7
_9-
| obtained from a knowledge of the volume of the air sampled.
This type of sampling has been carried out et the earth's surface,
in the lower atmosphere by jet planes,
balloons.
and in the stratosphere by
The mejor difference between these samples lies in the
amount of air that can be sampled and thus in the activity level
which can be collected on a filter.
The analysis consists of the separation of Sr-90 from the inactive constituents of the dust on the filter end the seperation from
naturel redioactive materials end other fission products.
Activity
levels at the surface or in the lower etmosphere are sufficient that
simple beta geiger counters can be used.
The volume of air that
can be sampled in the stratosphere, when converted by calculation to
normal temperature and pressure, is small.
Consequently a small
amount of particulete material is collected end low background
counters are an absolute necessity.
Estimation of the atmospheric reservoir of Sr-90 is needed
to predict the level which will be finelly deposited on the ground
when ell the material is deposited.
Because of non-uniformity in
the distribution of the redioactive debris in the atmosphere, both
laterally end vertically, the sampling progrem must be very ex~
tensive to develop a reliable picture.
Air samples at the surface of the earth are the simplest to
obtein but ere the most heavily influenced by locel meteorological
conditions.
A better estimate cen be obtained from stratospheric
samples which are the most costly in terms of both sampling and
anelysis.
(DOE ARCHIVES
LF