Nuclear weapons and Uranium

In summary, the choice between using U-235 or Pu-239 in nuclear weapons is primarily based on cost and ease of production. U-235 requires a highly enriched form which is difficult and expensive to produce, while Pu-239 can be bred in a reactor and chemically separated. However, Pu-239 has a smaller critical mass and larger neutron capture cross section, making it more efficient for bomb-making. Additionally, U-235 can be set off by simpler means compared to the more sophisticated implosion technique needed for Pu-239.
  • #1
The Prince
15
0
Hey there ,

1-I wonder why PU-239 is basically used in nuclear destructive weapons, while U-33, U-35,U-38 (with Energy more than 1 Mev) are fissionable materials as well??!


_ The Prince .
 
Engineering news on Phys.org
  • #2
The Prince said:
Hey there ,

1-I wonder why PU-239 is basically used in nuclear destructive weapons, while U-33, U-35,U-38 (with Energy more than 1 Mev) are fissionable materials as well??!


_ The Prince .
The Prince,

As far as using U-238; as you point out, it is "fissionable" [ fissions for neutrons above
a 1 MeV threshold], instead of "fissile". So you don't get U-238 to go critical by itself.

As far as U-235 vs Pu-239; both can be used to make nuclear weapons, and have been.
The Little Boy bomb that destroyed Hiroshima was fueled by U-235.
The Fat Man bomb that destroyed Nagasaki was fueled by Pu-239.

The reason for using one over the other has to do with the cost of making the stuff.
In order to make a weapon with U-235, it has to be highly enriched. Natural Uranium
is only 0.7% U-235; the other 99.3% is mostly U-238.

In order to get a highly enriched Uranium; one that has a very high percentage of U-235;
you must separate the U-235 and U-238 isotopically. You can't do that by chemistry,
since they are both Uranium. It is difficult to separate the two isotopes.

The way you make Plutonium, is to fuel a reactor with a mix of U-235 and U-238. The
U-235 fuels the reaction, and the U-238 is a fertile material that can turn into Pu-239
when it absorbs a neutron. After irradiation in the reactor, one needs to separate out
the Pu-239. However, because the desired product is Plutonium and not Uranium;
it is chemically different, and chemical means can be used to separate out the Pu-239.

Dr. Gregory Greenman
Physicist
 
  • #3
Pu-239 also gives you a smaller critical mass due to more neutrons/fission (Nu) and a larger neutron capture cross section
 
  • #4
And the U-233 is too radioactive...
 
  • #5
Other aspect.
Enrichment of uranium is very difficult, and breeding of plutonium also.
I think the theory of hungarian guys is dangerous (other topic), because that process open possibility to breeding of plutonium with spallation neutrons, without uranium enrichment.
 
  • #6
tehfrr said:
Pu-239 also gives you a smaller critical mass due to more neutrons/fission (Nu) and a larger neutron capture cross section
tehfrr,

Yes - however that is offset by the larger neutron background of Plutonium vis-a-vis
Uranium. You have to assemble Plutonium faster than Uranium.

Of course that is a solved problem.

Dr. Gregory Greenman
Physicist
 
  • #7
One advantage that U-235 has over Pu-239 is that the bomb making is easier. U-235 bomb can be set off by slamming two pieces together, while Pu-239 requires a much more sophisitcated technique (implosion).
 

1. What are nuclear weapons and how do they work?

Nuclear weapons are explosive devices that derive their destructive power from nuclear reactions. They work by initiating a chain reaction of nuclear fission, which releases an enormous amount of energy in the form of heat, blast, and radiation.

2. How is uranium used in nuclear weapons?

Uranium is used as the main fuel in nuclear weapons. The most commonly used type of uranium is uranium-235, which is highly enriched to increase its concentration of fissile material. This allows for a more efficient chain reaction and a more powerful explosion.

3. Can nuclear weapons be dismantled and how?

Yes, nuclear weapons can be dismantled. The process of dismantling a nuclear weapon involves disassembling its components and separating the highly enriched uranium from other materials. This is a delicate and highly regulated process that requires specialized equipment and expertise.

4. What are the potential dangers of uranium and nuclear weapons?

The potential dangers of uranium and nuclear weapons are numerous. In addition to the obvious destructive power of nuclear weapons, there are also concerns about the environmental and health impacts of uranium mining and processing. Accidental or intentional use of nuclear weapons could also lead to catastrophic consequences for the world.

5. Is uranium used for any other purposes besides nuclear weapons?

Yes, uranium has many other uses besides nuclear weapons. It is used as a source of fuel for nuclear power plants, as well as in medical and industrial applications. However, the use of uranium in nuclear weapons remains the most controversial and heavily regulated aspect of its use.

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