Thursday, March 8, 2012

Plutonium-241 of Fukushima Origin Found 32 Kilometers from the Plant, Says National Institute of Radiological Sciences After Nearly One Year

The National Institute of Radiological Sciences (NIRS) knew about it since May last year, but decided to keep quiet. Why? It's yet another case of the researchers waiting until their data collection is published in a peer-review scientific magazine (the paper is linked at the bottom of the post).

For the NIRS researchers, their data has just been published in the UK's Scientific Reports (electronic version), reports Kyodo News (3/8/2012):


The National Institute of Radiological Sciences (NIRS, in Chiba City, Chiba) published the result of their measurement of plutonium-241 at three locations in Fukushima Prefecture 20 to 32 kilometers northwest and south of Fukushima I Nuclear Power Plant in the electronic version of the UK's science magazine "Scientific Reports" issued on March 8, 2012.

 人体に影響のないレベルだが、プルトニウム241は他の同位体に比べて半減期が14年と比較的短く、崩壊してできるアメリシウム241は土壌を経由して主に豆類に取り込まれやすい。放医研は「内部被ばくを避けるためにも 原発20キロ圏内での分布状況を確かめる必要がある」としている。

The level [of plutonium-241] will not affect human health. Plutonium-241 has relatively short half life of 14 years compared to other isotopes of plutonium. It decays into americium-241, which is easily absorbed through soil into legumes. The NIRS says "To avoid internal radiation exposure, it is necessary to survey the spread of plutonium-241 inside the 20 kilometer zone around the plant."

 昨年4~5月に採取した福島県飯舘村、浪江町の森林の落ち葉と、スポーツ施設で現在事故対応拠点となったJヴィレッジ(広野町など)の土から検出。他の同位体プルトニウム239(半減期2万4千年)、240(同6600年)も検出 、同位体の比率から今回の事故が原因と分かった。

[Plutonium-241] was detected from the samples they collected in April and May last year - the dead leaves from the forests in Iitate-mura and Namie-machi, and the soil at J-village, which has been used as the staging area for the work after the Fukushima I Nuke Plant accident. Other isotopes of plutonium, plutonium-239 (half life 24,000 years) and plutonium-240 (half life 6,600 years), were also detected. From the ratio of isotopes, the NIRS researchers concluded that they were from the Fukushima nuclear accident.


The density of plutonium-241 [detected this time] is higher than that being detected in Japan after the atmospheric nuclear tests in the past. However, plutonium-241 has a short half life, and the density is lower than that during the 1960s when the radioactive fallout from the nuclear tests fell on Japan.


Plutonium is a radionuclide that hardly exists in nature. It is created when uranium in the reactor fuel absorbs neutrons.

Hmmm. If you want to avoid internal radiation exposure by ingesting food that may contain americium-241, a decay product of plutonium-241, don't you want to survey the area outside the 20 kilometer zone? After all, outside the 20 kilometer zone, Fukushima farmers will be tilling the land, ready to grow crops of all kinds again this year.

Half life of americium-241 is 432.7 years. As it decays, americium-241 emits alpha and gamma rays.

Asahi Shinbun has the numbers for plutonium-241:

  • Dead leaves in Namie-machi (26 kilometers NW of the plant): 34.8 becquerels/kg

  • Dead leaves in Iitate-mura (32 kilometers NW of the plant): 20.2 becquerels/kg

  • Soil at J-Village (20 kilometer south of the plant: 4.52 becquerels/kg

Farmers in Fukushima, are you still going to grow stuff on your land?

Researchers at the NIRS, did you think of at least informally telling the local authorities or the farmers about your findings? Or did you just sit and wait until your paper was published by a peer-review magazine?

(I know I'm wasting my breath.)

Scientific Reports carries their full paper online.


Anonymous said...

Do you even know what "angst" means? It doesn't mean "anger", if that's what you're thinking. Check your dictionary, or go away.

arevamirpal::laprimavera said...

Why do I have to fear the researchers?

I don't thank these researchers for revealing the information after 11 months, and for not having revealed when it might have made a huge difference in people's decision, particularly in Fukushima. If that's not your focus, fine. Don't dictate mine.

Anonymous said...

Nice world we live in.

Anonymous said...

I don't have any anxiety or fear of these researchers. I am angry at them.

JAnonymous said...

I have yet to see a solid paper be rejected from a peer-reviewed conference or journal, on the basis that the information is already out in the msm press.

This is what scientific papers are made for : to be scientific. As a researcher, you don't expect the same kind of contents from Scientific American and from The New York Times.

Hiding the result to make the publication is just a hint at the researcher's own laziness, because putting the result out would allow other researchers to make concurrent and potentially better papers.

Anonymous said...

After all, it is EVERY taxpayer who PAID for the researchers' educations. I would think they should AT LEAST show enough RESPECT for those who WORKED AND TOILED ALL THEIR LIVES, paying the DUES which made "higher education" possible, by WARNING them of the invisible death lurking all around them.

Anonymous said...

Important information for people trying to make decisions.
Like this, ~6:35 into the presentation from TEDxSapporo

Anonymous said...

Karen, seeing one of your posts gives me angst.

Anonymous said...

This is only relevant in that it screams "ex-vessel".

In May last year TEPCO were still doing their little song and dance about how the reactor vessels were kinda sorta okayish and all the fuel was still inside them.

Atomfritz said...

At least it becomes more and more difficult for the nuclear lobby to falsely indoctrinate people that stuff like Strontium, Plutonium etc doesn't stay in the immediate vicinity of the nuclear plants.

As people begin to realize that these statements "Plutonium and Strontium will not spread" are wanton baseless rumors intended to betray them, another vital lie of the nuclear mafia begins to crumble.

Imho this is the most important effect of this research.

Hope these findings will put pressure on the Japanese govt. to survey Japan for plutonium and strontium as well as for cesium to reveal a more complete picture of the contamination impact of the Fukushima events.

arevamirpal::laprimavera said...

I'm reading the paper:

"The relatively higher 241Pu/239+240Pu activity ratio of the Fukushima DNPP accident might be because of the damage to the Unit 3 reactor, which had a mixed core, containing both uranium fuel and mixed uranium and plutonium oxide (MOX) fuel; the latter was about 6% of the core fuel. The additional production of 241Pu from the 239Pu fuel may have enhanced the 241Pu/239+240Pu activity ratio and 241Pu/239Pu atom ratio inside the reactor during normal operation before the accident."

Are they saying Pu is from the reactor core of Reactor 3? Not from SFP as some people (like Gundersen and Busby) have said?

Anonymous said...

I remember in the first few days of the disaster the only place I could find any info about what was happening at the plant was the CNIC website. They had daily video updates given by a Japanese ex nuclear engineer whistleblower who's name I do not remember and he feared that because the pressure in the vessel was higher than the pressure rating of the gasket in the reactor vessel lid there that would be the likeliest place to fail.

This Engineer had a hand in designing this reactor so I was very interested in his opinion. He feared that the gasket would fail and the bolts would stretch causing a release of gases from the reactor core.

Anonymous said...

"Are they saying Pu is from the reactor core of Reactor 3? Not from SFP as some people (like Gundersen and Busby) have said?"

they try to. it is the most logical thing to think that the sfp's of 3 and 4 blew up, but it can't be. so, it has to be the reactor of no. 3. it's macabre! and somehow funny, because at first they tried every thing to hide the fact, that the reactors might be broken and now...they are like, f*** that, lets tell it's the reactors. it's still better than to admit the truth. for that we wait another year. let's make a poolparty in basement.
one could make a comic out of it. it would be creepy and hilarious.

next they'll tell us, it was gozilla.

Atomfritz said...

@ LaPrimavera 12:08

The signature (high relative Pu-241 contents) indeed points to MOX fuel.

Sadly the analysis seems not to have included Pu-242, which accumulates much more in reprocessed fuel (and is one of the reasons why it is impractical to reprocess more than one cycle, but that would be another topic).
High Pu-242 content thus is a way clearer "reactor 3 marker".

To say in short, it is near to impossible to exclude one particular contamination source (except unit 3) just because of the plutoniums ratios, as practically all the contamination is a mix from four reactor buildings.

So this does not give an indication that Gundersen etc are wrong.
I am afraid that only a thorough forensic examination of the fuel recovered from from the SFP 4 will give a final answer whether it has released part of its contents.

However, I have to admit that the apparently (relatively) low radiation on the unit 4 floors remains at first seem contradictory to the assumption that there was a big release. But there might be other possible explanations for this observation.

Anonymous said...

In the days following the earthquake the CNIC held live press conferences on with presentations by Dr Masashi Goto. If anyone is interested recordings of them can be found here

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