Abstract
In the case of Fukushima Daiichi nuclear power plant (FNP) accident, the radioactive material was released from reactor units 1–3 and transported to short and long distances due to the atmospheric pathways-motions. Power sources for monitoring posts were lost due to earthquake and tsunami. Based on air dose rates and other data measured by monitoring cars, the amount of radioactive material released to the atmosphere from the power station was obtained. The atmospheric dispersion and the transport model used in the RASCAL code, estimate the radionuclide concentrations downwind, both in the air and on the ground due to deposition. The calculated concentrations are then used to estimate the projected doses for workers in vicinity of the accident area in the first minutes of accident time. For dose modeling, we assumed that each worker was 15 min in vicinity of FNP in accident situation, once without and once with protective clothes or respirator. According to Tokyo Electric Power Company (TEPCO) report six workers had received doses over 250 mSv (309 to 678 mSv) apparently due to inhaling Iodine-131 fume. In this paper the calculated dose results using RASCAL code shows that, if emergency workers who work in early phase of accident had not used protective equipment, for 15 min, inhalation doses from iodine in their thyroid gland up to 12 March afternoon would have been 520 mSv. A comparison between calculation results and TEPCO report shows that dose calculated virtually is nearly equal to TEPCO measurement results.
Kurzfassung
Bei dem Unfall im Fukushima-Daiichi-Kernkraftwerk wurden radioaktive Stoffe freigesetzt und durch atmosphärische Ausbreitung über kurze und weite Entfernungen transportiert. Auf der Grundlage von Dosisleistungsmessungen in Luft und Messdaten von Überwachungsfahrzeugen wurde die in die Atmosphäre freigesetzte Menge an radioaktiven Stoffen bestimmt. Mit Hilfe der im RASCAL Rechencode verwendeten Transportmodelle wurden die Radionuklidkonzentrationen in der Luft und am Boden bestimmt. Die berechneten Konzentrationen wurden dann verwendet um Dosisabschätzungen von Beschäftigten in den ersten Minuten nach dem Unfall zu machen. Für die Modellrechnungen wurde angenommen, dass sich jeder Beschäftigte 15 Minuten in unmittelbarer Nähe des Unfallortes aufhielt, mit und ohne Schutzkleidung und Atemschutzgerät. Nach Angaben der Tokyo Electric Power Company (TEPCO) haben 6 Beschäftigte Dosen über 250 mSv (309 to 678 mSv) durch Inhalation von Iod-131 erhalten. In diesem Beitrag zeigen die mit Hilfe des RASCAL-Codes berechneten Ergebnisse, dass die Notfalleinsatzkräfte in der frühen Phase des Unfalls nach 15 Minuten ohne Schutzkleidung bereits eine Dosis von 520 mSv erhalten hätten. Ein Vergleich mit dem TEPCO-Report zeigt, dass die berechneten Dosen mit den dort berichteten Dosen nahezu übereinstimmen.
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