[NHK] Science ministry releases Fukushima radiation map
Estimated cumulative dose over one year (in milliSieverts), starting from March 11, to someone spending 8 hours a day outdoors:
http://www.asahi.com/national/gallery_e/view_photo.html?national-pg/0426/TKY201104260415.jpg
What's the bold line (black) at 20 mSv mean? According to reports (e.g. this NYT article), 20 mSv over one year is the Japanese government's threshold for evacuation. So if I interpret correctly, that enclosed area is likely to be evacuated within a month or so, for a long period of time. (Since much of the dose comes from long-lived 137Cs, this could be a very long time. A permanent-exclusion zone.) That's around 500 km2 in there, which based on district-level population densities probably encloses (very roughly) around 50,000 people.
Some related data sources are
- MEXT radiation monitoring data (measurements)
- Independent academic radiation survey (with more isotopes)
- NNSA monitoring data (mostly overflights)
Very helpful graph. Although, it's difficult when you consider that it goes from March 11 through the entire year. I believe that a large fraction of that comes from a week or so following the accident as the major Iodine isotopes were decaying away. The other difficult thing is that I'm almost positive that this is external dose.
ReplyDeleteWe already had plenty of dose readings and I already made a post trying to use those readings to get cumulative doses, which is very consistent with that numbers shown in that graph. I found that some cities integrated dose numbers exceeded 10 mSv but only slightly. I'm interested to know what the dose from this point on for an entire year would be.
Yes, 20 mSv is the evacuation criteria, but that is totally irrelevant. If the people have already gotten 17 mSv of that dose, then who cares? And what are the major biological pathways of Cs-137, which probably dominate the dose from here on out.
As you can see, this doesn't help all that much to put the picture together and resolve my questions. Although I do want to get to work and make a comprehensive post on the numbers available for the 1 year dose predictions. The DOE blog published something on this too.
MEXT reports integrated doses also.
ReplyDeletehttp://www.mext.go.jp/english/incident/1304275.htm
The independent report had some interesting illumination. The current major component of dose is currently Cs-134, at more than twice Cs-137. This will fall more rapidly, since it has a halflife of 2 years (compared to 30 years). Given that much of the projected dose above is from the short-lived radionuclides that will be gone by the end of May, and no account is taken of the likelihood that much of the rest will be washed away in the summer, I very much doubt we are looking at anything - even on the highly-cautious 20mSv/yr criterion - that would produce a long-term evacuation zone beyond a km or two from the plant.
ReplyDeleteThe review of the zone at the point when cold shutdown is achieved will be based on measurements at that time, I guess. I hope. Actually I am quite surprised that the Science ministry would put out an extrapolated year's dose that implies that the contamination will stay in place, but at least they promise regular updates.
uvdiv:
ReplyDeleteI seriously studied the MEXT link you offered and really racked my brain over it, but I conclude that it's really not useful. Yes, it appears to give an integrated dose reading, the problem is what it represents. There are 70-some monitoring posts that they are getting this from, but they only report on a handful of them with each release. On top of that, the instillation date for most of them is too recent to be useful. If something was installed in the 3rd week of March, it won't give anything close to a good measure of the dose to someone who was there the entire time.
I realize I might be reading these wrong - they are very confusing. But if I're right, it's useless compared to the other higher quality data available.