Friday, July 23, 2010

Radioactive Steel

A interesting side note about nuclear testing: all steel made since 1945 is contaminated. For millenia to come. Radioactive iron and carbon isotopes from atmospheric detonations have introduced a very small amount of radioactivity to all steel produced. It's not a harmful amount. Not even close. It's been decades sonce there were atmospheric tests. It's not even detectable by most detectors. But, it's enough that certain sensitive detectors, particularly Geiger counters, cannot be made of radioactive steel.

Usually aluminium* can be used, but if it's not, then there's only one thing to do. Pre-1945 steel must be found that has not been exposed to air that carries radioisotopes. There's not a lot of it around.

Fortunately, water is one of the best moderators known. A few feet will stop a lot of radiation, and prevent the radioisotopes in the air from reaching any steel.

Now, no one had the bright idea to stockpile a bunch of steel underwater before the first atmospheric test, but we do have the next best thing. Shipwrecks. Thousands of tons of pre-radiation steel, underwater. Unfortunately, most shipwrecks are in inconveniently deep water. The deep waters of the Atlantic and Pacific, from WWI and WWII shipping and warships.

There is one source of convenient steel, though. In June 1919, Admiral Von Reuter ordered his German fleet scuttled under the noses of their British captors to spite them. When it was over, the scuttling of the fleet left 52 ships on the seafloor of Scapa Flow, a Scottish bay. 45 of them were later raised, but 3 battleships and 4 cruisers remain. Small piece are retrieved occasionally by divers for use in instruments.


Jake said...

That's awesome! (And rather frustrating that we've contaminated almost all the steel in the world) What book is this from?

The EGE said...

Well, contaminated is a relative word. It's obscenely low-level contamination, but even a few hundred atoms per mL of metal will make a sensitive radiation detector not work.

Mostly from memory, oddly enough. Reading the book about nuclear weapons just reminded me of it.

dave.heath said...

Sorry - the essence of the story is true (that old shipwreck steel is prized for being less radioactive) but the explanation is totally false.

It's nothing to do with A-bomb tests, rather that modern steel furnaces have a radioactive trace plug in the lining to DELIBERATELY introduce a tiny amount of radioactivity into the steel. The reason is to be able to measure wear on the lining by detecting the trace radioactivity in the output metal.

The EGE said...

Interesting. I will have to check that out more, and add it to the post if it checks out.