-7Collection in pots is open to the criticism that more fallout nay
be collected then would be deposited in the open air.
by impaction on the inner sides of the vessel.
This is caused
Studies are under way
to determine the best shape and size of vessel for collections.
However, it should be noted thet comparison of annual pot increments
with soil increments have shown good agreement.
Gummed Film Collections
The need for a simple collecting technique suitable for network
operations, where large numbers of collecting stations employ untrained personnel, led to the development of the gummed film collector.
This collector has an adhesive surface of one square foot which
is exposed for twenty-four hours.
A network of up to 200 stations
collecting daily samples hes been operated by the Health and Safety
Leboratory since 1951.
analyses ere performed.
Samples are nailed to the laboratory where the
It is not possible to determine Sr-90 directly
in gummed film -- first, because the amoumt of Sr-90 deposited in
twenty-four hours is too small, and second, because during reinfall
e verieble fraction of the Sr-90 is lost by preferential solubility.
The Sr-90 component has in the past been estimated by calculation
from the mixed product velues.
In addition, en estimete has been
made of the gamme dose resulting from this fallout.
The increzsed
weapons test ectivity has mede these calculations extrerely difficult
end the methods originally followed have been found inadequate.
At
the present time a new celcwlation procedure has been devised and
is being tested.
The gummed film samples are eshed to reduce their eree end the
totel mixed fission product activity is measured with eutomatic beta
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