Re: SNAP generators and Pu-238 -Reply

[Bruce Busby <bbusby@umich.edu>]

Hi,

The following is from Environmental Radioactivity from Natural, Industrial
and Military Sources by Merril Eisenbud, Academic Press, Inc. 3rd (and the
soon to be forth w/ Tom Gesell co-author) Edition. 

Of interest, it can be ordered at the following web site:

http://www.apcatalog.com/cgi-bin/AP?ISBN=0122351533&LOCATION=US&FORM=FORM2


Chapter 14:

ABORTIVE REENTRY OF THE SNAP 9-A



     A navigational satellite launched on April 21, 1964, and carrying a
radioisotope power generator failed to reach orbital velocity and
reentered the atmosphere at about 150,000 ft over the Indian Ocean.  The
isotopic power unit was known as SNAP 9-A and contained about 17,000 Ci
of 238Pu (Krey, 1967).

     Pu-238 was present in the upper atmosphere at the time as a residue
from earlier nuclear weapon tests, but the system of high-altitude balloon
sampling, mentioned in Chapter 13, served to demonstrate the sudden
appearance of a new source of 238Pu which was first detected at an
altitude of 108,000 ft 4 months following the abort.  The stratospheric
distribution of the debris during the next several years followed the
predictions that had been made on the basis of transport models of the
stratosphere developed through studies of the behavior of debris from
weapons testing (Kleinman, 1971).  However, the concentration of 238Pu
from SNAP 9-A was somewhat lower in ground-level air than had been
predicted (Shleien et al., 1970). About 16 kCi of 239Pu, representing
95% of the amount originally injected, was estimated to have been
deposited by the end of 1970.  The estimated stratospheric inventories are
given in Fig. 14-4, in which it is seen that the debris apparently took
about 2 years in which to diffuse to the sampling altitudes, following
which depletion of the stratospheric inventory proceeded exponentially
with a half-time of about 14 months (Krey et al., 1970).  Particle-size
analysis of the debris indicates that the particles ranged from 5 to 58
m$mu$.

     The 238Pu content of ground-level air has been monitored by de
Bartoli and Gaglione (1969) and by Shleien et al., 1970), on the basis of
which it has been concluded that the 50-year dose commitment to the
pulmonary lymph node from 238Pu exposure between 1961 and 1968 was 36
mrem (Shleien et al., 1970).

(Eisenbud Env. Rad. 3rd Ed.)