Latest on Fukachima soil, weed and water samples

As of 10:00 JPN-time, March 25, 2011, as reported by the Ministry of Education, Culture, Sports, Science and Technology (MEXT):

http://www.mext.go.jp/component/english/__icsFiles/afieldfile/2011/03/25/1304097_2510.pdf

I’m picking some of the higher readings found at different distances from the Fukachima Daiichi disaster site:

DUST Samples:  (the brief time the wind blew radiation northwest-inland is very noticeable in the measurements.  Makes you wonder how much fell in the Pacific Ocean, where most of the radiation was blown to…).

On land (direction from Fukachima Daiichi NNP, date, dose rate)

30 km …… NW …….. 3/24 …….. 30.0 μSv/h

40 km …… NW …….. 3/23 …….  9.0 μSv/h

60 km …… NW …….. 3/19 …….. 7.2 μSv/h

25 km …… S …………. 3/23 ……. 14.0 μSv/h

WEED (LEAFY GREEN) Samples:

40 km …… NW …… 3/19 …… 26.5 μSv/h

40 km …… W ……… 3/21 …….. 0.7 μSv/h

INLAND WATER…

So What I’m still not clear on is what the standard DISTANCE is that is used to make calculations to get μSv/h once they know the activity levels of different isotopes; and if the μSv/h provided is always the combination of both gamma and beta rays.   Without that information I can’t really calculate what the reported activity levels (right column in Bq/Kg) could be (in µSv/hr), below.  I suppose this is making it increasingly clear that µSv/hr dose rates of distant radiation sources (such as from natural background radiation originating from the cosmos and earth, as well as medical doses) cannot be linearly compared to radiation from radiation-emitting particles, for which concentrations and distance to those concentrations makes all difference in the equivalent dose one would receive. So, right below is an excerpt of this past week’s survey results from 40 & 45 km distance, well outside the Japanese 20-30 km evacuation zone. To see the full report, or the latest, visit MEXT (mentioned above, or at my JPN page).  What those radioactivity concentrations would mean in trms of exposure completely depends on the break-up between gamma & beta rays, as well as the distance to these concentrations.  From what I’m gathering, most are only truly dangerous when you were to come in direct or very close contact with them.  Given the distance, however (40+ km), in an area only briefly exposed to being downwind, it shows the gravity of the releases.


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