Many sources of radioac=vity

Transcription

1 Radionuclides in the ocean Ken Buesseler Department of Marine Chemistry and Geochemistry Woods Hole Oceanographic Ins;tu;on Woods Hole, Massachuse>s, USA h>p://cafethorium.whoi.edu Yokohama June 2011

2 Many sources of radioac=vity - We live in a sea of radioac=vity - Natural sources are larger than man- made sources - Danger is in the dose - one banana = 12 Bq 40 K - need to eat 20 million banana s go get dose of radia=on concern - We can measure less than 1 Bq 1 Bq = 1 Becquerel = one radioac=ve decay per second 1 PBq = peta- Becquerel = one million billion Bq = 1,000,000,000,000,000 Bq - In the ocean (and human body) different radionuclides have different fate and toxicity Ken Buesseler WHOI

3 Various Routes to the Ocean: Boundary Condi5ons 80% Fukushima contamina=on in ocean There are s=ll some uncertain=es on where and how much of different radionuclides were released to the environment. Mid- March 5 30 P Bq P (peta) = small and con=nues small and con=nues? ASer late- March (3 15 P Bq) small source today

4 One year history of cesium- 137 in ocean immediately off Fukushima one banana Levels prior to March 11 Data from TEPCO At nuclear power plant Ocean Cs levels peak on April 6th - possible reproduc=ve effects and mortality for marine biota US drinking water limit April 1 June 1 Aug 1 Oct 1 Dec 1 Feb Levels of concern for seafood Highest ocean levels post Chernobyl - Fukushima NPP represents unprecedented release of radionuclides to the ocean - levels decreased rapidly, then leveled off - so reactors are s=ll a source (through Sept. 12) - but levels now safe for marine biota & human exposure - what about seafood?

5 JCOPE2 model Masamoto et al. JAMSTEC (Bq/L)

6 JCOPE2 Tracer- Run <Observed data is assimilated =ll June 16, 2012> Nov May Kuroshio current important 2011 for Aug rapid cesium transport Mar 2012 Posi=on of >10 Bq m - 3 (Bq/L)

7 Cesium- 137 today off Japan Fukushima Dai- ichi Nuclear Power Plant Power plant >0.3 TBq/month River water <<1 TBq/month Seawater 15 TBq (TBq = Bq) River sediment 0.8 TBq/month Kanda et al TUMST Seafloor 94 TBq

8 Lessons learned Fukushima NPP represents unprecedented release of radionuclides to the ocean off Japan Easier to measure Cs than to determine health effects Many reasons for study- Human health- internal/external dose assessments Radioecology- marine biota & fish Modeling/predic5ons of future accidents Japan is leading studies, but more work is needed than any one lab, or any one country can take on Confirma5on by mul5ple interna5onal and independent labs will build public confidence in Japan (and increase scien5fic insights) Studies of fish are not enough- need long term studies of ocean, seafloor, rivers, etc.

9 Sponsors of today s event Arigatou Gozaimasu!

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11 What about fish off Japan- where are fish most contaminated? - highest off Fukushima Bomom dwelling fish only Data source- Japan Fisheries Buesseler, in review for Science

12 What types of fish are most contaminated? - bomom fish & freshwater fish - s=ll high aser 1 year - variability unpredictable - 18% of fish reported are above limit Data source- Japan Fisheries Buesseler, in review for Science Ken Buesseler WHOI

13 Leak from the plant 137 Cs release in summer 2012 Harbor- water: 2.3 x 10 6 m 3 Exchange rate: 0.44 day - 1 (6 19 April 2011) Average 137 Cs at Unloading dock : 9.9Bq L - 1 (1 April 30 September 2012) 10 GBq day TBq month - 1 Plant harbor Unloading dock 137 Cs radioac=vity (Bq/L) 0.44 day Bq L Cs radioac=vity at Unloading dock inside the plant harbor Data source: TEPCO

14 Highly- contaminated water under the plant Water volume (m 3 ) 137 Cs Volume 137 Cs inventory (PBq) Remaining 137 Cs 156 PBq (May 2011) 3 PBq (September 2012) Processed 137 Cs 220 PBq (June 2011 September 2012) Diluted by groundwater inflow Possible groundwater seepage from nearby seafloor??? Contaminated water underneath the reactor/turbine housings of Reactors 1-4 Calculated by JK based on data released by TEPCO

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16 Radioac=vity in the Oceans - We live in a sea of radioac=vity Three Mile Island Fukushima 8-45 PBq Cesium- 137 Chernobyl 85 PBq Global fallout 1960 s 400 PBq - Natural sources are larger than man- made sources - Danger is in the dose - one banana = 10 Bq - need to eat 20 million banana s go get dose of radia=on concern - We can measure less than 1 Bq - In the ocean (and human body) different radionuclides have different fate and toxicity 1 Bq = 1 Becquerel = one radioac=ve decay per second 1 PBq = petabecquerel = one million billion Bq = 1,000,000,000,000,000 Bq Oceanus, June 2012 Ken Buesseler WHOI

17 Wed. Nov. 14th 16:00 Ito Hall U. Tokyo Public Event- panel w/ Q&A Special Oceanus issue on Fukushima and the ocean Goal is to bring content of our presenta5ons and discussions to general audiences Hard/web copies early May 2013 In English and Japanese Coincides with 2nd Colloquium in Woods Hole

18 Exploring the impacts of the Fukushima Dai- ichi Nuclear Power Plants on the Ocean goal: present a scien=fic review of what we know and don t know about contaminants released at Fukushima, their fate in the ocean, and their poten=al to impact marine ecosystems and human health What are the lessons learned? Goal is to inform, not alarm

19 government agencies 19% other founda5ons, companies 11% symposium par5cipants ocean scien5sts 29% nuclear/health physics 11% media- print, TV, Japan, interna5onal 13% academics- policy, law, economics, history 17%

20 JCOPE2 Tracer- Run <Observed data is assimilated =ll June 16, 2012> Kurashio current important for cesium transport (Bq/L)

21 ? 134 Cs / Bq m /11 5/10 7/9 9/7 11/6 1/5 3/5 5/4 7/ Date? LNT??!

22 Summary of sources and fate of Fukushima Cs in the ocean Direct ocean discharge PBq FNPP Rivers Atmospheric fallout PBq Rapid offshore transport >99% Cs soluble groundwater? sinking marine snow ver=cal mixing seafloor burial 0.04 PBq? remineraliza=on near bomom sediment flow