Duff UK nukes risk 'popcorn' multi-blast accident apocalypse
Atom bombs very dangerous, says CND man
Last week many Britons were amazed to read in the quality press that the UK's nuclear weapons are thought to have a "design fault" which could see a transport accident detonating multiple warheads in a devastating chain reaction apparently known as "popcorning".
"More than 1,700 warheads are affected by the problem which would cause them to explode one after another," trumpets the Daily Telegraph. Holy Crap.
The Telegraph, veering somewhat from its normally establishment right-wing stance, picked up the scoop from New Scientist scribe Rob Edwards. Edwards cites "a nuclear-weapons safety manual drawn up by the MoD's internal nuclear-weapons regulator".
The manual was "seen by New Scientist", as the Telegraph notes, lending the story a frisson of newsworthiness - no doubt Edwards was shown it by a worried whistleblower, or perhaps a mysterious Deep Throat-style insider source.
The document apparently says that the present impact-safety standard for warheads is "single-point". That is, the warheads cannot be made to go off or partially function by a violent blow, or a succession of blows, as they might sustain for instance in the case of falling off a crane.
However, the MoD nuke boffins say that a recommended "design objective" should be to produce warheads which can provably resist multiple simultaneous impacts from different directions. It isn't that the current ones are thought likely to go off in such a scenario; it's just that you can't prove they won't, as this wasn't part of the design spec.
Not really a design fault as such, then. Tomorrow's cars will be safer than today's - do today's therefore have design flaws?
As for popcorning, you can't say that would happen - or how much it would happen - if one warhead partially functioned close to others, but it's at least theoretically possible.
"For popcorning to happen, a significant number of specific and unlikely events would need to occur in sequence," the MoD said in a statement. "The likelihood of this sequence of events occurring is incredibly remote."
So it could happen; but realistically it would make more sense to worry about a rogue submarine crew firing the weapons on purpose than a popcorning accident. Indeed, it would surely make more sense to worry about a rogue prime minister, or a rogue head of a different nuclear-armed state with a grudge against the UK.
But "the effects of a popcorning accident would be dire," says Edwards. "In the worst-case scenario, people a kilometre away would receive a radiation dose of 100 sieverts - that's 16 times the lethal dose."
Dire indeed - though not in the same league as a warhead actually functioning as designed, and immensely less likely. Popcorning requires many implausible events to happen in sequence, then yet another multiple roll of double sixes has to occur for the effects to become serious. An undetectably insane or simply evil person or group of persons getting firing authority somewhere is likelier.
Still, secret MoD nuke documents are always interesting. Although these ones aren't actually secret; without giving details, Edwards admits that the manual he quotes was "declassified last month".
In fact, a redacted copy of Joint Service Publication (JSP) 538 Regulation of the Naval Nuclear Weapons Programme was placed in the House of Commons library last month in response to a Parliamentary question. You can't read it online, though; it's hard copy only.
Only someone with a very good reason would go and read an entire fist-chewingly dull MoD manual and then struggle so desperately to squeeze a scary headline out of it. Funnily enough, Edwards has just such a reason. He is a former leading light of the Scottish Campaign to Resist the Atomic Menace, a former CND campaigner, and the co-author of Britain's Nuclear Nightmare and Still Fighting for Gemma.
The latter work focuses on the harrowing death of a young girl from leukaemia, and lays the blame squarely on atomic power. It's a simple message: Nuclear technology equals little children dying in agony. Be afraid and horrified.
In more recent times, Edwards has tended every year to dredge up a dusty MoD publication and run a scare story during the summer news drought. Last year it was "UK nuclear accidents blamed on poor safety". In 2006 it was "Road Crash could set off Nuclear Blast".
So "popcorn warhead design fault will lead to innocent kids dying in agony" can probably be filed in the same place you'd file "terror threat means all civil liberties must be suspended", "reefer skunk death puff will make your kids go insane", "drinking booze is the most evil thing you can ever do". Etc, etc.
In fact, it might be best to
just stop reading the news for the next couple of months always check the Reg for the unvarnished scoop. ®
If UK atomic weapon storage sites are not protected against time traveling interdimensional gateways being used to abscond with said weapons, then the public needs to be warned about that too.
I can't believe (at time of submission) this hasn't been posted already...
...but I just can't wait for the ID cards to come, they'll save us all.
Interesting comments, picking up some interesting snippets from further research etc
@ Neoc: "Nuclear *reactors* can't blow up on their own, they're not designed for it."
I fully understand there's some fairly rock solid safeguards preventing a nuclear reactor blowing up of its own accord, however I'm not sure "they're not designed for it" really suffices as a reason, I'm sure there's plenty of appropriate analogies to reinforce what I'm trying to say but it's gone 5 o'clock and I'm hungover as it is.
I've never really looked into the whole nuclear good/bad thing very deeply but thinking about it, they're rather obsolete currently, they were designed for a time when "Prior to satellite intelligence, each side lacked precise knowledge of the location of the other side's military and industrial facilities" and I suppose one big bang to do as much damage as possible is a pretty good idea if that's what you're after. But I believe MIRVs are now the preferred weapon of choice, combined with all the satellite information available they seem to make pretty good sense.
UK atomic weapons part 2 - popcorning
In part 1 I described how in order to reshape and compress the plutonium pit in order to get a 300-ton yield the conventional explosives must be very accurately detonated, but what happens if the explosive is not detonated accurately?
The details are complex and the knowledge needed to give accurate answers is well beyond what's publicly available, but for high yields the supercritical mass must be formed very quickly so that it doesn't blow itself apart before it has time for a lot of the mass to undergo fission - in the 300 ton case "a lot" is about1% of the plutonium.
If a critical mass of formed more slowly, perhaps because the explosives were not detonated correctly, then a small yield "fizzle" can happen. This isn't very likely, as there isn't a lot of extra plutonium in a modern primary, and it has to be shaped into a sphere and also be compressed before a critical mass can be assembled, but it is perhaps possible. This is the other main cause of single point sensitivity, but what would the yield of such a low-order detonation be?
Well it can't be more than 300 tons, because getting 300 tons is the maximum that can be done with accurate detonation, but it may be ten kilos, a ton or even ten tons depending on the speed of assembly and the degree of supercriticality. More than ten tons or so yield is very unlikely, bordering on impossible.
Could this set off another low-order detonation in a nearby warhead? It's possible, although unlikely. How unlikely? Only the MOD could answer that, it depends on classified details of the design.
Lets look at a worst-case popcorning scenario, where the 48 warheads in a sub or in a store do set each other off in low order detonations. Note that a single medium-order 300-ton detonation will be enough to disrupt the remaining warheads.
If each warhead yielded the maximum10 tons then the total would be 480 tons, but for two too-long-to-explain-here reasons 350 tons is a better maximum figure, and even this is extremely unlikely - even 50 tons is pushing probability.
However lets say the maximum credible total yield for a single point failure or popcorn event is 350 tons - now this isn't spare change by any means.
The effects of sub-kiloton explosions are a bit different to multi-kiloton explosions, and it is quite possible to be killed by prompt radiation without suffering lethal blast or burn damage (though you will still get knocked ass-over-tit). That's what the 100 sieverts at 1 km figure is about. Think "neutron bomb", although neutron bombs are designed to give off lots of neutrons, and typically have yields in the low kiloton range.
However, any remotely likely popcorning event can only take place where there are several warheads close together, ie either in a sub or in a bunker, and the prompt radiation will be attenuated by the hull of the sub and perhaps the water, or the walls of the bunker. The raw radiation will consist of neutrons and gamma rays of approximately equal lethality.
The gamma rays will be attenuated by the hull of the sub by a factor of at least 500, and would not be a great concern at 1 km. The neutrons are much more of a worry, but a few feet of water or bunker walls would stop them from being lethal at 1 km.
In general, at 1 km distance from a popcorning event I'd be far more worried about contamination from plutonium than prompt radiation.
Is a popcorning event possible at all? For some early warheads undoubtedly the answer is yes, but could today's UK warheads popcorn? I don't think so, but that depends on classified design details I have no access to. The official line is "It's perhaps possible but extremely unlikely, we can't prove it but it may well be impossible". I'd agree in general, though perhaps not on exactly how unlikely.