On Tuesday President George W. Bush acknowledged that the al Qaeda network
terrorist network has been attempting to acquire nuclear materials for use in
terrorist plots against the West. Construction of a nuclear device from the
ground-up, however, is not an easy task. The following excerpt from Tracking
Nuclear Proliferation, A Guide in Maps and Charts 1998 provides insight
into the level of expertise and technological sophistication that are required to build a nuclear
weapon.
A state or group seeking to manufacture nuclear arms must complete a number
of essential, often extremely demanding steps. The aspiring actor must:
- Develop a design for its nuclear device or obtain such a design from a weapon-
holding state.
- Produce the fissile material for the core of the device or obtain it from
an external source and then machine the fissile material to fabricate the
nuclear parts of the weapon.
- Fabricate, or obtain from outside, the non-nuclear parts of the device,
including the high-explosive elements and triggering components that will
detonate the nuclear core.
- Verify the reliability of these various elements individually and as a system.
- Assemble all of these elements into a deliverable nuclear armament, commonly
referred to as "weaponization."
Design
It is generally accepted today that designing an early generation atomic bomb—drawing
a blueprint—is within the capabilities of most contemporary states. Indeed,
a number of American college students have come up with plausible designs based
on unclassified information. But developing a reliable, militarily-acceptable
weapon would take a technical team with special facilities and financial support,
and is not likely a project that could be carried out by an individual in a
home workshop.
Acquiring Fissile Materials
The major technical barrier to making a nuclear device is obtaining the necessary
fissile material, i.e., weapons-grade uranium or plutonium, for the weapon’s
core.
How much fissile material would be needed for a nuclear weapon depends
on the technical capabilities of the country involved and the size of the weapon
it sought to produce. International Atomic Energy Agency (IAEA) regulations
assume that 25 kg of weapons-grade uranium or 8 kg of plutonium are the minimum
amounts that would constitute a "critical mass" (that could spontaneously
fission) with a yield up to about 20 Kt (equivalent to the explosive force of
20,000 tons of TNT), roughly the size of the Nagasaki bomb. However, by utilizing
more sophisticated designs that rely on high compression of the core material,
neutron reflecting "tampers," or both, a state could build such a
weapon with considerably less fissile material. According to one recent estimate,
a country possessing a "low technical capability" could build a 20-Kt
device with only 6 kg of plutonium or 16 kg of weapons-grade uranium. A state
with a "high technological capability" could potentially build such
a device with as little as 5 kg of weapons-grade uranium or 3 kg of plutonium;
a 1 -Kt device, which would require considerable sophistication to manufacture,
might need only about half these amounts.1
Non-Nuclear Components, Assembly, Delivery
Finally, the manufacture of nuclear weapons requires the design and fabrication
of: specially designed high-explosive components to compress the fissile-material
core of the device; high-speed electronic firing circuits, or "triggering
packages" to set off the high explosives uniformly at precisely the correct
instant; and, in most designs, an "initiator"—an intense source of
neutrons to initiate the nuclear chain reaction in the core. Developing all
of these components necessitates considerable technical skill and, though less
demanding than producing fissile material, can nonetheless be quite challenging.
Iraq’s effort to develop these elements of nuclear weapons, for example, is
known to have suffered considerable setbacks and had not succeeded prior to
the 1991 Gulf War, despite several years of effort.
Assembly of the completed components of nuclear weapons and delivery by aircraft
or as cargo by ship or truck are relatively less demanding. To produce nuclear
warheads for ballistic missiles, however, additional steps are necessary, such
as the development of reentry vehicles, the miniaturization and/or reconfiguration
of nuclear weapons to fit into missile nose cones, and certifying the weapons
to withstand the rigors of blast-off, extremely high altitudes, and reentry.
For an interactive web site with a wealth of information on the physics of
nuclear fission, how nuclear bombs are designed and what happens after a nuclear
explosion click here.
Click here for selected chapters and appendicies from the book Tracking
Nuclear Proliferation: A Guide in Maps and Charts, 1998 (pdf)