DNA 1240H-2
17.4
17.4.1.
FIREBALL-PLUME-CLOUD RADIATION
Introduction
As noted in 17,33, for surface or very shallow underwater bursts,
four components contribute sipnificantly to the total F.P.C. radiation”
incident on a target.
The relative contribution of each component
depends primarily on the weapon type |! (The prompt, or fission-process,
gomma rays are emitted within a fraction of a second after burst, and
are irmored in this discussior since they are almost complictely
absorbed by the bomb materials.) js brief review of the 4& components
follows.
Many of the prompt neutrons emitted in the fission or fusion
process are slowed down and captured by the bomb materials.
However,
a sufficient number escape co that the resulting prompt neutron flux
forms a significant direct contribution to F.P.C. radiation. In add-
ition, gamma rays, resulting from inelastic scattering of neutrons and
nitrogen-capture gamma rays also contribute sirpnificantly.
These three
components of F.P.C. radiation are all due to neutrons, and will re-
sult only from surface or very shallow underwater bursts, since the
prompt neutrons are completely absorbed by oa thin (about 3 ft) layer
of water.
The early-time tission-product gamma rays emitted during
the first minute after detonation (once the bomb materials have
vaporized) by the rapidly decaying radioactive fission fragments are
the fourth significant component of F.P.c.
17,12,
radiation.
As noted in
the fission products will be carried into the air and mixed
with the water thrown up by a water-surface or underwater burst.
Thus,
F.P.C. radiation is also emitted by the fission products carried in
the column, plumes, and cloud.
Those characteristics of the above four F.P.C. radiations that
affect their interaction with ships are discussed in this section,
along with shipboard shielding iweinst F.P.C. radiation and available
field-test dose and dose-rate data.
Curves that may be used to
estimate
F.P.C. neutron dose vs distance ure presented, as well as
curves for free-field F.P.C. ganuna dose.
When both doses are expressed
in rads they are additive.
In the discussion of the interaction of
the target ship with F.P.C. radiation, the effects of neutrons and
gama rays are considered separately, since the two kinds of radiation
differ in many respects.
No method of calculating F.P.C. dose at
shielded locations is presented, since no such method exists explicitly
in current literature.
Current information as to the effects of F.P.C.
radiation on shipboard equipment will also be summarized.
“Fireball-plume-cloud radiation is defined in 17. 3. 3.
EGT AVAILABLE COPY
eS
17-20
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