To recap, uranium-239, whose half life is about 24 minutes, decays into neptunium-239 with a half life of about 2.5 days, which then decays into plutonium-239 whose half life is 24,200 years.
Again, the reason for withholding the information is explained in the article below as "the research paper being peer-reviewed by a foreign scientific journal" - a make-or-break event, apparently, for a young researcher at a prestigious university in Japan - and as precaution against the possible Japanese government action to squash the information. The article was written by the same husband & wife comedian couple who first wrote about neptunium in Iitate-mura on their blog magazine in early August.
I'm sure the nuclear experts who have appeared on TV to soothe the populace ever since the March 11 nuclear accident has the good explanation for neptunium-239 in these locations. They've kept saying "No way plutonium will be found outside the compound, because it is heavy and it doesn't fly". Oh I get it. It's plutonium they were talking about, not neptunium which decays into plutonium. My bad.
From Nikkan SPA September 13 issue (part on Date City only):
メールはこう始まっていた。
The email began thus:
「放射線測定を専門とする大学研究者に直接聞いたのですが、プルトニウムが核変する前のネプツニウムという核種が、少なくとも飯舘村や伊達市まで大量に飛んでいたそうです。今のγ線メインの測定方法ではどんなに頑張ってもセシウムしか検出できないため、本来の危険性が見逃されてしまう。α 線核種を無視した今のやり方を続けていたら、飯舘村はまた“見殺し”にされかねない……」
"I heard it directly from a university researcher whose specialty is radiation measurement. Neptunium, the nuclide that decays into plutonium, flew at least to Iitate-mura and Date City in large quantity. The current survey method focuses only on gamma ray, and all it detects is radioactive cesium. The real danger is alpha-nuclides, which continues to be ignored. Iitate-mura may be being betrayed again..."
The article by the comedian cum independent journalist couple continues and says this person attended a lecture given by this researcher.
It still doesn't make sense to me that the information already freely given at a public lecture has to be withheld because of the peer-review process, but oh well.
Date City by the way has been selected by the national government to conduct "decontamination" experiments. So is Iitate-mura. They are using high-pressure spray washers to blast roofs, sidings and roads, and digging up the soil. Plutonium? What plutonium?
Unlike Iitate-mura, though, almost all residents in Date City still live within the city. Even those who are ordered to move because of high radiation level in their homes have moved to temporary housing that the city has provided, within the city.