[ RadSafe ] Preexisting Global Fallout Data Comparison- was: RE: Japanese Radioactive Levels Claimed to be too high for Farming

[Stewart Farber]

Jim,
Thanks for posting the links to measurements in Japan.

Of note to levels of fallout deposition that proved to be of absolutely no
long-term concern to farming in the US, take a look at the attached Slide 7
from a paper I presented about Cs-137 in woodash to the 5th Annual Biofuels
Conference. Figure 7 was taken from an old US Health and Safety Lab [HASL]
report about global fallout from atmospheric bomb testing for which I don't
have the citation right at hand.

Slide 7 shows the isolines of cumulative Sr-90 deposition in the continental
US [ millicuries per square kilometer ==> conversions to SI below] after all
fallout essentially stopped from global atmospheric bomb testing which ended
in 1963 by the US and Soviets. 

As seen in Slide 7, large parts of the US were contaminated with Sr-90 at 60
to 90 millicuries per km^2. [Sorry for the mixed units used in the original
HASL document]. The Cs-137 levels across most of the US were 1.6 times as
high  [the ratio of Cs-137/Sr-90 in fresh fission of U-238 or Pu-239 in
bombs ]. So Cs-137 in open-air bomb test fallout in the US equalled
approximately 0.10 to 0.15 mCi/km^2 [ = 3.7 E10 - 5.55 E10  Bq/km^2 or per
sq. meter = 3.7 E4 to 5.5 E4 Bq/m^2 ]. So 37,000 to 50,000 Bq/km^2
cumulative deposition of Cs-137 and 60% of this areal deposition of Sr-90
had no impact on farming in the US or the rest of the world at these levels.


Of MAJOR importance, although the global areal deposition of Sr-90 was 60%
of Cs-137,  the dose from Sr-90 deposition from bomb test fallout is often
10X higher than that due to Cs-137 because of the very much higher uptake
factors for Sr-90 from soil to plant, vs. Cs-137 uptake from soil to plant.
In some cases the transfer factors for Sr-90 can be far in excess of 10X
that of Cs-137.