10.2 Characteristics of Surface and Air Burst Detonations
99
ground in particular—is ionized and is available to transmit the induced electrical
current for a surface burst, and many conductors (buried pipes, utility lines, etc.) are
buried in the ground or are in contact with it; thus the effects are more intense than
for a blast at a greater distance from the ground [1].
The physical force of the blast wave will excavate a crater from the soil and rock
beneath the weapon. Some of that material will be vaporized by the heat of the
fireball and some will be thrown into the air by the blast. The precise dimensions
will depend on variables that include the density and cohesion of the ground (e.g.
sand, clay, shale, granite, etc.), the yield of the weapon, and its elevation or depth
of burial. For a 10 kt nuclear device exploding on contact with the ground the crater
will be about 75 m in diameter and 20 m in depth. This is deep enough to intersect
with many underground utility lines and, in cities with subways, to do the same with
train tunnels that are not buried too deeply [1, 3].
In addition to the cratering, the shock wave from the weapon will be transmitted
through the rock and soil; denser and more-consolidated materials will transmit the
shock more effectively than will softer sediments such as sand or loose soil. This
shock wave can, in and of itself, sever utility lines, sewer and water mains, fire mains,
and can collapse subway tunnels; it might also collapse basements and even deeper
structures depending on their construction, distance, and the cross-sectional area
presented to the blast wave. The precise effects of a surface burst on the underground
infrastructure have not been published in the unclassified literature.
With regards to fallout, the vapors that had once been rock, soil, buildings, streets,
and so forth will rise and cool and as they cool the vapors will begin to condense
into a sandy substance with a fine to medium grain size [1, 4]. Some of these grains
will incorporate radioactive fission products into them and more fission products will
adhere to the grains’ exterior.
The fallout plume will drift downwind, settling out as it travels. The heaviest
and most radioactive fallout will tend to be found close to the site of the detonation
and will decrease with distance. To a first approximation the fallout plume can be
assumed to be Gaussian in nature with the highest concentration of fallout along
the plume centerline and lowest at the edge. The tremendous thermal energy of the
explosion and the subsequent fires will loft the plume to altitudes of a few to several
km, and the winds at high elevations frequently blow in directions different than do
surface winds. Thus, a nuclear explosion might well produce a complexly shaped
plume with the major plume following the direction of the surface winds and the
minor plume following the upper-level wind direction [5].
According to mathematical models the fallout from a 10 kt surface burst can
produce dangerous radiation levels to distances of a few tens of km downwind with
dose rates in the tens of Gy hr
−1 in the centerline of the plume shortly after the
explosion. Those who are in this area will be exposed to doses of radiation that can
be harmful or fatal to a distance of 10 km downwind; in New York City this might
include as many as one million residents, depending on the direction of the plume.
The amount of radioactivity present and the concomitant radiation dose rate will
change with time because, as short-lived fission products decay to their longer-lived
progeny (and longer-lived nuclides tend to have lower decay energies), the number
99
ground in particular—is ionized and is available to transmit the induced electrical
current for a surface burst, and many conductors (buried pipes, utility lines, etc.) are
buried in the ground or are in contact with it; thus the effects are more intense than
for a blast at a greater distance from the ground [1].
The physical force of the blast wave will excavate a crater from the soil and rock
beneath the weapon. Some of that material will be vaporized by the heat of the
fireball and some will be thrown into the air by the blast. The precise dimensions
will depend on variables that include the density and cohesion of the ground (e.g.
sand, clay, shale, granite, etc.), the yield of the weapon, and its elevation or depth
of burial. For a 10 kt nuclear device exploding on contact with the ground the crater
will be about 75 m in diameter and 20 m in depth. This is deep enough to intersect
with many underground utility lines and, in cities with subways, to do the same with
train tunnels that are not buried too deeply [1, 3].
In addition to the cratering, the shock wave from the weapon will be transmitted
through the rock and soil; denser and more-consolidated materials will transmit the
shock more effectively than will softer sediments such as sand or loose soil. This
shock wave can, in and of itself, sever utility lines, sewer and water mains, fire mains,
and can collapse subway tunnels; it might also collapse basements and even deeper
structures depending on their construction, distance, and the cross-sectional area
presented to the blast wave. The precise effects of a surface burst on the underground
infrastructure have not been published in the unclassified literature.
With regards to fallout, the vapors that had once been rock, soil, buildings, streets,
and so forth will rise and cool and as they cool the vapors will begin to condense
into a sandy substance with a fine to medium grain size [1, 4]. Some of these grains
will incorporate radioactive fission products into them and more fission products will
adhere to the grains’ exterior.
The fallout plume will drift downwind, settling out as it travels. The heaviest
and most radioactive fallout will tend to be found close to the site of the detonation
and will decrease with distance. To a first approximation the fallout plume can be
assumed to be Gaussian in nature with the highest concentration of fallout along
the plume centerline and lowest at the edge. The tremendous thermal energy of the
explosion and the subsequent fires will loft the plume to altitudes of a few to several
km, and the winds at high elevations frequently blow in directions different than do
surface winds. Thus, a nuclear explosion might well produce a complexly shaped
plume with the major plume following the direction of the surface winds and the
minor plume following the upper-level wind direction [5].
According to mathematical models the fallout from a 10 kt surface burst can
produce dangerous radiation levels to distances of a few tens of km downwind with
dose rates in the tens of Gy hr
−1 in the centerline of the plume shortly after the
explosion. Those who are in this area will be exposed to doses of radiation that can
be harmful or fatal to a distance of 10 km downwind; in New York City this might
include as many as one million residents, depending on the direction of the plume.
The amount of radioactivity present and the concomitant radiation dose rate will
change with time because, as short-lived fission products decay to their longer-lived
progeny (and longer-lived nuclides tend to have lower decay energies), the number