EVALUATION OF RADIOACTIVE FALL-OUT
I.
INTRODUTION
The purpose of this report is to assess the magnitude and extent
of the hazard to human life imposed by radioactive debris deposited in
the human environment by large numbers of nuclear weapons.
‘The large
amount of data which has been accumulated from field tests of nuclear
weapons, laboratory findings, and field research is so voluminous that
an evaluation of these is indicated.
The evaluation is made in the
light of known facts of nature, nuclear weapon test experience, and
pertinent theoretical considerations.
All explosive nuclear devices Imown to have been constructed or
envisioned thus far utilize either wholly or in part a nuclear process |
known as fission to achieve the energy release desired.
The energy
yield of a pure fission device is limited by the fact that the quantity
of fissionable material that can be assembled in a given configuration
cannot sefely exceed a particular amount, called a critical mass.
This
amount can be increased indefinitely by expanding or dispersing the
configuration; however, a practical limit is soon reached because the
size of the configuration becomes cumbersome and the problem of assem-
bly at the desired instant of detonation becomes more and more difficult.
A companion process to the fission process is that of fusion.
Al-
though the unit energy yield is less, there is no criticality problem
for fusionable materials; thus large quantities of fusionable material
can be engineered into weapon designs with no attendant nuclear safety
problem.
"Boosted" finsion weapons and all thermonuclear devices make
some use of this process-
Since very high temperatures are required to
initiate the fusion reaction, a fission "trigger" or primary is a necessary component of the fusion devices successfully built thus far.
The fission process is a phenomenon whereby radioactive nuclides
are formed from the splitting of large atoms, with concurrent release
of large amounts of energy.
Under the proper physical conditions,
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