteer has collected more data than Joe.

Joe Moross
In fact, the road I'm aiming for today has not been covered ever.

Mark Horstman
New territory for Safecast.

Joe Moross
Yeah, which is surprising, considering it's in Fukushima and we're at year three - we've covered almost all the roads multiple times.

NARRATION
In the last few years, he's driven almost 80,000km, as his Geiger counter takes a reading every five seconds. This town was under the radioactive plume and heavily contaminated.

Joe Moross
The contamination was severe here and so it was evacuated, but obviously people are back now.

NARRATION
One of Joe's aims is to check how well decontamination has worked.

Joe Moross
Well, if you want to have the most effectiveness in cleaning up, you need to of course clean basically everything but you should concentrate on the areas where the stuff is likely to accumulate. In the bottom of these gutters, there's going to be run-off and dust that's settled that's likely to be more contaminated than the surfaces right around it.

Mark Horstman
Do you take a measurement like this?

Joe Moross
You can, but it's a little bit far 'cause this gutter's about a metre deep. But the sediment down there is probably very highly contaminated unless it's been swept out.

Mark Horstman
Even from here I'm getting a higher reading than anything we've seen so far on this street.

Joe Moross
And we've found that, you know, in even just a couple of metres, the downhill side of a road has higher contamination than the uphill side. Maybe the contamination was uniform on the day it came down, but different environmental factors cause it to wear out and move at different rates. So the radiation hasn't disappeared in the areas where the levels have fallen, it's just moved and gotten covered or concentrated in certain areas. You look at the bottom of this pipe here. Put your detector there, you'll see that it's really active.

Mark Horstman
Much noisier.

NARRATION
These measurements are in CPM, or counts per minute, of ionising events that indicate the intensity of radiation. At least if residents are aware of these hotspots, they can avoid them.

Joe Moross
Do you have any concerns about radiation levels in this street?

Local resident
I've heard it's OK, so I'm living my life as it is.

Joe Moross
She thinks it's OK, she's not really sure, but basically she feels it's alright. Arigatou gozaimashita.

Local resident
Arigatou gozaimashita.

Mark Horstman
Arigatou.

Joe Moross
See, people come around.

Mark Horstman
So, in a community where you've got a mixture of houses and gardens and agricultural areas, do you expect to see more variation there?

Joe Moross
We originally, at one time, tried to make a map of how contaminated the land was to try and get an estimate of how dangerous the food might be that was grown there. And what we found is that there's almost no correlation between the contamination level or the dose rate reading in a field and how the food might come out because there are factors like the organic content of the soil or how sandy or other inorganic material used in the soil. Apparently spinach, the Japanese herb shiso, those tend to concentrate the cesium and shouldn't be grown in areas that are contaminated at all.

NARRATION
But the good news here is that cleaning has reduced the initially high dose rates to within safer levels. However, within areas that remain evacuated, armies of workers are still decontaminating forested land and rice paddies. In a flurry of activity, vegetation is cleared and the topsoil removed. The contaminated material is stored in bags and carted away.

Mark Horstman
The sheer scale of the work needed to clean up this country is mind-boggling. Imagine if you had to cut and scrape and wash an area the size of Sydney or Perth or Brisbane. Well, the area of Japan that's officially contaminated, requiring this kind of clean-up, is larger than the area of all of the Australian capital cities combined.

NARRATION
But how to dispose of what's in the bags has yet to be resolved. And there's no guarantee that all this work to clean the land will be enough to decontaminate it to a safe level. Joe has just compared radiation readings in forest a few hundred metres up the road with this area that's just been cleaned, and he doesn't find any difference.

Joe Moross
The levels we're seeing around here are about 0.6 microsieverts an hour to 0.7 microsieverts an hour. And the goal the Japanese Government has set for people to move back into evacuated areas is 0.23 microsieverts an hour, so this is about three times the level that would be required to meet the standard the government has tried to set.

Mark Horstman
Even after it's been treated?

Joe Moross
Even after it's been cleaned up.

NARRATION
In addition, the research by Olivier's team shows that erosion from areas where decontamination works are underway actually increases contamination downstream. It reflects their finding that rivers are continuous sources of contamination to the sea.

Olivier Evrard
We're very surprised to see that in the upstream part of the catchments we have depletion of the contamination in the recent riverine sediments.

Mark Horstman
So they're the white dots?

Olivier Evrard
Indeed, the white dots. Whereas, in the coastal parts, you see a concentration of heavily contaminated sediment, which is pictured here by the black dots.

NARRATION
Over several years, more than 75% of their sample sites show a rapid and massive transfer of radioactivity from the highlands to the coast with each snow melt and rainy season - a new source of contamination that, until now, has not been taken into account.

Olivier Evrard
I find it really striking, this story of you try to do something, but then you think you control it but, in fact, you don't. It's just nature controlling everything.

NARRATION
How the radiation might affect human health in Japan is yet to be seen. For a problem that will last at least a generation, providing people with online maps of accurate and standardised data is an essential step.

Joe Moross
We found a way to get people involved and make them trust what we're doing because they're involved themselves. When they help gather the data, they have an inherent belief in its trustworthiness, so this has helped us get the message to people in a way that they can understand and believe.

Munemitsu Kikuchi
The accident at the nuclear power plant was a terrible disaster for the people of Fukishima and for Japan, but we are doing our best to recover. Nuclear researchers, environmental scientists and various people from all over the world have provided their support, and we hope to recover as soon as possible. Please continue to cooperate with us.
Topics: Health, Environment

Reporter: Mark Horstman
Producer: Mark Horstman
Researcher: Dominique Pile
Camera: Kevin May
Sound: Steve Ravich
Editor: Vaughan Smith

Story Contacts

Dr Olivier Evrard
Laboratory for Climate Sciences & Environment,
France

Prof Kenji Nanba
Environmental microbiologist
Fukushima University, Japan

Azby Brown
Director, KIT Future Design Institute
Safecast volunteer, Tokyo

Joe Moross
Safecast volunteer,
Japan

Pieter Franken
Co-Founder & Japan Director,
Safecast, Japan

Munemitsu Kikuchi
Director, Radiation Health Care
Koriyama City, Japan
Related Info

A map of radiation levels from Catalyst’s journey through Fukushima, created by data from a Safecast bGeigie attached to our crew car and carried off road. Radiation levels are in CPM (ionisation counts per minute) and µSv/h (microsieverts per hour)

Safecast - crowd-sourced radiation maps

Safecast - how effective is remediation?

Olivier Evrard et al. - Renewed soil erosion and remobilisation of radioactive sediment in Fukushima coastal rivers after the 2013 typhoons

Transport of radiocesium fallout from Fukushima nuclear plant by Abukuma River

ARPANSA - Understanding Radiation Risks

Assessment of the impact on Australia from the Fukushima Dai-ichi nuclear power plant accident.

Fukushima and Ocean Radioactivity

UNSW research – Fukushima Cesium-137 radioactive plume in the Pacific Ocean

Fukushima Radiation Ocean Plume animation

Japan Times - Radiation dose rates predicted to drop off

Catalyst story-Radiation 101