Captain Caveman 76:
Bking:
Stresshead:
If the prime movers were green, they carry either the missle or the warhead, never both, so no danger of a chain reaction.
If the prime mover was blue, and was an old foden, then you have the plutonium Being moved.
Why carry Plutonium these are hydrogen bombs or are we going to fry Hiroshima again?
A uranium bomb is enough to set off a thermonuclear weapon dont need none of that dirty plutonium crap.
After all we all want to live in a nice clean world after a good old global thermonuclear war dont we?
Who needs a half life of 2.4 million years when uranium decays in half the time?
Thats why they keep over a hundred tons (and growing every day) at Windscale at a cost of a million a day because nobody wants or needs the crap.
From an engineering perspective, there is not a major difference between Plutonium and Uranium weapons. They can both be used in different configurations, and both require roughly the same masses to become supercritical (ie, they use roughly the same amount of metal). From the “weapon” perspective (ie, “The boom”) Plutonium and Uranium are functionally the same.
Most US weapons are Plutonium based. Plutonium has favorable nuclear characteristics as compared with Uranium (namely: it has a broader neutron cross section - if that means anything to you (I will explain in a bit) - and it releases a slightly larger amount of energy per fission event.
Fission is the word used to describe what happens when an atom’s nucleus’s binding energy is broken and released into the surrounding environment. The “binding energy” is the effect of the residual strong force that keeps the same-charged positive protons stuck together, even though their electric charge wants to push them apart. This energy can become unstable/unbalanced, and when it does atoms become radioactive. If the instability is large enough, the nucleus can collapse into a fission event, which cleaves the atom into two or more pieces, and the binding energy is released in the form of heat and the motion of the fragments of the nucleus.
The way that we ‘trigger’ this fission event (for weapons and power) is to rapidly ramp up the instability by injecting neutrons into the nucleus of the atom. There are some atoms that, when we shoot neutrons, the binding energy always collapses. These are called “fissile isotopes.”
There are three major fissile isotopes: Uranium 235 (used in the Hiroshima bomb, and almost all nuclear power reactors); Uranium 233 (used in Thorium reactors, but basically never in weapons); and Plutonium 239. These are the “major” isotopes because they are the easiest to find. Uranium 235 is naturally occurring - 0.7% of all uranium metal on the Earth is the 235 isotope, so all we need to do is dig up some Uranium from the ground.
Plutonium and Uranium 233 (heretofore 233) are both ‘synthetic’ elements. They don’t occur naturally in any appreciable quantity - they have to be manufactured. This is done in exactly the way that we trigger fission - we shoot neutrons at a metal, and effectively “transmute” it from its current state into what we want it to be. The metal of choice for 233 is Thorium 232, and the metal of choice for Plutonium is raw Uranium (238). We expose the metal to a lot of neutrons, and it slowly becomes the isotope we desire by absorbing neutrons.
It turns out that it’s much easier to make Plutonium than it is to separate natural Uranium into 235 and its other isotopes. So that’s one reason that we use Plutonium in weapons.
Now, regarding the “cross section” - as you’ve probably heard, most of an atom is empty space. Because of the binding energy of the nucleus, however, the nucleus of some elements appears to be a larger ‘target’ than that of others. This is a favorable characteristic, because in a nuclear weapon the whole idea is that we want as many fission events to happen as quickly as possible. Since the fission event is triggered by a neutron hitting a nucleus, making the nucleus a bigger target works to our advantage.
As an interesting side-note, the first nuclear weapons used Uranium. This is because Plutonium had to be made rather than simply dug up and separated chemically - and to “make” plutonium you need neutrons. By far and away the best (and only realistic) source of neutrons is a fission reaction - which means that before you could even consider Plutonium, you needed to enrich some Uranium. It wasn’t a chicken-and-the-egg at all, Uranium had to come first.
In summary:
Modern nuclear weapons almost always use Plutonium.
Plutonium is used because it has favorable weapons characteristics (it’s easier to get it to go ‘boom’)
Plutonium is also used because it’s easier to make than weapons-grade uranium.
Thermonuclear (Hydrogen) bombs start with the same fission reaction that powers atomic bombs — but the majority of the uranium or plutonium in atomic bombs actually goes unused. In a thermonuclear bomb, an additional step means that more of the bomb’s explosive power becomes available. Bigger boom = better bomb.
First, an igniting explosion compresses a sphere of plutonium-239, the material that will then undergo fission. Inside this pit of plutonium-239 is a chamber of hydrogen gas. The high temperatures and pressures created by the plutonium-239 fission cause the hydrogen atoms to fuse. This fusion process releases neutrons, which feed back into the plutonium-239, splitting more atoms and boosting the fission chain reaction.
Sorry, I thought you’d asked!
