8 ms·

We should all take the bit about being able to construct a “relatively sophisticated nuclear device,” with a grain of salt. An actual bomb is beyond the capabi

by Amadou 13y ago

We should all take the bit about being able to construct a “relatively sophisticated nuclear device,” with a grain of salt. An actual bomb is beyond the capability of anybody but a nation-state. Al-qaeda, et al don't have a chance of anything more than a dirty bomb. While dirty bombs suck too, they are limited to contamination of a couple of city blocks - not actual kinetic destruction of those blocks and the contaminated have a high survivability level given the kind of treatment immediately available in a city. Also, in this day and age of the NSA and supporters using weasel words, I have to wonder if (a) this info was declassified to support justifications for the NSA and (b) if the line about a "nuclear device" is more weasel wording to sound scary without literally claiming they could build a bomb.

phkamp 13y ago
This is old cold-war spin, and it has been refuted so many times, yet it still surfaces. Read "The curve of binding energy", and you will learn from Ted Taylor, one of the worlds best nuclear warhead designers, that you can make the simplest atomic bomb by dropping one piece of fissile material on another, provided they are big enough to become a critical mass. It won't be tens of megatons, but it will be a perfect terror weapon, spreading panic, making a large-ish area uninhabitable and costing a fortune and many years to clean up. If the terrorists are smart enough bring a couple of sacks of salt, it makes the mess much worse. There are damn good reasons to go out of the way to prevent access to the funny end of the periodic table.
- srean 13y ago
  More qualified people will correct me, but I think there is more to it than dropping a piece of fissile material over another. I think the trick is to keep the pieces together long enough before the forces of explosion rips them apart. As far as I know there have been several examples of accidents were scientists did actually drop a fissile blob over another, and the material did go critical, but thankfully the scientist(s) involved were fast enough to separate the pieces so that no catastrophes ensued. They themselves died as a result of exposure to radiation. As I said, more qualified people will be able to fill in the details and citations.
  - louthy 13y ago
    I suspect you're referring to this: https://en.wikipedia.org/wiki/Louis_Slotin#Criticality_accident https://en.wikipedia.org/wiki/Louis_Slotin#Criticality_accid... "At 3:20 p.m., the screwdriver slipped and the upper beryllium hemisphere fell, causing a "prompt critical" reaction and a burst of hard radiation. At the time, the scientists in the room observed the blue glow of air ionization and felt a heat wave. In addition Slotin experienced a sour taste in his mouth and an intense burning sensation in his left hand. Slotin jerked his left hand upward, lifting the upper beryllium hemisphere and dropping it to the floor, ending the reaction. However, he had already been exposed to a lethal dose of neutron radiation."
    - caf 13y ago
      That wasn't even the first fatal criticality incident involving that particular plutonium core (known as the "Demon Core"). Funnily enough, I submitted an interesting article just a few hours ago on the history of this core: https://news.ycombinator.com/item?id=6229011 https://news.ycombinator.com/item?id=6229011
  - 6d0debc071 13y ago
    > More qualified people will correct me, but I think there is more to it than dropping a piece of fissile material over another “With modern weapons-grade uranium, the background neutron rate is so low that terrorists, if they have such material, would have a good chance of setting off a high-yield explosion simply by dropping one half of the material onto the other half. Most people seem unaware that if separated HEU [Highly Enriched Uranium] is at hand it’s a trivial job to set off a nuclear explosion … even a high school kid could make a bomb in short order.” - Luis Alvarez, Nobel Laureate in Physics, 1988 The key being, as I understand it, actually getting weapons-grade material of sufficient purity. Though the actual design of a practical, controlled and efficient, weapon would doubtless be more somewhat more complex. For which the n-th country project is well worth reading about: http://www.theguardian.com/world/2003/jun/24/usa.science http://www.theguardian.com/world/2003/jun/24/usa.science
    - fitumpich 13y ago
- Amadou 13y ago
  you can make the simplest atomic bomb by dropping one piece of fissile material on another, provided they are big enough to become a critical mass. My understanding of Ted Taylor's claims about compact fission bombs is that, absent high-grade manufacturing processes to properly shape the fissile material, we are looking at a couple of hundred kilograms to achieve critical mass. Actual "suitcase nukes" in the 10-20 kilogram range require perfectly shaped components and are also very high maintenance due to their electronics degrading rapidly from such close proximity to radiation sources. Then there is the question of testing. They say you can recognize veteran bomb makers by their missing fingers because they don't get things right the first time. Any testing of a fission bomb anywhere in the world is going to be noticed by seismographs at the very least.
  - archgoon 13y ago
    Why is testing an issue? The Trinity test was successful on the first run. Nation-states only conduct tests to calibrate destructive capabilities and fallout effects (a non-issue if you just want a big boom) and signal to other nation-states 'Don't mess with me'. Furthermore, states such as Israel, are believed to be nuclear, without ever having conducted any (known) tests. An unsuccessful nuclear explosion would just be a dirty bomb, which would still have the desired effects from a terrorist attack perspective. So there's no real reason to test before hand.
    - Amadou 13y ago
      In the case of a ultra-simple design available to terrorists that reaches critical mass by simply "dropping" one chunk of fissile material on another there is no explosion if it doesn't actually reach critical mass. Israel is a nation-state with a lot more resources available to it like the ability to measure purity and to conduct simulations. In fact a key part of nuclear politics for the last 20 or so years has been super-computer based simulations in lieu of testing. In the US the programs have been responsible for the construction of some of the largest super-computers of their time(s). https://en.wikipedia.org/wiki/Accelerated_Strategic_Computing_Initiative https://en.wikipedia.org/wiki/Accelerated_Strategic_Computin...
- rdl 13y ago
  I think a dirty bomb would be more than "scary" enough, given general anti-nuclear phobia, and is still objectively far easier than even a simple gun-type weapon. OTOH, I'm pretty sure I could build a gun-type weapon with pretty modest resources. More than Kickstarter, less than $50mm. The hard part would just be doing it in secret, especially since there are dual-use controls and people trying to actively find people making covert weapons. However, almost all nonproliferation controls are still based around restricting access to fissile material; if you solved that, I'd be comfortable doing this in a third-tier US city (away from the border), maybe in an old mine.
  - tlrobinson 13y ago
    "Kickstarter for Terrorists" is terrifying prospect. But also slightly amusing, I'd like to see a parody done.
a3n 13y ago
> An actual bomb is beyond the capability of anybody but a nation-state. And so one danger is that the material makes its way to such a nation state. > I have to wonder if (a) this info was declassified to support justifications for the NSA And there's one of the dangers of running a program that supposedly[0] depends on utter secrecy, requiring the government to outright lie about it: the inevitable leak exposes the government as liers, further eroding trust in government. [0] I say "supposedly" because I think the main danger to the programs from exposure is knowledge that what they're doing is illegal or reprehensible. The programs are now exposed, and I assume they're going full bore, producing exactly the same results as they did pre-Snowden.
fotbr 13y ago
>An actual bomb is beyond the capability of anybody but a nation-state. No, no it isn't. The theory is well known. More importantly, the theory has been been put into practice before, and the practice is pretty well known too. Actually making the parts would be relatively easy. The hard part, as usual, is getting one's hands on the fissile material. In a study* from either the late 40s or early 50s, the US put a handful of "normal" physicists (ie, not exceptionally brilliant) in a room without access to any classified nuclear research, and told them to design a bomb based only on what information was publicly available. Their design was handed to the people actually designing and building atomic bombs for evaluation. The result? The design was a viable a-bomb, not the most efficient, but it would have worked. *I don't have details handy, but the guy who wrote "Dark Sun" covered it in either "Dark Sun" or his first book.
- gdy 13y ago
  It's http://en.wikipedia.org/wiki/The_Making_of_the_Atomic_Bomb http://en.wikipedia.org/wiki/The_Making_of_the_Atomic_Bomb
rdl 13y ago
It's clearly false, too -- a multinational corporation or large research university could make a weapon more effectively than North Korea or Pakistan, if they wanted to -- the only limitation would be hiding the work, but that wouldn't be too hard. Jihadis living in caves probably couldn't, true. I wonder if a multinational could hide purchases in enough companies to avoid being identified. Even more interesting would be using something like decentralized task markets and subcontracting to have a group of agents/companies/etc. build you a bomb without them knowing they're building a bomb. Things like "provide an HPC cluster" "simulate high-energy physics for a research paper" "high precision timing circuit" "high accuracy 3d machining for arbitrary purposes" etc. could all be contracted fairly blindly.
caf 13y ago
This program wasn't always classified - it started life as an open project, and later "went dark" when scavengers started showing up at Semipalatinsk - see this blog posting from 2011: http://lewis.armscontrolwonk.com/archive/4021/tunnel-re-sealing-at-semipalatinsk http://lewis.armscontrolwonk.com/archive/4021/tunnel-re-seal... The same author as the original article here, Ellen Barry, actually wrote about this program back in 2011 too. So it hasn't been suddenly declassified.
fitumpich 13y ago
I understand you don't trust the NSA, but the viability of what it takes to make a bomb is just basic well understood physics. There's no conspiracy there. You either have enough mass, at a higher enough level of enrichment and you can force them to go critical or you can't. For Uranium you need over 100lbs to build a basic gun type bomd, what's terrifying is how little Plutonium you need. The Fat Man bomb needed just over 6 kg of Pu. So a little less than 14 pounds, and that was with 1940s grade material. The USSR got pretty good at making good quality Pu. The trick to keeping nuclear weapons out of the hands of someone is the security of the material, its hard to enrich. Its not hard to build the bomb. Enrichment is really really really hard. And its currently impossible to hide that your enriching. So you basically secure the material, and look out for people trying to make it. Thats how all non-proliferation works. Nothings hard about the know how, everything you need to know is in the public domain. And dont forget, pure fission bomds are 1940s tech. It's not a big secret how to build a simple gun type bomb. You don't need much precision for that. You get enough HEU, and it's game on. You get the right shaped Pu and a few other items, and you have an even higher yield bomb than that of the HEU bomb. Again, 1940s technology is all you need. Fusion bombs, yes much harder. But who needs that when you can build a Nagasaki yield bomb?
- ippisl 13y ago
  >>impossible to hide you're enriching. With laser enrichment, you can do enrichment in a typical house with typical power consumption, so it seems easy to hide. But building the tech today is quite complicated, and hopefully that stays that way in the future.

by Amadou 13y ago

phkamp 13y ago

This is old cold-war spin, and it has been refuted so many times, yet it still surfaces. Read "The curve of binding energy", and you will learn from Ted Taylor, one of the worlds best nuclear warhead designers, that you can make the simplest atomic bomb by dropping one piece of fissile material on another, provided they are big enough to become a critical mass. It won't be tens of megatons, but it will be a perfect terror weapon, spreading panic, making a large-ish area uninhabitable and costing a fortune and many years to clean up. If the terrorists are smart enough bring a couple of sacks of salt, it makes the mess much worse. There are damn good reasons to go out of the way to prevent access to the funny end of the periodic table.

srean 13y ago
More qualified people will correct me, but I think there is more to it than dropping a piece of fissile material over another. I think the trick is to keep the pieces together long enough before the forces of explosion rips them apart. As far as I know there have been several examples of accidents were scientists did actually drop a fissile blob over another, and the material did go critical, but thankfully the scientist(s) involved were fast enough to separate the pieces so that no catastrophes ensued. They themselves died as a result of exposure to radiation. As I said, more qualified people will be able to fill in the details and citations.
- louthy 13y ago
  I suspect you're referring to this: https://en.wikipedia.org/wiki/Louis_Slotin#Criticality_accident https://en.wikipedia.org/wiki/Louis_Slotin#Criticality_accid... "At 3:20 p.m., the screwdriver slipped and the upper beryllium hemisphere fell, causing a "prompt critical" reaction and a burst of hard radiation. At the time, the scientists in the room observed the blue glow of air ionization and felt a heat wave. In addition Slotin experienced a sour taste in his mouth and an intense burning sensation in his left hand. Slotin jerked his left hand upward, lifting the upper beryllium hemisphere and dropping it to the floor, ending the reaction. However, he had already been exposed to a lethal dose of neutron radiation."
  - caf 13y ago
    That wasn't even the first fatal criticality incident involving that particular plutonium core (known as the "Demon Core"). Funnily enough, I submitted an interesting article just a few hours ago on the history of this core: https://news.ycombinator.com/item?id=6229011 https://news.ycombinator.com/item?id=6229011
- 6d0debc071 13y ago
  > More qualified people will correct me, but I think there is more to it than dropping a piece of fissile material over another “With modern weapons-grade uranium, the background neutron rate is so low that terrorists, if they have such material, would have a good chance of setting off a high-yield explosion simply by dropping one half of the material onto the other half. Most people seem unaware that if separated HEU [Highly Enriched Uranium] is at hand it’s a trivial job to set off a nuclear explosion … even a high school kid could make a bomb in short order.” - Luis Alvarez, Nobel Laureate in Physics, 1988 The key being, as I understand it, actually getting weapons-grade material of sufficient purity. Though the actual design of a practical, controlled and efficient, weapon would doubtless be more somewhat more complex. For which the n-th country project is well worth reading about: http://www.theguardian.com/world/2003/jun/24/usa.science http://www.theguardian.com/world/2003/jun/24/usa.science
  - fitumpich 13y ago
Amadou 13y ago
you can make the simplest atomic bomb by dropping one piece of fissile material on another, provided they are big enough to become a critical mass. My understanding of Ted Taylor's claims about compact fission bombs is that, absent high-grade manufacturing processes to properly shape the fissile material, we are looking at a couple of hundred kilograms to achieve critical mass. Actual "suitcase nukes" in the 10-20 kilogram range require perfectly shaped components and are also very high maintenance due to their electronics degrading rapidly from such close proximity to radiation sources. Then there is the question of testing. They say you can recognize veteran bomb makers by their missing fingers because they don't get things right the first time. Any testing of a fission bomb anywhere in the world is going to be noticed by seismographs at the very least.
- archgoon 13y ago
  Why is testing an issue? The Trinity test was successful on the first run. Nation-states only conduct tests to calibrate destructive capabilities and fallout effects (a non-issue if you just want a big boom) and signal to other nation-states 'Don't mess with me'. Furthermore, states such as Israel, are believed to be nuclear, without ever having conducted any (known) tests. An unsuccessful nuclear explosion would just be a dirty bomb, which would still have the desired effects from a terrorist attack perspective. So there's no real reason to test before hand.
  - Amadou 13y ago
    In the case of a ultra-simple design available to terrorists that reaches critical mass by simply "dropping" one chunk of fissile material on another there is no explosion if it doesn't actually reach critical mass. Israel is a nation-state with a lot more resources available to it like the ability to measure purity and to conduct simulations. In fact a key part of nuclear politics for the last 20 or so years has been super-computer based simulations in lieu of testing. In the US the programs have been responsible for the construction of some of the largest super-computers of their time(s). https://en.wikipedia.org/wiki/Accelerated_Strategic_Computing_Initiative https://en.wikipedia.org/wiki/Accelerated_Strategic_Computin...
rdl 13y ago
I think a dirty bomb would be more than "scary" enough, given general anti-nuclear phobia, and is still objectively far easier than even a simple gun-type weapon. OTOH, I'm pretty sure I could build a gun-type weapon with pretty modest resources. More than Kickstarter, less than $50mm. The hard part would just be doing it in secret, especially since there are dual-use controls and people trying to actively find people making covert weapons. However, almost all nonproliferation controls are still based around restricting access to fissile material; if you solved that, I'd be comfortable doing this in a third-tier US city (away from the border), maybe in an old mine.
- tlrobinson 13y ago
  "Kickstarter for Terrorists" is terrifying prospect. But also slightly amusing, I'd like to see a parody done.

a3n 13y ago

> An actual bomb is beyond the capability of anybody but a nation-state. And so one danger is that the material makes its way to such a nation state. > I have to wonder if (a) this info was declassified to support justifications for the NSA And there's one of the dangers of running a program that supposedly[0] depends on utter secrecy, requiring the government to outright lie about it: the inevitable leak exposes the government as liers, further eroding trust in government. [0] I say "supposedly" because I think the main danger to the programs from exposure is knowledge that what they're doing is illegal or reprehensible. The programs are now exposed, and I assume they're going full bore, producing exactly the same results as they did pre-Snowden.

fotbr 13y ago

>An actual bomb is beyond the capability of anybody but a nation-state. No, no it isn't. The theory is well known. More importantly, the theory has been been put into practice before, and the practice is pretty well known too. Actually making the parts would be relatively easy. The hard part, as usual, is getting one's hands on the fissile material. In a study* from either the late 40s or early 50s, the US put a handful of "normal" physicists (ie, not exceptionally brilliant) in a room without access to any classified nuclear research, and told them to design a bomb based only on what information was publicly available. Their design was handed to the people actually designing and building atomic bombs for evaluation. The result? The design was a viable a-bomb, not the most efficient, but it would have worked. *I don't have details handy, but the guy who wrote "Dark Sun" covered it in either "Dark Sun" or his first book.

gdy 13y ago
It's http://en.wikipedia.org/wiki/The_Making_of_the_Atomic_Bomb http://en.wikipedia.org/wiki/The_Making_of_the_Atomic_Bomb

rdl 13y ago

It's clearly false, too -- a multinational corporation or large research university could make a weapon more effectively than North Korea or Pakistan, if they wanted to -- the only limitation would be hiding the work, but that wouldn't be too hard. Jihadis living in caves probably couldn't, true. I wonder if a multinational could hide purchases in enough companies to avoid being identified. Even more interesting would be using something like decentralized task markets and subcontracting to have a group of agents/companies/etc. build you a bomb without them knowing they're building a bomb. Things like "provide an HPC cluster" "simulate high-energy physics for a research paper" "high precision timing circuit" "high accuracy 3d machining for arbitrary purposes" etc. could all be contracted fairly blindly.

caf 13y ago

This program wasn't always classified - it started life as an open project, and later "went dark" when scavengers started showing up at Semipalatinsk - see this blog posting from 2011: http://lewis.armscontrolwonk.com/archive/4021/tunnel-re-sealing-at-semipalatinsk http://lewis.armscontrolwonk.com/archive/4021/tunnel-re-seal... The same author as the original article here, Ellen Barry, actually wrote about this program back in 2011 too. So it hasn't been suddenly declassified.

fitumpich 13y ago

I understand you don't trust the NSA, but the viability of what it takes to make a bomb is just basic well understood physics. There's no conspiracy there. You either have enough mass, at a higher enough level of enrichment and you can force them to go critical or you can't. For Uranium you need over 100lbs to build a basic gun type bomd, what's terrifying is how little Plutonium you need. The Fat Man bomb needed just over 6 kg of Pu. So a little less than 14 pounds, and that was with 1940s grade material. The USSR got pretty good at making good quality Pu. The trick to keeping nuclear weapons out of the hands of someone is the security of the material, its hard to enrich. Its not hard to build the bomb. Enrichment is really really really hard. And its currently impossible to hide that your enriching. So you basically secure the material, and look out for people trying to make it. Thats how all non-proliferation works. Nothings hard about the know how, everything you need to know is in the public domain. And dont forget, pure fission bomds are 1940s tech. It's not a big secret how to build a simple gun type bomb. You don't need much precision for that. You get enough HEU, and it's game on. You get the right shaped Pu and a few other items, and you have an even higher yield bomb than that of the HEU bomb. Again, 1940s technology is all you need. Fusion bombs, yes much harder. But who needs that when you can build a Nagasaki yield bomb?

ippisl 13y ago
>>impossible to hide you're enriching. With laser enrichment, you can do enrichment in a typical house with typical power consumption, so it seems easy to hide. But building the tech today is quite complicated, and hopefully that stays that way in the future.