Tufa @ Dec 20 2009, 11:34 AM wrote:
McCob 4 Dec 19 2009, 10:37 PM wrote:
When uranium 235 (or plutonium 240 something) is bombarded by Neutrons it will break apart into smaller atoms
The odd-numbered atom weight is what you are looking for. Natural Uranium U238 or the Plutonium Pu240 ain't any good, U239 and Pu239 shall be used.
When the atom split, some 2-3 new neutrons are emitted as well, and much energy is released. The deficiency in mass is a peculiar thing not much relevant to the industrial application; when you have burned-out fuel cell packages from a nuclear reactor submerged 15m below the surface the mass deficiency 0.5% of the fuel calls; I guarantee the smallest of your concerns!
The nuetrons have to be going within a certain range of speed when they hit the nuclear fuel.
Precisely. In fact, the new produced neutrons that have a high energy will go vary fast, and unfortunately the cross-section of your target is low for fast neutorons. In a reactor you usually put a lot of water around the fuel to slow the neutrons, and they can then find an acceptable cross section in Pu240.
So, dear friend, if you pour out the water from your reactor (!!!!!!!!!!) the reaction will actually stop rather quickly. There is a residue energy production, that unfortunately prevent this being used as a security measure.
This is why you need the (U239/Pu239) fuel for you bomb. The odd-numbered atoms have a small cross-section for fast neutrons, so neutrons from one split atom can go and split the atom next to it (if it hit the cross-section). This is the basis for the chain-reaction.
In industrial terms, the tricky part is producing a first neutron to start from. There are natural neutrons, but you don't gamble on having one when you need them, right? So you need some device to produce neutrons by technical means.
A typical solution would be an electrical energy source -> X-ray flash ->beam hit a target in the centre of your bomb -> neutrons produced, most likely in a two-step process.
The "Critical mass concept" is important, if you could imagine a bomb sitting on a rack to be loaded on a plane .... and it start raining .. and then the bomb starts heating up with some modest amount, like 1 degree each second --- I promise, it will spoil your coffee break! Especially if some deck-nerd try to extinguish the "fire" and pull out a hose!
Compressing the metal sphere by explosives. You often find pictures on this, the "fast" and "slow" explosives are often replaced, as well as the initiator at the wrong place. I'll thought this to be a "security" feature, before :huh:. It could, possibly, set back the so-called "Terrorists" several minutes, to figure this out, but I much doubt that. If I can upload some pictures, I'll show you.
The usual U238 metal is reported to have a small cross-section for fast neutrons. You cannot build a bomb using it, but if your nuclear device sits close to some tons of U238, you should get a bigger blast.
I seen some report, that physical consequences of Bombs is much exaggerated such as the "atomic Winter" scenario. Since the air density is a bit low, it is difficult to transfer the energy long distances. So a bigger bomb is not that much more effective.
If public "Atomic tests" was made to scare an enemy, there would be much incentive to "improve" on the test results. Most likely the "pictures" would be backed up with "adjusted" pressure sensors, that send "secret" signals protected by some moderate encryption that the enemy could work on, and also "spies" that leak some "reports" that tell the real "truth".
If the bomb is a complete LIE, it should be easy to check it by beeing careful with the basic facts.