Making the Bomb: Understanding Nuclear Weapons June 11, 2004 Teaching Nonproliferation Summer Institute University of North Carolina, Asheville Dr. Charles D. Ferguson Scientist-in-Residence Center for Nonproliferation Studies Monterey Institute of International Studies
June 11, 2004
Teaching Nonproliferation Summer Institute
University of North Carolina, Asheville
Dr. Charles D. Ferguson
Center for Nonproliferation Studies
Monterey Institute of International Studies
Supported by the John D. and Catherine T. MacArthur Foundation,
the Ploughshares Fund, and the Nuclear Threat Initiative
India, Israel, North Korea, and Pakistan
1,000 pounds of TNT explosive equivalent, or about ½ ton.
<= 5 kilotons or 5,000 tons
≈13 kilotons or 13,000 tons
100 to 300 kilotons or
100,000 to 300,000 tons
Alpha (α): Helium nucleus: 2 neutrons and 2 protons
Beta (β): Highly energetic electron or positron (positively charged electron)
Gamma (γ): Highly energetic particles of light
after 7 half-lives
Number of Fissions = 2Generation
After 80 generations, 280 fissions or about 1024 have occurred.
This number of fissions is required to produce the explosive energy in a typical nuclear weapon – within a small fraction of a second – within microseconds.
Time or # Generations
Uranium is found in several
types of minerals:
Pitchblende, Uranite, Carnotite,
Autunite, Uranophane, Tobernite
Also found in:
Milling: Extraction of uranium oxide from ore in order to concentrate it
Over 99% is U-238.
U-238 are essentially identical
> 0.7% but < 20% U-235
> 20% U-235
> 90% U-235
Relies on molecular effusion (the flow of gas
through small holes) to separate U-235 from U-238.
The lighter gas travels faster than the heavier gas.
The difference in velocity is small (about 0.4%).
So, it takes many cascade stages to achieve even
U.S. first employed this enrichment
technique during W.W. II. Currently,
only one U.S. plant is operating to
produce LEU for reactor fuel.
China and France also
Uranium hexafluoride UF6: Solid at
Thin-walled cylinders, end caps, baffles, and bellows
Made of high-strength materials: Maraging steel, Aluminum alloys, or Composite materials (e.g., graphite fiber)
Other key components
Magnetic suspension bearings, vacuum
pumps, and motor stators
Prepare fissile material to fuel nuclear reactors.
PUREX = plutonium-uranium extraction
Three main stages:
1. Spent fuel assemblies are dismantled
and fuel rods are chopped up.
2. Extracted fuel is dissolved in hot nitric
3. (Most complex stage) Pu and U are
separated from other actinides
and fission products, and then
from each other. Technique is
known as “solvent extraction.”
Tributyl phosphate (TBP) is the
typical organic solvent.
Some (e.g., Cochran and Paine of NRDC) have argued that the SQs are much too high. For instance, low-yield weapons would require much less fissile material.
But IAEA has relied on input from nuclear weapons states to determine what is a significant quantity.
Gun Type – Easiest to design and build
(Hiroshima bomb was never tested)
About 13 kiloton explosive yield
About 22 kilotons explosive yield
Second detonated implosion weapon –
Required testing to prove concept
More efficient design than “Little Boy”
Hollow core, where D and T are injected for boosting.
Fissile material (WgU or WgPu)
WgU: 12 kg, 7 cm outside,
1.23 cm thick
WgPu: 4 kg, 5 cm outside,
0.75 cm thick
Beryllium reflector (2 cm)
Tamper (tungsten or
uranium) (3 cm)
High explosive (10 cm)
Aluminum case (1 cm)
Source: Steve Fetter et al., “Detecting Nuclear Weapons,” 1990
Tu-160 Blackjack Bomber
Russian Theater Missile