In which location would a free neutron from a decaying U-235 atom be most likely to cause another atom to split?
A.
in a sample of naturally occurring uranium
B.
in a sample of enriched uranium
C.
in a sample of rock or soil
D.
in the Sun’s core
E.
in a distant star

in a sample of enriched uranium

Explanation:

A fission reaction involves the breaking up of a large nucleus to yield daughter nuclei with the release of a tremendous amount of energy. The amount of energy released is so large that the reaction may go out of hand if not controlled. So much heat is evolved in the process.

The reaction often involves the bombardment of a large nucleus with neutrons. The neutrons cause the nucleus to become unstable and quickly disintegrate, producing daughter nuclei and more neutrons together with energy.

The more neutrons produced bombard more atoms of naturally occurring uranium-235 and the cycle continues. Hence nuclear fission is a self-sustaining cabin reaction sustained by the production of more neutrons in the process.

Natural uranium contains only a very small amount of fissile uranium isotope. Hence naturally occurring uranium is usually enriched with more of the fissile uranium isotope before it is used in a nuclear reactor.