Ask HN: What prevents more countries from creating nuclear weapons?

[anthonyrubin]

Why is it still so difficult to create a nuclear weapon? What information is not available through an advanced education at a top university? Is it simply a matter of difficult to find materials?

I ask here because I assume there is at least a small population of regulars with a great deal of knowledge in relevant areas such as physics.

[Ezra]

It's trivial to design and build a nuclear weapon.

The trick, as others have mentioned, is getting the Uranium.

You do not need billions in R&D, or a crack team of scientists.

A working bomb was actually designed by two (ableit, smart) students... in 30 months... in 1964. It would be far easier today.

Check: http://www.guardian.co.uk/world/2003/jun/24/usa.science

"You could have taken any number of classes at Beloit with Professor Dobson, until his recent retirement, without having any reason to know that in his mid-20s, working entirely as an amateur and equipped with little more than a notebook and a library card, he designed a nuclear bomb.

Today his experiences in 1964 - the year he was enlisted into a covert Pentagon operation known as the Nth Country Project - suddenly seem as terrifyingly relevant as ever. The question the project was designed to answer was a simple one: could a couple of non-experts, with brains but no access to classified research, crack the "nuclear secret"? In the aftermath of the Cuban missile crisis, panic had seeped into the arms debate. Only Britain, America, France and the Soviet Union had the bomb; the US military desperately hoped that if the instructions for building it could be kept secret, proliferation - to a fifth country, a sixth country, an "Nth country", hence the project's name - could be averted. Today, the fear is back: with al-Qaida resurgent, North Korea out of control, and nuclear rumours emanating from any number of "rogue states", we cling, at least, to the belief that not just anyone could figure out how to make an atom bomb. The trouble is that, 40 years ago, anyone did."

[streety]

All the comments so far seem to focus on Uranium based nuclear weapons but what about plutonium based?

My physics knowledge is basic at best but my understanding was that if you had a working nuclear reactor then plutonium could be extracted, relatively, easily from the waste.

Are there other obstacles in the making of a plutonium based weapon which means it's actually easier to enrich U235?

[orib]

The hard part is getting enough enriched uranium. it's chemically the same as all other uranium ore, and the only difference that you can use to separate it is a 0.85% mass difference of the atoms. Once you have the uranium extracted, the bomb itself is trivial, as far as these things go. You need some knowledge about how it works, but the actual parts are simple enough. In fact, you could probably put together one with steampunk technology without too much trouble if you had the uranium

[aristus]

The fissionable material is the big part. But don't underestimate technical details like the shaped & coordinated charges, etc. A few years ago the US government posted all of the documents turned over from Iraq's nuclear program. A few of those documents were taken down quick after nuclear experts warned them that they were releasing vital and hard-to-discover engineering details.

[jellicle]

Refining potentially fissionable material is difficult. Remember that U-235 and U-238 are chemically identical, so you can't separate them by any chemical means, and U-235 makes up only 0.7% of natural uranium ore.

The Manhattan Project employed 130,000 people... many of those were NOT the guys designing the bomb, but the guys trying to set up refining operations and the like. It cost the equivalent of $21 billion dollars in today's money, and took five years to get a bomb.

So, if you have a country that has $21 billion dollars and five years to spare, and can avoid getting bombed by the United States during that time, and is sitting on minable fissionable materials, they can develop a bomb... Even if you give them a 50% discount because it has already been done, still, $10 billion dollars.

[tlrobinson → jellicle]

$21 billion doesn't seem like much when we're talking about $700 billion financial system bailouts...

[known → jellicle]

How difficult is it refine Thorium?

[noodle]

iirc, the major issue is that you need some serious money, coordination, and brainpower to make it happen. many countries just aren't coordinated, rich, or connected enough to make it happen.

one of the major inhibitors are, indeed, the "nuclear secrets" as it were. there are a few special sauces that just take experimenting and tinkering and brainpower to work out. all of which also cost more and require more supplies.

or, at least, thats my simplified, non-physicist understanding of it.

[orib → noodle]

No. pretty much (gross oversimplification, but this is the essence of it) all you need for a nuclear bomb is to slam 2 or more subcritical chunks of sufficiently enriched uranium into each other fast enough to fuse them to a single supercritical chunk of the above, and you have a boom. The hard part is the uranium. Compared to producing the uranium, designing and manufacturing a viable bomb is trivial.

I remember reading about a US research project where someone with reasonable physics knowledge, but no specific knowledge on the workings of atomic bombs, managed to put together viable plans for a bomb from only publically available information.

[tesseract → orib]

It sounds simple but you've got two roadblocks to overcome. The first is "sufficiently enriched uranium" which is expensive to obtain.

The second is "fast enough", since if you don't assemble the material fast enough and hold it together for long enough it will blow itself apart before there is a chance for the chain reaction to build, and you will have a dud (at least compared to the intended yield). To get around this problem you will probably need some fairly advanced shaped charges and a properly designed tamper. This is what the "nuclear secrets" cover. Obviously it is possible to derive this information for oneself, but it's non-trivial to say the least.

[noodle → orib]

according to my understanding, again, one of the major issues of the fission-based bombs (that you describe here, instead of the thermonuclear weapons), is that one of the major issues and one of the "nuclear secrets" is thus:

how do you ensure that in that collision, how to ensure that the "slamming" consumes enough of the uranium, converting it into boom, before the boom destroys the weapon itself, halting the reaction.

but again, not an expert. i'd love to hear more on it if you or someone else are.

[kf]

http://www.guardian.co.uk/world/2003/jun/24/usa.science

[mechanical_fish]

I recommend Richard Rhodes' book, The Making of the Atomic Bomb.

[sprice]

Intelligence