Management of Commercially Generated Radioactive Waste - U.S. ...

5.75
If the meteorite had an energy equivalent of about 3 megatons of TNT, the overall effects
would be somewhat like those from a nuclear weapon but without the prompt radiation effect.(a)
Thus, a shock wave as well as thermal effects could be expected. If a 3-megaton nuclear
weapon were detonated, any individual residing within 4 km from the point of impact would be
killed or would suffer at least second-degree burns and other injuries from the blast, falling
buildings, and flying debris, etc.
Radioactive material suspended by a meteorite impact would be dispersed by two modes,
developed on the basis of nuclear cratering test results. A typical cloud formation consists
of a central column rising about a doughnut-shaped base surge, which rolls outward
from the crater. One-half of the suspended material is dispersed in the central column and
one-half is dispersed in the base cloud. For the reference midwest site, the material in
the central cloud is also dispersed evenly across the eastern half of the United States and
then moved around the world at high altitude. Compared to the base cloud, it does not con-
tribute significantly to local (radius of 80 km) fallout. Because of large overpressures
in air produced on impact of the meteorite, local low-altitude winds are assumed to have no
affect on dispersion of material.
If the meteorite impact penetrated to a depth of 600 m, the impact is arbitrarily
assumed to result in dispersion of about 1% of the repository inventory. The amounts of
various radionuclides ejected depend on the length of time between repository closure and
meteorite impact. This event was examined for a meteorite strike at the assumed time of
repository closure (therefore maximum waste disposal inventory) and for 1000, 100,000 or
1,000,000 years thereafter. Assumptions about dispersion of radioactive material after
meteorite impact are summarized below.
Ten percent of the particulate radioactive material dispersed is assumed to be of res-
pirable size (3H, 14 C, 8 5 Kr, and 1291 are assumed to be released as gases and all
other radionuclides are assumed to be in particulate form). The remaining 90% of the particulate
material falls back immediately into or near the crater and does not contribute to
the regional population dose. For calculation of the dose to the regional population, the
amount dispersed is also reduced by an additional one-half to account for the distribution
of material between central and base clouds.
First-year and 70-year cumulative doses to the whole-body for various times of repos-
itory breach and for repositories in various media are presented in Tables 5.5.1 and 5.5.2.
Doses to individual organs, a breakdown of dose by pathway, and tabulations of the radionuc-
lides of importance in the repository are given in DOE/ET-0029. Calculated doses are
directly proportional to the fraction of inventory released; thus, if it were postulated
that 10% rather than 1% of the inventory was dispersed, the reported dose would be 10 times
higher.
(a) There does not appear to be a direct equivalency between the energy of the meteorite and
the nuclear weapon. Claiborne and Gera.(1978) conclude that the largest presently
deployed missile capable of carrying a 25-megaton bomb would form a 270-m crater; if a
50-megaton bomb were deployed a crater up to 500 m may be formed. Other calculations
made for this Statement based on the work of Glasstone (1964) suggest that a bomb on the
order of 130-megatons (air blast) would be required to produce a crater 2 km in diameter
and 600 m deep.