Archaeology vs. Physics
December 23, 2013 6:41 AM   Subscribe

Conflicting roles for old lead
The use of old lead for shielding increases the sensitivity of our most delicate experiments by orders of magnitude, an increase that is crucial when looking for a reaction that sheds light on new physics. Lead recovered from roofs, old plumbing, and even stained glass windows has been used, but Roman lead from a shipwreck is the best you can find.
posted by Jpfed (25 comments total) 21 users marked this as a favorite

 
Weirdly, this isn't the only time that shipwrecks have served as a valuable source of low-radiation materials. The German WWI High Seas Fleet, scuttled at Scapa Flow, was "mined" as a source of low-radiation steel for sensitive scientific instruments - since any steel since the 1940s has been contaminated by radiation from nuclear testing. Rumor was that some was used in the Voyager spacecraft, but that has never been confirmed.
posted by blahblahblah at 7:14 AM on December 23, 2013 [7 favorites]


We should bury all our bullets now, deeply, for science. Cough cough pacifism cough.
posted by lalochezia at 7:16 AM on December 23, 2013 [4 favorites]


Lead is weird. I mean on the one hand, it looks like in many ways it is responsible for a lot of violence (discussed around here previously somewhere). On the other, it lets us push forward the boundaries of our understanding.

there's a lesson here somewhere maybe
posted by feckless fecal fear mongering at 7:53 AM on December 23, 2013


lalochezia:

Sorry, the ammunition industry (at least in the USA) runs off of scrap/recycled Lead. Of no use for low background radiation shielding...

I do bury lots of bullets, however! Got a nice berm on the North 40 I had faced with a couple of feet of clean sand just for that purpose. I bury as many as I can there, and occasionally I will screen the sand and recycle them by smelting and casting the recovered Lead into MORE bullets.
posted by bert2368 at 7:56 AM on December 23, 2013 [2 favorites]


Uh isn't burying lead-based bullets kind of exactly the same as deliberately polluting the ground with a toxic substance?
posted by feckless fecal fear mongering at 7:58 AM on December 23, 2013 [4 favorites]


any steel since the 1940s has been contaminated by radiation from nuclear testing

What I thought was interesting was the different mechanism of action here. At least from the description, it doesn't sound like modern lead is contaminated with residue from nuclear testing. Instead it sounds like:

(1) Lead (ore) is naturally mixed with other heavy metals like U-238
(2) Smelting removes the U-238 and otherwise purifies the lead, but that still leaves lead-210.
(3) So smelted lead starts out less radioactive than lead ore and as the lead-210 decays through its chain down to stable lead, the already-reduced radioactivity drops by half every 22 years
(4) So Roman lead is almost completely made up of stable lead-206
posted by ROU_Xenophobe at 7:59 AM on December 23, 2013 [13 favorites]


If anyone is interested, the original Nature News brief from 2010 is here (and it seems to be fully available), the Rosetta piece (I think it's the one mentioned anyway) is available as a pre-print here and a couple of other archaeological sites with lead are mentioned here. If you're interested in how archaeologists study lead ingots, check out these past articles/dissertations.
posted by jetlagaddict at 8:07 AM on December 23, 2013 [1 favorite]


And a previous Metafilter discussion on the wreck.
posted by jetlagaddict at 8:09 AM on December 23, 2013


ROU_Xenophobe: makes sense, and after being baffled by how the lead-210 was in the ore but eventually decayed away in the smelted lead, I think I figured it out. The uranium in the lead ore decays into lead-210!
posted by Freen at 9:30 AM on December 23, 2013


ROU_Xenophobe: So Roman lead is almost completely made up of stable lead-206

Not quite. Natural lead has a standard atomic mass of 207.2, with about: 204, 206, 207 and 208 are stable. The trace isotopes aren't, but only 210 has a half-life of more than a day.
posted by Monday, stony Monday at 10:48 AM on December 23, 2013 [1 favorite]


Uh the lesson is that elements can't be separated into a list of the good elements and a list of the bad elements.
posted by kiltedtaco at 11:10 AM on December 23, 2013


/me slaps himself on the back of the hand and wanders off muttering STUPID STUPID STUPID
posted by ROU_Xenophobe at 11:19 AM on December 23, 2013


elements can't be separated into a list of the good elements and a list of the bad elements.

Oh yeah? Well then ... what planet was Superman from, then?
How about Iron Man, huh?
Golden rings join hands in true love, right?
Lone Ranger's horse?
Come and get me, copper!!
Jason and the argonnauts??
Who was The One? Neon of course!

I think I've made my point.
posted by Twang at 12:08 PM on December 23, 2013 [2 favorites]


I find it hard to think of a hypothetical situation in which some significant (or even insignificant) historical or archeological finding will turn on the availability of the lead that was repurposed for this experiment. If they used only the damaged ingots and preserved all the stamps, marks etc. then what further information could be gleaned from the lead itself that you wouldn't be able to learn from the preserved undamaged ingots?
posted by yoink at 12:58 PM on December 23, 2013


Yoink: I think the argument might be getting confirmation of the origin of those particular lead ingots, other kinds of isotope analysis, and probably other kinds of analyses in the future that aren't possible right now, especially if it required more lead than was preserved with the stamps. I mean archaeologists/explorers also used to throw out all the human bones they found and light fires with Roman charcoal/scrolls, but we don't do that now. Generally speaking even experimental archaeologists don't use actual archaeological materials for their projects, so it's a bit of a new direction. I think there's also a slight worry about a slippery slope-- if you take these materials for one project, then what happens the next time it turns out that artefacts are useful in another context? Or what if it created a market for further looting of lead materials on land or wrecks? I actually haven't heard a lot of debate about this particular project, probably because funding for maritime archaeology is so very, very expensive, and it seems like the division was handled pretty sensitively.
posted by jetlagaddict at 1:06 PM on December 23, 2013 [2 favorites]


Why not just use a centrifuge to separate the good stuff out?
posted by humanfont at 1:10 PM on December 23, 2013


The German WWI High Seas Fleet, scuttled at Scapa Flow,

I had never heard of that event until today. That was a great read, thanks for the link.
posted by entropicamericana at 1:17 PM on December 23, 2013


Why not just use a centrifuge to separate the good stuff out?

Well, it did take the concentrated might of the US nuclear weapons program several decades and vast piles of money to produce only *looks* 750 tons of U-235, or a cube about 11 feet on a side.
posted by ROU_Xenophobe at 1:24 PM on December 23, 2013 [1 favorite]


I think there's also a slight worry about a slippery slope

Yes, I think it's really entirely a slippery slope argument (I don't really buy the "getting confirmation of the origin" argument because they only took a small portion of the cargo and they kept sufficient quantities of the ingots they did take to be able to compare the 'harvested' samples to the rest. Any test that needs larger quantities can be performed on the many preserved ingots.)

The problem is, though, that slippery slope arguments are based on an illogical premise--by definition. If the problem is "destroying something of real archeological value for some other purpose" then you just muddy the waters by treating a case where nothing of real archeological value was destroyed as an "example" of the problem. If anything, the danger is in making the genuine concerns archeologists have about such things seem trivial: the boy who cried lead, so to speak.
posted by yoink at 1:28 PM on December 23, 2013


humanfont: "Why not just use a centrifuge to separate the good stuff out?"

It's extremely expensive. Doubly so in this case because ease of separation is directly proportional to the square root of the mass ratio of the two isotopes and lead is both heavy and only a single number separates the desirable from the undesirable. So it's basically limited to extremely high payback critical processes in nuclear processes.
posted by Mitheral at 1:31 PM on December 23, 2013 [1 favorite]


... and so once again, recycling proves its importance.

Seriously.
posted by IAmBroom at 7:44 PM on December 23, 2013


Why is all steel contaminated with radioactive fallout? Surely uncontaminated ingredients are available?
posted by Joe in Australia at 10:39 PM on December 23, 2013


The dust in the air is contaminated. You would have to maintain some sort of clean room standard in the entire chain of your mine, smelter and steel mill to eliminate the fall out contamination.
posted by Mitheral at 11:09 PM on December 23, 2013


Why is all steel contaminated with radioactive fallout?

This is why. If you're looking for an excuse to have a stiff drink, skip to 3:30 and keep watching from there.
posted by justsomebodythatyouusedtoknow at 10:07 AM on December 24, 2013


Industrial espionage scenario: I know you need really good lead, and are using a centrifuge. So I attack using a carefully constructed computer virus.

Don't tell the US and Israeli military industrial complexes.
posted by clvrmnky at 7:32 PM on December 24, 2013


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