In the news it is often mentioned that some countries are going to enrich uranium to "military grade" (i.e. 80%+) and that it is possible to use it for a nuclear bomb.
1) Is that correct that there are no nuclear warheads in service made of U-235, as plutonium ones are much smaller & much more efficient (i.e. burn most of it's fissile fuel unlike U-235 cannon-type ones)?
2) Is that correct, that the only current military uses for 80%+ U-235 are naval nuclear reactors and in rare occurrences – case and/or X-Ray "reflector" in Teller–Ulam configuration as it is slightly better neutron breeder compared to more commonly used U-238 and allows to slightly reduce mass of "high-tech" plutonium charge at the same yield?
Best Answer
Maybe. Who knows precisely what people use. But publicly available information from US warheads is that they moved away from Uranium to Plutonium fission devices soon after world war II.
I would replace 'naval reactors' with 'any small yet powerful reactor`.
In most cases that might come down to the same thing, but it also allows the use of them in space probes etc.
Then you would replace the cheap, bountiful U238 with a more efficient but very expensive to separate U-235? And with a lot of U-235, which would be sensitive to external neutron flux, thus forcing you to add extra shielding (e.g with an extra layer of Boron).
I am not a bomb design expert, but thus sounds uneconomical. Even if you save some Plutonium.