[ RadSafe ] Sr-90 Deposition in Japan -ROUTINE FALLOUT DATA--RE: Panic time --- 195 Bq found in Yokohama

[Stewart Farber]

Regarding the  earlier news report below posted by Steve Dapra: 
>"About 195 becquerels of the radioactive isotope [Sr-90], believed to 
> be from the crippled Fukushima nuclear plant, was discovered in dust 
> on top of an apartment building in the port of Yokohama, about 15 
> miles south of Tokyo." ---

The above claim about Fukushima being the source of 195 Bq of Sr-90 is
suspect. Some info regarding pre-existing Sr-90 Deposition follows:

According to UNSCEAR 2008 -United Nations Scientific Committee on the
Effects of Atomic Radiation - [Sources and Effect of Ionizing Radiation"],
Vol. 1,  Table 35 [Latitudinal distribution of radionuclides from
atmospheric nuclear tests..."], the Integrated Deposition of Sr-90 in
Latitude Band 30-40 N [Tokyo]  is 85.3 PBq [85 E15 Bq ]. 

For those scaremongers out there who like to quote radioactivity in GBq for
some reason [perhaps its Carl Sagan envy: "billions and billions" ],  85 PBq
in latitude band 30 -40 N is 85 Mega GBq = 85,000,000,000,000,000 Bq. This
total Sr-90 activity in 30 - 40 N lat from pre-existing fallout may help
various unethical opportunists sell things like $75 a bottle magic detox
pills so scared people can "protect the DNA" with 4 minerals found at
similar concentrations in any vitamin pill for a cost of pennies.

The average areal Sr-90 Deposition Density in Tokyo's latitude band is
approximately 430 Bq/m^2 vs. "195 Bq" reported in the recent news report.
It is absolutely fascinating how scaremongers ignore, and the media don't
know or wish to recognize, that 502 atmospheric nuclear bomb tests by the
following countries were conducted: 

COUNTRY     NUMBER OF OPEN AIR 
           NUCLEAR WEAPON TESTS
China          [22]
France         [45]
United Kingdom [21]
US             [185] 
--Former 
Soviet Union   [219]

Total open air 
Nuclear tests:  502
Total Fission Yield:  189 MegaTons

Based on global fallout, and residual Sr-90 radioactivity across the entire
globe at 30-40 N latitude, one would expect to see 195 Bq [give or take a
likely variation of about 10],  on every 0.45 square meters [ 4.8 ft^2]  of
the earth's surface at Latitude band 30 -40 N.

So 195 Bq of Sr-90 on a rooftop near Tokyo isn't much, and could simply and
most likely be residual from global nuclear fallout from open air testing of
502 nuclear weapons.

When I was involved some years ago in widespread sampling of Cs-137 residual
in woodash in the US from domestic burning of mature hardwoods, an
interesting, and relevant situation was reported to me.

The wood smoke at a single family home had left the stack of a single family
home and deposited onto the roof. Anyone who has ever seen the smoke from a
fireplace or woodstove wafting out of a chimney or stack has seen it "wash"
over the roof since it does not have the exit velocity to leave the boundary
layer surround the roof.  The Cs-137 [and there would have been about 60% as
much Sr-90 as Cs-137 in the wood smoke leaving the home up the chinmney
since the ratio of Cs-137/Sr-90 in nuclear fission is about 1.6 to 1]
deposited on the roof of the home. In this case, Cs-137 and Sr-90 from the
roof apparently washed off the roof into the gutters,  and down the gutter
downspouts to the ground.  Where the water washed out on the ground around
the downspout the concentration of Cs-137 [and Sr-90 was to be expected at
about 0.6 of any measured Cs-137 concentration] was greatly elevated vs.
normal soil.

On a flat roof in Japan, it can hypothesize that some deposition over the
entire roof might concentrate in dusts/soil buildup at certain spots.
Depending on the configuration and runoff from the roof, Sr-90 could
concentrate in dust/soil buildup in relatively small areas on the roof. A
small amount of soil/dust on the roof could contain the deposition from much
of a very large roof so that sampling some dust on the roof would mean very
little vs. the average areal deposition.

Stewart Farber, MS Public Health

=================================
---- Steven Dapra <sjd at swcp.com> schrieb:
> Oct. 18
> 
> 	Quote is from "Earthweek A Diary of the Planet."
> 
> "About 195 becquerels of the radioactive isotope [Sr-90], believed to 
> be from the crippled Fukushima nuclear plant, was discovered in dust 
> on top of an apartment building in the port of Yokohama, about 15 
> miles south of Tokyo."
> 
> 	Link is to the squib about the Sr-90.
> 
> http://www.earthweek.com/2011/ew111014/ew111014a.html
> 
> Steven Dapra
> 
> _______________________________________________