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Wednesday, 27 August 2014

Japan Researchers: Models show North America hit with ‘very high’ levels from Fukushima plume — Radioactive material in ocean off West Coast was up to 500 times more than expected


Source term estimation of atmospheric release due to the Fukushima Dai-ichi Nuclear Power Plant accident by atmospheric and oceanic dispersion simulations, Japan Atomic Energy Agency, 2013 (emphasis added):
  • FNPP1 accident widely dispersed radionuclides across the entire North Pacific region… simulation results in some area of the eastern North Pacific showed a tendency of underestimation against observed data… the simulation results in the eastern North Pacific [for 134Cs] were also lower than the measurement results. This tendency indicates that the actual abundance of 134Cs in the eastern North Pacific was higher… We attributed this tendency to an underestimation of the release rate in the initial source term… source term was estimated on the basis of environmental monitoring data on land. However, monitoring data in the ocean were not considered… accuracy of the initial source term [from March 12-14] was low…  it was impossible to classify the volume of the amount released as a result of [Unit 3's] explosion.
  • Cesium-134 simulation with the new source term… the new source term increased the traffic transport of radionuclides to the east… the new release rates at all 18 terms increased… However, the simulation results [using new source term] in some areas of the eastern North Pacific remain underestimated.
Note: Rightmost point inside large oval in the graph above shows a calculated (i.e. estimated) Cs-134 level of below 2E-05 Bq/L (.02 Bq/m³). The observed CS-134 level exceeded 1E-02 Bq/L (10 Bq/m³) — 500+ times than estimated.

94th Annual American Meteorological Society Meeting, 2014:
  • The Science Council of Japan launched a model intercomparison project to review the capability of current numerical models to reproduce the transport of radioactive materials released to the environment as a result of the Fukushima Dai-ichi Nuclear Power Plant… results show relatively good agreement of the deposition pattern of 137Cs, indicating significant deposition of 137Cs over the northwestern Pacific up to the Aleutian Islands, and reaching to the western part of North America.
  • 7:30 in — TY Tanaka, Japan Meteorological Agency: This map shows the horizontal distribution of cesium-137. As you can see, they show similar patterns of results from Fukushima power plant to the northwest Pacific Ocean and to the Aleutians. Some models reach very low North America — but some of them reach very high  
  •  Source: Watch Tanaka’s presentation here
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