Mapping Rivers and Seabed radioactivity around Fukushima

Cesar Harada
Nov 4, 2014 · 8 min read

Peace and Knowledge as the foundation for a Japanese Renaissance

The Process: Sediment Sampling and Analysis

We have collected 33 sediment samples from riverbeds and the seabed as close as 1.5km away from the Fukushima Daiichi Nuclear Power Plant (FDNPP) — see video above.
The locations : Olivier Evrard’s team demonstrated that radioactivity levels “move” seasonally, mostly depending on precipitation (rain). After a rainy season, the radioactive particles gets “washed” from the mountain tops, down into the rivers and into the ocean (video of our approximate analog simulation). We collected samples from the most affected rivers and at sea in the immediate vicinity of the crippled, leaking nuclear power plant.
The time : the video was taken on October 9, between Typhoon 4 Phanfone (Oct 7th over Tohoku) and Typhoon 5 Vong Fong (Oct 14th). RT reports “Radiation levels at Fukushima rise to record highs after typhoon” :

“Samples from October 9 indicate that there are 150,000 becquerels of tritium per liter in the groundwater near Fukushima, according to Japan’s JIJI agency. Compared to levels recorded last week, that’s an increase of more than 10 times.”

We were “lucky” in that our predictions of the best time and place to collect the samples was accurate. The samples are currently being analyzed now.

Our Instrument

The Umilabo group and Prof Nagaoka use the Ekman or Van Veen Grab Sampler. I decided to develop our own sampling equipment called the “Rolling Micro-Trawler”. Our low cost, Open Hardware machine can be operated from any sized-boat, collecting only the top surface layer of sediment (the most recent and potentially most radioactive), where as the Ekman or Van Veen Grab “digs” and mixes the surface with deeper, older, less radioactive sediments, giving us an average radioactivity levels that can date many years back. However, even with the conventional instrument Professor Nagaoka writes:

“In order to identify the FDNPP accident influence, the spatial distribution of radionuclides in seabed sediments off Ibaraki coast was investigated. Cesium-137 activity was over hundreds of times higher than that before the accident.”

Locations sampled

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The locations we have sampled :

- Map :
- Table :
- CSV locations :
- KML file – to open with Google Earth :
- [updated] Measurements and map

What we have collected

Bagging 330 samples. Thanks to Prof Yoshida, at the Space Robotics Lab of Tohoku University.

33 locations, split into 10 bags dispatched to volunteer labs:
1. Dr Olivier Evrard Team, LSCE, CNRS France.
2. Fukushima University, Department of Environmental Radioactivity, JP.
3. Safecast, Tokyo JP.
4. Safecast, Tokyo JP.
5. Acquaintance in Tokyo, JP.
6. Backup set in Sendai, JP, (#available).
7. Backup set in Sendai, JP, (#available).

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Reading 0.087µSv/h

Please note : #available means that we can send you a sample set if you commit to publish your results under a Public Domain Dedication online. If you are interested in a free sample set, please send me an email at []. According to our measurements, handling and posting the sealed samples are safe. Take appropriate precautions while handling our samples.

Who we are and why we do this

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2012, Cesar Harada cycling alone from Tokyo to Sendai measuring radioactivity

I am Cesar Harada. I am 31-years-old French-Japanese man based in Hong Kong. Half of my family lives in Niigata, approximately 100km away from Fukushima. I am the CEO of two companies specializing in ocean robotics and shape-shifting sailing robots. I worked as Project Leader at MIT, I am a TED Senior Fellow, IBM figure of Progress, GOOD100 2014.
This was my third voyage in Tohoku and the Fukushima region. I first visited the area in 2012 when I cycled alone from Tokyo to Sendai. The second time I visited was in 2012 when we drove with Safecast and measured radioactivity with a custom underwater geiger counter. This third time in 2014, we have been able to rent a car and use a boat with which we were able to best access the underwater sediments.

When I say “we”, I refer to all the people whom have helped us along the way, our network, the fishermen, my assistant, the documentary film maker, the University Professors, researchers that shared so much knowledge, the online supporters that opened so many doors for us, the TEDx network and my students at the Hong Kong Harbour School.

I care deeply about the environment, and I am concerned with the effects of radioactivity on my family, friends, the people of Tohoku and on our shared environment overall. My dream is that one day a fleet of our sailing robots can explore and protect the oceans. I want to help, learn and share.

I admire what Safecast has achieved on land and I hope to do the same for the ocean. While we now have a lot of data about land-based radioactivity , we are missing accurate data for the ocean.

The Missing data : Seabed radiation levels

Model simulations on the long-term dispersal of Cesium-137 released into the Pacific Ocean currents off Fukushima. Link to the original paper, Behrens, Schwarzkopf, Lübbecke and Böning.

This video is an animated map of the ocean currents dispersing Cesium-137. It is NOT an indication of the ocean floor radioactivity levels.

If we compare this map with a similar map of the land, it is equivalent of having a map of the wind contamination (above land). While this type of map is very useful for oceanographers using radioactive tracers to understand ocean currents, we really need an accurate measurement of the ocean floor radiation levels in order to allow the safe return of Fukushima/Tohoku’s coastal economy and lifestyle. This includes the safe return of the coastal population, the re-opening of fisheries, allowing commercial cargo to navigate, and the return of surfers, divers, swimmers and sailors. The environmental question mark represented by the missing seabed radiation data has critical social and economical implications.

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We need a map of the ocean floor radioactivity. A “Safecast Ocean”.

For the short term, anyone living and/or working in the Tohoku region should have this radiation level information available for safety reasons.

For the long term— just like CO2 has it’s Keeling curve — Japan could be at the forefront of studying the increase of anthropogenic radioactivity in the ocean. As the Keeling curve is helping us to understand and anticipate climate change, ocean radioactivity is becoming an essential feature of our ocean chemistry, influencing ocean life evolution (including mutations). Newly developed expertise about ocean radiation and remediation could potentially become an industry that Japan could export abroad, as more nuclear accidents will happen in the future. Japan has suffered multiple catastrophes ; let’s not add to the challenges a missed opportunity to learn and possibly heal.

Why is this data Important for Japan now?

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Photo by Cesar Harada

Prejudice & Reconstruction effort
After suffering a one of the largest earthquakes on record, several tsunamis, the loss of family and friends, a triple nuclear meltdown and radioactivity in the environment, the residents of Tohoku are now suffering a lof of prejudice as some are courageously rebuilding their broken homes. This prejudice takes on many forms, and is primarily due to a lack of scientific information which has led to excess of fear and fed the media appetite for “breaking news”. Many people still will not buy products or food coming from the areas of Tohoku even if they are certified to not be contaminated. The economic impact of this causes tensions to arise. Communities are now divided between those who believe in the Government and TEPCO, and those who don’t. More significantly than radiation poisoning, depression and suicide levels have sadly increased in Japan.

Scientist responsibility, and why Open Hardware is the way
Many scientists, whistleblowers and those working in the media feel the conflicting pressure between telling the truth and remaining quiet, particularly since Japan has enforced the State Secret Law in Dec 2013 — “Hailed By U.S., Denounced By Japanese” NPR reports. In the Guardian :

Whistleblowers and journalists in Japan could soon find themselves facing long spells in prison for divulging and reporting state secrets, possibly including sensitive information about the Fukushima nuclear disaster and the country’s souring relations with China.

About six months after the State Secret Law was passed “in a shocking display of brute force” (NPR), Japan’s ruling party reinterpreted the National Constitution ; “After 70 years, nation changes the rules so it can go to war” despite of the disapprobation of the majority of the Japanese population in July 2014.

Japan’s ruling party is essentially silencing the population and preparing for war.
I believe that Japan foundations should be that of truth and peace.

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Open Hardware is one facet of promoting this truth and peace by providing transparency, collaboration, cost reduction, speed and reliability. It allows everyone to work together and expand human knowledge while providing a safer environment.

Let’s make a map of seabed radioactivity

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Photo by Julie Nagai

How are we going to produce this map of ocean radioactivity?
From my research and work with Open Hardware ocean-mapping robots, it is clear that we can develop low cost, efficient and transparent tools.
However :
A/ Who will collect samples?
B/ Who will analyze them?
C/ Who will benefit from the data?
D/ Who could suffer from the data?
E/ Who will pay?
F/ Who will review the data?
These are questions that need answers…and soon.
Please share your ideas and suggestions in the comment section.

Japan Renaissance

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Photo by Julie Nagai

We need better data. We need residents to be involved in the collection, aggregation and analysis of this data. [updated] Measurements and map.

We need transparency to unite communities again.
We need the truth to rebuild a peaceful Japan.

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