Nuclear Weapons - Introduction
Source: Federation of American Scientists Since their introduction in 1945, nuclear explosives
have been the most feared of the weapons of mass destruction, in part
because of their ability to cause enormous instantaneous devastation
and of the persistent effects of the radiation they emit, unseen and
undetectable by unaided human senses. The Manhattan Project cost the
United States $2 billion in 1945 spending power and required the
combined efforts of
a continent-spanning industrial enterprise and a pool of scientists,
many of whom had already been awarded the Nobel Prize and many more
who would go on to become Nobel Laureates. This array of talent was
needed in 1942 if there were to be any hope of completing a weapon
during the Second World War. Because nuclear fission was discovered in
Germany, which remained the home of many brilliant scientists, the
United States perceived itself to be in a race to build an atomic
bomb.
When the Manhattan Project began far less than a
microgram of plutonium had been made throughout the world, and
plutonium chemistry could only be guessed at; the numbers of neutrons
released on average in U-235 and Pu-239 fissions were unknown; the
fission cross sections (probabilities that an interaction would occur)
were equally unknown, as was the neutron absorption cross section of
carbon. experiment. Although talented people are essential to the
success of any nuclear
weapons program, the fundamental physics, chemistry, and engineering
involved are widely under-stood; no basic research is required to
construct a nuclear weapon. Therefore, a nuclear weapons project begun
in 1996 does not require the brilliant scientists who were needed for
the Manhattan Project.
For many decades the Manhattan Project provided the
paradigm against which any potential proliferator's efforts would be
measured. Fifty years after the Trinity explosion, it has been
recognized that the Manhattan Project is just one of a spectrum of
approaches to the acquisition of a nuclear capability. At the low end
of the scale, a nation may find a way to obtain a complete working
nuclear bomb from a willing or unwilling supplier; at the other end,
it may elect to construct a complete nuclear infrastructure including
the mining of
uranium, the enrichment of uranium metal in the fissile isotope U-235,
the production and extraction of plutonium, the production of tritium,
and the separation of deuterium and 6 Li to build thermonuclear
weapons. At an intermediate level, the Republic of South Africa
constructed six quite simple nuclear devices for a total project cost
of less than $1 billion (1980's purchasing power) using no more than
400 people and indigenous technology. Fissile materials can produce
energy by nuclear fission, either in nuclear reactors or in nuclear
weapons. A country choosing to join the nuclear weapons community must
acquire the necessary weapons (fissile) material (U-235 U or Pu-239).
It is generally recognized that the acquisition of fissile material in
sufficient quantity is the most formidable obstacle to the production
of nuclear weapons. Fissile material production consumes the vast
majority of the technical, industrial, and financial resources
required to produce nuclear
weapons. For example, production of fissile materials -- highly
enriched uranium (HEU) and plutonium -- accounted for more than 80
percent of the $1.9 billion (1945 dollars) spent on the Manhattan
Project.
Some analysts believe that the difficulties of enriching
uranium are offset by the simpler weapon designs which enriched
uranium allows. In the United States, HEU is considered less expensive
to use in a weapon than plutonium. Operation of a reactor to produce
plutonium requires the extraction and purification of uranium and, in
some cases, at least modest enrichment. Given international safeguards
on reactors using enriched uranium obtained from another nation or
heavy water
moderated reactors, a proliferant may be forced in any case to
construct an enrichment facility. The choice is likely to be
determined by the indigenous availability of uranium and the national
surplus (or shortage) of electricity.
Acquisition of a militarily significant nuclear
capability involves, however, more than simply the purchase or
construction of a single nuclear device or weapon. It requires
attention to issues of safety and handling of the weapons, reliability
and pre-dictability of entire systems, efficient use of scarce and
valuable special nuclear material (SNM) (plutonium and enriched
uranium), chains of custody and procedures for authorizing the use of
the weapons, and the careful training of the military personnel who
will deliver weapons to their targets.
In contrast, a nuclear device used for terrorism need
not be constructed to survive a complex stockpile-to-target sequence,
need not have a predictable and reliable yield, and need not be
efficient in its use of nuclear material. Although major acts of
terrorism are often rehearsed and the terrorists trained for the
operation, the level of training probably is not remotely comparable
to that necessary in a military establishment entrusted with the
nuclear mission.
The United States has developed a complex and
sophisticated system to ensure that nuclear weapons are used only on
the orders of the President or his delegated representative. Some
elements of the custodial system are the "two-man rule," which
requires that no person be left alone with a weapon; permissive action
links (PALs), coded locks which prevent detonation of the weapon
unless the correct combination is entered; and careful psychological
testing of personnel charged with the custody or eventual use of
nuclear weapons. In
addition, U.S. nuclear weapons must be certified as "one point safe,"
which means that there is less than a one-in-a-million chance of a
nuclear yield greater than the equivalent of four pounds of TNT
resulting from an accident in which the high explosive in the device
is detonated at the point most likely to cause a nuclear yield.
It is believed to be unlikely that a new proliferator
would insist upon one point safety as an inherent part of pit design;
the United States did not until the late 1950's, relying instead upon
other means to prevent detonation (e.g., a component of Little Boy was
not inserted until after the Enola Gay had departed Tinian for
Hiroshima). It is also unlikely that a new actor in the nuclear world
would insist
upon fitting PALs to every (or to any) nuclear weapon; the United
States did not equip its submarine-launched strategic ballistic
missiles with PALs until, at the earliest, 1996, and the very first
U.S. PALs were not introduced until the mid-1950's, when American
weapons were stationed at foreign bases where the possibility of theft
or misuse was thought to be real.
Nonetheless, any possessor of nuclear weapons will take
care that they are not used by unauthorized personnel and can be
employed on the orders of duly constituted authority. Even -- or,
perhaps, especially -- a dictator such as Saddam Hussein will insist
upon a fairly sophisticated nuclear chain of command, if only to
ensure that his weapons cannot be used by a revolutionary movement. It
is also quite likely that even the newest proliferator would handle
his weapons with care and seek to build some kind of safety devices
and a reliable SAFF system into the units. On the basis of experience,
one might expect to observe significant nuclear planning activity and
the evolution of situation-specific nuclear doctrine on the part of a
new
proliferator who would have to allocate carefully the "family jewels."
The development of a nuclear strategy might be visible in the
professional military literature of the proliferator.
Sources and Methods:
Adapted from - Nuclear Weapons Technology Militarily
Critical Technologies List (MCTL) Part II: Weapons of Mass Destruction
Technologies.
http://www.fas.org/nuke/intro/nuke/intro.htm