RADIATION STANDARDS, INCLUDING FALLOUT
33
nuclear war, but also of significance in terms of the application of
nuclear energy to our space program.
;
During your committee hearings in June 1959 on the biological and
environmentaleffects of nuclear war, it became apparent that the 1957
edition of the Effects of Nuclear Weapons required updating. The
Department of Defense, with the full cooperation of the AECandits
laboratories, has completed the revision, and the 1962 edition was
issued May 8, 1962.
.
The detonation of nuclear devices produces fission products in
greater or lesser amounts depending on the characteristics of the particular device employed. Fission devices, which are generally in the
lowyield range, derive their explosive force from nuclearfission which
gives rise to amounts of radioactive fission products roughly proportional to explosive yield. Thermonuclear devices have a large fraction of their explosive force produced by a thermonuclear or fusion
reaction.
Such devices derive only a part of their explosive force
from the fission reaction. Of the fission products produced in the
fission reaction, those with the greatest potential health significance
are Sr®, C5187, 141, Sr®, Ba-La™°, and Zr-Nb® (half lives 28 years, 30
years, 8 days, 54 days, 13 days, and 65 days respectively).
Thermonuclear reactions may give rise to tritium (radioactive
hydrogen, half life 12.8 years). The very large number of neutrons
released in the reactions transform nitrogen in the air into radiocarbon (carbon 14, half life 5,760 years).
In addition, the neutrons produced in either fission or fusion reactions induce radioactivity in certain chemical elements used in the
construction of the devices themselves. If detonated from towers,
radioactivity is induced in the materials of the towers, and if detonated relatively close to a land or ocean surface, in elements in these
surface. materials. Most of these induced activities are, aside from
carbon 14, short lived and although they may be very important constituents of early or near-in fallout, they havelittle health significance
in worldwide fallout. Fe®, Mn‘, Si, Cl°*, Na?# with half lives of
47 days, 310 days, 2.6 hours, 37 minutes, and 14.8 hours, respectively,
are the most prominent ones.
Measurable amount of Zn**, half life 250 days, and Co, half life
5.3 years, have also been detected in fallout. Plutonium and uranium
isotopes, basic materials in the fissionable components of nuclear
weapons,are also contained in fallout material.
There are three different classes of fallout from tests, local or
near-in fallout, tropospheric fallout, and stratospheric fallout.
(See fig. 1, p. 34.)
sylbs hipaaefi teeieithaites
ta
“Shh