How Scientists Actually Dismantle a Nuclear Bomb

By Benjamin Plackett | February 8, 2019 2:30 pm
nuclear warhead

A Mark 28 thermo-nuclear bomb is unloaded from a U.S. Air Force Boeing B-52H Stratofortress aircraft. Credit: TSgt. Boyd Belcher, USAF)

(Inside Science) — There are enough nuclear weapons in the world to cause atomic Armageddon many times over, according to scientists, who estimate that no country could fire more than 100 nuclear warheads without wreaking such devastation that their own citizens back home would be killed.

Most nuclear nations recognized by the Treaty on the Non-Proliferation of Nuclear Weapons — namely, France, Russia, the United Kingdom and the United States — have set about reducing their arsenals. China is a notable exception. The exact number of the country’s warheads is unknown, but many analysts say its cache is slowly growing in size. North Korea, on the other hand, while notoriously difficult to predict, could eventually scale back its nuclear program if its diplomatic rapprochement with the West continues.

Negotiations on nuclear disarmament are politically tricky. But when agreements are reached, scientists and engineers can provide a variety of tools to take apart some of humanity’s most deadly weapons and store or repurpose the dangerous nuclear material. It’s a long and complex procedure, but experts say it’s one worth doing.

How to disassemble an armed “Swiss watch”

Nuclear disassembly is a coordinated process, which involves politicians, scientists and engineers working together.

It all begins with the blueprints that designers used to build the weapon in the first place, according to experts.

“It’s like any other kind of machine,” explained Robert Rosner, chair of the Bulletin of the Atomic Scientists Science and Security Board. “It’s a case of taking it apart piece by piece.”

To unpick a nuclear device, engineers need to know the exact sequence in which the pieces were originally put together.

“The design of atomic bombs is what I’d call an open secret. There aren’t that many ways of designing them and so if the Americans had to deal with the North Korean bombs, for example, it wouldn’t be much of a mystery to them,” said Rosner.

But the more sophisticated and destructive hydrogen bombs that the Americans, British, Chinese, French and Russians possess is a different story.

“There are many different designs and so the disassembly is very difficult. You have to be awfully careful,” said Rosner. “From a mechanical engineer’s perspective, they’re like a highly tuned Swiss watch. They’re mechanical artwork with amazingly clever designs.”

Other experts agree that unpacking the design is the most challenging part of the process.

“It’s less about the nuclear material and more about the engineering,” said Tom Plant, director of Proliferation and Nuclear Policy at the Royal United Services Institute for Defence and Security Studies, an independent think tank in the United Kingdom.

It would be significantly harder and therefore less likely that a team of engineers could disassemble a hydrogen bomb without knowing the exact design sequence, but still not technically impossible.

“It’s very unlikely that it would blow up if a mistake was made in the process of disassembly, unless it was designed to blow up in that eventuality, which is possible though not likely,” said Rosner.

Plant agrees the worst-case scenario is accidental detonation, but there are other possible perils if disassembly goes wrong. The people doing it could be electrocuted or exposed to the nuclear material or other toxic chemicals.

But a country, knowing its own design, should be able to disassemble its own modern nuclear weapons, and many have. As of 2014, the U.S. had dismantled 85 percent of its declared stockpile of nuclear weapons since 1967 when it had more than 31,000 war-ready nuclear warheads, according to the U.S. Department of State.

Before any nuclear dismantling can even take place, the right political atmosphere needs to exist, said Plant. He still isn’t optimistic that the current dialogue between Pyongyang and Washington has enough political will to see the Korean peninsular through to denuclearization. “The overwhelming likelihood is that everything falls apart as before.”

What do you do with the leftover uranium or plutonium?

Once the weapon has been taken apart, the process of dealing with what’s left is identical for both the older and the more sophisticated bombs.

“When the great powers decided to reduce their stockpiles, we were left with fairly substantial quantities of plutonium,” said Rosner. “So, what do you do?”

One obvious answer is to repurpose the radioactive material — either plutonium or uranium — to produce electricity. To make it suitable for a power plant, the material needs to be diluted with less enriched versions.

“There are no power reactors anywhere in the world that are designed to deal with weapons-grade material,” said Plant. “You have to down-blend it before you can turn it into fuel.”

But that isn’t what actually happens to most of the radioactive material.

“It’s not always economically viable. It can be cheaper to enrich new material than it is to downgrade it and repurpose it,” said Rosner. “Shipping plutonium or uranium all over the place from storage to reactor isn’t popular either.”

“Mostly it’s just stuck in storage facilities,” said Rosner.

Decommissioning the radioactive waste and keeping it safe is a science in its own right. The extracted uranium or plutonium will contain different isotopes — variants of themselves that have different atomic masses, which means their radioactivity decays at different rates.

The highly radioactive isotopes have short half-lives, which means they decay much faster than the less radioactive ones, and that creates a lot of heat.

“The material has to be put in water pools for about half a decade to cool the rods while they decay,” said Rosner. “Then you’re left with relatively low-level waste that’s less radioactive.”

The less radioactive isotopes are slower to decay, which presents its own problem.

“They have nuclei that are heavier, so they have very long half-lives of millions of years and you still have to do something with them. You can’t just leave them hanging around,” said Rosner.

The answer is to store the radioactive rods in specially designed containers, often called “dry casks.” These vessels are usually made from steel and welded shut to prevent leaking. Each of the casks is then encased in another steel shell and then in a thick layer of concrete to prevent radiation escaping.

“If you were standing outside of the container then you wouldn’t be able to detect radiation,” explained Rosner.

But even this containment option has its drawbacks — the cost of building, maintaining and monitoring these facilities will never go away so long as the rods inside are producing radiation. “That’s basically eternity for humans,” said Rosner.

Additionally, there’s national security to consider, said Plant. “Governments will be keeping it somewhere safe in case they want to reuse it or in case a terrorist tried to get hold of it.”

That’s why a third option has become more popular in recent years: partial disassembly.

After all, unless the bomb is detonated, the nuclear material inside is in a steady and contained state — partial disassembly keeps it there while removing the opportunity for the bomb to be used. “If you remover the trigger, then what’s left can’t be used as a bomb,” said Rosner.

But partial disassembly is reversible; the trigger can be put back in and the warhead can therefore be reactivated. “You couldn’t put it back in a matter of hours so they can’t be on standby. You’re talking about weeks to do it,” said Rosner.

If North Korea should ever agree to denuclearize, it has a few options to consider — none of them are perfect and all of them come with long-term strings attached, but when nuclear powers work together to control their arsenals, the world is a safer place, said Plant.

[This article originally appeared on]

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  • Uncle Al

    Old pits have Pu thermogenic heavier isotopes well decayed, plus their helium production so reduced. Recycle old Pu to obtain more stable and predictable Ga-stabilized delta-Pu pits. Given modern reduced CEPs and burrowing warheads, a massive thermonuclear strike with modest-yield warheads is strategically justified.

    … Here, try it yourself. Surface damage goes up as the cube root of individual weapon size increase. Ten 50 kt bombs are hugely more effective than one 500 kt burst. Two point detonation rather than solid explosive lenses shrinks weapons to golf bags near enough.

    • Dana Steinhoff Hawn

      The average Joe is not going to understand what your saying. Speak in layman terms so that lesser educated folks will be able to clearly understand what your saying, because I think it could make for some very interesting conversation. I understood what you were saying. :)

      • jonathanpulliam

        Uncle Al Operates at cross-purposes to 6 sigma precision

      • Erik Bosma

        Hey, that’s our Uncle Al. He keeps us smart, I think.

    • Teresa Wendorff

      Would you like to sit there during your strategically justified massive strike? The fallout is still there even if you aren’t on the receiving end. War is not an answer. What has been the issue with nukes is that taking them apart has not been as safe as you say and whether it detonates at one or 2 points is moot. They had a blue flash incident in this country as well as France. Overseas the stuff gets vitrified but it still has a huge half life so the kids in Britain and France have strontium teeth and the danger of reprocessing is nearby and the result yields much more product to store for 150,000 years. We need to build one sodium or similar type reactor not in range of a plant that removes the Pu. The casks can be transferred underground by rail from the plant to the reactor and the power used to provide electricity to a grid to power cars by a caternary system for long distance driving. The lithium storage capacity would no longer be a drawback as it would only be used on local roads and not expressways. Hooking up the poles and keeping the points supplied would provide jobs and be clean energy.

      • Erik Bosma

        Or they could drill deep holes in the Canadian Shield and drop the stuff in there. I think that is actually under consideration.

    • jonathanpulliam

      Brilliant, Oppenheimer

  • charles

    Brakes were invented to address the unforeseen success of the practical application of the wheel.

    • Dickybow

      Ha Ha – runaway success even…

      • jonathanpulliam

        The “Governor” was invented so that a motor would not run out of control and fly apart, and “Government” came to be applied to what we now intuitively know as the “Deep State”.

        The whole sordid business should send a shiver of revulsion up the spine of any God-fearing man, I should fink.

  • Pro_spark

    This article starts talking about nuclear weapons pits, then gets off in the weeds about used fuel rods – which are unrelated have very different disposal requirements.
    Also, weapons grade plutonium can be used pretty much as-is for the radio-thermal generators on spacecraft, material for which there is actually a shortage of at the moment.

    • Uncle Al

      Radioisotope thermal generators use Pu-238, half-life 87.7 years. Each gram generates 0.568 watts of heat. It is not,fissionable.

      Be a terrorist. We will laugh.

      • Dana Steinhoff Hawn

        LOL your harsh! Thank you for the good laugh.

        • Uncle Al

          “you’re” Language matters when transferring content. Alternatives are Ebonics, Hispanish, and dialectic.

          Indoctrination is politicized fluff. The plural of “anecdote” is not “data,” data are not information, information is not understanding.

          • jonathanpulliam

            Your last, um, transmission you say “information is not understanding”. Boy, ain’t that the truth, brudda

      • ph

        Pu-238 is fissionable but not fissile.

        • jonathanpulliam

          It is not fashionable to be fungible.

    • jonathanpulliam

      You are a steely-eyed Poindexter, Propeller-Head!!

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  • jonathanpulliam

    Basically, these nuclear physicists who foisted this “miracle” on humankind are one-trick pony mini-me Edward Tellers who ultimately lose perspective and embark on a suicidal race to doomsday. The doomsday clock is currently set at what, 2 minutes to midnight, right??
    That’s put there by some very smart peeps. Its’ 2019, peeps. If peeps want to see 2020, “You watch how you set yo feet in them nuclear-proliferation pies, Epaminandas!”

    • RaymondSwenson

      Even if World War II and fear of Werner Heisenberg’s German nuclear bomb project had not driven US nuclear weapon technology, the value of nuclear energy generation would have created the technology for uranium enrichment and transmutation into plutonium as a byproduct. The challenge of using plutonium in a bomb was getting the chemical explosives to form a perfect impulsive shockwave to compress the plutonium into a critical mass. But the development of modern solid state electronics and computers for designing the implosion system would make that problem easy. The development of long range jet aircraft and of orbital rockets capable of delivering a weapon would have come along soon. So by 2000 we would still have the potential for any medium size country to develop nuclear weapons. Hating on nuclear physicists is irrational, and is not going to provide solutions for the problem of nuclear weapon proliferation.

      • jonathanpulliam

        Please. I’m not “hating” on anyone. Enough with the celebrity worship. and I’ll include “God” in that. I stick by what I said. I don’t hate “Quants” either, but they add no Value. Your defense of Physics is weak as H20, yo.

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  • RaymondSwenson

    This article is very vague about the actual design of modern nuclear weapons, and therefore of what is involved in disabling one. A standard atomic bomb has a sphere of plutonium that is encased in a sphere of chemical explosives with a system of triggering the explosives simultaneously so they create a spherical implosive shock wave that perfectly compresses the plutonium sphere into a critical mass for a runaway chain reaction. A thermonuclear weapon has a mass of lithium or other light element alongside the plutonium “trigger” so the explosion of the atomic bomb produces a flood of neutrons, high energy photons and compression to drive the large mass into nuclear fusion.

    The reason the first plutonium bomb was tested at Alamogordo was that the scientists and engineers were unsure their triggering system, using the primitive electronics of the day, would cause the implosion wave and go critical. The Nagasaki bomb was experiment number 2. Of the next ten bombs tested, only one or two produced a nuclear explosion. To prevent a nuclear weapon from producing a nuclear explosion, you only need to disable the perfection of the conventional implosion bomb. This won’t necessarily prevent the conventional explosives from going off, but the difference is between an artillery shell and a nuclear explosion.

    This fact has only been appreciated in one popular entertainment, the movie “The Peacemaker” (1997) with George Clooney and Nicole Kidman. In the story, a Russian nuclear bomb is stolen, and the “trigger” bomb removed and smuggled into Manhattan. The heroes find the bomb with only minutes to disable it, not enough time to do the careful disassembly. So Kidman wails away at it with a hammer, to disrupt the perfect symmetry that is necessary for it to go critical. The chemical explosives demolish the building, but New York is saved.

    You could do the same thing with a bomb taped onto the nuclear weapon.

    Similarly, to ensure that a weapon does not go nuclear before it reaches its target, you just need to disable the ignition of some of the conventional explosives. This enables you to transport them out of a missile silo or bomber base and to a storage and disassembly site.

    Unlike some of the bombs dropped on Britain by the Nazis, there is no reason with nuclear weapons to assume it might land without going off, so creating fake wiring to prevent it being disarmed on the ground. Nuclear weapons are most destructive when they explode in the air above the target. The crews of the Enola Gay and the other B-29s in the 509th Bomb Group trained at Wendover, Utah, for the unusual high altitude detonation of the bombs.

    If the bomb impacts the ground, the symmetry of the trigger elements would have been disrupted and no nuclear explosion could occur. A nuclear weapon designed to explode in the ground needs an added system to absorb the impact.

    The bottom line is, if there is no time for careful disassembly, banging on the side of the bomb with a hammer, or preferably a remotely detonated explosive, is a way to prevent a nuclear explosion.

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