Kuu

Thanks for your input so far, Corwin.

As I said I have very little knowledge of explosions and yet I could see faults in what was said at the site about the bombing but my friend's son says that that is because I was already prejudice against the site because I totally disagree with what the site says about the Port Arthur massacre.

Corwin

Ask your son to take a look at pictures of the Oklahoma City Federal Building.

That was a (very large) ammonium nitrate bomb. (Much larger than 330 lbs.... but it took out most of a good sized office building.)

Derec

Actually Pu is quite enough. Uranium 238 is used in very high yield bombs (>1MT) in the tertiary stage of the bombs (not neutron producing fast fission of U238 by fusion neutrons from the Secondary).
U-235 can also be used as a neutron reflector in the Primary but that is not necessary, as other materials (such as graphite) can also be used as neutron reflectors.

<strong> Yet yields significantly lower than 1 kt are possible.

<strong> Duh indeed.

<strong> That is more due to hard gamma (high energy photons) than to alpha radiation. Alpha of any energy has a rather short range so it is virtually undetectable unless you have Plutonium particles right next to the window. There is also beta and more gamma from any of dozens of fission products, many of which are orders of magnitude more active than Plutonium.

Corwin

Making a pure plutonium bomb is more trouble than it's worth. Briefcase nukes (so far as anyone outside the former Soviet Union knows) use a 2.2kg combination of uranium and plutonium. Uranium is easier to get... (you don't need access to a heavily guarded and monitored breeder reactor) and it's MUCH safer to use. (Uranium is a gamma emitter... and a high energy one if I remember right... plutonium is a low energy alpha emitter, but unlike uranium is also amazingly toxic in addition to being radioactive.) Power reactors and primitive nukes use uranium because it's easier to get and much safer to handle.

And, put simply... why would anyone build a sub 1kt nuke? I admit it's possible.... but when you're talking about less than one kiloton... you can do the same amount of damage, and do it much more cheaply and easily with a fuel-air or fertilizer bomb. People keep talking about micronukes but nobody ever mentions why someone would spend hundreds of millions of dollars designing, and millions of dollars building such a bomb.

Semi-truck rental: 500 dollars*.

5 tons of ammonium nitrate: 1000 dollars*.

50 gallons of deisel oil: 50 dollars*.

Realizing that for the investment of 1550 USD, you've created an explosive device that will achieve the same end result as a 50 million dollar briefcase nuke, and can be used WITHOUT being nuked in retaliation**: Priceless.

(*wild guesses on all prices except the diesel oil... which is going for about a buck a gallon, right? I don't drive a diesel engine so I haven't been paying all THAT much attention...)

(**note that I do NOT endorse doing this anyway.... this example is provided simply as an example of why micronukes are relegated to the field of nutcase conspiracy theories...)

Bookman

Before you take Corwin's word for any science info, you may wish to persue this memorable thread, <a href="http://iidb.org/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=57&t=000107&p=" target="_blank">Will the Center of the Earth ever cool?</a>

His take on science appears to be more intuitive than learned.

Bookman

Corwin

And before you listen to slams against me... possibly you'd like to check my facts?

Of course not. It's much more fun the other way.

Derec

Depends on what you want to do.

<strong> </strong>

As I said, Uranium can be used, but not as the actual fissible material but as nuclear reflector.

<strong> [quote]
Uranium is easier to get... (you don't need access to a heavily guarded and monitored breeder reactor) and it's MUCH safer to use.
[QB][QUOTE]

U-238 is much easier to get, yet. Highly Enriched Uranium is much harder to make than Plutonium (isotope separation required). That is why all modern nukes are Plutonijm bombs, not Uranium bombs. The reason first bomb was Uranium bomb lies in the fact that with uranium a much simpler device - the gun device - can be used. However, once the implosion device was depeloped there was really no reason for nuclear powers to bother enriching Uranium for the bombs.

[QB]Both emit both alpha and gamma particles. For U235 alphas have the energy between 4 and 4.5 MeV and gammas have the energy between 20 and 800 keV. For Pu239 alphas range between 4 and 5 MeV and gammas between 0 and 1 MeV. So the energies are cpmparable. However, Pu239 has a much higer activity (decay rate) than U235.

<strong> That is true. Besides being much more radioactive than Uranium, Plutonium is also much more chemically toxic. Whoever gave it its name chose well.

<strong> Power reactors mostly use Uranium because they do not require highly enriched (&gt;80%) Uranium-235 to operate. Few percent is fine.
Primitive nukes used Uranium because a simple gun setup can be used, rather than the more complex implosion device.
Safety is a bonus too I guess. If I was a terrorist I would prefer Uranium myself.

<strong> Actually the American "bunker-buster" B61 has a warhaed whose yield can be varied between 300 t and 300 kt. So it is done.

<strong> I guess size/weight is a factor, for example the B61 Mod 11 is supposed to penetrate ground a few meters before detonating in order to destroy an underground instalation. A bulky fertilizer bomb would not be able to achieve that.
A flexibility is another reason too, as you can chose the yield literally a few moments before separation by varying the amouns of boosting the nuclear reaction receives.

<strong> And I suppose you can drop a 300 t equivalent yield fertilizer bomb from an A/F-18 plane as well?

Military has different goals and therefore quite different solutions than terrorists.

Corwin

Both of them also operate under budgetary constraints. Plutonium is amazingly expensive, and has virtually no natrual source. (There's a TINY bit in pitchblende, but only a little. The only source where you can get any substantial amount... like enough to power a bomb... is from a breeder reactor.) 'Terrorists' also would have very little use for a bunker buster.... since they generally avoid attacking military targets... (I mean.... they shoot BACK!!!) and most terrorist groups would have a lot of trouble affording any sort of plane that could deliver that kind of weapon.

Let's face it. We're talking about someone bombing civilian targets for shock value. A briefcase nuke could take out most of a downtown area in a major city.... but when it comes down to it it's a waste of time, energy, and money. Flattened and destroyed is flattened and destroyed. The only real difference is that using an atomic weapon to flatten and destroy will just about gaurantee that you will in turn have atomic weapons used against you in retaliation. Even most terrorists aren't THAT stupid. (And if they are, they probably can't figure out how to build a small nuke.)

Jobar

Corwin is correct here. (Re the reasons why the Bali explosion could not have been nuclear.) No radiation, and if Al Queda had the sort of tech and materials required for such a small nuke they would NOT make a small nuke. They'd wipe some major city off the map. Kuu, tell your friend's son that.

Derec

Jobar, I wasn't arguing any of that. It is perfectly clear to me that Bali was no nuke and that small yield nukes are not very attractive to terrorists. I was mainly arguing some of the more general things with Corwin.