Fukushima NPPs Potential Impact on the Marine Environment, 28 March 2011

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  • 1. Marine Environment - Fukushima NPPs Potential Impact on the Marine Environment – Assessment of IAEA Environmental Laboratories on Data provided by Japan IAEA-Environmental Laboratories, Monaco
  • 2. General Comments
    • Contamination of the marine environment has occurred both by fallout or washout and discharges of contaminated water into the sea
    • Japanese Institutes continue to perform measurements in sea water about 330 m east of the discharge as well at a North-South transect about 30 km off-shore
    • Concentration data were reported for several days and they show quite heterogeneous distribution, as expected
    • Data on dose rates above seawater were also reported and they showed only slightly elevated levels
    • It is assumed that the contamination at the monitored stations 30 km off-shore is also due to fallout and washout from air contamination
    • It can be expected that the initial levels will decrease soon by dilution into deeper layers and dispersion by ocean currents
  • 3. Seawater sampling off Fukushima (26 March 2011) carried out by Japanese Authorities
    • Seawater sampling locations of Japanese Authorities
    • Transect about 30 km offshore, sample locations separated by 10 kilometres
    • Levels of dose rates were also measured as indicated
  • 4. Seawater sampling off Fukushima (24 March 2011)
    • Seawater sampling locations
    • Repetition of the transect about 30 km offshore at the 24 th March
    • Levels of dose rates are included
  • 5. Temporal trend on concentrations Data submitted by Japanese authorities Cs-137
  • 6. Temporal trend on concentrations Data submitted by Japanese authorities I-131
  • 7. Monitoring of the Marine environment
    • Comparison of Cs-137 seawater concentration with historical data
    • 30 km offshore surface water concentrations are 3 to 4 orders of magnitude higher than the values measured in 2005
    • 330 m East of Fukushima Dai-ichi concentrations are up to 3 orders of magnitude higher than the values measured offshore
    1 10 3 10 4 10 5 10 6 10 2 10 1 10 7 10 8 April 2005 30 km Bq.m -3 [1 – 10 1 ] 1 10 3 10 4 10 5 10 6 10 2 10 1 10 7 10 8 24, 25 March 2011 Bq.m -3 [10 3 – 10 4 ] [10 5 – 10 7 ]
  • 8. Conclusions
    • Measurements of the marine environment was carried out by Japanese authorities since 23 March and data reported to the IAEA for information and assessment.
    • Measurement were done at 30 km off-short section on 8 locations, on 26 March on 4 Stations.
    • I-131 and Cs-137 were detected with highest activity concentration of about 80 Bq/L and 26 Bq/L in surface layer, respectively, at the 23 and 24 March.
    • Data were reported for 26 March and they show now decreasing trend between 6 and 18 Bq/L for I-131 and „not detectable“ and 16.4 Bq/L for Cs-137.
  • 9. Conclusions
    • Dose rates were also given above seawater level on 26 March. They are between 0.041 and 0.100 micro-Sv/h
    • Levels at about 330 m east of the discharge area showed increasing concentrations with 74000 Bq/L for I-131, 12000 Bq/L for both radionuclides Cs-134 and Cs-137
    • Modelling of the dispersion of radionuclides was initiated and first results were available. The results show an initial transport into north-east direction and the contaminated seawater could reach the 30 km off-shore sampling section between 7 and 14 days after release
    • It can be expected that the marine dispersion will take months or years to reach other riparian Pacific countries. At resent, the main transport of contamination takes place by atmospheric transport over long distances with high dilution capacity.