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Public Lecture Slides (3.19.2019) Fukushima - A View from the Oceanan-english-wide(1)

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

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Public Lecture Slides (3.19.2019) Fukushima - A View from the Oceanan-english-wide(1)

  1. 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. 2. We live in a radioactive world. Where do Fukushima Dai-ichi radionuclides go in the ocean? What does the future look like?
  3. 3. Woods Hole Oceanographic Institution September 2018
  4. 4. We live in a radioactive world
  5. 5. What is radiation? • Radiationiscausedbyunstableatoms breakingdownandemittinghighenergy particles • Thenumberofthesedecayeventsper secondiscalledaBecquerel(Bq) • ThetotalnumberofBqisoftenreportedper cubicmeterofseawaterorkilogramoffish
  6. 6. There are many sources of radioactivity in our world Naturally occurring Cosmogenic Human activity
  7. 7. Radioactivity in the ocean
  8. 8. Sources of Fukushima Dai-ichi Radionuclides
  9. 9. Radioactivity in seawater
  10. 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. 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. 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. 13. Radioactivity in marine life
  14. 14. Pathways to marine life airborne surface run-off groundwater Taken up by biota in food & water
  15. 15. Radioactivity in fish DAYS WEEKS YEARS Time to it takes for radioactive contaminants to cycle through fish
  16. 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. 17. Japanese seafood monitoring is extensive Limit allowed in Japanese seafood Fish >20 km off Japan Tohoku Buesseler et al., 2017 Bq/kgCesium
  18. 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. 19. Radioactivity on the sea floor
  20. 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. 21. How is radioactive cesium transported in the ocean?
  22. 22. Ocean currents carry cesium across Pacific
  23. 23. Rossi et al., 2013, 2014, 2018 Models predict cesium moving quickly with dilution
  24. 24. How do we know the levels on the North American West Coast? OurRadioactiveOcean.org
  25. 25. Surface Ocean Cesium-137 2011-2018
  26. 26. What does the future ocean look like?
  27. 27. Sources of Fukushima Dai-ichi radionuclides
  28. 28. Radioactive decay will set future levels of any radionuclide Radionuclides will decay at different rates.
  29. 29. Ongoing sources would be detected in the ocean Real-time sensors, regular monitoring, scientific cruises 1000 Bq/m3
  30. 30. Over time cesium plume moves east and levels continue to decrease 2011 2013 2016 2019
  31. 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. 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. 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. 34. Remaining Issues
  35. 35. 1000s of tanks with radioactive cooling waters What else besides tritium is in the tanks?
  36. 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. 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. 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