Analysis of Stratuspheric Strontium-90 Measurements
L. Machta and R. J. List
U. S. Weather Bureau
March, 1959
I.
Introduction
Since it was first proposed by Dr. W. F. Lippy?) in 1953, the concept
of stratospheric storage of long-lived fission products resulting from the
detonation of high-yield nuclear devices has become generally accepted.As of
the end of 1958, Libpy'2) has estimated that about 65 megatons of fission
products had been injected into the stratosphere.
Knowledge of the fate of
this debris, which may remain in the stratosphere for a period of years, is
vital to our evaluation of the problem of long-lived fission products, such
as Strontium-90 and Cesium-137.
The atmospheric processes which control the movement of debris in the
stratosphere, its eventual removal into the troposphere and its deposition
in the biosphere are determining factors in being able to predict future
levels of contamination from debris already in the atmosphere and from
debris which may possibly be injected in the future.
This understanding will
also permit the design of an optimum monitoring and sampling program to keep
track of the stratospheric Sr-90.
A corollary of the study will be a better
understanding of the meteorology of the stratosphere, since these fission
products represent one of the few tracers available to study stratospheric
motions.
In this paper we should like to review the estimates of what is expected
to be found in the stratosphere, the various hypotheses advanced concerning
the distribution of radioactivity in the stratosphere and its subsequent
removal, and how this fits the observed stratospheric concentrations, along
with an estimate of the quality of the data obtained.
II.
NAS
°
Estimated Stratospheric Content
Tt has been customary to divide the radioactive debris resulting from
the detonation of nuclear devices into three categories: (1) close-in fallout,
(2) tropospheric debris and (3) stratospheric debris.
The apportionment in
any individual case is a function of the energy of the burst and the conditions of firing (e.g., surface, tower, air,underground, etc.).
1
,
-*
¢
og ELAN
For bursts