Verification of screening level for decontamination implemented after Fukushima nuclear accident

Abstract

The screening level for decontamination that has been applied for the surface of the human body and contaminated handled objects after the Fukushima nuclear accident was verified by assessing the doses that arise from external irradiation, ingestion, inhalation and skin contamination. The result shows that the annual effective dose that arises from handled objects contaminated with the screening level for decontamination (i.e. 100 000 counts per minute) is <1 mSv y−1, which can be considered as the intervention exemption level in accordance with the International Commission on Radiological Protection recommendations. Furthermore, the screening level is also found to protect the skin from the incidence of a deterministic effect because the absorbed dose of the skin that arises from direct deposition on the surface of the human body is calculated to be lower than the threshold of the deterministic effect assuming a practical exposure duration.

Public health response and medical management of internal contamination in past radiological or nuclear incidents: A narrative review

“…Evacuees were screened for contamination using Geiger-Mueller (GM) survey meters ( Kondo et al, 2013 ). The number of persons screened during 11–21 March 2011 was 72,660, reaching 244,281 by 10 February 2012 ( Ogino et al, 2012 ; Kondo et al, 2013 ).…”

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“…I turned my attention to the screening levels that were being applied to surface contamination of body surfaces and objects. It was found that even if surface contamination equivalent to the screening value existed on an item, the radiation dose would be below the intervention exemption level (Ogino et al., 2012). Subsequently, operational levels for the unconditional release of non-food commodities from the areas affected were proposed (Ogino and Hattori, 2013).…”

Application of Reference Levels in the Existing Exposure Situations

“…The results exhibited that the whole-body effective dose from the material was below 1 mSv per year, which was the lower limit of source-related reference level, and that the local skin-absorbed dose was also lower than 1 mGy per hour. By considering a realistic exposure time, the skin was observed to be protected from deterministic effects such as hair loss and ulcers (threshold is of the Gy order) 4) . On August 29, 2011, the NSC recommended that the screening levels should be reduced in phases to prevent further expansion of contamination by radioactive materials outside the evacuation areas (restricted areas).…”