How does neutron absorption turn uranium into plutonium?


by ampakine
Tags: absorption, neutron, plutonium, turn, uranium
ampakine
ampakine is offline
#1
May22-11, 11:49 AM
P: 60
I keep reading that when a U-238 atom absorbs a neutron it turns into Pu-239. How does that happen? If I'm not mistaken Pu-239 is U-238 plus 2 protons and 2 electrons and minus 2 neutrons. When U-238 absorbs the neutron and becomes U-239 I can see that it can turn into Pu-239 if 2 neutrons decay into 2 protons + 2 electrons. Is that what happens? Are the electrons expelled like in regular beta decay or do they remain in the nucleus so that a neutral atom is formed rather than an ion?
Phys.Org News Partner Science news on Phys.org
Simplicity is key to co-operative robots
Chemical vapor deposition used to grow atomic layer materials on top of each other
Earliest ancestor of land herbivores discovered
Astronuc
Astronuc is offline
#2
May22-11, 02:14 PM
Admin
Astronuc's Avatar
P: 21,625
U (Z=92), Np (Z=93), Pu (Z=94)

U238 + n => U239 => Np239 + => Pu239 + (leaving out the electron-associated antineutrinos that accompany beta emission) The particles slow down in the vicinity of the decay. Electrons are quite mobile and they generally migrate toward positive charges or up the electric potential.

The U239, Np239 and Pu239 can also absorb neutrons and elevate A to 240, which can also absorb neutrons to A=241. Pu239 is more likely to fission upon neutron absorption. Np-240,241 appear to have low n-capture cross-sections, or the cross-sections are not measured, and the half-lives are relatively short, so the isotopes aren't around long enough to capture neutrons. See figures.
Attached Thumbnails
z94n147zl1csigg5085.png   z93n146zl1ct129754.png  
Astronuc
Astronuc is offline
#3
May22-11, 04:45 PM
Admin
Astronuc's Avatar
P: 21,625
Here are the principal transuranics in a uranium/plutonium based fissile system.

Isotope   Half life (yr)
 Pu-236        2.858
 Pu-238       87.7
 Pu-239    24110
 Pu-240     6561
 Pu-241       14.29
 Am-241      432
 Pu-242    37500
 Am-243     7370
from www.nndc.bnl.gov/chart/
Attached Thumbnails
lwr-tranuranics.jpg   z94n147zl1cdm4054.png  


Register to reply

Related Discussions
Touching weps grade uranium/plutonium Nuclear Engineering 44
Uranium/Plutonium hot to the touch? General Physics 15
help! uranium and plutonium costs Introductory Physics Homework 7
uranium versus plutonium Nuclear Engineering 9
How do you get Plutonium from Uranium? High Energy, Nuclear, Particle Physics 2