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Chernobyl Source Term, Atmospheric Dispersion, and Dose Estimation
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1989
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Environmental RadiochemistryMeteorologyEarth ScienceEngineeringChernobyl Source TermAtmospheric ScienceRadioactive ContaminationRadiation ExposureRadiation DoseRadiation MeasurementCosmic RayChernobyl EventAir PollutionAtmospheric Dispersion ModelingMedicineNuclear MedicineDosimetry
The Chernobyl source term for long‑range transport was derived by combining radiological measurements, atmospheric dispersion modeling, and reactor core inventory estimates using WASH‑1400 release fractions for specific chemical groups. Analyses showed that nearly all noble gases, 60 % of radioiodines, 40 % of radiocesium, 10 % of tellurium, and ~1 % of refractory elements were released; the cloud split into a lower plume heading to Scandinavia and an upper plume moving southeast across Asia, with inhalation doses exceeding 10 mGy near Chernobyl, 0.1–0.001 mGy in most of Europe, and <10⁻⁵ mGy in the United States, and the source term was orders of magnitude larger than Windscale and TMI but only 6 % of the ¹³⁷Cs released by U.S./Soviet nuclear tests (with ¹³¹I and ⁹⁰Sr at ~0.1 %).
The Chernobyl source term available for long-range transport was estimated by integration of radiological measurements with atmospheric dispersion modeling and by reactor core radionuclide inventory estimation in conjunction with WASH-1400 release fractions associated with specific chemical groups. These analyses indicated that essentially all of the noble gases, 60% of the radioiodines, 40% of the radiocesium, 10% of the tellurium, and about 1% or less of the more refractory elements were released. Atmospheric dispersion modeling of the radioactive cloud over the Northern Hemisphere revealed that the cloud became segmented during the first day, with the lower section heading toward Scandinavia and the upper part heading in a southeasterly direction with subsequent transport across Asia to Japan, the North Pacific, and the west coast of North America. The inhalation doses due to direct cloud exposure were estimated to exceed 10 mGy near the Chernobyl area, to range between 0.1 and 0.001 mGy within most of Europe, and to be generally less than 0.00001 mGy within the United States. The Chernobyl source term was several orders of magnitude greater than those associated with the Windscale and TMI reactor accidents. However, the 137Cs from the Chernobyl event is about 6% of that released by the U.S. and U.S.S.R. atmospheric nuclear weapon tests, while the 131I and 90Sr released by the Chernobyl accident was only about 0.1% of that released by the weapon tests.