Encyclopedia > Critical mass

  Article Content

Critical mass

The critical mass of fissile material is the amount needed for a sustained nuclear chain reaction. It depends upon the material, its shape, its purity as well as whether it is surrounded by a neutron reflector. In the case of a sphere surrounded by a neutron reflector it is about 15 kg for U-235 and 10 kg for Pu-239.

Until detonation is desired, a nuclear weapon must consist of a number of separate pieces, each below the critical size either because they are too small or unfavorably shaped. To produce detonation, the fissile material must be brought together rapidly.

See also Nuclear weapon design.


The term is also used figuratively, meaning something like "be sufficient to work properly", especially when a sufficiently large amount is needed to cause growth.


For the car-free environment event, see Critical Mass.



All Wikipedia text is available under the terms of the GNU Free Documentation License

 
  Search Encyclopedia

Search over one million articles, find something about almost anything!
 
 
  
  Featured Article
Kuru Kuru Kururin

... Contents Kuru Kuru Kururin Kuru Kuru Kururin is a game for the Game Boy Advance. The player controls a slowly spinning stick and must get it through a series of mazes ...

 
 
 
This page was created in 38.8 ms