How easy is it to build a nuclear bomb?

[Dancing David]

.
It's probably better to not assist in any manner.
The paranoid net of suspicion can be thrown pretty wide, when the nuke goes off.
Let'em do their own work.

Um you do know you can get a degree is nuclear engineering right? Why not send a bright person to school?

 

[geni]

.
It's probably better to not assist in any manner.
The paranoid net of suspicion can be thrown pretty wide, when the nuke goes off.
Let'em do their own work.

Well I would but it's become pretty obvious at this point that goverments have used poor understanding of nuclear weaponry and the like to provide people with further worries with regards to terrorists and countries we don't like.

 

[Loss Leader]

If anyone needs to know how to make a nuke, let -them- look it up! Don't assist them!

Anyone with a mountain of uranium and the sports stadium full of equipment he needs to sort out the U235 is far enough ahead in his project that a little extra help won't matter. Frankly, I'm not sure why he doesn't just ask the physicist who designed his enrichment facility. I'm sure that guy probably knows the rest of the steps.

 

[kalen]

The hardest part is getting the U235. It has to be separated from the non-radioactive U238.

U238 is radioactive. It has a half-life of 4.5 billion years.

 

[Loss Leader]

U238 is radioactive. It has a half-life of 4.5 billion years.

No kidding. I bought a pound of it last week and now I only have 15 and 0.9999999999659 ounces left.

 

[dudalb]

The bottom line is building a nuclear bomb in and of itself is not that difficult; anybody whith a good engineering and/or physics background could do it. What makes it hard is getting the nuclear materials with which to build it;you would have to buy or steal them;making them in your garage is not feasible.

 

[catsmate]

The bottom line is building a nuclear bomb in and of itself is not that difficult; anybody whith a good engineering and/or physics background could do it. What makes it hard is getting the nuclear materials with which to build it;you would have to buy or steal them;making them in your garage is not feasible.

Exactly. And there's quite a bit of effort put into making it difficult to acquire significant amounts of fissile material. And in the US, post 2001, security at civilian/commercial plants and for shipments has been increased enormously.
Back in the old days a visit to 1717 H Street in DC would get you data on any
of the civil plants (including the reprocessing facilities which stored literally tonnes of viable Plutonium) down to floorplans and fuel shipments. Not any more.

 

[NutCracker]

Really, the basic idea isn't difficult a bright undergraduate could work out the details.

Well, my questions where not intended to be answered. They where a kind of rhetorical to illustrate that quite a bit more is involved in nuke design than the kind of pop-sci 'just slam to hemi-spheres of nuke stuff, Pu or U, whatever is easier to come by, together and you have a big boom' kind of articles from the 80's, someone mentioned in this thread, suggest. Thankfully.

It's nice to see confirmed that it requires a non-trivial amount of science skills and serious engineering to get it done. Thank heavens.

It's also to see that with your reply you provide some more complexities that I did not think of when writing my post. One being: what is the relationship between the degree of enrichment of U and the amount needed?

Only generally a problem with gun-barrel designs; spherical implosion designs require a complex series of actions to occur, in sequence, to function.

If I'm not mistaken during the Manhattan project the implosion route for a Pu based bomb was taken exactly to circumvent the predetonation problem. I don't know whether implosion designs are not prone to predetonation at all.

However using Uranium this [predetonation] is less of a problem as the most common impurity in HEU (U²³⁸) isn't fissile using thermal neutrons. Nor is this a significant concern with implosion designs.

I'm confused. Do you mean that the presence of U238 wrt predetonation isn't a problem 'cause U238 doesn't fission spontaneously? I believe the problem of the presence of U238 is of a different nature: it absorbing neutrons that are thus no longer able to sustain a chain reaction.

I'm not sure what you mean by this.

I understood that for maximum efficiency one wouldn't want to rely on an ambient neutron or a spontanious fissioning to start the chain reaction. The critical assembly might have less than optimal density/geometry by the time a spontaneous neutron arrives.

IIRC Klaus Fuchs spent a significant amount of time and effort during the Manhattan project designing a device that assured to that: release a bunch of neutrons at the moment of maximum density. Littlle Boy had a initiator as well, I believe.

 

[Thunder]

How easy is it to build a nuclear bomb?

not as easy as it is for me to call Interpol.

 

[dudalb]

Well, my questions where not intended to be answered. They where a kind of rhetorical to illustrate that quite a bit more is involved in nuke design than the kind of pop-sci 'just slam to hemi-spheres of nuke stuff, Pu or U, whatever is easier to come by, together and you have a big boom' kind of articles from the 80's, someone mentioned in this thread, suggest. Thankfully.

It's nice to see confirmed that it requires a non-trivial amount of science skills and serious engineering to get it done. Thank heavens.

It's also to see that with your reply you provide some more complexities that I did not think of when writing my post. One being: what is the relationship between the degree of enrichment of U and the amount needed?



If I'm not mistaken during the Manhattan project the implosion route for a Pu based bomb was taken exactly to circumvent the predetonation problem. I don't know whether implosion designs are not prone to predetonation at all.



I'm confused. Do you mean that the presence of U238 wrt predetonation isn't a problem 'cause U238 doesn't fission spontaneously? I believe the problem of the presence of U238 is of a different nature: it absorbing neutrons that are thus no longer able to sustain a chain reaction.



I understood that for maximum efficiency one wouldn't want to rely on an ambient neutron or a spontanious fissioning to start the chain reaction. The critical assembly might have less than optimal density/geometry by the time a spontaneous neutron arrives.

IIRC Klaus Fuchs spent a significant amount of time and effort during the Manhattan project designing a device that assured to that: release a bunch of neutrons at the moment of maximum density. Littlle Boy had a initiator as well, I believe.

It would take a good background in science and engineering to build a nuke, but nothing that could not be learned in just about any decent college offering a engineering degree. Not trivial, I agree but not difficult enough so we should not be concerned at the possiblity.

 

[dtugg]

I don't think that handling plutonium is really that dangerous. Dozens of people did it at Los Alamos with no real safety precautions without suffering ill effects. A couple people did die but they were performing particularly dangerous experiments and their careless actions caused the plutonium core (the same exact core, a year apart) to go critical, releasing large amounts of radiation.

 

[Loss Leader]

what is the relationship between the degree of enrichment of U and the amount needed?

It's not a straightforward one. The presence of too much U238 will inhibit fission altogether. When the U235 ejects neutrons, there has to be a very good chance that they will hit the nucleus of another U235 atom. Reactor-grade U neads to be about 4% U235. Weapons-grade U, where an uncontrolled cascade reaction can be guaranteed to occur, is 90% U235.

 

[Beanbag]

The simple fact is that when you assemble a critical mass, something will happen. Exactly what happens depends on the engineering surrounding the device. The catch is holding everything together for as long as possible to get the maximum energy release. When you assemble a critical mass, it tries to take itself apart. The slower you assemble the mass, the less fission you get because the mass blows itself apart way too early for optimal fission to take place.

Explosives were used in the "shotgun" style bombs for a couple reasons. First, they assembled the mass quickly. Secondly, the pressure from the explosive detonating managed to hold the mass together a little bit longer until the pressure from the reaction blew things apart, so you got more atoms soaking up more neutrons, which generate more neutrons to get caught by more atoms, until things got out of hand. The early atomic weapons only produced a small fraction of their theoretical yield, simply because the bomb disassembled itself before things could run to completion.

Implosion bombs are several orders of magnitude greater in engineering complexity. Where the shotgun design required basically a single trigger of an explosive charge to get things going, implosion designs require a precisely-timed series of multiple detonations to have a true nuclear detonation, and they have to occur timed out to the microsecond level. Oddly enough, the implosion devices tend to be inherently "safe" from accidental detonation from, say, an airplane crash or a fire. Sure, the explosive charges go off and scatter nuclear material around, but because the detonation sequence is essentially random, the right containment needed for nuclear detonation doesn't happen.

Personally, I'm more concerned about "dirty" bombs and chemical weapons, especially the latter. All the wonderful chemical weapons used in WW1 can be synthesized in a high school chem lab, and the necessary chemical compounds are a lot less tightly controlled than nuclear material. I see more of an issue with somebody synthesizing a couple ten gallons of mustard gas and then spreading it around either by a cropduster or a spray truck in a crowded venue.

Beanbag

 

[BTMO]

.
It's probably better to not assist in any manner.
The paranoid net of suspicion can be thrown pretty wide, when the nuke goes off.
Let'em do their own work.

Do you *seriously* think anyone actually capable of building a nuke, with the contacts to get the material, the place to do it, the funds and the means to deliver it to whereever they want to let one off would learn *anything* from an internet forum?

Jeeze - they only have to go wikipedia or pick up one of many, many books on the subject. (EDIT: Or go to school for several years...)

We aren't helping them or anyone else by discussing this here or anywhere else.

It is time for the paranoia to go away.

**** the terrorists.

 

[fuelair]

Well how hard is it? I have some knowledge about particle physics and related things but i have no practical knowledge about hard it would be. Let's discard the missile.

What things would you need? How easy would it be for people to discover the project? I mean you see the US and the Soviets having thousands upon thousands of nuclear weapons but then you see a country like north korea struggle to achieve just a little fizzle...

Not that hard - except several of the steps can kill you pretty fast if you do anything wrong during them. Not really for amateurs.

 

[fuelair]

The simple fact is that when you assemble a critical mass, something will happen. Exactly what happens depends on the engineering surrounding the device. The catch is holding everything together for as long as possible to get the maximum energy release. When you assemble a critical mass, it tries to take itself apart. The slower you assemble the mass, the less fission you get because the mass blows itself apart way too early for optimal fission to take place.

Explosives were used in the "shotgun" style bombs for a couple reasons. First, they assembled the mass quickly. Secondly, the pressure from the explosive detonating managed to hold the mass together a little bit longer until the pressure from the reaction blew things apart, so you got more atoms soaking up more neutrons, which generate more neutrons to get caught by more atoms, until things got out of hand. The early atomic weapons only produced a small fraction of their theoretical yield, simply because the bomb disassembled itself before things could run to completion.

Implosion bombs are several orders of magnitude greater in engineering complexity. Where the shotgun design required basically a single trigger of an explosive charge to get things going, implosion designs require a precisely-timed series of multiple detonations to have a true nuclear detonation, and they have to occur timed out to the microsecond level. Oddly enough, the implosion devices tend to be inherently "safe" from accidental detonation from, say, an airplane crash or a fire. Sure, the explosive charges go off and scatter nuclear material around, but because the detonation sequence is essentially random, the right containment needed for nuclear detonation doesn't happen.

Personally, I'm more concerned about "dirty" bombs and chemical weapons, especially the latter. All the wonderful chemical weapons used in WW1 can be synthesized in a high school chem lab, and the necessary chemical compounds are a lot less tightly controlled than nuclear material. I see more of an issue with somebody synthesizing a couple ten gallons of mustard gas and then spreading it around either by a cropduster or a spray truck in a crowded venue.

Beanbag

And, a lovely site on the net with old textbooks/manuals including two lovelies: one on military/commercial explosives and one on military poisonous/irritant gasses. Don't think I'll post that one though-- but printed them out for my collection.

 

[shadron]

Pretty much all nuclear weapons use plutonium 239. It is made in a nuclear reactor and somehow separated from the other material (don't ask me how they do this, I dunno). This is most certainly not something that an individual could do in his garage. You can also make a nuclear bomb using uranium 235. But it is very hard to enrich from natural uranium in the necessary quantities. The entire Manhattan project only made enough for one bomb.

Actually, most now use a product called Uralloy, which is a mixture of Pu and U-235. The U-235 is apparently cheaper to produce than the plutonium. No, the Manhattan Project made enough for four bombs (Nagasaki, the demon core used in Xroads Baker, Xroads Able and another for Xroads Charlie that was cancelled), and by the Spring of 1946 was ramping up towards two cores a month.

As with deciphering codes, by far the easiest way to obtain fissionables is to steal them.

 

[shadron]

I don't think that handling plutonium is really that dangerous. Dozens of people did it at Los Alamos with no real safety precautions without suffering ill effects. A couple people did die but they were performing particularly dangerous experiments and their careless actions caused the plutonium core (the same exact core, a year apart) to go critical, releasing large amounts of radiation.

Plutonium and U-235 are alpha emitters with loooooong half-lives, which means they are not very intense. They are poisonous, similar to arsenic in that regard, and they are pyrophoric, which means they'll ignite at room temperature. Usually the core components are plated in nickel or some such to keep them from combusting (which only happens readily when they are thin shavings) or oxidizing. In that wrapper they are human handleable. Just don't inhale dust or gas emanations.

 

[rjh01]

It is very hard to build a nuclear bomb without outside help. Several countries have tried and failed.

 

[nvidiot]

It is very hard to build a nuclear bomb without outside help. Several countries have tried and failed.

No, its just very hard to build a deliverable, consistent and effective nuclear bomb with other nations deliberately attempting to prevent it.