I saw a comment the other day that “steel forged before the nuclear age is very valuable.” and talked about the lengths they go to salvage old battleships etc. for steel made “before the Manhattan project.” What does this mean? How did nuclear testing permanently affect steel worldwide?

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I saw a comment the other day that “steel forged before the nuclear age is very valuable.” and talked about the lengths they go to salvage old battleships etc. for steel made “before the Manhattan project.” What does this mean? How did nuclear testing permanently affect steel worldwide?

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Basically, the global radiation level has gone up because of nuclear testing. It’s not a super harmful amount, but it creates small imperfections in steel. It’s called low-background steel.

It’s mostly valuable for super sensitive devices used to direct radiation.

To keep the topic simplified, the usage of nuclear weapons introduced trace amounts of radioactive isotopes (atoms) into the atmosphere.

Because the process of producing iron involves air, it’s impossible (or very expensive/difficult) to avoid a slight radioactive contamination of the finished iron.

As such, steel produced before the era of nuclear weapons is very desirable for applications where little background radiation activity is required.

[Wikipedia could probably also provide a better explanation](https://en.m.wikipedia.org/wiki/Low-background_steel)

Certain applications require steel with very very very low radioactivity, and the [Low Background Steel](https://en.wikipedia.org/wiki/Low-background_steel) is generally only acquired through salvaging steel made before the first nuclear tests

Steel is generally made using air from the atmosphere which now contains a low level of Cobalt-60 which is radioactive. This cobalt gets trapped in the steel and gives it a low radiation signature.

Unless you’re building a tool to detect low level radiation it doesn’t really matter, but if you’re trying to build a Geiger counter or an even more precise instrument then the low level radiation from the trapped cobalt 60 can give you false readings.

Nuclear weapons were detonated in the atmosphere, starting with the Trinity blast in New Mexico (no Japan wasn’t the first place atomic bombed). Previously unknown radioactive atoms were released, and they went everywhere, including junkyards and iron mines.

Removing these elements in the steel making process is unaffordable, as their concentration is very low. Steel is not just used for structural things, it’s used for shielding in certain scientific sensors because of unique magnetic and radiation properties. When you’ve put up a meter thick steel shield to block radiation, it’s super-bad if the steel has radioactive impurities in it. So, you are willing to pay more for low background steel. Yes, large pieces of steel with this property were used to make WWII battleships, and it’s worth salvaging.

Lots of good answers here, and I’ll add one point: natural iron ore in the ground isn’t contaminated with radiation; this happens *in the refining process*, which involves exposure to *contaminated air* at high temperatures.

In principle, we *could* make low-background steel from freshly-mined ore, but it would be expensive — and it’s a lot cheaper to just salvage pre-WW2 shipwrecks, because we have a *lot* of those. At the end of WW1 the German fleet surrendered to the Allies and was interned at Scapa Flow in Scotland, and their admiral pulled a fast one by scuttling the ships one night to keep them out of the Royal Navy. They are there to this day, gradually being stripped of steel parts.

Modern steel is made by blowing a huge amount of air through the furnace.

Since the first nuclear weapon detonation, the air has a small amount of radioactive isotopes, which attach to the steel when the air is blown through it. That means that all steel made today steel has very low radioactivity, and it remains through forging, recycling, or other manufacturing.

Steel that was smelt before the first nuclear detonation has much, much lower levels of radioactive particles. Because the air was blown through it before WWII.

It’s important for products that require very low levels of radioactivity in their construction (like a Geiger counter, which wouldn’t be very useful if it constantly detected it’s own steel’s radioactivity).

One of the best sources of steel that was absolutely made prior to WWII is a battleship that sank early in WWII.

Also, keep in mind, since this is explain like i’m five. Many here have missed a detail. Steel and Cast Iron are very similar in elemental makeup. Steel is iron with less than 2% carbon. If that same iron has 2.1% or greater it becomes classified as Cast Iron. This doesn’t directly answer the question, it’s just a detail that shouldn’t be looked over.

[https://www.youtube.com/watch?v=Rme9cGXyY8M](https://www.youtube.com/watch?v=Rme9cGXyY8M)

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Here is a short video explaining it

I see the other comments on low background radioactivity. I argue that it is for use in historic forgeries.

If the steel was worth that much then I wouldn’t know about all of the 1930’s-and-earlier vehicles I know about that are still just sitting. You can argue that they are rusty and need processed to make technical steels but that processing could be done in a noble gas environment.