Smugglers arrested with bomb-grade uranium

This is scary:

A gang arrested by Slovakian police was trafficking uranium so enriched that it could have been used by terrorists in a dirty bomb, it emerged today.

Two Hungarians and a Ukrainian man were arrested as they tried to sell the uranium last night. The consignment had been tracked by police after it came to their attention inside the former Soviet Union.

A total of 481.4 grams of uranium was found and investigators believe it contained 98.6 per cent uranium-235. Uranium is considered weapons-grade if it contains at least 85 per cent uranium-235.

There appears to be a lot of nonsense in the international press about this incident written by journalists who don’t understand a thing about radiation – not to mention a police chief who doesn’t either, given he spoke about a “dirty bomb” when no terrorist group would waste such a valuable commodity on a dirty bomb if the material is as described.

Natural uranium is a mixture of two isotopes – uranium-238, and uranium-235. Natural uranium contains about 99.3% uranium-238, with the balance u-235. Neither sort is particularly radioactive; they are very weak emitters of something called an alpha particle, which is only dangerous if you swallow it or inhale it. And, frankly, there’s probably more risk from the chemical toxicity of even highly enriched uranium (it’s a nasty heavy metal, just like lead) than there is from the radioactivity of the stuff. So it’s a very poor material to use as a dirty bomb, compared to the stuff in some medical devices, which emits much, much larger doses of much more penetrating gamma radiation. Even given the use of those materials, a dirty bomb is not nearly as deadly as you’d assume – but that’s a story for another day.

Why this stuff is scary is its potential use in a nuclear weapon. From natural uranium, there are two ways to get material you can make a nuclear weapon out of. First, you can put the uranium in a nuclear reactor, and convert some of the uranium-238 into plutonium. Secondly, you can use a variety of highly elaborate filtering schemes (uranium enrichment) to filter out the u-238 and get uranium with higher quantities of u-235 in it. Power reactors use about 5% enriched uranium. Modern research reactors generally use uranium with around 20% u-235 content. Anything above that is regarded as bomb-usable, and anything above 80% or so “bomb-grade” or “highly enriched” uranium, or HEU for short.

If you can get your hands on roughly 50 kilograms of HEU, you can almost put together a nuclear weapon in your local welders fabrication shop. It’s pretty simple – you get two bits of uranium and you slam them together at high speed, usually by propelling them together with explosives. No precision engineering required. If you do have a few physics PhDs handy, some high-precision machine tools, and the like, you can get the minimum quantity required down to maybe 12 kilograms, apparently. But the ease with which HEU can be turned into a crude bomb, if you have enough, is what makes it one of the scariest substances on Earth.

The quantities involved here are far lower than that. But, still, it’s a non-trivial quantity of the only material that Al-Queda or any other plausible terrorist group would ever fashion into a bomb. I’ll bet intelligence agencies around the world are currently trying to figure out exactly where the stuff came from, and whether there’s any more of it there.

Anyway, if this report is accurate and the material being smuggled was HEU, it should serve as a warning. As this article in the Bulletin of Atomic Scientists notes, HEU is used in research reactors across the world, and notably in many facilities across Russia. That material should be put in centralized, well guarded storage facilities, and, ultimately, disposed of – a process already happening, but sadly incomplete.

Posted in politics, Security, Terrorism
41 comments on “Smugglers arrested with bomb-grade uranium
  1. FDB says:

    As far as I know, this is the first time I’ve needed to thank the Slovakian police.

    Scary shit.

  2. derrida derider says:

    “… if this report is accurate …”
    An important if. And if it is I’d lay quids the intended destination was not terrorists but an aspiring nuclear state. Cause for concern but not panic – half a kilo is not good for anything other than R&D.

  3. wasjotoo says:

    Any chance that “Smugglers arrested with bomb-grade uranium” might nuke “Friday Funnies: 24 spoof – 1994 technology”?

    Just askin…

  4. wasjotoo says:

    Or the other way around would be O.K.

  5. philiptravers says:

    Good comments..the Slovakian Police are communicating with the world,out here, the N.S.W. Police have been flying their helicopters looking for Mari me Wanna,and I probably would,if they introduced themselves,still, I feel I wanna get up em for the jolly cost of doing so..flying the choppers and even negotiating the turbulence to have a good look at me,so they think I am attractive!!![Long sentence…a joke].Mind you I do not like proposals with Tasers guns,and I am admiring Slovak Police from a distance.At least they dont fly at night!?Which leaves me with a question,non subject,did the chopper Police carry tasers in the last two days!?And do the N.S.W. Police know the UNO considers them a weapon of torture!Not map or people reading ,but more mind reading..because like those who have been at the wrong end of them my mind is easily read!

  6. Bruce says:

    As you noted Robert, Uranium 235, like all uranium isotopes, emits alpha particles which are only weakly penetrating. This makes it virtually useless as a material for a dirty bomb. A far greater danger would be its chemical toxicity if inhaled.

    Given 50-60kg of weapons grade U235 is needed to make a crude bomb, the 481.5 grams won’t go very far in that direction. (A sophisticated bomb still requires 12-15 kg.)

    I’m also puzzled at the claimed level of enrichment – 98.6% is unnecessarily high for a bomb. Around 90% is sufficient. It takes a lot more effort to get to 98.6% and little is gained for weapons use. A research/laboratory source makes sense in this respect.

    All in all the Times story is a bit suss. I am far more worried that ex-USSR tactical nuclear weapons have already been acquired by 3rd parties, principally governments with the resources to succeed in this sort of smuggling. (My guess is countries like Iran and North Korea – to name two – have already picked up a few loose nukes.) I would question whether terrorist groups could do it, although it’s not impossible, and they may be used as arms-length delivery agents by so-called rogue states.

  7. wasjotoo says:

    While I am just hoping to have a good pair of underpants on, when these morons blow the place up, you talk.

  8. Paul Burns says:

    And I was still on my election high.
    Suppose its time to get back to reality and doing things that make the world a better place.

  9. bjohns says:

    Strange that only two days ago I watched a movie called PU-239 ( which could very well describe how such uranium finds its way onto the black market.

  10. Lucas says:

    (channeling JWH) Dang those Slovaks .. They’re a week and a half late…

  11. Paul: if you’re worried about nuclear terrorism, this is where the threat comes from, not sending yellowcake to China or India.

  12. Katz says:

    Why would these clowns try to sell a sample with a ridiculously high concentration of U235 in Slovakia?

    If the high concentration is correct, then the sample could only have come from a Soviet or Russian research facility and not from some nuke left lying around after the collapse of the Soviet Union.

    The Soviet Union collapsed more than 15 years ago. If this sample was purloined at about this time, where has it been stored all of these years?

    If this sample was purloined more recently, from a Russian (post-Soviet) facility, then this is a truly troubling story.

    If these clowns were trying to sell the sample, presumably they were caught in a sting operation. Whom did they think they were selling the sample to?

    The story implies that the sample is now in the hands of Slovak authorities. How long had the sample been on Slovak territory? If it has been on Slovak territory for some time, why did Hungarians and a Ukrainian think it was safer there than (say) in Hungary or the Ukraine?

    If this part of the story is true, then it is likely that the Slovak authorities only recently tricked the smugglers to bring it over the border into Slovakia. This implies that the Slovakian authorities did not inform Russian, Ukrainian and perhaps Hungarian authorities about their operation. Possession of this material is as illegal in those countries as it is in Slovakia.

    It would therefore appear that this is Russian U235 recently stolen from a Russian facility by persons who have nothing to do with Russian authorities. It appears that these thieves were encouraged by Slovakian authorities to transport this sample into Slovakia by a sting operation. It is almost certain that Russian authorities were not told about this operation.

    This has all the hallmarks of the beginning of a new Cold War.

  13. Enemy Combatant says:

    People should be totally afraid that a suitcase bomb is going to be manufactured and detonated in a public place, like all the other suitcase nuclear bombs that have been detonated in public places since Uncle Sammy’s “US Marine life-saving” nuke went bang over Nagasaki. A State of Perpetual Fear remains our only option.

    We must at once rescind all our personal liberties so that the wise and powerful Neoconservative Superheroes who dictate US Foreign Policy can protect us. Uber Alles.
    We should be similarly fearful that Earth could be whacked with a rogue meteorite at any moment. Thwack! Game over.

    Or, we could let Euro coppers do what they do best, keep a weather eye on ’em, and get on with life.

  14. EC: Fair enough, but the other thing I’d emphasise is that highly enriched uranium is a substance that is a) very difficult to make, and b) is only necessary for one thing – making nuclear weapons. There is no justification for keeping surplus amounts of the stuff around; research reactors can and should be converted to run on LEU, as should nuclear submarines (France runs its nuclear submarines on LEU).

    Katz: good questions, though there are a number of other Eastern bloc countries other than Russia who might conceivably have stocks of HEU; it’s used as fuel for some research reactors.

  15. Sam Clifford says:

    Those dastardly uranium sniglers.

  16. Mercurius says:

    Ah-HA! Saddam’s WMD were in Slovakia the whole time!

  17. Paul Burns says:

    Do you think Howard knew?

  18. Birdie says:

    how do you know if wasn’t Australian uranium?

  19. Paul Burns says:

    I was only about eight months old when the nuclear bomb was dropped on Hiroshima. We grew up with the fear that some evil Communist country might drop a bomb on Sydney, most likely.It never happened – yet.
    Having got quite used to the idea of nucleart war over the years, though I wouldn’t like to be in one, I find global warming a hell of a lot acarier.

  20. Jane says:

    If the Rodent knew, we would all have been in bomb shelters by now and he would still be Emperor of Rodentia. Looks like all his luck drained away-must have had the horseshoe the wrong way up. Probably didn’t offer a high enough bribe to the Slovakians or wanted to put them on AWAs. Snicker.

  21. Birdie: we don’t. But getting uranium metal is easy. Enriching it to bomb grade is the difficult bit.

  22. David says:

    This is scary. Is there any point comparing it to the scariness of global warming? Is it some kind of competition?

  23. Paul Burns says:

    Agreed. But truly, after years of living under the threat of mutually assured destruction, experiencing the Cuban missile crisis, knowing that wingnuts like Israel, Iran, Pakistan and India have rhe bomb, realising that fallout might be blowing over from Mururoa etc, one kinda gets used to the nuclear threat. And its vaguely within our control.
    Besides, JWH would want you to be scared, which is a good enough reason for me not to be, as well as all the others I’ve mention.
    We may well not be able to do anything about global warming because its too close to tipping point ans all our politicians are in thrall to the oil and coal industries.I include the ALP here, otherwise it would have told the advocates of clean coal technology they were living in fairyland.

  24. David says:

    “JWH would want you to be scared, which is a good enough reason for me not to be”

    If John Howard said not to jump off the harbour bridge…?

  25. Paul Burns says:

    I’d bungey jump.

  26. Katz says:

    As the nuclear age developed ordinary citizens came to believe that nations with the capability of creating nuclear arsenals had a stake in ensuring that these arsenals weren’t used. Mutually Assured Destruction was strangely consoling. Once the first strike fantasy was laid to rest folks learned to build their lives around the presence of The Bomb.

    I don’t have enough knowledge to say anything sensible about how likely it is that an al Qaeda-style outfit has the capability to detonate an A-Bomb in some US city.

    And I cannot begin to imagine what would limit the scope of the response of the US under a president like Bush to such an horrendous act.

  27. Paul Burns says:

    Bush would almost undoubredly nuke the entire Middle East, unless the Israelis or big oil could persuade him not to do it.
    Ever since the collapse of the Soviet Union, after the initial flush of relief that the nuclear threat had more or less past, weapons grade uranium hass been going missing in small amounts.There are apparently quite a number of stockpiles rhey simply can’t account for.That was nearly 20 years ago. I reckon if something was going to happen through Al-Queda or other terrorist groups with nuclear bombs it would have happened by now. As I understand it they as yet simply do not have the technological ability to manufacture a nuclear bomb and from memory this is on their own admission, not via some dodgy intelligence report meant to either console or scare us. There is always the possibility they will develop that technological expertise, perhaps even in the near future. Unril then I, for one, am not going to worry about it.On regard to dirty bombs, I heard somewhere they were very difficult to make, but then again this may be propaganda to reassure us.
    More worrying is the fact that the Americans have not yet caught Ben Laden, partly because of the distraction in Iraq.Some US inteligence experts claim that he can actually be easily apprehended, bhut that the Americans have not done so due to sheer incompetence.Apparently some time ago he was only hours away from capture, but the Americans stopped their advance.
    One has to wonder why this is so.I suspect the American industrial military complex don’t want him caught because they would then, politically speaking, lose their casus belli.
    Of course, even if he was caught, the organisation of Al Quaeda has now changed so much, it might not mean a great deal, except as a psychological blow. It is also interesting to note, again according to intelligence reports, thsat the incidence of terrorist attacks since 9/11, hass in facxt decreased, in comparison with the same time period.
    I wish I could give you references for all this, but its information I’ve picked up from watching world news and the occasional doco. and so can’t be referenced.

  28. Tony D says:

    A-Q would hesitate to use a nuke Katz… as would anyone vaguely rational. They are well aware of what would happen to their credibility amongst their base of support.

    It’s a common misconception that terrorists are irrational or immoral. Usually they are highly rational and extremely moralistic.

  29. Paul Burns says:

    Lost a very long comment here, but can’t be bothered repeating it. Don’t think I could anyway.It was one of those long, vaguely inspired pieces.

  30. No terrorist group will ever be able to manufacture enriched uranium or plutonium on their own. It’s simply too massive an industrial enterprise to hide from intelligence agencies.

    I’m pretty sure they won’t be able to manufacture a bomb out of spent reactor fuel, either; just obtaining the material is a pretty big ask, given that it is so lethal without very extensive and extremely bulky shielding, that it’d kill anyone who tries to steal it. But given access to highly enriched uranium, it’s not a particularly difficult task to make a nuclear weapon – and that’s the conclusion of experts in the field.

    But while I don’t claim any special insight into the psychology of Al-Queda, there’s good evidence that they are very interested in nuclear technology, and, furthermore, they are invulnerable to nuclear deterrence. And they have shown in the past their preparedness to engage in the deliberate mass slaughter of civilians in foreign countries. So I would think it imprudent to rule out the possibility that they might try such a thing.

  31. David says:

    “A-Q would hesitate to use a nuke Katz… as would anyone vaguely rational. They are well aware of what would happen to their credibility amongst their base of support.”

    Well, Tony D, if you are prepared to bank your life on the “rationality”, “morality” and image-consciousness of terrorists, good luck to you. But these qualities didn’t seem to stop them from flying planes into buildings. This was many times bigger than anything they’d done before. How do you know they won’t do something many times bigger again?

    The thing is, any nutter in any subdivision of some barely known ratbag terrorist organisation could wake up and decide the world must pay for his shitty day. This is much more dangerous than a handful of nation states with defined procedures and relatively dispersed power holding nukes.

    Unfortunately, some lefties really do lose all cognitive skills when talking about terrorism. Paul Burns summed up the deliberate blindness with commendable honesty: if reality suits a rightwinger’s political strategy, it’s better to live in fantasy.

    Yeah, great. Just wait until there is a horrible terrorist attack, and then watch the end of liberal-democracy, as the public will support just about any intrusion on their rights. Best admit the danger, and do our best to prevent it? no?

  32. Bruce says:

    Katz, RC and others,
    My personal concern is not the theft of nuclear materials by terrorist groups. It would be exceptionally difficult for them to assemble a working nuclear bomb and if they did it would be impractically huge. My concern is that during the breakap of the Soviet Union an unknown number of tactical nuclear weapons disappeared.

    In 1997 the then Russian natioinal security adviser Alexander Lebed said that up to 100 suitcase nukes were unaccounted for. See here:
    The story was investigated by the US Congress, but never satisfactorily resolved. The Russian government sacked and sought to discredit Lebed, issued denials even denying such weapons exist (they do) and may even have been complicit in Lebed’s subsequent death.

    Suitcase nukes are a very sophisticated nuclear device using a linear implosion rather than a spherical implosion. A somewhat technical discussion of the miniumum size and dimensions of nuclear weapons can be found here:
    They have reduced yields (around 1 kilotonne or less) due to an “inefficient design”. Few governments could make them, let alone terrorists.

    Suitcase nukes are just the tip of the iceberg. There were an enormous number of tactical nuclear weapons of many forms – artillary shells, rocket warheads, torpedos, depth charges, gravity bombs, nuclear land mines etc. floating around at the time of the collapse of the USSR.

    If the Russian approach to the suitcase nuke story is any guide (denial of their existence, cover up , assurance of securiuty), then we will never learn from the Russian government if any are missing.

    The most likely thieves of these devices are government agencies, because of their ability to infiltrate former Soviet states. For example, Kazakhstan has a huge minority Korean population. The following quote comes from this site:
    “Hundreds of Koreans in Kazakhstan received Ph.D. degrees, and worked as professors and researchers at the universities, institutes and scientific centers. Koreans were elected members of the parliament of the Soviet Union and Kazakhstan, were given ministerial posts in Kazakhstan and were also found among the generals of the Soviet Army. ”
    The same is true of ethnic groups found in Iran, Pakistan etc.
    My contention is a surprisingly large number of Central Asian-Mid Eastern states have ex-Soviet tactical nukes sored away for a rainy day – perhaps a nuclear winter? 😉

  33. Andyc says:

    David 31:”Yeah, great. Just wait until there is a horrible terrorist attack, and then watch the end of liberal-democracy, as the public will support just about any intrusion on their rights. ”

    Invalid cause-effect pair. I was in the UK right through the endless horrible terrorist atrocities of the late sixties through to the early nineties. While being Irish in the wrong place at the wrong time was occasionally a very bad idea, the ongoing threat was not abused as an excuse to clamp down on liberties for all in Great Britain.

    Liberties have been under attack in Neocon Land over the last few years, not because descent into totalitarianism is an appropriate response to terrorist threat (hint: it doesn’t work), but because hyped-up terrorist threats can be used as an excuse for predation upon civil liberties, if governments are unscrupulous and people let the get away with it.

  34. Katz says:

    Bruce, I have no reason to doubt your story about the plethora of nuclear devices and the breadth of nuclear expertise floating around Central Asia.

    That being the case, however, the clowns who are alleged to have been nabbed in Slovakia traipsing around a chunk of highly enriched U235 would appear to be a fair way down the nuclear food chain.

  35. Tony D says:

    Hi David,

    Just some thoughts, and way, way off the post-topic sorry;

    “But these qualities didn’t seem to stop them from flying planes into buildings. This was many times bigger than anything they’d done before. How do you know they won’t do something many times bigger again?”

    Quick answer: they may well do so, if it suits their purposes. Realise though that an act of terrorism has at least two target audiences – those attacked directly and those watching indirectly (probably on TV), hence that oh so media friendly timing between the two planes hitting their towers respectively. Waiting for the cameras. The point is that not everyone will interpret the attack through the lens’ used by the attacker or attacked – something the A-Q ideology exploits well. Attacks are intended to intimidate but can act as a form of advertising to the A-Q cause.

    The intel captured in Afghanistan post US occupation showed that A-Q had misjudged the US’ reactions. Bergen’s article (if you scroll down a bit) includes an extract from KSM claiming that A-Q’s “adherents have lost confidence in us and in our ability to manage the action.” Essentially due to the loss of Afghan bases and personnel losses.

    Oh, and then that Iraq thing happened. Oops.

    Didn’t we have the same arguments about Saddam’s rationality or lack thereof at the time?

    “Best admit the danger, and do our best to prevent it?”

    Completely agree with you here David, though I suspect we disagree on how to go about preventing it: I would favour accommodation/criminalisation methods as this style at least attempts to address the underlying social issues that produce terrorism. I suspect you would favour suppression/criminalisation approach.

    My opinion is based on acknowledging those pesky ‘root causes’, a perspective that may lead some to conclude that “some lefties really do lose all cognitive skills when talking about terrorism”. The disagreement is over perceptions of cause-effect relationships; we think different things cause the problem, hence we envisage different solutions.

    My objections to the suppression model is based on the French experience in Algeria. The French suppressed FLM so well they completely alienated the local population, with the result that they were kicked out eventually.

  36. Tony D says:

    Slightly back on topic though, one way of reducing the threat of nuclear weapons is obsolescence.

    There are ways to produce similar destructive effects without nasty radiological, biological and chemical hang-overs.

    At an extremely basic level take a rocket, give it a really good ablative nosecone, as much mass as you can and a guidance system. Fire in straight up. Decide where you want it to ‘land’. Aim. Fire. Kinetic impact does the damage (think asteroid impact).

    Anyone deploying nuclear weapons can be retaliated against, even if the demolition of mountain ranges occurs.

    Still very, very, very nasty. But effectively makes the traditional WMD troika obsolete.

    Or we could get back to that root causes of terrorism thing and reduce the supply of potential terrorists.

  37. derrida derider says:

    The thing about nukes is that they need constant and sophisticated maintenance – the radiation damages the surrounding trigger materials and even the casing. Any weapons that got stolen in the early 90s won’t still be operational.

    In fact as the half life of U235 is only 7 years HEU stolen more than a few years ago won’t still be bomb grade (that’s a possible reason that people would want it extremely enriched – it stays bomb grade a bit longer). One of the advantages of plutonium is that the half life is much longer, but of course both getting the fuel and building a plutonium bomb is harder.

  38. Tony D says:

    Oh and;

    “Just wait until there is a horrible terrorist attack, and then watch the end of liberal-democracy, as the public will support just about any intrusion on their rights.”

    The cause-effect relationship is: attack occurs, legislate to prevent the attack that just occurred; another attack, legislate to prevent that attack; attack, more legislation; another attack, yet more legislation; etc. It’s a never-ending product of the suppression approach, and the ‘being tough on terror’ mindset. And yes, it does result in the decay of liberal democracy, or at least the ‘liberal’ bit anyway. It’s a trend already in evidence in the US, UK and Aus.

    Instead, isn’t it better to address the reasons these people might want to attack us? “Undermine their cause and destroy their cohesion by demonstrating integrity and competence of government to represent and serve needs of people – rather than exploit and impoverish them for the benefit of a few,” was how it was put once – in 1968.

    “Where there’s a will there’s a way”, as they say. ‘Way’s are plentiful. Undermine the ‘will’ part.’

  39. Andyc says:

    DD 37: “In fact as the half life of U235 is only 7 years”

    Facts, please. The half-life of U235 is 700 MILLION years. It decays 7 times faster than U238, but still not particularly fast compared with, say, medical tracer isotopes. (ref: wikipedia, or almost any chemistry or geochemistry text).

    I am sure that you are right that weapons-grade stuff doesn’t stay that way for more than a few years, but the problem is more likely that some of the accumulating fission products are rare earth elements like gadolinium, which absorb neutrons and stuff up the ability to go into chain reaction. Hence, the U235 would need re-purifying after a while, even though only a tiny proportion of it had decayed. And this requires well-equipped, very expensive fancy labs and people who really know what they are doing.

    Without that reprocessing, curios and antiques are just that.

    1. major advantage of plutonium: you can go fissile with a much smaller lump.
    2. major disadvantage of plutonium #1: ditto.
    3. major disadvantage of plutonium #2: the extreme physiological toxicity, even if we forget the radioactivity. If there is any leakage from a visible lump of it, the odds are that the handlers die soon afterwards. The inability of presumably trained criminals to manipulate radiopoisons without leakage is well demonstrated by the Polonium 210 contamination trail left all over Europe by the assassins of Alexander Litvinenko last year.

    No-one who had any intention of survival would handle plutonium as an amateur.

  40. Bruce says:

    Re DD and Andyc,
    Yes, shelf-life is an issue, but it’s far more complex than the half-life of U235 or Pu239.
    The most important issue is the neutron initiator incorporated into most weapon designs – not the gun type “Little-Boy”. Spherical implosion produces a bounce that is too fast to get an efficient self-sustaining chain reaction out of Pu239 (I’m unsure of U235). So these designs use a neutron initiator to introduce a huge number of neutrons during the implosion.

    From my reading there are 3 main typre of initiators in increasing order of sophitication and shelf-life:
    1. Polonium 210 (mixed with Beryllium) – Alexander Litivenko was poisoned with Polonium . It has a half-life of 138 days.
    2. A mixture of tritium and deuterium gas. Tritium has a half-life of about 12 years. It is introduced into the centre of the weapon just before detonation.
    3. Pulse neutron tube – uses deuterium or a mix of deuterium/tritium. Using pure deuterium, which is not radioactivbe gioves a very long shelf life. (US tested these in 1955 and are the main initiators used by them.)

    Unless the last of these is built into the weapon, it is clear that shelf-life is a major issue for terrorist theft of nukes.

  41. Yes, you need an initiator for any type of implosion bomb.

    Little Boy used an initiator as well, though it was apparently a last-minute addition to guarantee detonation at the exact moment they desired.

    With regards to the life of a gun-type weapon, it’s a hypothetical question because nobody has maintained a stock of them for any significant period of time. That said, the life of plutonium pits, with a much, much shorter half-life, is at least several decades and current thinking is that it might be fine for a century or so. Given that, I doubt that buildup of fission products in a HEU gun bomb is going to be an issue for a very, very long time.

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