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 Post subject: Recent Fukushima maps
PostPosted: Feb 22, 2015 3:57 am 
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Earlier on there were maps comparing the radioactive contamination from Fukushima from 2011 to 2012 showing a large decline over the year. Does anyone have or know where to find a map for 2015?

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PostPosted: Feb 22, 2015 4:11 am 
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Ok did find maps till 2014:

http://radioactivity.nsr.go.jp/ja/conte ... th_air.pdf

There appears to be little area left above the 0.22-0.45 mSv/day level (orange). 0.5 mSv/day is a very safe level to live in. The red area is mostly safe too but to be totally safe return to the red area could be postponed till more detailed investigations of local hot spots are done. It is just a thin strip of land, looks a couple km wide only, and it is thinning quickly.


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PostPosted: Feb 22, 2015 5:45 am 
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Cyril R wrote:
Ok did find maps till 2014:

http://radioactivity.nsr.go.jp/ja/conte ... th_air.pdf

There appears to be little area left above the 0.22-0.45 mSv/day level (orange). 0.5 mSv/day is a very safe level to live in. The red area is mostly safe too but to be totally safe return to the red area could be postponed till more detailed investigations of local hot spots are done. It is just a thin strip of land, looks a couple km wide only, and it is thinning quickly.


Goal should be red and orange gone for full return of people (full lifting of evac) ?
Would this happen in 3-4 years ?
Regardless, I am in favor of making the evac optional. People should have the option to return, right now, except zones that were red 12 months ago.
Sounds like a reasonable approach.
More area needs rebuilding anyways.

What is the most common rad source ? (Sr, Cs, Pu) ?

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PostPosted: Feb 22, 2015 6:40 am 
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The orange area is fine, below 0.5 mSv/day. Some areas elsewhere in the world have this high background radiation from natural sources, and the people there are just fine.

We know from various animal experiments combined with various human exposure data, that 2 mSv/day is likely a treshold to health damage so pretty much all the red area would be fine on that basis. 0.5 mSv/day is a large safety factor to that treshold.

Virtually all the contamination is cesium. Cs134 and Cs137. The 134 is decaying rapidly, most is already gone. So the decay will be slower from now on as Cs137 dominates.

I was expecting strontium to show up but its minute. Really shows how reduced volatility of Sr helped to contain it.

I think that evacuation must not be forced but people should have the choice. If their homes have more than say 1 mSv/day they should receive compensation for the additional dose. Right now the Japanese government is paying over $1 billion a year in compensation payments for evacuated people whose homes are just fine which is stupid. The Japanese government response has so far done a heck of a lot more damage, in health, mental trauma and finances, than the whole nuclear accident ever could if the government did nothing. It is really disappointing to see a modern country with a large modern government fail in such so utterly.


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PostPosted: Feb 22, 2015 1:47 pm 
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They should just offer to buy any and all land in teh contamination area at its pre-accident value, then allow anyone who does not want to sell to return at their own risk.


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PostPosted: Feb 23, 2015 10:23 am 
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macpacheco wrote:
Goal should be red and orange gone for full return of people (full lifting of evac) ?
Would this happen in 3-4 years ?

Actually, it has pretty much happened already. There is a phenomenon called ground shielding (IIRC) that basically reduces the real ground-shine measurements by a factor of about 3. With fair consistency, the properly measured ground-shine values are about 1/3 the ones taken from the air, which are the ones shown in that link. If you go to Safecast.org you can download many semi-properly taken measurements and they indicate that basically only the crosshatched area in the linked maps are places where Rad-Con exceeds the dangerous.

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PostPosted: Feb 23, 2015 12:01 pm 
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Ok I think I understand this ground shielding effect. It has to do with line of sight over the virtual sphere of the target vs. source. If the target is in the air it will see a lot of radiation as it has a wide LOS, if it is on the ground it has a limited LOS to cesium that is further away.

So are you saying that the peak values for a person standing upright on the ground are not around 2 mSv/day but actually 0.7 mSv/day?


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PostPosted: Feb 23, 2015 12:11 pm 
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I have an ASCII problem with m's and mu's. The chart has a tiny bit of "English" that says (mu)Sv per hour. The orange legend says 9.5-19 (mu)Sv/hr. Times 24, that's 228-456 (mu-micro)Sv or 0.5m(milli)Sv per day, right?

If Cyril's 2mSv/day figure for health damage is correct (and I'd like to see a reference for that) - and toss in a 4x safety factor - then the max 0.5 orange area is OK. So,
Quote:
so pretty much all the red area would be fine on that basis.


should read "all but the red area", right?

Graphically, what color is Denver on these charts? For public consumption, micros and millis suck. I forget where I saw the average Finn is radiated more than a resident of Denver. We need a new measure called Finns!


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PostPosted: Feb 23, 2015 12:52 pm 
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Hi Steve,

The readings are microsieverts/hour, yes. So orange is below 0.5 mSv/day. The microsievert sign is also in the comparison maps:

http://radioactivity.nsr.go.jp/ja/conte ... th_air.pdf

Quote:
should read "all but the red area", right?


In other refs they are talking about peak hotspots of around 2 mSv/day. So near the border of health damage. But most of the red area would be fine on the basis of the actual threshold. If we use 0.5 mSv/day which seems reasonable the the red area would not be fine.

Quote:
If Cyril's 2mSv/day figure for health damage is correct (and I'd like to see a reference for that)


Here's one source, a presentation from Dr. Jerry Cuttler to the CNSC. The data suggest that at 3 mSv/day level (chronic, lifetime dose) and onward there starts to be a slight reduction in life expectancy.

http://nuclearsafety.gc.ca/eng/pdfs/Pre ... iation.pdf


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PostPosted: Feb 23, 2015 10:50 pm 
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Gee..... wasn't it supposed to be "centuries" ??

PS. if anyone finds updated maps of resettlement of former exclusion zones, please post them (or links) here, thnx.


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PostPosted: Feb 24, 2015 8:10 am 
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It looks like about 10km2 are "Red" - as of September last year.

Which colours are evacuated according to Japanese guidelines?

As with the NASA debate on radiation exposure for Mars crew, what level of exposure can be traded off by a thorough annual or six monthly cancer investigation?


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PostPosted: Feb 24, 2015 10:24 am 
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Alex, the Japanese government has set a 20 mSv/year limit. This is 0.054 mSv/day or 2.3 microsieverts/hour. So that's the top 3 colors plus some of the fourth color (greenish yellow). Far too stringent, this does a lot more harm than good. To start with they should set the limit 10x higher.


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PostPosted: Feb 24, 2015 10:45 am 
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Cyril, the Engineer in me agrees. But I just have to check with my lawyer.....

http://www.nhs.uk/Conditions/Radiation/ ... ction.aspx
It seems the UK allows 20mS/year for nuclear workers. If a resident were allowed back, and got more than this dose, he might sue the Government for making him worry.

Would air conditioning and filters reduce the dose indoors?

It seems in Ramsar they get 70-130mS/year.

Again, the key to reducing cancer deaths is frequent checking (and probably a good antioxidant diet). Would 100mS/year and a six monthly check be better than 2mS/year and no checks?


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PostPosted: Feb 24, 2015 10:47 am 
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alexterrell wrote:
As with the NASA debate on radiation exposure for Mars crew, what level of exposure can be traded off by a thorough annual or six monthly cancer investigation?


One of the odd things with chronic gamma radiation exposure is that it doesn't appear to increase solid cancers at all. It does have detectable effects on the hematopoietic system above 3 mSv/day. It definately reduces life expectancy at and above 3 mSv/day. Probably not much we can do about that proactively, then again I'm not a doctor.


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PostPosted: Feb 24, 2015 10:54 am 
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alexterrell wrote:
Cyril, the Engineer in me agrees. But I just have to check with my lawyer.....


Don't do that, leave the lawyers out. Lawyers are for the guilty and the uncooperative.


Quote:
Again, the key to reducing cancer deaths is frequent checking (and probably a good antioxidant diet). Would 100mS/year and a six monthly check be better than 2mS/year and no checks?


Yes, it would be better. 2 mSv/day does not appear to increase cancer mortatility even with zero checks so any checks you do will reduce cancer mortality.

Quote:
Would air conditioning and filters reduce the dose indoors?


Yes, if it is a tight house with the aircon flow being most of the ventilation flow. But the indoors dose doesn't appear a problem. The cesium is stuck on the soil outside. It tends to not deposit inside buildings though it can stick to the walls and that would result in increased dose if the walls are thin.


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