Fukushima- A View From The Ocean Ken Buesseler, Senior Scientist, Woods Hole Oceanographic Institution, USA

1. Fukushima Dai-ichi:Aview from the ocean
Ken Buesseler, Senior Scientist
Woods Hole Oceanographic Institution
福島第一 海からの眺め

2. We live in a radioactive world.
Where do Fukushima Dai-ichi radionuclides
go in the ocean?
What does the future look like?

3. Woods Hole Oceanographic Institution
September 2018

4. We live in a
radioactive world

5. What is radiation?
• Radiationiscausedbyunstableatoms
breakingdownandemittinghighenergy
particles
• Thenumberofthesedecayeventsper
secondiscalledaBecquerel(Bq)
• ThetotalnumberofBqisoftenreportedper
cubicmeterofseawaterorkilogramoffish

6. There are many sources of radioactivity in our world
Naturally
occurring
Cosmogenic Human
activity

7. Radioactivity in the ocean

8. Sources of Fukushima Dai-ichi Radionuclides

9. Radioactivity in seawater

10. How high were radioactivity levels near Fukushima Dai-ichi in 2011?
The accident in 2011
represents an
unprecedented release
of radionuclides into the
ocean
Buesseler, Aoyama, Fukasawa, 2012
Levels off Japan prior to March 11, 2011
Highest levels in ocean after Chernobyl
Cesium-137

11. How did cesium levels near Fukushima Dai-ichi change since 2011?
Levels decreased rapidly
and then leveled off
Cesium remained at
more than 1000 Bq/m3
through end of 2015
Reactor site remains a
source
Levels prior to March 11, 2011
Japan Nuclear Regulatory Agency, 2019
Cesium-137

12. What are levels of concern?
Direct health effects on
marine biota
Concern with
consumption of seafood
Below concern for seafood
or swimming
Japan Nuclear Regulatory Agency, 2019
Japanese drinking water limit
Cesium-137

13. Radioactivity in marine life

14. Pathways to marine life
airborne
surface
run-off
groundwater
Taken up by biota
in food & water

15. Radioactivity in fish
DAYS WEEKS YEARS
Time to it takes for radioactive contaminants to cycle through fish

16. Demersal (bottom dwelling) fish
Fish near
Japan off
Fukushima
remained
high in
cesium for
the first two
years
Limit allowed in Japanese seafood
Buesseler, 2012
Bq/kg
Bq/kg
Cesium

17. Japanese seafood monitoring is extensive
Limit allowed in Japanese seafood
Fish >20 km off Japan Tohoku
Buesseler et al., 2017
Bq/kgCesium

18. Levels of radioactive cesium in fish are decreasing
Seafood caught above Japan’s radiation limits
2011
Near Fukushima
2015
Near Fukushima
2011-2018
U. S. West Coast

19. Radioactivity on the sea floor

20. Radioactive cesium in top 10cm of seafloor sediments
Less than 1% of radioactive cesium released
from reactors found in sea floor sediments
Highest close to Fukushima Daiichi Nuclear
Power Plant
Highest in fine-grained sediments
Long-term repository: years to decades
Buesseler et al., 2017

21. How is radioactive cesium
transported in the ocean?

22. Ocean currents carry cesium across Pacific

23. Rossi et al., 2013, 2014, 2018
Models predict cesium moving quickly with dilution

24. How do we know the levels on the North American West Coast?
OurRadioactiveOcean.org

25. Surface
Ocean
Cesium-137
2011-2018

26. What does the
future ocean look like?

27. Sources of Fukushima Dai-ichi radionuclides

28. Radioactive decay will set future levels of any radionuclide
Radionuclides will decay at different rates.

29. Ongoing sources would be detected in the ocean
Real-time sensors, regular monitoring, scientific cruises
1000 Bq/m3

30. Over time cesium plume moves east and levels continue to decrease
2011
2013
2016
2019

31. More than 50,000 fish have been tested
No fish above Japanese limit have been found since April 2015
Fish in ocean > 20 km from Fukushima Dai-ichi. Data from Fisheries Agency of Japan, MAFF
2011 2012 2013 2014 2015 2016
>100 Bq/kg <100 Bq/kg Fraction above limits

32. Levels in fish will remain elevated for decades
15-30 years after Chernobyl
Average = 6.9 Bq/kg
4 years after 2011
Average = 2.3 Bq/kg
Baltic Sea
Fukushima
Chernobyl
Fish in North Pacific
average 0.3 Bq/kg

33. Seafloor sediments are variable and decreasing
Baltic Sea
Fukushima
Chernobyl
0
200
400
600
800
1,000
Mar-11 Mar-12 Mar-13 Mar-14 Mar-15 Mar-16 Mar-17 Mar-18 Mar-19
Surface seafloor near Fukushima Dia-ichi NPP
Japan Nuclear Regulation Authority, NRA
Cesium-137Bq/kg

34. Remaining Issues

35. 1000s of tanks with radioactive cooling waters
What else besides tritium is in the tanks?

36. Storage Tanks
Large volume and increasing
Tritium is difficult to remove from tanks
Cleanup is not 100% effective for all
radionuclides
• If diluted and released slowly, limits might not be exceeded
• All nuclear power plants release tritium, low health risk
• Ocean contains thousands of times more tritium from
nuclear weapons testing and natural sources
• Ruthenium-106, strontium-90, technicium-99 reported to be
still at levels of concern in tanks
• Approaching 1 million tons

37. Cesium microparticles
• A small fraction of initial release
found in high-intensity, small
particles
• Doesn’t impact total radioactivity
• Health impacts if inhaled poses
risk that needs further study
Credit: Dr. Satoshi Utsunomiya
• Microparticles are not uncommon
from other sources

38. We live in a radioactive world.
There are many sources
Where do Fukushima Dai-ichi radionuclides
go in the ocean?
Seawater, marine biota, marine sediments
What does the future look like?
Ongoing sources, lingering radioactivity, continuous monitoring
and research needed