Are you making your own decisions and mainlining causality like a sucker? Why go through the agony, when you could hand over the railway switch of determinism to a machine that can decide things for you! Enter the DeDeterminator, a decision machine from [Oliver Child].
The construction is simple enough, being built inside a small tin. One kind of wishes it had a secret third “PERHAPS” bulb that illuminates only when the universe’s continued existence has been called into question.
The idea is simple. At the press of a button, the DeDeterminator illuminates a bulb—indicating either yes or no. The decision for which bulb to illuminate is truly random, as it’s determined by the radioactive decay of a Americium-241 alpha particle source. A Geiger-Muller tube is used to detect alpha particles, with the timing between detections used to determine the yes-or-no output of the device.
It’s a neat concept, and it’s kind of fun knowing that your decision is both out of your hands and as random as it could possibly be. Would the universe guide you wrong? Who could possibly question the reasoning of the particles? The only rational move could be to comply with whatever directive the box hath given. Just don’t ask it to make any decisions with dangerous outcomes.
We’ve featured other projects using radioactive decay for random number generation before, though they weren’t quite as philosophically intriguing as the DeDeterminator. Mostly they’re just about cryptographic security and such, but some do deal with causality in imaginary spaces, which has its own magic about it.
Meanwhile, if you’ve untangled the quantum chains of cause and effect, or you’ve just found a way to break RSA encryption using a Pi Pico, do drop us a line, won’t you?
The nuclear age changed steel, and for decades we had to pay the price for it. The first tests of the atomic bomb were a milestone in many ways, and have left a mark in history and in the surface of the Earth. The level of background radiation in the air increased, and this had an effect on the production of steel, so that steel produced since 1945 has had elevated levels of radioactivity. This can be a problem for sensitive instruments, so there was a demand for steel called low background steel, which was made before the trinity tests.
The Bessemer process pumps air through the iron to remove impurities. shropshirehistory.com
The production of steel is done with the Bessemer process, which takes the molten pig iron and blasts air through it. By pumping air through the steel, the oxygen reacts with impurities and oxidizes, and the impurities are drawn out either as gas or slag, which is then skimmed off. The problem is that the atmospheric air has radioactive impurities of its own, which are deposited into the steel, yielding a slightly radioactive material. Since the late 1960s steel production uses a slightly modified technique called the BOS, or Basic Oxygen Steelmaking, in which pure oxygen is pumped through the iron. This is better, but radioactive material can still slip through. In particular, we’re interested in cobalt, which dissolves very easily in steel, so it isn’t as affected by the Bessemer or BOS methods. Sometimes cobalt is intentionally added to steel, though not the radioactive isotope, and only for very specialized purposes.
Recycling is another reason that modern steel stays radioactive. We’ve been great about recycling steel, but the downside is that some of those impurities stick around.
Why Do We Need Low Background Steel?
Imagine you have a sensor that needs to be extremely sensitive to low levels of radiation. This could be Geiger counters, medical devices, or vehicles destined for space exploration. If they have a container that is slightly radioactive it creates an unacceptable noise floor. That’s where Low Background Steel comes in.
A person is placed into a low background steel container with sensitive equipment to measure the radioactivity of the body, which may be near the background level. Photo from orau.org
So where do you get steel, which is a man-made material, that was made before 1945? Primarily from the ocean, in sunken ships from WWII. They weren’t exposed to the atomic age air when they were made, and haven’t been recycled and mixed with newer radioactive steel. We literally cut the ships apart underwater, scrape off the barnacles, and reuse the steel.
Fortunately, this is a problem that’s going away on its own, so the headline is really only appropriate as a great reference to a popular movie. After 1975, testing moved underground, reducing, but not eliminating, the amount of radiation pumped into the air. Since various treaties ending the testing of nuclear weapons, and thanks to the short half-life of some of the radioactive isotopes, the background radiation in the air has been decreasing. Cobalt-60 has a half-life of 5.26 years, which means that steel is getting less and less radioactive on its own (Cobalt-60 from 1945 would now be at .008% of original levels). The newer BOS technique exposes the steel to fewer impurities from the air, too. Eventually the need for special low background steel will be just a memory.
Oddly enough, steel isn’t the only thing that we’ve dragged from the bottom of the ocean. Ancient Roman lead has also had a part in modern sensing.
Here’s a hypothesis for you: radioactive decay varies over time, possibly with a yearly cycle. [Panteltje] decided to test this hypothesis, and so far has two year’s worth of data to comb over.
Radioactive decay can be easily detected with a photomultiplier tube, but these tubes are sensitive to magnetic fields and cosmic rays that would easily fly through just about any shielding [Pantelje] could come up with. Instead, the radiation in this setup is detected with simple photo detectors, pressed right up against a tritium-filled glass ampoule, a somewhat common lighting solution for fishing lures, watch faces, and compasses.
The experimental setup records the photo detectors, a temperature sensor, and a voltage reference, recording all the data to an EEPROM once an hour. All the important electronics are stuffed into a heatsinked, insulated, light-proof box, while the control electronics reside on a larger board with battery backup, alarm, indicator LEDs, and an RS232 connection.
After one year, [Pantelje] recorded the data and reset the experiment for another year. There are now two years worth of data available, ready for anyone to analyze. Of course, evidence that radioactive decay changes over the course of a few years would turn just about every scientific discipline on its head, so at the very least [Panteltje] has a great record of the output of tritium lights against the expected half-life.
Fortunately, this is a problem that’s going away on its own, so the headline is really only appropriate as a great reference to a 
