Do bombs 'go off'?

[Mr.Kobayashi]

“Dammit, Bob. There were plenty of brand new bombs, but you had to go for that retro 50s charm!”

By which I mean expire, pass a sell-by-date. Pun intended.

Here in the UK we occasionally get the bomb squad called out for UXBs (unexploded bombs) from WWII that the Germans dropped or from an old firing range, they generally look like bits of rusted scrap which the authorities make safe just in case.

Do grenades, shells and the like become duds over time? What about the big boys like hydrogen bombs or neutron bombs? Would an a-bomb from 1945 still give a big boom?

[silenus]

Well, there are still French farmers going to meet St. Peter every year because their plows hit a shell left over from the Great War. If the casing is intact bombs and ammunition can have an amazingly long shelf life. I regularly shoot ammo that is 50-70 years old with no problems.

Just wait until the SS Richard Montgomery goes off. Then you’ll see!

[Duckster]

New York (CNN) – This could have caused a major blast from the past.
Workers cleaning a cannon, last fired more than 200 years ago, were shocked to find Friday that it was still loaded with gunpowder, wadding and a cannonball.
The preservation workers from New York’s Central Park Conservancy were removing rust from the antique cannon, which once fired munitions aboard the British warship HMS Hussar, when they made the explosive discovery, New York police Detective Brian Sessa said.
Dena Libner, a spokeswoman for the Central Park Conservancy, said the workers found the munitions after removing a concrete plug from the mouth of the cannon.
Workers immediately called 911, and technicians determined that the gunpowder was still active.

http://www.cnn.com/2013/01/13/us/new-york-loaded-antique-cannon/index.html?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+rss%2Fcnn_us+(RSS%3A+U.S.)

[friedo]

Just like a New York City contractor to plug a cannon without bothering to check if it’s loaded.

[smithsb]

Google WWII horrors relived as allied bomb detonated in Munich | Mail Online

for a pdf on the demolition of a discovered bomb in Munich last year. There are still thousands of these munitions, some with chemical detonators as described in this bomb.

[sweeteviljesus]

I don’t know about military ordinance, but old fashioned dynamite could become unstable over time if not turned (the nitroglycerin weeps out of the cartridges - see the film The Sorcerer). Unexploded ordinance is often unstable as the trigger mechanism has been fired, but somehow “got stuck”. As far as becoming duds, the cases could rust through. I believe TNT, Comp B and modern explosives used in bombs are waterproof, but I am not sure. The firing mechanisms could corrode and I believe many fuse compounds are not waterproof.

Nuclear weapons have a stockpile maintenance program associated with them. IIRC, the tritium can leak out over time which would cause a fizzle (a big explosion, but not as big as it’s supposed to be). A while back, I saw a program that criticized the American style of stockpile maintenance (so-called scientific maintenance) versus the hands-on maintenance the Russians used, but unfortunately, I don’t remember the details. Where is Stranger on a Train?

Rob

[pravnik]

Like silenus said, in France there is unexploded ordnance from World War I still killing people fairly regulary today, so whatever the “expiration date” is, it appears to be approaching 100 years at a minimum.

Iron harvest
Unexploded ordnance

[Der_Trihs]

Tritium in nuclear weapons has a half life of 12.32 years, and so needs to be replenished periodically.

The tritium in a warhead is continually undergoing radioactive decay, hence becoming unavailable for fusion. Furthermore its decay product, helium-3, absorbs neutrons if exposed to the ones emitted by nuclear fission. This potentially offsets or reverses the intended effect of the tritium, which was to generate many free neutrons, if too much helium-3 has accumulated from the decay of tritium. Therefore, it is necessary to replenish tritium in boosted bombs periodically. The estimated quantity needed is 4 grams per warhead. To maintain constant levels of tritium, about 0.20 grams per warhead per year must be supplied to the bomb.

[Chronos]

Contrary to popular belief, something being really good at blowing up does not make it a useful explosive. For an explosive to be useful, it has to blow up well when triggered appropriately, but it also has to not blow up at other times, so you can safely deliver it to where you want the explosion. When old explosives go bad, it’s generally this second trait that fails: It’ll still blow up, it just might not refrain from blowing up.

[Bullitt]

Artillery shells and gunpowder do have shelf lifes. In Marine Corps field artillery, we would pay attention to shelf life dates and if ammo was starting to get old, oh well, we just had to use it up.

“Expend all remaining!”

As for duds, a USMC base, 29 Palms, combines impact and maneuver areas: we could be maneuvering where bombs and arty were dropping not long ago. We always got the EOD section’s “dud lecture” before training there. Regularly, a young Marine would be walking in the desert and see a fin sticking out of the sand, and he’d just give it a kick. And that would be the very last thing he’d kick with that foot, because it’d be gone. And he’d be lucky if it’s only the foot that blew off. EOD told us it happens every year. Or so the story goes.

ETA: most bases separate maneuver areas from impact areas. For the impact areas there are big Keep Out signs, and I don’t know if EOD bothered to locate all unexploded ordinance from there.