Just wondering how concerned we should be about a rogue state acquiring a Berkelium bomb. :eek:
Neptunium bombs would be possible, but I don’t think anyone has made them.
I’ve wondered - are U-235 HEU and plutonium essentially interchangeable for fission weapons, except that plutonium is prone to spontaneous fission?
The design details are very different for the two. But the big picture concept of “quickly assemble a critical mass from smaller piece(s) & KABLOOEY” works the same in either case.
Californium should work, with a much smaller critical mass. There was speculation about building tiny californium-warhead nuclear weapons, before it became clear how incredibly expensive that would be.
Hmmm. Just how small a critical mass? What isotope? Californium may be the highest numbered element that has commercial applications - CF 252 is used as a neutron source in such things as neutron moisture gauges. A sizeable fraction of a gram of the stuff is produced annually for such uses (compare to a few Kg of Americium produced for commercial use per year, mostly in smoke detectors). One presumes is would not be practical for somebody to subvert the industries making legitimate uses of it in order to obtain enough fissile material for a weapon.
In addition to the more usual U-235, U-233 can theoretically be used in a nuclear bomb. Much as Pu-239 is bred from U-238, U-233 can be bred from thorium-232 (which is quite common in the earth’s crust). There are a number of technical reasons why it’s nobody’s first choice for making a nuclear bomb. I think that during the Cold War the US and USSR both experimented with devices that used a combination of U-233 with Pu-239 or U-235 but the results were disappointing. In 1998 India tested a device (Shakti V) that supposedly used pure U-233, but the yield was very small (0.2 kilotons).
Way too much - like 5Kg.
The spontaneous fission of Pu pretty much rules out gun assembly, so that’s a way that they’re not interchangeable.
Otherwise, I get the impression that an implosion bomb for one is much the same in broad strokes as for the other, and indeed some bombs could use multiple types of pits, at least various composite (blend of U/Pu) and straight HEU pits anyway.
As for the OP… sure, most transuranic elements have critical masses, but as far as I know, the issue is that making/purifying useful amounts of them is problematic when compared to Pu-239 or U-235, which are relatively easily generated in nuclear reactors and separated by physical/chemical means, or mined, and separated in similar ways.
In other words, getting a 7 kilogram (or whatever smaller amount may necessary for a bomb) critical mass of Neptunium-236 is a LOT harder and more expensive than getting 52 kg of appropriately enriched U-235.
Weapon-grade uranium and plutonium are interchangeable in the sense that getting the fissionable material is the hardest part of making a bomb. If you have one or the other, then you design your bomb to use that.
This Wikipedia table says that [sup]252[/sup]Cf has a critical mass of less than 3 kg. Dunno if there are other limitations, but that seems to be the smallest in that table. It also appears to have a short (but not infinitesimal) half-life, less than seven years.
Ooh, there’s a memory from my misspent (geek) youth. The SF role-playing game Traveller had in-game a heavy weapon (such as a tank hypervelocity main gun) which fired specially-shaped subcritical Californium slugs. The slugs would deform and compress on impact with a hard target and go prompt critical.
Think, “tank with nuclear shells”. On a smallish scale.
Of course, I’m sure they were thinking about [sup]252[/sup]Cf (for the lower critical mass), because they also invented in game a “high tech magic” (never explained) “nuclear damper field” which could stop the decay of a radioisotope as long as power could be provided. So the Californium slugs never decayed. Because most military logistics has stuff in inventory more than seven years old.
/end hijack. thanks for indulging.
Correction after the edit window: less than three years. Which is significantly less than seven years. :smack:
Heck, DoD & DoE have enough trouble with current real world weapons that use tritium with a 12+ year half life. I can’t imagine the logistics mess dealing with 3 year half-lives.
As implosion design works for both, surely you could make a Gadget-type bomb from a mixture of them two? Perhaps even a gun-type (Hiroshima) bomb could be made to work with, say, a properly dimensioned plug of weapons-grade uranium and a (less expensive) shell of something-less-than-weapons-grade plutonium?
Absolutely! Composite pits of uranium and plutonium were common (may still be) in implosion weapons in the tests in the 1950s and 1960s.
The issue with the plutonium and gun assembly is that there’s always a non-negligible amount of Pu-240 in even weapons grade Pu, and its spontaneous fission rate means that it emits so many neutrons that any relatively “slow” attempt at assembling a weapon from it will end up in a fizzle, because the spontaneous neutrons will cause fissions and the pit to basically explode too early, not giving much yield at all.
Implosion weapons avoid this by being fast, and uranium doesn’t have any spontaneous fission like that, so it can be used for gun weapons.
amusingly enough…as i started reading the thread i was thinking the same thing.
Section “6.2.4 Other Fissile Elements” is the pertinent part.
In general, that FAQ will answer just about ANY nuclear weapon question anyone may have.