Radioactive Japan: Strange Case of 1,660 Bq/kg of Cesium from Ornamental Apple in Abiko City, Chiba

When I saw the tweet, I thought it was another prank. The tweet had a link to a PDF file about the high levels of radioactive cesium in one tree in the yard of a resident in Abiko City located on the west corridor of Chiba with relatively high radiation contamination. The web address of the link indicated it was from the city government, but there was no mention of the city in the document. So I went to the homepage of Abiko City, and see if I could find the same document from the links at the homepage.

Well I could. After 4 clicks, I landed on this particular page which has a link to the PDF: http://www.city.abiko.chiba.jp/index.cfm/18,101468,241,1019,html

The apple in question was brought by a city resident and tested on August 20, 2012 using the city's NaI scintillation survey meter. As the number was extraordinarily high, the city sent officials to the resident's home to collect more samples and tested them using the germanium semiconductor detector to be more precise. The result using the germanium detector was even higher.

The city says it was cautious in releasing the information, for fear that it might generate "baseless rumors". The amount of radioactive cesium in the apples, leaves and branches from the particular tree was extremely high, and couldn't be explained by comparing it to the samples taken in the same yard and in the neighborhood.

The apple tree is an ornamental apple tree, though the fruit is edible. It was planted by the resident of the house about 6 years ago when the resident moved in. The resident brought the apple to the city's testing lab, and the test was conducted on August 20, 2012.

I am pasting Beppe’s response to you on the OT article website (Ex-skf.blogspot.com) here in case others have missed it. Beppe’s answer was just so much more precise than mine.

“Anonymous said...

@anonymous banana

Bananas at 31,000 Bq/kg??? come on.

Let me try to redo the arithmetic:

As you say, 1 banana contains .5gr of K and 1gr of K emits 31 Bq.

1 banana therefore emits 15Bq.

1 banana weights 120gr, hence 1kg of bananas contains 125Bq

This contaminated apple contains 1660Bq/kg, hence this apple is 13 times more radioactive than bananas (per kg). A banana weights about half an apple, hence it takes 26 bananas to match this apple dose rate.

Furthermore, if we compare apples to apples, an apple contains .2gr of potassium and weights 250 gr so 1 kg of apples contains .2*1000/250*31 = 25Bq of potassum. It takes therefore 1660/25=66 clean apples to match the dose rate of the contaminated one.

But there is more: Cesium has a biological half life of 70 days whereas potassium is 30 days; the internal exposure caused by this apple is therefore 70/30*66=154 times larger than the exposure of a clean apple.

Your comparison describes clean bananas as 18 times higher than this apple; my comparison evaluates clean apple as 154 times lower than the contaminated apple so we are apart by nearly 2800 times.

Readers should also note that this kind of estimates are still very approximate (aside from any mistakes I might have made, I am not a professional in the field). Some discussion can be found under the Criticism section at http://en.wikipedia.org/wiki/Banana_equivalent_dose.

Furthermore the above calculation does not take into account differences in terms of site of accumulation of cesium vs. potassium.

Beppe”

Uhmmm....did you follow what Justa-HairyApe wrote? The Japanese say that the three fuel cores are no longer in the reactors. Is it likely that they...ahem...exited the reactors without dispersing the radiation? Tons of it?

Don’t you think a few people took a few measurements following Hiroshima? Ya know, radiation levels in Japan over time?

METI (Japanese govt. released survey results which indicated elevated radiation levels everywhere on the mainland (yes - I mean everywhere) As much as Japan/Tepco have been lying about all this- do you think they would have missed the opportunity to claim that the complete blanketing of the mainland with varying levels of radiation (the map they distributed was color coded to show the disappointing news that low level radiation contamination stretched from north to south - then was concentrated in fukushima with large hot spots north west) was there before the disaster? Uhmmm... no.

How about the hot spots? The exclusion zones? Chunks of fuel that prompted them to flag areas as impassible? Uhmmm...the photographs of the explosions blowing the domes off the power plants along with fuel assemblies? How about the oceanic surveys indicating high levels of radiation dispersed off the east coast (fukushima region?). The SPEEDI Data that METI withheld from the public showing the dispersal of radiation? No?

How about the power plant sensors that detected radiation at the start of the catastrophe? Before the tsunami hit, sensors detected radiation release - now that implies an elevation over background.

It’s spectacular how nuke pimps pretend all of the Ukraine contamination is a rumor, the medical studies are all hysterical old wives tales, and that Japan can blow tons of fuel out of three power plants (with water, air, and heat) and not elevate radiation in the environment. It’s just like magic! SELF SERVING TWO FACED LYING magic! You don’t have a ‘basis’ for your argument, you have PR magic.

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