Physics Archives

September 6, 2005

An Atomic Bomb in 5 Easy Steps

I was reading the September/October issue of the California Monthly and there is an intriguing article on the "Big Bang report" It included a sidebar on the 5 steps required to make a bomb"

1. Mining—the easy part. Uranium is heavier than gold and has the largest atoms of any natural element, which makes the magnitude of its explosive potential greater than that of all elements except hydrogen, the lightest element. Uranium exists in large deposits easily mined on virtually every continent. It even can be harvested from seawater.

But the yield is low.
For every 25,000 tons mined, only 50 tons of uranium metal remain.

2. Extraction—almost any lab tech can do it.
Pure uranium is dried and filtered into coarse powder called yellowcake.
The substance is exposed to fluoride gas and heated to 133 degrees F.
This creates a gas, uranium hexafluoride.

3. Diffusion—the hard part.
The gas consists of two isotopes—U-238, which is too stable for atomic detonation, and U-235, which is lighter and highly fissionable. To separate the isotopes, the gas is pumped through a succession of fine, porous barriers—centrifuges. U-235 isotopes are lighter and propel faster through the barriers and concentrate. After passing through several thousand barriers, the gas contains about 2 percent of U-235—enough for a nuclear reactor.

But an atom bomb requires nearly 95 percent purity.

4. Refinement—the sophisticated, expensive, and time-consuming part.
The slightly enriched uranium undergoes magnetic separation before being fed into another centrifuge. After passing through more than 1,500 barriers, the gas is about 20 percent pure. The process is repeated for nearly a year until the purity reaches nearly 90 percent. At this point, the uranium gas is considered bomb grade. It is then converted into metal powder.

5. Detonation—the easiest part.
The metal is molded into a ball weighing between 50 and 100 pounds.
Size matters less than the purity of the uranium. It is packed into a warhead containing a detonator (the United States used artillery shells in its early versions) and fuse, which can be remotely set.

A 10-megaton bomb equals 10 million tons of TNT.

So now you know.

About Physics

This page contains an archive of all entries posted to Project in the Physics category. They are listed from oldest to newest.

Meteorology is the previous category.

Psychology is the next category.

Many more can be found on the main index page or by looking through the archives.

Creative Commons License
This weblog is licensed under a Creative Commons License.
Powered by
Movable Type 3.34