An expert from the Nuclear Waste Management Organization of Japan has calculated more alarming radioactive contamination estimates for the surrounding Fukushima area

With Tepco releasing reliable data the way Enron disclosed its financials on the way down, independent experts have felt compelled to calculate and come forward with various estimates of their own. At a recent policy setting meeting with the Japan Atomic Energy Commission, Dr. Tomio Kawata, utilizing whatever reliable isotope release data he could get his hands on (the non-Tepco variety), shed further light on how heavily contaminated the soil is in areas northwest of the plant.

"According to Kawata, soil in a 600 square kilometer area mostly to the northwest of the Fukushima plant is likely to have absorbed radioactive cesium of over 1.48 million becquerels per square meter, the yardstick for compulsory migration orders in the 1986 Chernobyl catastrophe.

Kawata also said soil in a 700 square km area is likely to have absorbed 555,000-1.48 million becquerels per square meter, which was a criteria for temporary migration during the Chernobyl disaster.

Kawata estimated the soil contamination using data on radiation levels in the air monitored by the Ministry of Education, Culture, Sports, Science and Technology.

The size of the contaminated areas in the Fukushima crisis is one-tenth to one-fifth of those polluted in the Chernobyl disaster, Kawata said.

While the expected radiation exposure from 1.48 million becquerels of cesium is around five millisieverts a year, below the government’s benchmark of 20 millisieverts for evacuation orders, decontamination will still be necessary before evacuees can return as radioactive cesium binds strongly to soil, making it hard to reduce radiation levels, Kawata said."

Since this seems to be as legit as the Fukushima-Chernobyl comparisons get, let's pull up a map of the Chernobyl control-zone to get a visual idea of Dr. Kawata's numbers and their implications:

1.48 million Becquerels/m² = 40 Curies/km²

600 km² of area in the Fukushima Prefecture have radioactivity equivalent to the confiscated/closed zones on this map (red).  An additional 700 km² of area fit the "permanent control zone" criteria (dark pink), as it stands in Chernobyl today.

Edit:  Here's a recently released French IRSN map based on MEXT data.  This map breaks down the isotope concentration in the Fukushima and surrounding area:

Source:  IRSN.fr

How long will it take for Cs-137 to work it's way out of the environment?  Considering the Chernobyl situation further, we can see from the following chart that a long, slow slog in dose rate reduction is ahead for Japan as well. Measurements are in air, with Cs-137 as the main contributor.

Source: Wikipedia

Read the original story here