For surface bursts of high (million ton range) yield from
50-80 percent of the radioactive debris is deposited as "early faliout:, i.e. within 24 hours.
Air bursts - where the fireball does
not approach the surface - create little, if any, local fallout.
Table 2 tabulates some of the key data on estimated nuclear
energy yields from all past nuclear weapons tests.
rei:
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The total energy
release is of interest in estimating the amount of carbon-14 produced.
it is assumed that the carbon-14 is distributed more or less uniformly
around the world.
Of the total energy release of 511 million tons
equivalent of INT about 70 percent resulted from USSR tests.
un
Table 2 also shows that tons of the fission products from 161
million tons was scattered globally. Approximately two-thirds of
this amount originated from USSR tests.
It will, however, account
for about three-quarters of the long-term fallout in the United
States because of meteorological] factors - there will be more deposition in the North Temperate Zone from a nuclear detonation in
the lower atmosphere at a northerly latitude than from the same shot
at an equatorial site.
Atmospheric tests at the Nevada Test Site
have contributed very little to the deposition of long-lived radioisotopes but at times have been the source of relatively high amounts
of short-lived iodine-131 in the local environment.
At the time of a nuclear detonation something like 200 different
radioactive substances are formed by fission and additional ones by
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