Facts:
1) 60 kilograms of chain-reacting
uranium destroyed Hiroshima consisting of
80% of highly enriched uranium (HEU) U-235. A concentration of 20% of more is
labeled HEU.
2) It exploded with the
force of 15 kilotons of TNT.
3) To produce an explosion
a concentration of uranium 235 (the isotope capable of sustaining a nuclear chain reaction) has to be concentrated to levels
of 20% or more. Under 20% the critical mass becomes too large to fit in a reasonable
size device.
4) The mechanism was quite
simple and capable of being produced by a terrorist group.
5) It is called a gun time,
for it uses an explosive charge to move one portion of the 60 kilograms total down a gun barrel to a target at the base of
the bomb where it forms a critical mass.
6) The mechanism which destroyed
Nagasaki used plutonium rather than uranium, and required much more complex technology to set
it off. Even so such information is available for a price.
7) HEU is scattered around the world. Around 50 nations have HEU, almost entirely supplied by U.S. and the Soviet Union during the 50s
and 60s. Much of the HEU is approximately 90% uranium 235.
8) Currently there are about
10 metric tons of exported bomb-grade HEU still residing in nations that do not posses nuclear weapons in their nuclear research
facilities—enough to make 150-200 gun-type devices.
9) There has been, beginning
in the 90s thefts of HEU from the Soviet Union and other countries—the amount has been grossly under reported. Much of the HEU is in hockey-puck size metal discs that are easy-to-handle.
10) Spent fuel from reactors
typically contain 80% U-235. It is then blended down to make fresh low-enriched
fuel for nuclear power plants.
11). In 2005 the US program to acquire
HEU from other countries amounted to $70 million.
12). In Russia the government
shows little concern about the danger of nuclear terrorists. Much of the HEU
there is unguarded.
13) There are more than
70 HEU-fueled critical assemblies and pulsed reactors world wide—over half in Russia. Only a few are needed for research, most were built in the 60s & 70s and are not technically obsolete,
and much of their mission can now be accomplished with desktop-computer simulations that calculate the progress of neutron
chain reactions occurring in detailed three-dimensional reactor models.
