Low-background lead is also sought after in shipwrecks [0]. With lead it isn't contamination from nuclear tests that's the issue, but natural radioactivity that needs hundreds of years to decay.
It's always confused me how mined lead somehow has more radioactivity. Shouldn't the lead in the ground also have decayed over time?
Also, it makes me wonder why someone enterprising hasn't stockpiled a few tons of the stuff somewhere to let it become low background lead for the future. You'd think that some government or another would be able to drop a million dollars on putting a lead stockpile somewhere safe for the future.
> It's always confused me how mined lead somehow has more radioactivity. Shouldn't the lead in the ground also have decayed over time?
Looking into this a bit, it seems that the radiation in refined lead isn't coming from the lead ore, but from the other materials used in the smelting process. Old lead would have had time for all those things to decay.
So this is all kinds of wrong. When you make steel, you typically use 99+% pure oxygen - modern mills do air separation and reject nitrogen and argon (which makes steel brittle when it's dissolved in) and basically anything they can reasonably separate out but oxygen.
But furthermore, it's not radioactive oxygen isotopes that get into the steel in the first place - they're scant to non-existent in nature, since all three common isotopes of oxygen are stable and most of the rest decay in seconds. It's other radioactive isotopes in the air from the bomb tests.
99+% isn't 100%, and it turns out those tiny fractions of a percent of junk contain the isotopes that are the real problem, namely Cobalt-60 created by the nuclear tests. Carbon-14 isn't nearly as big of a problem, since its decay mode is just beta and can be designed around, but the gamma decay from Cobalt-60 contamination is much harder to deal with.
Furthermore, because of Cobalt's position on the periodic table and the desire to have a small amount of cobalt in steel anyways to give it better working properties, it's not something that's easily filtered out, even in processes that reform steel like vacuum remelting which exist to make mechanically harder and better quality steel by slow melting and recrystalization. Once the Cobalt's in there, it's in there - you just have to wait for it to decay.
As it turns out, we're in luck, most of the fallout from those bomb tests has passed through numerous half-lives and is much less of a problem today than it was in the 1980s and 1990s when the low background stuff became such a hot commodity. So it doesn't really matter as much that we're running out. Furthermore, oxygen separation technologies and cryogenic liquid handling have improved, so we can do an even better job keeping contamination out. If someone wanted to set up a low background mill, they probably could do it today with commodity molecular sieves and centrifugation of the oxygen rejecting all but the light fraction...
> How is the cobalt getting mixed with the stuff mined from the ground?
So the term "fallout" is actually a pretty piece of propaganda. While a lot of it did or does indeed "fall out", there's still a lot of radioactivity in the air and on the surface from those nuclear tests in the form of fine particulate. It's in the fine dust all around you as 100nm and smaller particles, dancing around the air through Brownian motion. It's all over everything all of the time. It's in the water and the ocean. Nanograms here and there and everywhere. Not enough to really cause you health problems anymore, but plenty enough to increase the background radiation of the entire surface of the planet by a tiny amount.
How it gets into the steel is through the actual blasting of oxygen into the steel - hundreds of cubic meters of oxygen are used per ton of steel made, concentrating those tiny particulates into the steel they're going into and dissolving them throughout the melt, which is precisely why using ultrapure oxygen and vacuum processes could be used to make lower background steel today... if there was high enough demand to justify the absurd cost of that kind of handling. Fortunately though, there was plenty of steel made before the 1940s, and the demand is not all that high since it's usually used as a shielding material and not as large structural elements. As long as they don't remelt it, or do so in a high vacuum reformer, the metal can retain its low background nature.
Intermediate-lived gamma-emitting isotopes (cobalt-60, strontium-90, cesium-137, and so on) are the particular problem children of nuclear fallout in steel making. The cesium and strontium are largely removed by the same processes as steel is made in the first place - they're simply reactive enough to bond with the silicon and carbon and aluminum impurities being removed and will happily exclude the majority of themselves as part of the slag. So while they do contribute to the background, they're not the main problem. Cobalt, on the other hand, is right next to iron on the periodic table and its happy to stay stuck to the iron, even through rounds of recrystallization. Once the cobalt is in the steel, it's in there until it decays away to nickel over the next century or so. (This is also why it's much less of a problem now than it was even 20 years ago; the halflife of cobalt-60 is about 5 years, which means much of it from the nuclear testing is already gone - most of what remains is from nuclear reactor releases and neutron activation products.)
The more sensitive your instrument needs to be, the more radioactive contamination wrecks your instrument, which is already why physics experiments have to go to extreme lengths to keep everything clean of dust and debris, and are often located underground or underwater to avoid exposure to cosmic rays and atmospheric muons decaying. But the even higher sensitivity experiments like dark matter searches and measurements of cosmic background radiation have little choice but to reach for low background steels and lead as shielding material.
I'm not sure about this; smelting lead is generally done in a blast furnace, fed with coke. Burning that coke is going to produce a ton of CO2. Is that good enough because the carbon in the coke is all very old? (Searching for information relating to C-14 and coal lead me to a bunch of wacko new earth creationist websites claiming that carbon dating indicates coal is young...)
Also, maybe this isn't really a concern, but "high temperature and pure oxygen" makes me think "metal fire."
Money-oriented thinking is a road to economic misunderstanding. The economy is about stuff. In practice one often measures all the stuff using money, yes, because what else would one use? but as a proxy measure for its value; it's never actually about the money itself.
(stuff = "final goods and services" to be technical)
Energy witch can be food, oil, gas, the energy transformator is a human (or his brain) a maschine or a animal, and the exchange between energie to the endresult is often money. So money/exchangemedium has just the worth both partys agreed on.
Now you are measuring electricity instead of the light you read by, and fuel instead of the vacation trip you take with it. You have worsened the problem I refer to.
Surely energy input is the right metric. If I use a gallon of gas to power a life-saving ambulance or if I burn it just for fun, those two actions should have the same importance.
Energy IS electricity, and to create a Lightbulp you NEED energy, it's exactly the same.
For your vacation trip you NEED energie in form of food an fuel, the vehicle you travel in, is made by food and fuel...exacly the same.
If the transport company accept your fuel (or workforce witch again is fulled by energie (your food)) as payment, you exchanged energie to energie, probably they dont and thats why you use a exchangemedium called money.
EDIT: You dont have to messure anything, if you need light exchange energy to light, travel exchange fuel to distance, working body food to (body)-energy. To make stuff you calculate the sum of the energie needed for, and thats the price of the product, sure exeptions like apple exists ;)
the fundamentally inescapable problem is your approach measures an input instead of output, and thus makes technology improvements look like an economic crash
Yes. The demand for low background steel and lead is in the few dozen tons per year max, not millions of tons per year. Salvaging it is probably at least an order of magnitude cheaper than making new low background steel once you realize the amount of hassle involved. Furthermore, it's fairly easily recycled if you're not launching it into space (which is a common use case for the stuff, since building space probes to study the cosmic background is all the rage these days).
As others said, simply separating the CO2 away would mostly get rid of the problem - all non-stable isotopes of Oxygen have a max half life of 122 seconds, but, for the record, isotopic separation is easy when there is a very large difference in atomic weight.
In Uranium's case it's difficult because it's 235/238 = 1.28% (actually way worse - Uranium hexafluoride is used, which adds 114 units, bringing the ratio down to 0.86%)
In Oxygen's case the ratio would be at least 6.6% (15 vs 16).
Most importantly in Uranium you are interested in the tiny amount of U235, while in Oxygen you'd be interested in the huge bulk of O16, O17, O18, which are the stable isotopes. O16 alone is 99.762% of all Oxygen, and you can afford to lose half in your centrifuge if it spares you a few cycles, it's not exactly hard to come by.
What would be the timeframe over which one would make a profit? Our global financial system is based on the 30 year U.S. Treasury bond. There are no economic incentives to plan beyond 30 years.
Probably a few hundred years, so yeah, it wouldn't be worth it to the people doing it at all within their lifetime. That's why I was suspecting a far-sighted government or such with enough money to squirrel it away for future use.
The US sorta has a few things like that already--the oil reserve & the stockpile of helium, though I understand the latter is winding down still. Given the importance of those materials to science, I would think that there might be some scientifically-motivated project to protect our access to such things.
I don't know of any good sources. But my understanding is that there are very few "Methuselah bonds" by which it is meant instruments that have lifespans of 50 years or more. So anybody with a profit motive has no advantage for putting money into something that would have a longer term focus. This explains to me why, for example, banks are still loaning money for buildings on Miami Beach. I would love to understand the dynamics better. It seems to me that only governments can be planning for longer terms. China, maybe?
Forget filters. It would have to be done in a vacuum and you would need to centrifuge the required gasses/carbon. It is possible in small batches, but the sunken ships do exist ready to harvest. Maybe in the future the market will come.
I had some low radiation lead for a while, makes for an interesting curio. As I recall its providence was re-melted musket balls from a shipwreck in the Bahamas.
Yeah :-) I kept it as a neat hack for selling lead from a shipwreck that had paid for itself by selling off the gold and other bits, and the salvage operator was effectively eeking out a few more bucks from the geek crowd :-).
Is this a case of someone stumbling into the concept and wanting to share it with the world? Is there some trend in SV around low-background steel right now?
Genuinely curious about the phenomenon of posts around topics that have a great deal of understanding and aren’t necessarily trending in the general news cycle.
No, low-background steel is mentioned in the replies. It's similar in the sense that GPT-3 generated text is going to contaminate the data we collect from now on.
OP answered in a sibling comment, but might additionally be interesting to know why a repost like this gets upvoted: I upvoted it because I didn't know of it (this is the first time I see it) and I wasn't aware that there is that much radiation lingering from tests decades ago, which was interesting to me.
There was a post a week or so ago where low-background steel was discussed in the comments. I can't find it on Google though. Probably someone saw that and either made a calendar reminder for a few days out to post it or had it in their open tab backlog.
Edit: I'm pretty sure it was the knife steel post.
The 75th anniversary of the first nuclear bomb test was just a few days ago, on July 16th. It's been in the news a bit lately, and this topic is related.
I'm not sure about some of the the claims of the Wikipedia article.
* First, the article implies that air continues to be the main reason for contamination of steel. It might have been the case, back when atmospheric levels for radioactive elements were higher. However now there is less contamination in the air [0], and the main source for contamination is recycled steel. Either because it itself is non-low-background steel or because e.g. medical radioactive sources were put into the scrap metal supply. See also this IAEA report on scrap metal [1].
* The article also says that the primary source for low background steel are shipwrecks, but I think that's an exaggeration. Especially, the topic came up on hn a few weeks ago and someone in the know debunked it [2].
If I understand it right, it's possible to produce non-radioactive steel but doing do is just a lot more expensive for the time being than just getting it from old sources.
The scene of the battle of Midway would also hold a hoard of nice steel (the Japanese lost a lot of ships including aircraft carriers). I understand that Scapa Flow has been heavily salvaged with only 7 out of 52 ships still down there.
The Battle of Midway was fought in spectacularly deep water, on the order of 17,000-18,000 feet deep. This would make salvaging difficult, if not impossible. Scapa Flow is shallow enough for divers.
Once we run out of cheaply salvageable steel, we'll likely turn to steel smelting processes that do not introduce air into the steel. These processes require dramatically more energy and are thus more expensive, but will still be way less expensive than attempting to salvage at deep ocean depths.
> Once we run out of cheaply salvageable steel, we'll likely turn to steel smelting processes that do not introduce air into the steel.
This would be exceptionally difficult, as oxygen is a basic requirement for steel making as we have ever known it. Steel is made from iron mixed with carbon and then heated to melt. Then oxygen is added which burns the excess carbon into carbon dioxide and reacts with all of the other reactive contaminants and brings them to the surface where they can be cupped off as slag. The melt is poured and cooled and you have steel. Early steel processes used air, blast into the furnace with high powered pumps. Modern steel is made with purified oxygen from cryogenic processes (and there are even designs floating around for steel mills which use the turboexpander from the oxygen processing to help generate electricity to drive the mill).
Without oxygen, you'd have to start with very, very clean iron ore (containing nothing but iron and whatever you wanted to alloy with the final steel), and add exactly the right amount of carbon (which is also exceptionally difficult, since carbon is light and the heat will want to make it sublime anyway). Odds are such a steel would still contain so much impurity as to require a second melt in a vacuum arc furnace, which also would dramatically drive up the cost.
While there might be a future making steel like this in space, I'm not counting it as very likely in the slightest to happen in this century.
It's much easier to use exceptionally clean oxygen - the mill could use an oxygen generation process (like a hydrogen peroxide chemical process plant being added to the mill), or by ultrafiltration of the process oxygen (which seems more realistic all told).
Iron bottom sound would definitely be a better bet, although the fact that it's a grave site definitely gives pause. Scapa Flow is relatively unique in that it's a large collection of ships, without being a grave site, and being near the surface.
> steel smelting processes that do not introduce air into the steel.
Air is perfectly fine. Both Oxygen and Nitrogen do not stay radioactive for longer than a few seconds. It's CO2 that is the problem, specifically the carbon.
And of course any other random impurity.
They could just use cryogenicaly distilled air, and take the nitrogen-oxygen part (the boiling points are very close).
Just search for the paper on the topic, written by the Phillip Morris Unbiased Research Group. it explains how frogs breathing air got more cancer then frogs trapped in airtight boxes and only allowed to breathe exhaled tobacco smoke, who mostly died for other reasons. seems legit...
Well there is much known fact about how tabacco absords radiating material. But until now I have not found anything about how that changed during the ages. But simple logic tells me there must have been an affect on how dangerous smoking is.
Im always curious how we will send messages to future civilizations. How will we ensure we’ll be remembered or even noted in 10,000, 100,000, 1 million years? How can we prevent the same disaster(s) that eventually wipes our civilisation out from repeating again in future intelligent generations (human or otherwise)
Could environmental markers like these be the way? After all, it’s how we look at the past today
This reminds me of Whisper, one of my favorite exotic alien concepts. The alien civilization in question has selected a planet with as stable environment as possible, and planted it full of genetically engineered grass. The sound of wind blowing through the grass creates an acoustic computer which hosts a virtual space its creators have uploaded themselves into.
A SF short story about a biologically encoded message from ancient aliens (written by one of the Autodesk founders):
We'll Return, After This Message by John Walker
It's fascinating that in 1983 it was thought that a 768-bit RSA number would take 40 million years to factor. (It actually took 26 - RSA-768 was factored in 2009.)
Or directly encode the message in DNA itself. I suppose the difficulty would be devising an encoding with enough redundancy or other features to preserve the information content over many generations of evolutionary pressures.
If by "stay" you mean spread microplatisc, that carries no information, then maybe. The jury is still out, but it looks like it'll last a long time.
But plastic is not a good candidate to hold messages for a long time. It degrades in a few years into some unusable stuff. Glass is a much better candidate.
Deep Time: How Humanity Communicates Across Millennia Paperback by Gregory Benford explores some of those questions. It comes into practical questions when trying to mark nuclear waste dumps.
The problem with that is, judging by our own behavior, an unknown ancient structure makes humans investigate it, try to dig it up, etc. Placing a marker isn't the problem, the hard part is communicating "nothing interesting, only death here, do not enter" in a way that someone in 10.000 years will heed the warning.
The solution is to build them everywhere and put the bad stuff in one of them. If you build enough then the chances of them excavating the one with nuclear waste is pretty low.
It occurred to me as they were taking down the cantilever (eastern) section of the Bay Bridge that lots of it would have been low-background, based on its construction in the 1930s.
It's been pointed out it's wrong but, as a sometime nuclear spectroscopist, I'm curious: why are people insisting that β-decay, i.e. ¹⁴C, is the issue?
Presumably no way that's cheaper than just getting it from shipwrecks. Doesn't seem like there's a huge demand, so old shipwrecks for the time being have enough supply.
[0] https://www.theatlantic.com/science/archive/2019/10/search-d...