WORLDWIDE EFFECTS OF NUCLEAR WAR - - - SOME PERSPECTIVES
U.S. Arms Control and Disarmament Agency, 1975.
CONTENTS
Foreword
Introduction
The Mechanics of Nuclear Explosions
Radioactive Fallout
A. Local Fallout
B. Worldwide Effects of Fallout
Alterations of the Global Environment
A. High Altitude Dust
B. Ozone
Some Conclusions
Note 1: Nuclear Weapons Yield
Note 2: Nuclear Weapons Design
Note 3: Radioactivity
Note 4: Nuclear Half-Life
Note 5: Oxygen, Ozone and Ultraviolet Radiation
FOREWORD
Much research has been devoted to the effects of nuclear weapons. But
studies have been concerned for the most part with those immediate
consequences which would be suffered by a country that was the direct
target of nuclear attack. Relatively few studies have examined the
worldwide, long term effects.
Realistic and responsible arms control policy calls for our knowing more
about these wider effects and for making this knowledge available to the
public. To learn more about them, the Arms Control and Disarmament Agency
(ACDA) has initiated a number of projects, including a National Academy of
Sciences study, requested in April 1974. The Academy's study, Long-Term
Worldwide Effects of Multiple Nuclear Weapons Detonations, a highly
technical document of more than 200 pages, is now available. The present
brief publication seeks to include its essential findings, along with the
results of related studies of this Agency, and to provide as well the basic
background facts necessary for informed perspectives on the issue.
New discoveries have been made, yet much uncertainty inevitably persists.
Our knowledge of nuclear warfare rests largely on theory and hypothesis,
fortunately untested by the usual processes of trial and error; the
paramount goal of statesmanship is that we should never learn from the
experience of nuclear war.
The uncertainties that remain are of such magnitude that of themselves they
must serve as a further deterrent to the use of nuclear weapons. At the
same time, knowledge, even fragmentary knowledge, of the broader effects of
nuclear weapons underlines the extreme difficulty that strategic planners
of any nation would face in attempting to predict the results of a nuclear
war. Uncertainty is one of the major conclusions in our studies, as the
haphazard and unpredicted derivation of many of our discoveries emphasizes.
Moreover, it now appears that a massive attack with many large-scale
nuclear detonations could cause such widespread and long-lasting
environmental damage that the aggressor country might suffer serious
physiological, economic, and environmental effects even without a nuclear
response by the country attacked.
An effort has been made to present this paper in language that does not
require a scientific background on the part of the reader. Nevertheless it
must deal in schematized processes, abstractions, and statistical
generalizations. Hence one supremely important perspective must be largely
supplied by the reader: the human perspective--the meaning of these
physical effects for individual human beings and for the fabric of
civilized life.
Fred C. Ikle
Director
U.S. Arms Control and Disarmament Agency
INTRODUCTION
It has now been two decades since the introduction of thermonuclear fusion
weapons into the military inventories of the great powers, and more than a
decade since the United States, Great Britain, and the Soviet Union ceased
to test nuclear weapons in the atmosphere. Today our understanding of the
technology of thermonuclear weapons seems highly advanced, but our
knowledge of the physical and biological consequences of nuclear war is
continuously evolving.
Only recently, new light was shed on the subject in a study which the Arms
Control and Disarmament Agency had asked the National Academy of Sciences
to undertake. Previous studies had tended to focus very largely on
radioactive fallout from a nuclear war; an important aspect of this new
study was its inquiry into all possible consequences, including the effects
of large-scale nuclear detonations on the ozone layer which helps protect
life on earth from the sun's ultraviolet radiations. Assuming a total
detonation of 10,000 megatons--a large-scale but less than total nuclear
"exchange," as one would say in the dehumanizing jargon of the
strategists--it was concluded that as much as 30-70 percent of the ozone
might be eliminated from the northern hemisphere (where a nuclear war would
presumably take place) and as much as 20-40 percent from the southern
hemisphere. Recovery would probably take about 3-10 years, but the
Academy's study notes that long term global changes cannot be completely
ruled out.
The reduced ozone concentrations would have a number of consequences
outside the areas in which the detonations occurred. The Academy study
notes, for example, that the resultant increase in ultraviolet would cause
"prompt incapacitating cases of sunburn in the temperate zones and snow
blindness in northern countries . . "
Strange though it might seem, the increased ultraviolet radiation could
also be accompanied by a drop in the average temperature. The size of the
change is open to question, but the largest changes would probably occur at
the higher latitudes, where crop production and ecological balances are
sensitively dependent on the number of frost-free days and other factors
related to average temperature. The Academy's study concluded that ozone
changes due to nuclear war might decrease global surface temperatures by
only negligible amounts or by as much as a few degrees. To calibrate the
significance of this, the study mentioned that a cooling of even 1 degree
centigrade would eliminate commercial wheat growing in Canada.
Thus, the possibility of a serious increase in ultraviolet radiation has
been added to widespread radioactive fallout as a fearsome consequence of
the large-scale use of nuclear weapons. And it is likely that we must
reckon with still other complex and subtle processes, global in scope,
which could seriously threaten the health of distant populations in the
event of an all-out nuclear war.
Up to now, many of the important discoveries about nuclear weapon effects
have been made not through deliberate scientific inquiry but by accident.
And as the following historical examples show, there has been a series of
surprises.
"Castle/Bravo" was the largest nuclear weapon ever detonated by the United
States. Before it was set off at Bikini on February 28, 1954, it was
expected to explode with an energy equivalent of about 8 million tons of
TNT. Actually, it produced almost twice that explosive power--equivalent
to 15 million tons of TNT.
If the power of the bomb was unexpected, so were the after-effects. About
6 hours after the explosion, a fine, sandy ash began to sprinkle the
Japanese fishing vessel Lucky Dragon, some 90 miles downwind of the burst
point, and Rongelap Atoll, 100 miles downwind. Though 40 to 50 miles away
from the proscribed test area, the vessel's crew and the islanders received
heavy doses of radiation from the weapon's "fallout”--the coral rock, soil,
and other debris sucked up in the fireball and made intensively radioactive
by the nuclear reaction. One radioactive isotope in the fallout,
iodine-131, rapidly built up to serious concentration in the thyroid glands
of the victims, particularly young Rongelapese children.
More than any other event in the decade of testing large nuclear weapons in
the atmosphere, Castle/Bravo's unexpected contamination of 7,000 square
miles of the Pacific Ocean dramatically illustrated how large-scale nuclear
war could produce casualties on a colossal scale, far beyond the local
effects of blast and fire alone.
A number of other surprises were encountered during 30 years of nuclear
weapons development. For example, what was probably man's most extensive
modification of the global environment to date occurred in September 1962,
when a nuclear device was detonated 250 miles above Johnson Island. The
1.4-megaton burst produced an artificial belt of charged particles trapped
in the earth's magnetic field. Though 98 percent of these particles were
removed by natural processes after the first year, traces could be detected
6 or 7 years later. A number of satellites in low earth orbit at the time
of the burst suffered severe electronic damage resulting in malfunctions
and early failure. It became obvious that man now had the power to make
long term changes in his near-space environment.
Another unexpected effect of high-altitude bursts was the blackout of
high-frequency radio communications. Disruption of the ionosphere (which
reflects radio signals back to the earth) by nuclear bursts over the
Pacific has wiped out long-distance radio communications for hours at
distances of up to 600 miles from the burst point.
Yet another surprise was the discovery that electromagnetic pulses can play
havoc with electrical equipment itself, including some in command systems
that control the nuclear arms themselves.
Much of our knowledge was thus gained by chance--a fact which should imbue
us with humility as we contemplate the remaining uncertainties (as well as
the certainties) about nuclear warfare. What we have learned enables us,
nonetheless, to see more clearly. We know, for instance, that some of the
earlier speculations about the after-effects of a global nuclear war were
as far-fetched as they were horrifying--such as the idea that the
worldwide accumulation of radioactive fallout would eliminate all life on
the planet, or that it might produce a train of monstrous genetic mutations
in all living things, making future life unrecognizable. And this
accumulation of knowledge which enables us to rule out the more fanciful
possibilities also allows us to reexamine, with some scientific rigor,
other phenomena which could seriously affect the global environment and the
populations of participant and nonparticipant countries alike.
This paper is an attempt to set in perspective some of the longer term
effects of nuclear war on the global environment, with emphasis on areas
and peoples distant from the actual targets of the weapons.
THE MECHANICS OF NUCLEAR EXPLOSIONS
In nuclear explosions, about 90 percent of the energy is released in less
than one millionth of a second. Most of this is in the form of the heat
and shock waves which produce the damage. It is this immediate and direct
explosive power which could devastate the urban centers in a major nuclear
war.
Compared with the immediate colossal destruction suffered in target areas,
the more subtle, longer term effects of the remaining 10 percent of the
energy released by nuclear weapons might seem a matter of secondary
concern. But the dimensions of the initial catastrophe should not
overshadow the after-effects of a nuclear war. They would be global,
affecting nations remote from the fighting for many years after the
holocaust, because of the way nuclear explosions behave in the atmosphere
and the radioactive products released by nuclear bursts.
When a weapon is detonated at the surface of the earth or at low altitudes,
the heat pulse vaporizes the bomb material, target, nearby structures, and
underlying soil and rock, all of which become entrained in an expanding,
fast-rising fireball. As the fireball rises, it expands and cools,
producing the distinctive mushroom cloud, signature of nuclear explosions.
The altitude reached by the cloud depends on the force of the explosion.
When yields are in the low-kiloton range, the cloud will remain in the
lower atmosphere and its effects will be entirely local. But as yields
exceed 30 kilotons, part of the cloud will punch into the stratosphere,
which begins about 7 miles up. With yields of 2-5 megatons or more,
virtually all of the cloud of radioactive debris and fine dust will climb
into the stratosphere. The heavier materials reaching the lower edge of
the stratosphere will soon settle out, as did the Castle/Bravo fallout at
Rongelap. But the lighter particles will penetrate high into the
stratosphere, to altitudes of 12 miles and more, and remain there for
months and even years. Stratospheric circulation and diffusion will spread
this material around the world.
RADIOACTIVE FALLOUT
Both the local and worldwide fallout hazards of nuclear explosions depend
on a variety of interacting factors: weapon design, explosive force,
altitude and latitude of detonation, time of year, and local weather
conditions.
All present nuclear weapon designs require the splitting of heavy elements
like uranium and plutonium. The energy released in this fission process is
many millions of times greater, pound for pound, than the most energetic
chemical reactions. The smaller nuclear weapon, in the low-kiloton range,
may rely solely on the energy released by the fission process, as did the
first bombs which devastated Hiroshima and Nagasaki in 1945. The larger
yield nuclear weapons derive a substantial part of their explosive force
from the fusion of heavy forms of hydrogen--deuterium and tritium. Since
there is virtually no limitation on the volume of fusion materials in a
weapon, and the materials are less costly than fissionable materials, the
fusion, "thermonuclear," or "hydrogen" bomb brought a radical increase in
the explosive power of weapons. However, the fission process is still
necessary to achieve the high temperatures and pressures needed to trigger
the hydrogen fusion reactions. Thus, all nuclear detonations produce
radioactive fragments of heavy elements fission, with the larger bursts
producing an additional radiation component from the fusion process.
The nuclear fragments of heavy-element fission which are of greatest
concern are those radioactive atoms (also called radionuclides) which decay
by emitting energetic electrons or gamma particles. (See "Radioactivity"
note.) An important characteristic here is the rate of decay. This is
measured in terms of "half-life"--the time required for one-half of the
original substance to decay--which ranges from days to thousands of years
for the bomb-produced radionuclides of principal interest. (See "Nuclear
Half-Life" note.) Another factor which is critical in determining the
hazard of radionuclides is the chemistry of the atoms. This determines
whether they will be taken up by the body through respiration or the food
cycle and incorporated into tissue. If this occurs, the risk of biological
damage from the destructive ionizing radiation (see "Radioactivity" note)
is multiplied.
Probably the most serious threat is cesium-137, a gamma emitter with a
half-life of 30 years. It is a major source of radiation in nuclear
fallout, and since it parallels potassium chemistry, it is readily taken
into the blood of animals and men and may be incorporated into tissue.
Other hazards are strontium-90, an electron emitter with a half-life of 28
years, and iodine-131 with a half-life of only 8 days. Strontium-90
follows calcium chemistry, so that it is readily incorporated into the
bones and teeth, particularly of young children who have received milk from
cows consuming contaminated forage. Iodine-131 is a similar threat to
infants and children because of its concentration in the thyroid gland.
In addition, there is plutonium-239, frequently used in nuclear explosives.
A bone-seeker like strontium-90, it may also become lodged in the lungs,
where its intense local radiation can cause cancer or other damage.
Plutonium-239 decays through emission of an alpha particle (helium nucleus)
and has a half-life of 24,000 years.
To the extent that hydrogen fusion contributes to the explosive force of a
weapon, two other radionuclides will be released: tritium (hydrogen-3), an
electron emitter with a half-life of 12 years, and carbon-14, an electron
emitter with a half-life of 5,730 years. Both are taken up through the
food cycle and readily incorporated in organic matter.
Three types of radiation damage may occur: bodily damage (mainly leukemia
and cancers of the thyroid, lung, breast, bone, and gastrointestinal
tract); genetic damage (birth defects and constitutional and degenerative
diseases due to gonodal damage suffered by parents); and development and
growth damage (primarily growth and mental retardation of unborn infants
and young children). Since heavy radiation doses of about 20 roentgen or
more (see "Radioactivity" note) are necessary to produce developmental
defects, these effects would probably be confined to areas of heavy local
fallout in the nuclear combatant nations and would not become a global
problem.
Most of the radiation hazard from nuclear bursts comes from short-lived
radionuclides external to the body; these are generally confined to the
locality downwind of the weapon burst point. This radiation hazard comes
from radioactive fission fragments with half-lives of seconds to a few
months, and from soil and other materials in the vicinity of the burst made
radioactive by the intense neutron flux of the fission and fusion
reactions.
It has been estimated that a weapon with a fission yield of 1 million tons
TNT equivalent power (1 megaton) exploded at ground level in a 15
miles-per-hour wind would produce fallout in an ellipse extending hundreds
of miles downwind from the burst point. At a distance of 20-25 miles
downwind, a lethal radiation dose (600 rads) would be accumulated by a
person who did not find shelter within 25 minutes after the time the
fallout began. At a distance of 40-45 miles, a person would have at most 3
hours after the fallout began to find shelter. Considerably smaller
radiation doses will make people seriously ill. Thus, the survival
prospects of persons immediately downwind of the burst point would be slim
unless they could be sheltered or evacuated.
It has been estimated that an attack on U.S. population centers by 100
weapons of one-megaton fission yield would kill up to 20 percent of the
population immediately through blast, heat, ground shock and instant
radiation effects (neutrons and gamma rays); an attack with 1,000 such
weapons would destroy immediately almost half the U.S. population. These
figures do not include additional deaths from fires, lack of medical
attention, starvation, or the lethal fallout showering to the ground
downwind of the burst points of the weapons.
Most of the bomb-produced radionuclides decay rapidly. Even so, beyond the
blast radius of the exploding weapons there would be areas ("hot spots")
the survivors coul...
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