Deployability of nuclear weapons

2010-09-01

in Bombs and rockets, Geek stuff, Politics, Science, Security

Being able to build a device that can produce a nuclear explosion is a significant challenge in itself. Also challenging is building such a device in a self-contained way which does not require difficult last-minute assembly, and which can be stored in a usable state for years. The first American bombs certainly did not meet this standard.

Captain William Parsons, a U.S. Navy weapons expert with the 509th Composite Group (the B-29 squadron that dropped the atomic bombs on Japan during WWII) described the complex and hazardous operation, in a letter intended to convince his superiors that dummy devices were required for practice runs:

It is believed fair to compare the assembly of the gun gadget [the uranium bomb] to the normal field assembly of a torpedo, as far as mechanical tests are involved… The case of the implosion gadget [the plutonium bomb] is very different, and is believed comparable in complexity to rebuilding an airplane in the field. Even this does not fully express the difficulty, since much of the assembly involves bare blocks of high explosives and, in all probability, will end with the securing in position of at least thirty-two boosters and detonators, and then connecting these to firing circuits, including special coaxial cables and high voltage condenser circuit… I believe that anyone familiar with advance base operations… would agree that this is the most complex and involved operation which has ever been attempted outside of a confined laboratory and ammunition depot.

Rhodes, Richard. The Making of the Atomic Bomb. p.590 (paperback)

Probably the reason why the bomb had to be so substantially assembled right before use had to do with the initiator – a sub-component at the very centre of the bomb, designed to produce a handful of neutrons at the critical moment to initiate fission. At the same time, it was critical that the initator not produce even a single neutron before the bomb was to be used.

In early American bombs, initiators were apparently comprised of the alpha particle emitter Polonium 210 (half life 138.4 days) sandwiched between metal foils to keep it from reacting prematurely with the beryllium metal nearby. When the high explosive shell wrapped around the natural uranium tamper and plutonium core of the implosion bomb detonated, the components of the initiator would mix and react, producing neutrons at the same time as the explosives were producing compression.

Details on initiators are still classified, so we can only speculate on how the implosion primaries in modern bombs function.

The whole issue of deployability is relevant to questions of nuclear proliferation insofar as it is more difficult to make a stable, battlefield-usable bomb than to make a device capable of generating a nuclear explosion. That being said, many of the technical details of bomb manufacture have been made available to states contemplating the development of nuclear weapons. That has partly been the product of clandestine activities like the operation of the A.Q. Khan proliferation network. It has also been the consequence of states being insufficiently cautious when it comes to safeguarding knowledge, materials, and equipment.

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{ 8 comments… read them below or add one }

. September 1, 2010 at 10:42 am

“STRATFOR has gone through three phases in its evaluation of the possibility of war. The first, which was in place until July 2009, held that while Iran was working toward a nuclear weapon, its progress could not be judged by its accumulation of enriched uranium. While that would give you an underground explosion, the creation of a weapon required sophisticated technologies for ruggedizing and miniaturizing the device, along with a very reliable delivery system. In our view, Iran might be nearing a testable device but it was far from a deliverable weapon. Therefore, we dismissed war talk and argued that there was no meaningful pressure for an attack on Iran.”

. September 1, 2010 at 10:43 am

Nuclear Weapons: Devices and Deliverable Warheads
June 17, 2008 | 2145 GMT

On July 16, 1945, at a remote testing range in southern New Mexico, the United States detonated the world’s first atomic bomb. Developing the device was probably the most complex and expensive exercise in applied physics in human history. Even today, weaponizing the atom remains one of the most challenging endeavors a country can engage in — and one few ultimately choose.

R.K. September 1, 2010 at 5:15 pm

Does Polonium 210 have any other uses? If not, the murder of Alexander Litvinenko looks even more suspicious. Who aside from a state intelligence agency would have access to a material made in cyclotrons and used in nuclear weapons?

Tristan September 2, 2010 at 6:46 am

“That being said, many of the technical details of bomb manufacture have been made available to states contemplating the development of nuclear weapons. That has partly been the product of clandestine activities like the operation of the A.Q. Khan proliferation network. It has also been the consequence of states being insufficiently cautious when it comes to safeguarding knowledge, materials, and equipment.”

Safeguarding knowledge about nuclear weapons seems a poor manner of protecting the world from nuclear proliferation. If the knowledge can be written down, it can be contained in a micro SD card, or likely something even smaller. It can (I assume) easily be clouded on the internet in difficult to trace manners.

Even if such knowledge is successfully kept from rogue states – they have the right under NPT to build nuclear power stations, which makes it trivial to assemble dirty bombs.

Nuclear safety can not be garnered by trying to prevent a few more states gaining nuclear weapons – but only by giving them, and states which already have them – good reasons to give them up. It’s essentially a game theory problem, which means it’s a trust problem. Which means, the question is really about peace-building.

Nuclear states could learn a lot from the tit-for-tat tactics employed by soldiers on both sides during WW1 (discussed by Dawkins in “the selfish gene”)

Milan September 2, 2010 at 10:04 am

Dirty bombs are a lot less worrisome than real atomic bombs, though you don’t even need a nuclear reactor to build one. Nasty isotopes like Cobalt-60 can be scavenged from medical equipment and other sources.

Safeguarding knowledge about nuclear weapons seems a poor manner of protecting the world from nuclear proliferation.

As one tactic among many, it does seem to have promise. As the discussion of initiators above suggests, there are many tricky things to get right when building even a simple fission bomb. Even someone with detailed blueprints might lack some important information about materials or manufacturing techniques, which could render their devices ineffective or increase the level of technical skill required to build one.

Milan September 2, 2010 at 10:06 am

Nuclear safety can not be garnered by trying to prevent a few more states gaining nuclear weapons – but only by giving them, and states which already have them – good reasons to give them up.

I think at least three major strategies should be used:

  1. Prevent states that are not nuclear weapon powers from becoming so, especially if they are situated in volatile parts of the world
  2. Reduce the readiness level of existing nuclear weapons, to reduce the chances of accidental or unauthorized launch
  3. Decrease the total number of nuclear weapons possessed by nuclear weapons powers

I think the second is actually more important than the third, because I think an accidental or unauthorized nuclear war is much more likely than one approved through legitimate channels. That is especially true for states like the U.S. and Russia which have elaborate control systems on their nuclear arsenals and delivery systems.

Tristan September 2, 2010 at 12:25 pm

So, you place no emphasis on peace building, or conflict resolution? You think the instability of the general political systems has no effect on nuclear security?

I’d suggest you read these selections from Blair’s new book on conflict resolution – but unfortunately they require the suspension of the believe that peace comes only from great powers imposing sanctions upon each other:

http://www.tonyblairjourney.co.uk/files/TB%20Northern%20Ireland.pdf

. August 23, 2012 at 2:35 pm

“In 1986, when I helped the Nobel Laureate physicist Luis W. Alvarez write his memoirs, Alvarez commented one day on the importance of keeping track of highly enriched uranium. Speaking of a quantity sufficient to form a supercritical mass, he told me, “You can make a fairly high-level nuclear explosion just by dropping one piece onto another by hand.” Alvarez had been intimately involved in the development of the first atomic bombs, and he knew whereof he spoke. Some years later I gave a talk at the National Atomic Museum in Albuquerque during which I quoted Alvarez’s comment. An audience member from one of the nearby weapons labs, Los Alamos or Sandia, told me afterward with some enthusiasm, probably speaking out of turn, “Yes, and if you can accelerate it even a little you get a much bigger explosion.””

Rhodes, Richard. The Twilight of the Bombs: Recent Challenges, New Dangers, and the Prospects for a World Without Nuclear Weapons. (2010) p.289 (hardcover)

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