Researchers at the Japan Atomic Energy Agency have just published a scientific paper reporting on detailed source term estimation for the airborne release from the Fukushima Daiichi Plant. The paper in “Journal of Nuclear Science and Technology” can be found here. The authors utilize the SPEEDI predictions with unit release rate in combination with a source term inversion, similar to the methodology they have employed for Chernobyl. Their analysis reveals that the greatest release from the Fukushima reactors occurred in the late morning/early afternoon of March 15. Later that afternoon and early evening, rain deposited cesium and iodine in a plume created by winds directed toward the northwest. (See SPEEDI prediction of this event). The authors estimate a 6-hour release on March 15 (from 9 AM to 3 PM JST) of 10^(16) Bq/h of radioactive iodine occurred.
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