Smoke from one of the Fukushima nuclear plant explosions billows over the sea.

26 March 2011 (Asahi Shimbun) -- Fukushima No. 1 nuclear plant, crippled by the Great East Japan Earthquake of March 11, has discharged more radiation than the infamous Three Mile Island nuclear plant in the United States, according to calculations by the central government.

It has already reached a level 6 serious accident on the International Nuclear and Radiological Event Scale (INES).

Separately, calculations made by experts place the level of soil contamination in some locations at levels comparable to those found after the Chernobyl accident in 1986.

With the Fukushima plant continuing to release radiation, there is the danger that the contaminated land will be unusable for many years.

To calculate the spread of radiation using the System for Prediction of Environmental Emergency Dose Information, the Nuclear Safety Commission of Japan estimates the discharge rate for radioactive iodine per hour from the Fukushima plant based on radiation measurements taken at various locations.

Using those figures to make a simple calculation of the amount of discharge between 6 a.m. March 12 and midnight Wednesday results in figures between 30,000 and 110,000 terabecquerels. Tera is a prefix meaning 1 trillion.

The INES defines a level 7 major accident such as Chernobyl as one in which radiation of more than several tens of thousands of terabecquerels is released.

The Fukushima accident is already at a level 6, which is defined as having a radiation discharge of several thousands to several tens of thousands of terabecquerels.

The discharge of radioactive iodine at the Chernobyl accident was said to be about 1.8 million terabecquerels. The Three Mile Island accident, which was considered the second-worst accident until now, had only a limited discharge of radioactive iodine into the outside atmosphere, but was classified as a level 5 accident because of the considerable damage done to the core. …

Meanwhile, calculations of soil contamination by experts have already produced results that are at the same level as for Chernobyl.

Cesium-137 levels of 163,000 becquerels per kilogram of soil was detected in Iitate, Fukushima Prefecture, about 40 kilometers northwest of the Fukushima plant, on March 20. That was the highest figure in the prefecture.

According to Tetsuji Imanaka, an associate professor of nuclear engineering at the Kyoto University Research Reactor Institute, if the Iitate figure was converted to one square meter, the figure would be 3.26 million becquerels.

After the Chernobyl accident, residents who lived in regions with cesium levels of 550,000 becquerels ore more per square meter were forcibly moved elsewhere.

"Iitate has reached a contamination level in which evacuation is necessary," Imanaka said. "Radiation is still being released from the Fukushima plant. The areas of high contamination can be considered to be on par with Chernobyl."

Residents who were forced to move after the Chernobyl accident were believed to have been exposed to an average of about 50 millisieverts of radiation. … 

The accumulated radiation level at Iitate as of Thursday afternoon was 3.7 millisieverts. …

[Update: IAEA concurs on Iitate: “Based on measurements of I-131 and Cs-137 in soil, sampled from 18 to 26 March in 9 municipalities at distances of 25 to 58 km from the Fukushima Nuclear Power Plant, the total deposition of iodine-131 and cesium-137 has been calculated. The results indicate a pronounced spatial variability of the total deposition of iodine-131 and cesium-137. The average total deposition determined at these locations for iodine-131 range from 0.2 to 25 Megabecquerel per square metre and for cesium-137 from 0.02-3.7 Megabecquerel per square metre. The highest values were found in a relatively small area in the Northwest from the Fukushima Nuclear Power Plant. First assessment indicates that one of the IAEA operational criteria for evacuation is exceeded in Iitate village. We advised the counterpart to carefully access the situation. They indicated that they are already assessing.” IAEA Briefing on Fukushima Nuclear Accident (30 March 2011, 16.30 UTC)]

[Update 2: Radioactive fallout forces evacuation of babies and pregnant women from Iitate village]

Radiation from Fukushima exceeds Three Mile Island


  1. Gail said...

    Aren't you glad you don't have children?  


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