Contamination of Japan – 8 Fallout Map – Deposition from the Fukushima Event.

Fallout Map – Deposition from the Fukushima Event.

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Radiological Assessment of effects from Fukushima Daiichi Nuclear Power Plant

Publication Date April 7, 2011


• Aerial Measuring Systems have totaled more than 262 flight hours in support of aerial monitoring operations
• NNSA’s Consequence Management Response Teams have collected approximately 100,000 total field measurements
taken by DOE, DoD, and Japanese monitoring assets
• 240 total air samples taken at US faciliDes throughout Japan undergoing lab analysis in the US


US radiological assessments are composed of aerial and ground measurements and indicate radiation levels from material that has settled on the ground
• Each measurement corresponds to the radiation a person receives in one hour at that location. AMS data is presented as
exposure rate 1 meter from the ground at the time the measurements occurred
• All measurements outside the Fukushima power plant site boundary are below 0.013 REM per hour – a low but not
insignificant level


An assessment of measurements gathered through April 6 continues to
• Rapid decay of deposited radiological material indicating Radioiodine is the most significant component of dose
• Radiation levels consistently below actionable levels for evacuation or relocation outside of 25 miles; and levels conDnue to decrease
• No measurable deposit of radiological material since March 19
• US bases and facilities all measure dose rates below 32 microrem/hr(32 millionths of a REM) – a level with no known health risks
• Agricultural monitoring and possible intervention will be required for several hundred square kilometers surrounding the site:
• Soil and water samples are the only definitive method to determine agricultural countermeasures
• Ground monitoring can give better fidelity to identify areas that require agricultural sampling


• The Nuclear Regulatory Commission estimates that the average
American absorbs 620 mRem a year* (or 0.071 mRem/hour)
• An average transatlantic flight produces an exposure of 2.5 mRem*
• A typical chest x‐ray produces 10 mRem per image
• EPA guidelines call for public health actions if exposure exceeds 1000 mRem over 4 days
* Source: NRC: hTp://‐nrc/radiation/factoid2‐lrg.gif