Friday, April 26, 2013

Long Shadow of Chernobyl: 224 Bq/kg of Cesium-137 in the Ashes from Burning Wood Pellets Made from Trees in Shikoku

And of atmospheric testing of nuclear weapons by world nuclear powers, which did not stop until 1980 (China).

One of my twitter followers lives in southwestern Japan. A while ago he sent me the result of the test he had it done with the ashes from burning wood pellets in his stove this winter. The lab test, using the germanium semiconductor detector, found 223.8 Bq/kg of cesium-137.

He was upset, thinking it is from Fukushima I Nuclear Power Plant, until I pointed out to him that there was no cesium-134 found. The cesium in the ashes is most likely from the fallout from atmospheric testing, and the Chernobyl accident in 1986.

He burned 600kg of wood pellets made from cedar trees in Ehime Prefecture in Shikoku Island in southwestern Japan. According to the pellet manufacturer, the concentration factor was about 375, and radioactive cesium (Cs-137) in the pellets was estimated to be about 0.59 Bq/kg.

He said he will "entomb" the ashes with concrete and bury.

The chart plotting the historical monthly fallout in entire Shikoku (4 prefectures, as they didn't start measuring the fallout in Ehime until 1977) shows the spike from the Chernobyl accident was less than that of the atmospheric testing, and larger than that from the Fukushima accident. (The chart was created from data at Japan Chemical Analysis Center. Y-axis in log scale.)

In 2012 he tested the ashes from burning the wood pellets from a different company, and to his great dismay the test found 1,000 Bq/kg of radioactive cesium (Cs-137) in the ashes. He had already spread some of those ashes on his home garden. Those pellets, it turned out, were made from trees from Europe (Sweden, Finland, Germany, Austria) that the manufacturer had started to purchase in 1994 . That manufacturer told him that it had never ever occurred to them that the trees were contaminated from the Chernobyl accident, and there was no regulation on importing. The manufacturer told him that they chose European trees because they were cheap, and supply was steady.

April 26 marks the 27th anniversary of the Chernobyl Nuclear Plant accident.


Anonymous said...

This is expectable: Cs fallout was heavy in specific places of Europe outside ex-USSR, of which regions of three countries you mention: Austria, Finland & Sweden:

Wood ash contains a lot of potassium (the name literally comes from "pot ash"): ca. 10%.
As most plants and animals, trees quite indiscriminately take up cesium together with potassium. At 10%, the natural K-40 radioactivity of ash would be expected to be 10% of 31'000 Bq/kg, so ~3'000 Bq/kg.

So 224 Bq/kg Cs may seem a lot, but even if 100% of your food is plants grown from such ash, you'd add something like 10 µSv/year to your dose (one exception: mushrooms, which specifically concentrate Cs).

Did your contact check for strontium (which similarly fills in for calcium, the main metal in ash)? Strontium emissions were high for Chernobyl…

Anonymous said...

In this case, measuring contamination in Bq per kilo also makes the numbers look big, but ash is a light material and you I guess would not use so many kilos of ash to fertilize your field?

Anyway, I saw an article about Cs-137 contamination in Japanese wild mushrooms before 2011 and in many cases they were higher than 100 Bq/Kg. Probably the same for wild berries.

Anyone interested already knew that there are detectable amounts of Cs-137 (and Sr-90, and plutonium, etc...) all over the planet, though, the problem is that after Fukushima there is more of it and the whole thing was preventable.

VyseLegendaire said...

Fukushima, meet your long lost big brother :)

Anonymous said...

hehe! as i live in the uk i really aappreciated how you delivered th punch line!! classy!

Those pellets, it turned out, were made from trees from Europe

near bottom of the article! haha!
posting this one to the subs!! quite a few europeans too! haha! should catch em out nicely!!
keep up the good work admin!!
you are appreciated you know!

Anonymous said...

I suggest comments could be written with a little more care in order to be understandable. Not everyone is a native english speaking person, nor has the same field of obvious meanings, and BTW Fuku's elder brother Tch. never was lost and seems as strong and alive just as Johnny Walker pretends to be - you'll probably have some information of the catastrophic health records related to Tchernobyl with this sad anniversary.

arevamirpal::laprimavera said...

Anon at 6:01AM, you do use many kilos of ashes to fertilize the garden, not even the field. Just my personal experience.

Atomfritz said...

Another brilliant article from Ex-SKF! Thank you!

Just to clear things up, the observed radioactivity of wood pellets varies quite a lot.
A big problem is that comparison is very difficult as it depends very much on the woods actually getting pelleted. Some tree species produce more(=less concentrated), other produce less (=more concentrated) ash.

According to a report of the renowned German "test" magazine of the "Stiftung Warentest", the Cs-137 radiation found in pellets from various European (non-Russian and non-Ukrainian, but including countries like Czechoslovakia) countries doesn't exceed 7 becquerels/kg.
However, they also found out that pellets of 6 Bq/kg resulted in ashes of 440 Bq/kg (wood species undisclosed).

I find much more disturbing what happens at Russian/Ukrainian forest fires.
Remember, the radiation in the (in?)famous Red Forest in the Ukraine, 27 years after the accident, still is near 0.1 millisievert/h.

Vast areas in Russia and Ukraine (far larger than Japan) are so radioactive that every larger forest fire releases trillions of Bq of Cs-137 and creates many new hotspots, constantly changing the radiological situation of vast areas in spite of the fact that Chernobyl is almost three decades ago.

However, the wood produces there are normally exported only for construction and paper production purposes, not for heating use. Thus there is no radioactivity checking. By the way, this lumber is _very_ cheap in the carpenters shops.

I'd really like to know more data about the Strontium , but nobody seems to be eager to boast with their free added value :(

(More reading,in German: )

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