Fourth Generation Nuclear Weapons

[selfAdjoint]

See http://www.arxiv.org/abs/physics/0510071" excellent paper on the latest technology research on using tiny pellets of DT to yield explosions in the 100 ton range. Also includes brief but illuminating discussion of earlier nuclear weapons, from an international standpoint.

 

[theCandyman]

What is the Independent Scientific Research Institute? The paper seems like an interesting read, but I do not like the idea of research into more powerful nuclear weapons. The current ones are already so powerful, there is not a need to get greedy and make sommething that has the probability of having an effect on something other than a target if a bomb absolutely has to be used, Earth is a confined space after all.

 

[Lapin Dormant]

100 ton range is less then the KILOtonnes of an A bomb, and less moreso then the MEGAtonnes of the H bomb.

If I have the inference of "100 tons range" read properly. Smaller weapons of destrucive force from Nuclear sourcing.

 

[selfAdjoint]

100 ton range is less then the KILOtonnes of an A bomb, and less moreso then the MEGAtonnes of the H bomb.
If I have the inference of "100 tons range" read properly. Smaller weapons of destrucive force from Nuclear sourcing.

Yes. And with only a tiny, very thin shell of actinide, so minimal radiation signature. DT is a clean reaction, and they only need milligrams of it per weapon, so "safe for battlefield use"!

 

[hitssquad]

with [...] a [...] thin shell of actinide

What are you referring to? I only skimmed the article, but it seemed to be saying that the trigger would be non-fission. Are you referring to a U-238 blanket? I didn't see the article mention a U-238 blanket.

 

[sharmans]

wow...Great

 

[selfAdjoint]

What are you referring to? I only skimmed the article, but it seemed to be saying that the trigger would be non-fission. Are you referring to a U-238 blanket? I didn't see the article mention a U-238 blanket.

I thought I saw a reference to a thin shell of Uranium or Plutonium surrounding the pellet, but maybe this was in the "sparkplug" pellets used in H-bombs.

 

[hitssquad]

I thought I saw a reference to a thin shell of Uranium or Plutonium surrounding the pellet, but maybe this was in the "sparkplug" pellets used in H-bombs.

I think that was part of the section discussing older-generation devices:

2.2 Two-stage thermonuclear weapons

In two-stage thermonuclear weapons, the fusion material(i.e., lithium-deuteride, LiD) is generally packaged as a cylindrical or spherical shell sandwiched between an outer-shell of heavy material (the pusher/tamper) and an inner-shell of fissile material. This inner-shell (the spark-plug) is generally boosted with some DT gas. As suggested by its name, the purpose of the spark-plug is to ignite the fusion material at the appropriate time, i.e, once it has been sufficiently compressed. This whole package is called the "secondary" of the thermonuclear weapon, and is enclosed together with the "primary" in a thick and heavy "radiation case" which is designed to contain the soft-X-rays from the primary as long as possible.

 

[theCandyman]

100 ton range is less then the KILOtonnes of an A bomb, and less moreso then the MEGAtonnes of the H bomb.

I did read it wrongly. I still do not agree with it, using smaller weapons like this would only encourage using larger ones.

 

[Pengwuino]

I did read it wrongly. I still do not agree with it, using smaller weapons like this would only encourage using larger ones.

That is if we actually ever use the smaller ones. Maybe there are actual applications for something like that (mining for example) although I wonder what kind fo radiation levels it creates. And I also believe the belief that using smaller will result in bigger is as baseless as when they started saying the cheaper/cleaner you can make them, the more people will start using them.

 

[theCandyman]

The machine gun comes to mind, the inventor wanted to make something so horrible that war would no longer be something humanity wanted. In the present, they are common place and unlike defending trenches in the world wars, they are mounted onto helicopters and vehicles.

Of course there are other applications for this, but they are looking into the "military effectiveness".

 

[Pengwuino]

I never really liked his reasoning for the machine gun. I don't see how he could have thought "humanity wants war" at the time and that the machine gun would have made people "not want it".

 

[sid_galt]

There is one weapon so horrible that humanity does not engage in major wars - the nuclear bomb.

Anyway, it's a pretty cool idea. I wonder how large they'll be. Could one for instance fit in a small UAV?

 

[Grogs]

That is if we actually ever use the smaller ones. Maybe there are actual applications for something like that (mining for example) although I wonder what kind fo radiation levels it creates. And I also believe the belief that using smaller will result in bigger is as baseless as when they started saying the cheaper/cleaner you can make them, the more people will start using them.

I think it's just the opposite really. I think most sane (ok, at least a little bit sane) world leaders realize that tossing ICBM's around will cause serious fallout in the international community. These seem to be an attempt to subvert that. It's seems like sort of an 'if we use a bunch of smaller nukes, maybe they won't mind so much' theory.

As for the long-term radiation effects on the landscape, it doesn't look like they'd be too bad. Of course the immediate effects for those near the weapon would be pretty horrible. The LD50/30 range for a 1-ton device would be about 300m and for a 100-ton one it would be around 1000m. This means that a person standing 1000m from a 100-ton detonation would have a 50% chance of dying (painfully!) from acute radiation sickness in the next 30 days. Of course people farther out still have a chance of dying either from ARS or from a cancer induced by the radiation. Closer in, people would literally drop dead in their tracks.

 

[Lapin Dormant]

What about the simplistic idea that the main reason is a manner of disposing of all {of some} of that nuclear waste, as this is seen as a Practical application for it's disposal?

Personally I don't think we need any more explosive devices as we already have enough to 'face off' the planet.

 

[Grogs]

What about the simplistic idea that the main reason is a manner of disposing of all {of some} of that nuclear waste, as this is seen as a Practical application for it's disposal?

I'm not sure I follow you. Was this something discussed in the paper? I don't see how these weapons could in any way help with waste disposal. The only radioactive isotope it would contain would be tritium (H-3). As radioactive substances go, Tritium is pretty benign, releasing only an 18.6 keV electron and no gammas whatsoever when it decays. We're also only talking about a few grams, so even if tritium *were* a serious disposal problem, it would take a *lot* of these bombs to make even a sizable dent in our inventory.

 

[Lapin Dormant]

Probably my error, as I did NOT read the paper, but in the manufacture of tritium, isn't that done by nuclear bombardment using radioactive isotopes?
Hence a 'use' for some of the waste?

 

[Grogs]

Probably my error, as I did NOT read the paper, but in the manufacture of tritium, isn't that done by nuclear bombardment using radioactive isotopes?
Hence a 'use' for some of the waste?

To the best of my knowledge, the easiest way to produce Tritium is to put some Li-6 inside of a reactor. The high-neutron flux in the reactor will produce Tritium using the reaction: Li-6 + n -> He4 + H-3. In spent fuel rods, there will be some residual neutron flux, but it's going to be considerably less than what you'd get inside of a reactor.

In an operating nuclear reactor, only about 0.7% of the neutron flux come from sources other than the fissions (we call these delayed neutrons and they're actually critical to our ability to control fission reactors.) Most of these delayed neutron sources have quite short half-lives though, typically less than 1 minute, so in spent fuel the neutron flux would fall off significantly after only a short period of time.

This isn't to say there aren't uses for nuclear waste though. We could pull about 99% of the material from spent fuel rods (the Uranium and Plutonium) plus a few other select isotopes which are useful for medical or commercial purposes (radioisotopic tracing and food irradiation for example.) Unfortunately, in order to do that we'd have to reprocess the waste and our current policy in the U.S. is that we don't recycle our fuel.


Back to the initial article, I noticed one item that I missed on my first initial skim. It completely ignores the problems associated with storing tritium-deuterium gas in a warhead. First, by it's very nature tritium is difficult to store as a pure gas. It tends to escape through the walls of most common storage materials (glass, steel) over a period of time. It's also radioactive, with a half-life of 12.3 years. The result is that after a period of time, your weapon will have considerably less yield than it did when it was first produced, giving it a fairly short shelf-life.

In the earliest thermonuclear weapons, they had to periodically disassemble the warhead, remove the pit, and refill it with tritium. This was less than desirable, so a solution was devised to use Li-D, which is stable, in the pit instead of D-T. When the first-stage (fission) trigger was ignited, it would provide the neutron flux to produce tritium from the Li to be used in the reaction. In the case of a conventional trigger, like the FGNW's, you wouldn't have the neutron flux so you'd have to use D-T gas in the pit. Has our technology improved enough that this is no longer a significant obstacle?

 

[hitssquad]

tritium [...] tends to escape through the walls of most common storage materials (glass

Glass is tritium-permeable?

 

[Grogs]

Glass is tritium-permeable?

No, actually that should be plastic, not glass.

 

[Lapin Dormant]

Nice answer Grogs

Had some experience at this have you?

(it shows)

 

[Grogs]

Nice answer Grogs
Had some experience at this have you?
(it shows)

Thanks. It's education rather than experience actually. My minor as an undergrad was nuclear engineering and I'm getting ready to start on a Master's degree in NE this spring. Sometimes what you learn in the classroom is quite a bit different than how things are actually done though, so it's nice to have folks like Astronuc and Morbius who have years of experience working in the field for sanity checking.

 

[Lapin Dormant]

Fooled me you did

Thanks. It's education rather than experience actually. My minor as an undergrad was nuclear engineering and I'm getting ready to start on a Master's degree in NE this spring. Sometimes what you learn in the classroom is quite a bit different than how things are actually done though, so it's nice to have folks like Astronuc and Morbius who have years of experience working in the field for sanity checking.

It is probably the usage of the "We" thing cause you make it sound like you have done it.

Fun stuff itsn't it, complex, yet simple, yet mightly Complex.

Potent.

 

[Morbius]

There is one weapon so horrible that humanity does not engage in major wars - the nuclear bomb.
Anyway, it's a pretty cool idea. I wonder how large they'll be. Could one for instance fit in a small UAV?

sid_galt,

We have had nuclear artillery shells!

No secret there.

Dr. Gregory Greenman
Physicist

 

[NavyMan]

Gotta love atomic annie.

 

[Morbius]

Gotta love atomic annie.

NavyMan,
Yes - but what I actually had in mind were regular 8" and 155mm shells.
For example, the W-79 was an 8 inch projectile:
http://nuclearweaponarchive.org/Usa/Weapons/W79.jpg
and the W-48 was a 155mm [ 6.1 inch ] projectile:
http://nuclearweaponarchive.org/Usa/Weapons/Mk48.jpg
"Atomic Annie" was the W-9 and was a 280 mm shell:
http://nuclearweaponarchive.org/Usa/Weapons/Mk9.jpg
Later designs like the W-48 were almost half the diameter of "Atomic Annie"
Dr. Gregory Greenman
Physicist

 

[theCandyman]

Yes - but what I actually had in mind were regular 8" and 155mm shells.
For example, the W-79 was an 8 inch projectile:
http://nuclearweaponarchive.org/Usa/Weapons/W79.jpg

I thought the bombs were big because a critical mass is needed, so what are the dimensions of the smallest critical mass?

 

[Astronuc]

I thought the bombs were big because a critical mass is needed, so what are the dimensions of the smallest critical mass?

That's a secret.

The smallest critical mass depends on how well one can compress a mass of fissile material (i.e. depends on max density achieveable) and on the purity of the fissile material. One certainly needs less Pu239 than U235.

 

[NavyMan]

I read recently it was possible to get the critical mass documents due to the freedom of information act, they are supposedly available from the National Archives and cost about $20. Scary thought

 

[Pengwuino]

I read recently it was possible to get the critical mass documents due to the freedom of information act, they are supposedly available from the National Archives and cost about $20. Scary thought

Well then go buy it :P

You'd think thatd be one of the things that were exempt from FOIA... unless the information is less useful then it seems.