The reactions that typically occur when a neutron strikes a uranium-238 nucleus and a uranium-235 nucleus are?

Question

The reactions that typically occur when a neutron strikes a uranium-238 nucleus and a uranium-235 nucleus are different. Explain how.


___ A. The uranium-235 nucleus absorbs the neutron and is converted to plutonium-238, whereas uranium-238 undergoes nuclear fission.
___ B. The uranium-238 nucleus absorbs the neutron and is converted to uranium-239, whereas uranium-235 undergoes nuclear fission.
___ C. The uranium-238 nucleus absorbs the neutron and is converted to plutonium-239, whereas uranium-235 undergoes nuclear fission.
___ D. The uranium-235 nucleus absorbs the neutron and is converted to uranium-238, whereas uranium-238 undergoes nuclear fission.

Answer 1

C.

The number in U235 is the number of neutrons in the isotope. U235 is the naturally occurring stuff, but atomic bombs need the U238 version.

A. Can't be true becsue U235 will under go fission.

B. can't be true because the U238 will absorb the neurton and become Pu 239.

D. if U235 absorbed a neutron then it would undergo fission, so that can't be true.

As the article below explains you have to bombard U238 with neutrons to create plutonium 239.

According to: http://www.fas.org/nuke/intro/nuke/plutonium.htm
"Plutonium, one of the two fissile elements used to fuel nuclear explosives, is not found in significant quantities in nature. Plutonium can only be made in sufficient quantities in a nuclear reactor. It must be “bred,” or produced, one atomic nucleus at a time by bombarding 238 U with neutrons to produce the isotope 239 U, which beta decays (half-life 23 minutes), emitting an electron to become the (almost equally) radioactive 239 Np (neptunium). The neptunium isotope again beta decays (half-life 56 hours) to 239 Pu, the desired fissile material."