Scientists are searching for 664 cubes of uranium developed by Nazis during World War II, the popular physics site Phys.org reported recently. The cubes are the result of unsuccessful efforts by German scientists to build a nuclear reactor. How far on the nuclear fuel cycle did they get?
Six years ago, a University of Maryland associate research professor named Timothy Koeth received one of the uranium cubes as a gift. Now, he and his partner are searching for the remaining cubes, which would’ve made part of the core of a nuclear reactor to power Germany under Hitler’s rule. However, the isolated and competitive nature of the Nazis’ energy race, led by noted scientist Werner Heisenberg, kept their nuclear dreams from becoming a reality. Their progress can be measured on what’s called the nuclear fuel cycle.
Nazi Nuclear Research – Detecting and Mining Uranium Ore
Uranium, like many metals, oxidizes after a very short amount of time outside, causing uranium ore to look like plain, brown rocks. Fortunately, uranium is always undergoing radioactive decay, thus emitting gamma rays that can be detected with a Geiger counter, which makes sounds as it passes over gamma rays and other radioactive substances. “Actually, uranium ore used to be found this way—geologists walking over the ground with a Geiger counter,” said Dr. Michael E. Wysession, Associate Professor of Earth and Planetary Sciences at Washington University in St. Louis. “Now you can fly over land in a plane equipped with a gamma-ray spectrometer. It’s like a digital camera, but it records gamma rays instead of visible light rays.”
Dr. Wysession explained that mining for uranium is largely done in open-air mining pits like other ores, but that a process called leaching is another popular method. With leaching, miners pump a liquid mixture of many chemicals into the ground that dissolve the oxidized uranium, then suck the mixture back up and separate the uranium from the initial chemicals.
Concentrating and Enriching Uranium
If uranium is mined traditionally, it must be stripped from other mined rocks, usually using sulfuric acid, then filtered and dried into a substance called yellowcake. Leaching performs the function of stripping the oxidized uranium from other rocks.
Of course, nuclear scientists can’t just dump the powdery yellowcake into a reactor, so they convert it into a usable form. “If a pressurized heavy-water reactor is used, then the uranium oxide doesn’t need to be concentrated into uranium-235,” Dr. Wysession said. “It’s fine as it is, and the yellowcake is smelted at high temperatures into pure uranium dioxide pitchblende.” According to the phys.org article, the Nazi uranium cubes had been pressurized in a heavy-water reactor. So, we know that Germany got this far at least in its nuclear process. Keep this in mind as we examine the remaining steps to achieving nuclear power.
Unlike the pressurizing heavy-water reactors, for light-water reactors, the uranium oxide gets combined with flourine and has its isotopes separated from it via centrifuge in a process called enrichment. “The outcome of enrichment is pellets enriched in uranium-235, which are very radioactive and have to be handled very carefully,” Dr. Wysession said.
Enriched or smelted uranium is then assembled into fuel rods which are lowered into the reactor core. “These fuel rods are what give off the heat in a controlled fission chain reaction,” Dr. Wysession said. “Each ton of these fuel rods will provide over 30 megawatts of electricity for five years.”
A nuclear-powered Germany may sound just one tiny step shy of coming to fruition, but according to the phys.org article, the 664 cubes of uranium still fell far short of the supply necessary to build a stable nuclear reactor. Even so, Koeth and his partner have a lot of searching to do.
Dr. Michael E. Wysession contributed to this article. Dr. Wysession is Associate Professor of Earth and Planetary Sciences at Washington University in St. Louis. He earned his Sc.B. in Geophysics from Brown University and his Ph.D. from Northwestern University.