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Why isn't neptunium used in nuclear reactors in nuclear power plants? Uranium is, and plutonium is. But neptunium isn't and it is in the middle of them. Is it like it is too hard to make it do fission? Can someone please explain it to me?

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up vote 5 down vote accepted

There are several reasons that neptunium may not be used.

The first is the abundance of neptunium. From Wikipedia, it states the best source is from spent fuel rods. Basically, someone would need to handle very radioactive material to obtain a small amount of neptunium.

Next would be the likelihood of fission when struck with a neutron. If it is the same or less than uranium, I would go with uranium. It would have to be substantially more than uranium to offset the cost of refinement.

Also, there is the energy output per gram. I don't think it would be much greater than uranium, probably less.

The isotopes of neptunium that have long half-lives are $\ce{{}^{236}Np}$ and $\ce{{}^{237}Np}$. These are not produced in great abundance from $\ce{{}^{235}U}$ or $\ce{{}^{238}U}$.

To make plutonium from uranium, the uranium must absorb neutrons without fission. This is much more likely to happen then to make $\ce{{}^{236}Np}$ or $\ce{{}^{237}Np}$

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>To make plutonium from uranium, the uranium must absorb an alpha particle. || Nope, $^{239}Pu$ is product of double beta decay of $^{239}U$, produced by neutron capture by $^{238}U$. Most transuranic elements are produced by neutron capture and beta-decay, though for heaviest ones that fails. – permeakra Jul 7 '14 at 5:58

Production rate is low for reactors using low-enrichment uranium. You get about one atom of 237Np per thousand atoms of 239Pu, so its easier to get the Pu out and use it rather than running and running your production reactor to get the 237Np.

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