"The discovery of nuclear chain reactions need not
bring about the destruction of mankind any more than did the
discovery of matches. We only must do everything in our power to
safeguard against its abuse."
One of the most mysterious phenomena in the universe is the conversion of
mass into energy. The whole universe is
"powered" by this process. The energy radiated by stars,
including the Sun, arises from nuclear reactions (called fusion)
deep in their interiors. The release of nuclear energy occurs
through the fusion of two light hydrogen nuclei into a heavier
nucleus of helium.
The Solar and Heliospheric Observatory
Until about 1800, the principal fuel on our planet was wood, its
energy originating from solar energy stored in plants during their
Since the Industrial Revolution, people have depended on fossil
fuels—coal, petroleum, and natural gas—also derived from stored
solar energy. When a fossil fuel such as coal is burned, atoms of
hydrogen and carbon in the coal combine with oxygen atoms in air.
Water and carbon dioxide are produced and heat is released.
This amount of energy is typical of chemical reactions resulting
from changes in the electronic structure of the atoms. A part of the
energy released as heat keeps the adjacent fuel hot enough to keep
the reaction going.
In a nuclear reaction, however, the energy
released is often about 10 million times greater than in a chemical
reaction, and the change in mass can easily be measured.
The history of generating huge amounts of energy in a nuclear
reaction, is basically the history of the atom bomb...Here are few important
steps that led to the release of nuclear energy on demand.
- In 1896, Antoine Henri Becquerel discovered radioactivity in
In 1902, Marie and Pierre Curie isolated a radioactive metal called
- In 1905, Albert Einstein formulated his Special Theory of
According to this theory, mass can be considered to be another form
of energy. According to Einstein, if somehow we could
transform mass into energy, it would be possible to
"liberate" huge amounts of energy.
- During the next decade, a major step was taken in that
direction when Ernest Rutherford and Niels Bohr described the
structure of an atom more precisely. It was made up, they said, of a
positively charged core, the nucleus, and of negatively charged
electrons that revolved around the nucleus. It was the nucleus,
scientists concluded, that had to be broken or "exploded"
if atomic energy was to be released.
In 1934, Enrico Fermi of Italy disintegrated heavy atoms by spraying
them with neutrons. However he didn't realize that he had achieved
- In December 1938, though, Otto Hahn and Fritz
Strassman in Berlin did a similar experiment with uranium and were
able to verify a world-shaking achievement.
They had produced nuclear fission (they had split an atom)
- 33 years after Einstein said it could be done mass was transformed
- On August 2, 1939, Albert Einstein wrote a letter to the
American President, Franklin D. Roosevelt. "In the course of
the last four months, it has been made probable - through the work of Joliot in France as well as Fermi and
Szilard in America - that it may become possible to set up nuclear
chain reactions in a large mass of uranium... And this new phenomenon
would also lead to the construction of bombs... A single bomb of
this type, carried by boat or exploded in a port, might very well
destroy the whole port together with some of the surrounding
territory." He urged Roosevelt to begin a nuclear program
In later years Einstein deplored the role he had
played in the development of such a destructive weapon: "I made
one great mistake in my life," he told Linus Pauling, another
prominent scientist, "when I signed the letter to President
Roosevelt recommending that atoms bombs be made."
- In December 1942 at the University of Chicago, the Italian
physicist Enrico Fermi succeeded in producing the first nuclear
chain reaction. This was done with an arrangement of natural uranium
lumps distributed within a large stack of pure graphite, a form of
carbon. In Fermi's “pile,” or nuclear reactor, the graphite
moderator served to slow the neutrons.
- In August 1942, during World War II, the United States
established the Manhattan Project. The purpose of this
project was to developed, construct, and test the A-bomb. Many
prominent American scientists, including the physicists Enrico Fermi
and J. Robert Oppenheimer and the chemist Harold Urey, were
associated with the project, which was headed by a U.S. Army
engineer, then-Brigadier General Leslie R. Groves.
- On May 31, 1945, sixteen men met in the
office of Secretary of War Henry L. Stimson. The sixteen men were there to make
decisions about a weapon the average American had never heard of - the atom bomb.
They picked future targets for "The Bomb." They were not talking about
"just another weapon." What they were discussing was "a new
relationship of man to the universe," as said by Stimson. Humankind, the
Secretary seemed to be saying, was at the most critical turning point in its
entire recorded history.
The super-secret group also had many questions about the future
- What were the chances of producing nuclear weapons more
powerful that the one being developed?
- How long would it take other nations, especially the
Soviet Union, to catch up with the United States?
- What hope was there to use atomic energy for peaceful
purposes, such generating as electricity?
- On July 16, 1945, the first atomic bomb (or A-bomb), was
tested at Alamogordo, New Mexico.
- On August 6, 1945, the
Enola Gay, an American airplane, dropped the first atomic bomb ever
used in warfare on Hiroshima, Japan, eventually killing over 140,000
people. On August 9, 1945, the United States dropped a second atomic
bomb, this time on the Japanese city of Nagasaki. The drop is one
mile off target, but it kills 75,000 people.
- On August 29, 1949, the Soviet Union tested its first atomic
device at the Semipalatinsk test range. (Up to 20kt yield)
November 1, 1952, a full-scale, successful experiment was conducted
by the United States with a fusion-type device.
In 1946, the Atomic Energy Commission (AEC), civilian agency of the
United States government, was established by the Atomic Energy Act
to administer and regulate the production and use of atomic
Among the major programs of the new commission were production of
fissionable materials; accident prevention; research in biology,
health, and metallurgy and production of electric power from the
atom; studies in the production of nuclear aircraft; and the
declassification of data on atomic energy.
The most important goal of the 1946 act, however, was to put the
immense power and possibilities of atomic energy under civilian
control, although nuclear materials and facilities remained in
A revised Atomic Energy Act in 1954 allowed for licensed private
ownership of facilities to produce fissionable materials.
In 1964 an amendment permitted private ownership of nuclear fuels,
which aided the growing nuclear power industry.
Under the Energy Reorganization Act of October 1974, the AEC was
abolished, and two new federal agencies were established to
administer and regulate atomic-energy activities: the Energy
Research and Development Administration and the Nuclear Regulatory
In 1977, the responsibilities of the former were transferred to the
newly established Department of Energy.
mass and energy
The Equivalence of Mass and Energy
In 1905, Albert Einstein formulated his Special Theory of
Relativity. According to this theory, mass can be considered to be another form
In our daily life, mass and energy
seem to be separate. In a nuclear reaction, however, the energy
released is often about a million times greater than in a chemical
reaction, and the change in mass can easily be measured.
Mass and energy are related by what is certainly the best-known
equation in physics:
in which E is the energy equivalent (called mass energy) of mass
m, and c is the speed of light.
small amount of matter is equivalent to a vast amount of energy.
example, 1 kg (2.2 lb) of matter converted completely into energy
would be equivalent to the energy released by exploding 22 megatons
"And Jesus said unto them, Because of your
unbelief: for verily I say unto you, If ye have faith as a grain of
mustard seed, ye shall say unto this mountain, Remove hence to
yonder place; and it shall remove; and nothing shall be impossible
Matthew, 17:20, The King James Bible
Nuclear Energy is released during the splitting (fission) or
atomic nuclei. The energy of any system, whether physical, chemical,
or nuclear, is manifested by the system's ability to do work or to
release heat or radiation. The total energy in a system is always
conserved, but it can be transferred to another system or changed in
form. According to the Law of Conservation of Energy, if we add up the
total amount of energy in the universe (we can describe energy
quantitatively with units such as Joules or kilowatt-hours), the
total amount never changes. In other words, energy is neither
created nor lost, even though it may be converted from one form to
another. Thus the law of conservation of energy is really the law
of conservation of mass-energy.
The atom consists of a small, massive, positively charged core,
nucleus, surrounded by electrons.
The nucleus contains most of the mass of the atom. It is itself composed of
neutrons and protons.
- The proton is 1,836 times as heavy as the
For an atom of hydrogen, which contains one electron and one
proton, the proton provides 99.95 percent of the mass.
- The neutron weighs a little more than the proton.
Elements heavier than hydrogen usually contain about the same
number of protons and neutrons in their nuclei, so the atomic
mass, or the mass of one atom, is usually about twice the atomic
Protons are affected by all four of the fundamental forces that
govern all interactions between particles and energy in the
- The electromagnetic force arises from matter carrying
an electrical charge. It causes positively charged protons to
attract negatively charged electrons and holds them in orbit
around the nucleus of the atom.
- The strong nuclear force binds the protons and neutrons
together into a compact nucleus. This force is 100 million times
stronger than the electrical attraction that binds the
electrons. It must be strong enough to overcome the repulsive force of the
positively charged nuclear protons and to bind both protons and
neutrons into the tiny nuclear volume. The nuclear force must also
be of short range because its influence does not extend very far
beyond the nuclear "surface." The nuclear force is due to
a strong force that binds quarks together to form neutrons and
- The other two fundamental forces, gravitation and the weak
nuclear force, also affect the proton. Gravitation is a
force that attracts anything with mass (such as the proton) to
every other thing in the universe that has mass. It is weak when
the masses are small, but can become very large when the masses
- The weak nuclear force is a feeble force that occurs
between certain types of elementary particles, including the
proton, and governs how some elementary particles break up into
The number of protons in the nucleus of an atom determines what
kind of chemical element it is. All substances in nature are
made up of combinations of the 92 different chemical elements,
substances that cannot be broken into simpler substances by chemical
processes. The atom is the smallest part of a chemical element that
still retains the properties of the element. The number of protons
in each atom can range from one in the hydrogen atom to 92 in the
uranium atom, the heaviest naturally occurring element.
For a very different and controversial theory of
The Living Atom Theory
Another controversial theory: Metaparticles
The nucleus contains most of the mass of the atom. It is itself composed of
neutrons and protons bound together by very strong nuclear forces,
much greater than the electrical forces that bind the electrons to
the nucleus. The nucleus of an atom is described by these
- The mass number "A" of a nucleus is the number of
nucleons (protons and neutrons) it contains.
- The atomic number "Z"
is the number of positively charged protons.
For example, the expression U,
represents uranium with A=235 (number of nucleons) and Z=92
(number of protons).
- The binding energy of a nucleus is a measure of how tightly its
protons and neutrons are held together by the nuclear forces.
binding energy per nucleon, the energy required to remove one
neutron or proton from a nucleus, is a function of the mass number
The total energy required to break up a nucleus into its
constituent protons and neutrons can be calculated from ,
called nuclear binding energy.
If we divide the binding energy of a nucleus by the number of
protons and neutrons (number of nucleons), we get the binding energy
per nucleon. This is the common term used to describe nuclear
reactions because atomic numbers vary and total binding energy would
be a relative term dependent upon that. The following figure, called
the binding energy curve, shows a plot of nuclear binding energy as
a function of mass number. The peak is at iron (Fe) with mass number
equal to 56.
The binding energy per nucleon is a
function of the mass number
The curve of binding energy implies that if two light nuclei near
the left end
of the curve coalesce to form a heavier nucleus (the process is called fusion),
a heavy nucleus at the far right splits into two lighter ones (the
called fission), more
tightly bound nuclei result, and energy will be released.
The rising of the binding energy curve at low mass numbers, tells us that energy will be released if two nuclides of
small mass number combine to form a single middle-mass nuclide. This process is
called nuclear fusion.
The eventual dropping of the binding energy curve at high
mass numbers tells us
on the other hand, that nucleons are more tightly bound when they are
assembled into two middle-mass nuclides rather than into a single high-mass
nuclide. In other words, energy can be released by the nuclear
fission, or splitting, of a single massive nucleus into two smaller
The binding energy curve shows that energy can be released if two
light nuclei combine to form a single larger nucleus. This process
is called nuclear fusion. The process is hindered by the electrical
repulsion that acts to prevent the two particles from getting close
enough to each other to be within range and "fusing."
To generate useful amounts of power, nuclear fusion must occur in
bulk matter. That is, many atoms need to fuse in order create a
significant amount of energy. The best hope for bringing this about
is to raise the temperature of the material so that the particles
have enough energy - due to their thermal motions alone - to penetrate
the electrical repulsion barrier. This process is known as
thermonuclear fusion. Calculations show that these temperatures need
to be close to the sun's temperature of 1.5 X 107K.
Nuclear energy, measured in millions of electron volts (MeV), is
released by the fusion of two light nuclei, as when two heavy
hydrogen nuclei, deuterons,
combine in the reactionproducing a helium-3 atom, a free neutron,
and 3.2 MeV (3.2x106eV).
Although the energy release in the fusion process is less per
nuclear reaction than in fission, 0.5 kg (1.1 lb) of the lighter
material contains many more atoms; thus, the energy liberated from
0.5 kg (1.1 lb) of hydrogen-isotope fuel is equivalent to that of
about 29 kilotons of TNT, or almost three times as much as from
uranium. This estimate, however, is based on complete fusion of all
hydrogen atoms. Fusion reactions occur only at temperatures of
several millions of degrees, the rate increasing enormously with
increasing temperature; such reactions consequently are known as
thermonuclear (heat-induced) reactions. Strictly speaking, the term
thermonuclear implies that the nuclei have a range (or distribution)
of energies characteristic of the temperature. This plays an
important role in making rapid fusion reactions possible by an
increase in temperature.
Development of the hydrogen bomb was impossible before the
perfection of A-bombs, for only the latter could yield that
tremendous heat necessary to achieve fusion of hydrogen atoms.
Atomic scientists regarded the A-bomb as the trigger of the
projected thermonuclear device.
Thermonuclear Fusion in the Sun and other Stars
The sun radiates energy at the rate of 3.9 X 1026 W (watts) and
has been doing so for several billion years. The sun burns hydrogen
in a "nuclear furnace." The fusion reaction in the sun is
a multi-step process in which hydrogen is burned into helium,
hydrogen being the "fuel" and helium the
"ashes." Hydrogen burning
has been going on in the sun for about 5 billion years and
calculations show that there is enough hydrogen left to keep the sun
going for about the same length of time into the future. The burning of hydrogen in the sun's core is alchemy on a grand
scale in the sense that one element is turned into another.
Fusion takes place when the nuclei of hydrogen atoms with one
proton each fuse together to form helium atoms with two protons. A
standard hydrogen atom has one proton in its nucleus. There are two
isotopes of hydrogen which also contain one proton, but contain
neutrons as well. Deuterium contains one neutron while Tritium
contains two. Deep within the star, A deuterium atom combines with a
tritium atom. This forms a helium atom and an extra neutron. In the
process, an incredible amount of energy is released.
When the star's supply of hydrogen is used up, it begins to
convert helium into oxygen and carbon. As a star evolves and
becomes still hotter, other elements can be formed by other fusion
reactions. If the star is massive enough, it will continue until it
converts carbon and oxygen into neon, sodium, magnesium, sulfur and
silicon. Eventually, these elements are transformed into calcium,
iron, nickel, chromium, copper and others until iron is formed. When
the core becomes primarily iron, the star's nuclear reaction can no
longer continue. Eements more massive than those with atomic
number equal to 56 (iron) cannot be manufactured by further fusion
processes as atomic number equal to 56 makes the peak of the binding
energy curve. If nuclides were to fuse after that, then energy would
be consumed as opposed to produced.
The inward pressure of gravity becomes stronger than the outward
pressure of the nuclear reaction. The star collapses in on itself.
What happens next depends on the star's mass.
Nuclear energy is also released when the fission of a heavy
nucleus such as U is
induced by the absorption of a neutron as in
producing cesium-140, rubidium-93, three neutrons, and 200 MeV.
fission reaction releases 10 million times as much energy as is
released in a typical chemical reaction.
units, the fission of 1 kg (2.2 lb) of uranium-235 releases 18.7
million kilowatt-hours as heat.
The fission process
initiated by the absorption of one neutron in uranium-235 releases
about 2.5 neutrons, on the average, from the split nuclei. The
neutrons released in this manner quickly cause the fission of two
more atoms, thereby releasing four or more additional neutrons and
initiating a self-sustaining series of nuclear fissions, or a chain
reaction, which results in continuous release of nuclear energy.
Using the binding
energy curve, we can estimate the energy released in this fission process.
From this curve, we see that for heavy nuclides (mass about 240u), the mean
biding energy per nucleon is about 7.6MeV. For middle-mass nuclides (mass about
120), it is about 8.5 MeV. This difference in total binding energy between a
single large nucleus and two fragments (assumed to be equal) into which it may
be split is then close to 200MeV. This is a relatively large amount of released energy per
fission event. When a chain reaction occurs, many atoms and nuclei are involved
so lots of energy is released.
Fission in Nuclear Reactors
To make large-scale use of the energy released in fission,
one fission event must trigger another, so that the process spreads throughout the nuclear fuel as in a set of dominos. The fact that more neutrons are
produced in fission than are consumed raises the possibility of a chain
reaction. Such a reaction can be either rapid (as in an atomic bomb) or
controlled (as in a reactor).
Core of the US Geological Survey (USGS)
nuclear research reactor, Triga
II, while operating.
In a nuclear reactor, control rods made of cadmium or
graphite or some other neutron-absorbing material are used to regulate the
number of neutrons. The more exposed control rods, the less neutrons and vice
versa. This also controls the multiplication factor k which is the ratio
of the number of neutrons present at the beginning of a particular generation to
the number present at the beginning of the next generation. For k=1, the
operation of the reactor is said to be exactly critical, which is what we
wish it to be for steady-power operation. Reactors are designed so that they are
inherently supercritical (k>1); the multiplication factor is
then adjusted to the critical operation by inserting the control rods.
An unavoidable feature of reactor operation is the
accumulation of radioactive wastes,
including both fission products and heavy "transuranic" nuclides such
as plutonium and americium.
In the 20th century, the rapid advance of industry and modern technology
greatly increased both the destructive power
of armed forces and the capacity of societies both to resist and to
recover from an attack. Nuclear weapons carry the possibilities of
destruction to a new level and are able to inflict far greater
damage within a few hours than previously resulted from years of
warfare. This not only makes the consequences of war worse but also
raises new concerns about controlling such a destructive process.
Indeed, nuclear weapons have not been used in war since the first
two atomic bombs were dropped on Japan in 1945, but many countries,
including many Third World countries, now have nuclear weapons.
Nuclear Weapons are explosive devices designed
to release nuclear energy on a large scale for military reasons.
The first atomic bomb (or A-bomb), was
tested on July 16, 1945, at Alamogordo, New Mexico.
||All explosives prior to
that time derived their power from the rapid burning or
decomposition of some chemical compound. Such chemical
processes release only the energy of the outermost electrons
in the atom.
Nuclear explosives, on the other hand, involve energy sources
within the nucleus of the atom.
The A-bomb gained
its power from the splitting (fission) of all the atomic
nuclei in several kilograms of plutonium. A sphere about the
size of a baseball produced an explosion equal to 20,000 tons
Although nuclear bombs were originally developed as
strategic weapons to be carried by large bombers, nuclear weapons
are now available for a variety of both strategic and tactical
applications. Not only can they be delivered by different types of
aircraft, but rockets and guided missiles of many sizes can now
carry nuclear warheads and can be launched from the ground, the air,
or underwater. Large rockets can carry multiple warheads for
delivery to separate targets.
The first USSR's ICBM thermonuclear warhead
Up to 3 Mt yield. Up to 8500 km flight range.
In service in 1960-1966
The Atom Bomb
The atomic bomb works by a physical phenomenon known as fission.
In this case, particles, specifically nuclei, are split and great amounts of
energy are released. This energy is expelled explosively and violently in the
atomic bomb. The massive power behind the reaction in an atomic bomb arises from
the forces that hold the atom together called the strong nuclear
The element used in atomic bombs is Uranium-235. Uranium's atoms are
unusually large, and henceforth, it is hard for them to hold together firmly.
This makes Uranium-235 an exceptional candidate for nuclear fission. Uranium is
a heavy metal and has many more neutrons than protons. This does not enhance
their capacity to split, but it does have an important bearing on their capacity
to facilitate an explosion.
Uranium is not the only material used for making atomic
bombs. Another material is the element Plutonium, in its isotope Pu-239.
However, Plutonium will not start a fast chain reaction by itself. The material
is not fissionable in and of itself, but may act as a catalyst to the greater
reaction. The bomb basically works with a detonating head starting off the
explosive chain reaction.
The Chain Reaction
When a uranium or other suitable nucleus fissions, it breaks up
into a pair of nuclear fragments and releases energy. At the same
time, the nucleus emits very quickly a number of fast neutrons, the
same type of particle that initiated the fission of the uranium
nucleus. This makes it possible to achieve a self-sustaining series
of nuclear fissions; the neutrons that are emitted in fission
produce a chain reaction, with continuous release of energy.
Fission of uranium 235 nucleus.
When a U-235 atom splits, it gives off energy in the form of
heat and Gamma radiation,
which is the most powerful form
of radioactivity and the most lethal. When this reaction occurs, the split
atom will also give off two or three of its "spare" neutrons, which
are not needed to make either of the parts after splitting. These spare neutrons
fly out with sufficient force to split other atoms they come in contact with. In
theory, it is necessary to split only one U-235 atom, and the neutrons from this
will split other atoms, which will split more...so on and so forth. This
progression does not take place arithmetically, but geometrically. All of this
will happen within a millionth of a second.
A small sphere of pure fissile material, such as uranium-235,
about the size of a golf ball, would not sustain a chain reaction.
Too many neutrons escape through the surface area, which is
relatively large compared with its volume, and thus are lost to the
chain reaction. In a mass of uranium-235 about the size of a
baseball, however, the number of neutrons lost through the surface
is compensated for by the neutrons generated in additional fissions
taking place within the sphere. The minimum amount of fissile
material (of a given shape) required to maintain the chain reaction
is known as the critical mass. Increasing the size of the sphere
produces a supercritical assembly, in which the successive
generations of fissions increase very rapidly, leading to a possible
explosion as a result of the extremely rapid release of a large
amount of energy.
In an atomic bomb, therefore, a mass of fissile
material greater than the critical mass must be assembled
instantaneously and held together for about a millionth of a second
to permit the chain reaction to propagate before the bomb explodes.
A heavy material, called a tamper, surrounds the fissile mass and
prevents its premature disruption. The tamper also reduces the
number of neutrons that escape.
If every atom in 0.5 kg (1.1 lb) of uranium were to split, the
energy produced would equal the explosive power of 9.9 kilotons of
TNT. In this hypothetical case, the efficiency of the process would
be 100 percent. In the first A-bomb tests, this kind of efficiency
was not approached. Moreover, a 0.5-kg (1.1-lb) mass is too small
for a critical assembly.
Detonation of Atomic Bombs
Various systems have been devised to detonate the atomic bomb.
The simplest system is the gun-type weapon, in which a projectile
made of fissile material is fired at a target of the same material
so that the two weld together into a supercritical assembly. The
atomic bomb exploded by the United States over Hiroshima, Japan, on
August 6, 1945, was a gun-type weapon. It had the energy of anywhere
between 12.5 and 15 kilotons of TNT. Three days later the United
States dropped a second atomic bomb over Nagasaki, Japan, with the
energy equivalent of about 20 kilotons of TNT.
On August 6, 1945, an American B-29 bomber named the
Enola Gay, dropped atomic bomb on Hiroshima.
The U-235 gun-type bomb, named Little Boy, exploded at
8:16:02 a.m. In an instant 140,000 people were killed and
100,000 more were seriously injured.
A more complex method, known as implosion, is used in a spherically
shaped weapon. The outer part of the sphere consists of a layer of
closely fitted and specially shaped devices, called lenses,
consisting of high explosive and designed to concentrate the blast
toward the center of the bomb. Each segment of the high explosive is
equipped with a detonator, which in turn is wired to all other
segments. An electrical impulse explodes all the chunks of high
explosive simultaneously, resulting in a detonation wave that
converges toward the core of the weapon. At the core is a sphere of
fissile material, which is compressed by the powerful, inwardly
directed pressure, or implosion. The density of the metal is
increased, and a supercritical assembly is produced.
test bomb, as well as the one dropped by the United States on
Nagasaki, Japan, on August 9, 1945, were of the implosion type. Each
was equivalent to about 20 kilotons of TNT.
||On August 9, 1945, the American B-29
bomber, Bock's Car dropped Fat Man, a plutonium
implosion-type bomb on Nagasaki.
Of the 286,00 people living in Nagasaki at the time of
the blast, 74,000 were killed and another 75,000 sustained
Regardless of the method used to attain a supercritical assembly,
the chain reaction proceeds for about a millionth of a second,
liberating vast amounts of heat energy. The extremely fast release
of a very large amount of energy in a relatively small volume causes
the temperature to rise to tens of millions of degrees. The
resulting rapid expansion and vaporization of the bomb material
causes a powerful explosion.
The Hydrogen Bomb
The Hydrogen bomb works on a different physical principle
known as nuclear fusion.
In nuclear fusion, the nuclei of atoms join together, or fuse to form a heavier
nucleus (specifically, nuclei of the isotopes of hydrogen combine to form
a heavier helium nucleus). This happens only under very hot conditions. The explosion of an atomic
bomb attached to a hydrogen bomb provides the heat to start fusion.
Fusion releases energy due to the overall loss in mass. The total of the masses of the particles which go into a fusion
reaction is bigger than the total of the masses of the particles which come
out. The "mass difference" takes the form of energy.
The hydrogen bomb is thousands of times more powerful than an
atomic bomb. There have not been any hydrogen bombs used in warfare, however
there have been hydrogen bomb tests. Most of these tests are done underwater due
to risk of destruction.
The H-bomb is extremely powerful. A common hydrogen bomb has the
power of up to 10 megatons. This atomic bomb dropped on Hiroshima, Japan which killed over
140,000 people had the power of 13 kilotons. All the explosions in World War II totaled "only" 2 megatons
- 20% of the power of ONE common hydrogen
November 1, 1952, a full-scale, successful experiment was conducted
by the United States with a fusion-type device. This test, called Mike,
which was part of Operation Ivy, produced an explosion with power
equivalent to several million tons of TNT (that is, several
||The first U.S. hydrogen bomb test, Mike, is
shown in the Pacific at Eniwetok Atoll, Marshall Islands,
November 1, 1952.
The Soviet Union detonated a thermonuclear weapon
on August 12, 1953 at the Semipalatinsk test range. Up to 400 kt
On March 1, 1954, the United States
exploded a fusion bomb with a power of 15 megatons. It created a
glowing fireball, more than 4.8 km (more than 3 mi) in diameter, and
a huge mushroom cloud, which quickly rose into the stratosphere.
The March 1954 explosion led to worldwide recognition of the nature
of radioactive fallout. The fallout of radioactive debris from the
huge bomb cloud also revealed much about the nature of the
thermonuclear bomb. Had the bomb been a weapon consisting of an
A-bomb trigger and a core of hydrogen isotopes, the only persistent
radioactivity from the explosion would have been the result of the
fission debris from the trigger and from the radioactivity induced
by neutrons in coral and seawater. Some of the radioactive debris,
however, fell on the Lucky Dragon, a Japanese vessel engaged in tuna
fishing about 160 km (about 100 mi) from the test site. This
radioactive dust was later analyzed by Japanese scientists. The
results demonstrated that the bomb that dusted the Lucky Dragon with
fallout was more than just an H-bomb.
||The world's most powerful experimental bomb.
Tested on November 30, 1961 at the Novaya Zemlya test range.
More that 100 Mt rated yield.
Test-detonated at half the yield.
The thermonuclear bomb exploded in 1954 was a three-stage weapon.
The first stage consisted of a big A-bomb, which acted as a trigger.
The second stage was the H-bomb phase resulting from the fusion of
deuterium and tritium within the bomb. In the process helium and
high-energy neutrons were formed. The third stage resulted from the
impact of these high-speed neutrons on the outer jacket of the bomb,
which consisted of natural uranium, or uranium-238. No chain
reaction was produced, but the fusion neutrons had sufficient energy
to cause fission of the uranium nuclei and thus added to the
explosive yield and also to the radioactivity of the bomb residues.
The Neutron Bomb - Clean H-Bomb
On the average, about 50 percent of the power of an H-bomb
results from thermonuclear-fusion reactions and the other 50 percent
from fission that occurs in the A-bomb trigger and in the uranium
jacket. A clean H-bomb is defined as one in which a significantly
smaller proportion than 50 percent of the energy arises from
fission. Because fusion does not produce any radioactive products
directly, the fallout from a clean weapon is less than that from a
normal or average H-bomb of the same total power. If an H-bomb were
made with no uranium jacket but with a fission trigger, it would be
relatively clean. Perhaps as little as 5 percent of the total
explosive force might result from fission; the weapon would thus be
95 percent clean. The enhanced-radiation fusion bomb, also called
the neutron bomb, which has been tested by the United States and
other nuclear powers, does not release long-lasting radioactive
fission products. However, the large number of neutrons released in
thermonuclear reactions is known to induce radioactivity in
materials, especially earth and water, within a relatively small
area around the explosion.
Thus the neutron bomb is considered a
tactical weapon because it can do serious damage on the battlefield,
penetrating tanks and other armored vehicles and causing death or
serious injury to exposed individuals, without producing the
radioactive fallout that endangers people or structures miles away.
Effects of Nuclear Weapons
Explosions produce both immediate and delayed destructive
effects. Blast, thermal radiation, prompt ionizing radiation are
produced and cause significant destruction within seconds or minutes
of a nuclear detonation. The delayed effects, such as radioactive
fallout and other possible environmental effects, inflict damage
over an extended period ranging from hours to years.
Destruction of a
military target by a nuclear fission weapon is comprehended
mainly by the effects of a powerful blast wave in air but
the more distant military consequences of a nuclear
explosion can be significantly augmented by the thermal
(heat) radiations emitted by the fireball that emerges from
the isothermal sphere. Furthermore, accurate anticipation of
the thermal characteristics and physical behavior of an
isothermal sphere as it endures and rises above a nuclear
explosion can be useful as a basis to predict the military
and environmental effects of radioactive fallout since most
of the dangerous fission byproducts of an atomic bomb
detonation are concentrated in the isothermal sphere.
The effects of nuclear weapons were carefully observed, both
after the bombings of Hiroshima and Nagasaki and after many test
explosions in the 1950s and early 1960s. The basic effects of
nuclear explosion are:
As is the case with explosions caused by conventional weapons,
most of the damage to buildings and other structures from a nuclear
explosion results, directly or indirectly, from the effects of
The very rapid expansion of the bomb materials produces a
high-pressure pulse, or shock wave, that moves rapidly outward from
the exploding bomb. In air, this shock wave is called a blast wave
because it is equivalent to and is accompanied by powerful winds of
much greater than hurricane force. Damage is caused both by the high
excess (or overpressure) of air at the front of the blast wave and
by the extremely strong winds that persist after the wave front has
In general, large buildings are destroyed by the change in air
pressure, while people and objects such as trees and utility poles
are destroyed by the wind.
The degree of blast damage suffered on the ground depends on:
TNT equivalent of the explosion;
the altitude at which the bomb
is exploded (the height of burst);
and the distance of
the structure from ground zero (the point directly under
Assuming a height of burst that will maximize the damage area, a
10-kiloton bomb will cause severe damage to wood-frame houses, such
as are common in the United States, to a distance of more than 1.6
km (more than 1 mi) from ground zero and moderate damage as far as
2.4 km (1.5 mi). (A severely damaged house probably would be beyond
repair.) The damage radius increases with the power of the bomb,
approximately in proportion to its cube root. If exploded at the
optimum height, therefore, a 10-megaton weapon, which is 1,000 times
as powerful as a 10-kiloton weapon, will increase the distance
tenfold, that is, out to 17.7 km (11 mi) for severe damage and 24 km
(15 mi) for moderate damage of a frame house.
When a nuclear weapon is detonated on or near Earth's surface,
the blast digs out a large crater. Some of the material that used in
be in the crater is deposited on the rim of the crater; the rest is
carried up into the air and returns to Earth as radioactive fallout.
An explosion that is farther above the Earth's surface than the
radius of the fireball does not dig a crater and produces negligible
immediate fallout. For the most part, a nuclear blast kills people
by indirect means rather than by direct pressure.
Approximately 35 percent of the energy from a nuclear explosion
is an intense burst of thermal radiation, i.e., heat. The effects
are similar to the effect of a two-second flash from an enormous
sunlamp. The very high temperatures attained in a nuclear explosion result
in the formation of an extremely hot incandescent mass of gas called
For a 10-kiloton explosion in the air, the fireball will
attain a maximum diameter of about 300 m (about 1,000 ft); for a
10-megaton weapon the fireball may be 4.8 km (3 mi) across. A flash
of thermal (or heat) radiation is emitted from the fireball and
spreads out over a large area, but with steadily decreasing
intensity. The amount of heat energy received a certain distance
from the nuclear explosion depends on the power of the weapon and
the state of the atmosphere. If the visibility is poor or the
explosion takes place above clouds, the effectiveness of the heat
flash is decreased.
The thermal radiation falling on exposed skin
can cause what are called flash burns. A 10-kiloton explosion in the
air can produce moderate (second-degree) flash burns, which require
some medical attention, as far as 2.4 km (1.5 mi) from ground zero;
for a 10-megaton bomb, the corresponding distance would be more than
32 km (more than 20 mi). Milder burns of bare skin would be
experienced even farther out. Most ordinary clothing provides
protection from the heat radiation, as does almost any opaque
object. Flash burns occur only when the bare skin is directly
exposed, or if the clothing is too thin to absorb the thermal
The heat radiation can initiate fires in dry, flammable materials,
for example, paper and some fabrics, and such fires may spread if
conditions are suitable.
The evidence from the A-bomb explosions
over Japan indicates that many fires, especially in the area near
ground zero, originated from secondary causes, such as electrical
short circuits, broken gas lines, and upset furnaces and boilers in
industrial plants. The blast damage produced debris that helped to
maintain the fires and denied access to fire-fighting equipment.
Thus, much of the fire damage in Japan was a secondary effect of the
Under some conditions, such as existed at Hiroshima but not at
Nagasaki, many individual fires can combine to produce a fire storm
similar to those that accompany some large forest fires. The heat of
the fire causes a strong updraft, which produces strong winds drawn
in toward the center of the burning area. These winds fan the flame
and convert the area into a holocaust in which everything flammable
is destroyed. Inasmuch as the flames are drawn inward, however, the
area over which such a fire spreads may be limited.
Since the thermal radiation travels at roughly the speed of
light, the flash of light and heat precedes the blast wave by
several seconds, just as lightning is seen before thunder is heard.
The visible light will produce "flashblindness" in people
who are looking in the direction of the explosion. Flashblindness
can last for several minutes, after which recovery is total. If the
flash is focused through the lens of the eye, a permanent retinal
burn will result. At Hiroshima and Nagasaki, there were many cases
of flashblindness, but only one case of retinal burn, among the
survivors. On the other hand, anyone flashblinded while driving a
car could easiIy cause permanent injury to himself and to others.
Besides heat and blast, an exploding nuclear bomb has a unique
effect—it releases penetrating nuclear radiation, which is quite
different from thermal (or heat) radiation. Direct radiation occurs
at the time of the explosion. It can be very intense, but its range
is limited. For large nuclear weapons, the range of intense direct
radiation is less than the range of lethal blast and thermal
radiation effects. However, in the case of smaller weapons, direct
radiation may be the lethal effect with the greatest range. Direct
radiation did substantial damage to the residents of Hiroshima and
Nagasaki. Human response to ionizing radiation is subject to great
scientific uncertainty and intense controversy. It seems likely that
even small doses of radiation do some harm.
absorbed by the body, nuclear radiation can cause serious injury.
For an explosion high in the air, the injury range for these
radiations is less than for blast and fire damage or flash burns. In
Japan, however, many individuals who were protected from blast and
burns succumbed later to radiation injury.
Nuclear radiation from an explosion may be divided into two
categories, namely, prompt radiation and residual radiation. The
prompt radiation consists of an instantaneous burst of neutrons and
gamma rays, which travel over an area of several square miles. Gamma
rays are identical in effect to X rays (see X Ray). Both neutrons
and gamma rays have the ability to penetrate solid matter, so that
substantial thicknesse of shielding materials are required.
The residual nuclear radiation, generally known as fallout, can be a
hazard over very large areas that are completely free from other
effects of a nuclear explosion. In bombs that gain their energy from
fission of uranium-235 or plutonium-239, two radioactive nuclei are
produced for every fissile nucleus split. These fission products
account for the persistent radioactivity in bomb debris, because
many of the atoms have half-lives measured in days, months, or
Two distinct categories of fallout, namely, early and delayed, are
known. If a nuclear explosion occurs near the surface, earth or
water is taken up into a mushroom-shaped cloud and becomes
contaminated with the radioactive weapon residues. The contaminated
material begins to descend within a few minutes and may continue to
fall for about 24 hours, covering an area of thousands of square
miles downwind from the explosion. This constitutes the early
fallout, which is an immediate hazard to human beings. No early
fallout is associated with high-altitude explosions. If a nuclear
bomb is exploded well above the ground, the radioactive residues
rise to a great height in the mushroom cloud and descend gradually
over a large area.
Human experience with radioactive fallout has been minimal. The
principal known case histories have been derived from the accidental
exposure of fishermen and local residents to the fallout from the
15-megaton explosion that occurred on March 1, 1954. The nature of
radioactivity, however, and the immense areas contaminable by a
single bomb undoubtedly make radioactive fallout potentially one of
the most lethal effects of nuclear weapons.
Spectacular photo album of Nuclear
Electromagnetic pulse (EMP) is an electromagnetic wave similar to
radio waves, which results from secondary reactions occurring when
the nuclear gamma radiation is absorbed in the air or ground. It
differs from the usual radio waves in two important ways. First, it
creates much higher electric field strengths. Whereas a radio signal
might produce a thousandth of a volt or less in a receiving antenna,
an EMP pulse might produce thousands of volts. Secondly, it is a
single pulse of energy that disappears completely in a small
fraction of a second. In this sense, it is rather similar to the
electrical signal from lightning, but the rise in voltage is
typically a hundred times faster. This means that most equipment
designed to protect electrical facilities from lightning works too
slowly to be effective against EMP.
An attacker might detonate a few weapons at high altitudes in an
effort to destroy or damage the communications and electric power
systems of the victim. There is no evidence that EMP is a physical
threat to humans. However, electrical or electronic systems,
particularly those connected to long wires such as power lines or
antennas, can undergo damage. There could be actual physical
damage to an electrical component or a temporary disruption of
Fallout radiation is received from particles that are made
radioactive by the effects of the explosion, and subsequently
distributed at varying distances from the site of the blast. While
any nuclear explosion in the atmosphere produces some fallout, the
fallout is far greater if the burst is on the surface, or at least
low enough for the firebal to touch the ground. The significant
hazards come from particles scooped up from the ground and
irradiated by the nuclear explosion. The radioactive particles that
rise only a short distance (those in the "stem" of the
familiar mushroom cloud) will fall back to earth within a matter of
minutes, landing close to the center of the explosion. Such
particles are unlikely to cause many deaths, because they will fall
in areas where most people have already been killed. However, the
radioactivity will complicate efforts at rescue or eventual
reconstruction. The radioactive particles that rise higher will be
carried some distance by the wind before returning to Earth, and
hence the area and intensity of the fallout is strongly influenced
by local weather conditions. Much of the material is simply blown
downwind in a long plume. Rainfall also can have a significant
influence on the ways in which radiation from smaller weapons is
deposited, since rain will carry contaminated particles to the
ground. The areas receiving such contaminated rainfall would become
"hot spots," with greater radiation intensity than their
Besides the blast and radiation damage from individual bombs, a
large-scale nuclear exchange between nations could conceivably have
a catastrophic global effect on climate. This possibility, proposed
in a paper published by an international group of scientists in
December 1983, has come to be known as the "nuclear
winter" theory. According to these scientists, the explosion of
not even one-half of the combined number of warheads in the United
States and Russia would throw enormous quantities of dust and smoke
into the atmosphere. The amount could be sufficient to block off
sunlight for several months, particularly in the northern
hemisphere, destroying plant life and creating a subfreezing climate
until the dust dispersed. The ozone layer might also be affected,
permitting further damage as a result of the sun's ultraviolet
radiation. Were the results sufficiently prolonged, they could spell
the virtual end of human civilization. The nuclear winter theory has
since become the subject of enormous controversy. It found support
in a study released in December 1984 by the U.S. National Research
Council, and other groups have undertaken similar research. In 1985,
however, the U.S. Department of Defense released a report
acknowledging the validity of the concept but saying that it would
not affect defense policies.
The Evidence for Ancient Atomic Warfare?
Religious texts and geological evidence suggest that several
parts of the world have experienced destructive atomic blasts in
The Atomic Bomb Movie (1995)
Run Time: 60 minutes
Available on DVD
In the salad days of nuclear-weapons testing,
the United States detonated 331 atomic, hydrogen, and
thermonuclear bombs. Many of those explosions appear in
Trinity and Beyond, which utilizes a lot of declassified
footage, most of it in color. Standouts include the United
States' South Pacific detonation of an atom bomb 90 feet
below the water to study the effects on a fleet of ships.
Surprise, surprise, they sink! If that wasn't enough, the
navy also loaded the decks with sheep to study the effects
of the blast on life forms. Surprise, surprise, they die!
Glowing leg of lamb anyone? This film will alternately amuse
and horrify you at the rampant irresponsibility of the
Soviets and Americans in their quest for nuclear domination.
The Russians have the honor of having detonated the largest
nuclear bomb ever at a whopping 58 megatons. The Hiroshima
bomb was barely a kiloton. Of course, after the U.S. and
Russia ceased their activities, the Chinese decided to get
in on the act. But that's a different story for a different
Journeys-Welcome to Ground Zero (1999)
Run Time: 52 minutes
Available on DVD and VHS
Our atomic heritage resides in sites all over
the country - from the Trinity test area to natural-gas
wells in Colorado - and many of them are open to the public.
Plan your vacation with Atomic Journeys: Welcome to Ground
Zero, a blast through memory lane narrated by the perfectly
suited William Shatner. Never-before-seen footage of test
explosions and top-secret and work labs explores the history
of America's nuclear programs, and interviews with current
and former atomic scientists and engineers give depth to
sights such as "the most bombed place on Earth" in
Nevada. Learn about nonmilitary uses of nuclear weapons, the
rationales behind the different programs, and where you can
find these strange places. The musical score is a special
bonus, performed by the Moscow Symphony Orchestra in a
goodwill gesture of post-cold-war cooperation.
Century Complete Guide to Bioterrorism, Biological and
Chemical Weapons, Germs and Germ Warfare, Nuclear and
Radiation Terrorism - Military Manuals and Federal Documents
with Practical Emergency Plans, Protective Measures, Medical
Treatment and Survival Information
by U.S. Government
This electronic book on CD-ROM provides the best, most
up-to-date and comprehensive collection available anywhere
of official information and documents on the threats posed
by terrorism and weapons of mass destruction: bioterror
agents like anthrax, smallpox, and plague; chemical agents
including nerve gas; military and improvised nuclear
weapons; radiological weapons; and radiation from nuclear
facility sabotage and accidents. This encyclopedic
collection of manuals, handbooks, self-study courses,
government plans and programs, and reference works includes
virtually every public domain document pertaining to every
aspect of the risk to civilians from terrorism, and military
personnel in warfare.
Over 30,000 pages in 146 documents (occupying
over 600 MB) from all major Federal agencies, including the
Department of Defense, U.S. Army, Federal Emergency
Management Agency (FEMA), Dept. of Health and Human
Services, Centers for Disease Control (CDC), Dept. of
Energy, Nuclear Regulatory Commission (NRC), EPA, and GAO
give detailed, useful, practical, current information on the
NBC (nuclear, biological, and chemical) threat:
Full descriptions of biological and chemical
agents * History * Agent Delivery Methods * Environmental
Detection * Prevention * Protection * Symptoms * Treatment *
Military Equipment and Hardware * Civilian Emergency Plans
and Preparedness * Technical Details * Nuclear bomb
radiation patterns * Radiation and bomb effects.
Army Survival Manual
by Department of Defense, Department of Defense
The U.S. Army Survival Manual is widely recognized as the
finest single-source on the subject. Used by all branches of
the U.S. Military, including Special Operations Forces and
Pilots. This book has been translated for use in foreign
militaries. Civilians have discovered this detailed
compilation as a very interesting and important addition to
their homes, cars and campers.
Describes and clearly illustrates a vast array
of topics, including… · The Will to Survive · Survival
Planning · Survival Medicine · Weapons and Tools · Water
procurement · Wild Plants for Food · Wildlife for Food ·
Shelter · Fire building · Water Crossings · Direction
Finding · Signaling · Desert Survival · Tropical Survival
· Arctic and Sub arctic Survival · Sea Survival ·
Poisonous Snakes · Knots · Climate · Weather.
Teaches you how to… · Overcome the desire
for Comfort · Recognize the onset of a dangerous passive
outlook · Tolerate Pain · Use the word “survival” as a
pneumonic device · Plan ahead for survival · Administer
the Heimlich Hug · Treat insect and Snake Bites · Make
wooden and stone knives · Make a rabbit stick · Start a
fire with a bow and drill · Procure water in nearly any
environment · Construct solar water still · Make polluted
water drinkable · Conduct the Universal Plant Edibility to
Test (very important) · Improvise containers for boiling
food · Catch and eat insects · Make fishhooks and fishing
lines · Build a stakeout for fishing secretly · Make spear
points · Capture amphibians and reptiles · Catch birds in
a net · Make Ojibwa bird snare · Make squirrel pole ·
Make a trip-string deadfall trap · Clean a snake · Skin
and butcher small and large game · Build a parachute tepee
· Construct a swamp bed · Build a shelter in the desert
sand · Make a Dakota fire hole · Cross a swift stream ·
Make an Australian poncho raft · Find direction using the
sun and stars · Signal aircraft with your body · Much,