Low-Background Steel (opens in new tab)

> 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.

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.

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.

nit: provenance

I saw it linked from the comments on a Tweet by Karpathy and found it intellectually curious.

> By posting GPT generated text we’re polluting the data for its future versions

https://twitter.com/karpathy/status/1284660899198820352

It could be as simple as OP being one of [today's lucky 10,000](https://xkcd.com/1053/).

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.

Low background lead was recently mentioned on xkcd[0]. Maybe that circled back to HN?

[0] https://xkcd.com/2321/

One of the latest xkcd comics mentioned low background steel. I assume that is the reason

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.

If I had to guess, the moderators curate certain technical discussions to the top.

But I’d wager that Reddit curates their front page too. There’s no way an organic algorithm is populating the front page.

> 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).

The grave site was in regards to Midway. 9 german sailors were killed while surrendering On land. None were killed on the the ships themselves.

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.

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.

https://www.orionsarm.com/eg-article/470007b39d192

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

https://www.fourmilab.ch/documents/sftriple/gpic.

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.

Unless a microbe finds a way to use it as fuel

It would certainly be big news.

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.

What about using trapped air in shipwrecks, or glaciers.