A small capsule measuring just six by eight millimeters has caused a stir in Western Australia. She fell off the truck unnoticed during a 1,400-kilometer truck journey from a mine to a depot sometime between January 10 and 16, 2023. The loss was extremely worrying because the capsule contains radioactive cesium-137 and emits intense gamma rays.
Anyone who gets too close to this object and is exposed to its radiation can suffer skin burns and also long-term radiation damage. The Western Australian Department of Health issued a warning, published a photo of the capsule and recommended that a minimum distance of five meters be maintained. However, this is easier said than done when a person on the route in question does not even notice what may be lying on the ground nearby.
The loss was only noticed on January 25 when the truck was unloaded. Since then there has been an intensive search for the radioactive capsule, and the much-cited comparison with the needle in a haystack comes to mind. After all, in contrast to the proverbial needle, the capsule makes itself felt through the emitted radiation. Therefore, the lost capsule can always be tracked down with a measuring device.
With a distance of 1400 kilometers, however, this was a huge challenge. The relief that the dangerous capsule could actually be tracked down after days of searching is all the greater. She was spotted by a search vehicle equipped with radiation detectors, which was traveling the route at a speed of 70 kilometers per hour.
A higher speed would probably have prevented success, because the detector has to be in the vicinity of the source for a while for the locally increased radiation to be able to stand out from the general noise. The search vehicles and teams had used the GPS data recorded in the truck to be able to trace the exact course of the route.
In the meantime, it had not been ruled out that the small capsule could have become lodged in the profile of a vehicle traveling on the Great Northern Highway. Then the capsule could have been taken somewhere. Drivers who were traveling on the said route were asked to check the tires of their vehicles - but unfortunately this could not be done with a minimum distance of five meters. All in all, the probability was quite high that the capsule would never be tracked down again.
The gamma radiation emitted by cesium-137 is used in many technical and medical ways. It is used, for example, to irradiate tumors in cancer medicine, to calibrate radiation meters or to measure the thickness of pipe walls.
In addition to gamma radiation, cesium-137 also emits so-called beta radiation, which consists of high-energy electrons. These only have a short range in air and even more so in solid matter, so that they play no role in the technical applications of radiation and they also pose a significantly lower risk than gamma radiation. It can enter the human body and damage biomolecules there due to its energy. This can induce cancer cells.
Cesium-137 is formed during nuclear reactions in nuclear power plants. When a reactor exploded in Chernobyl in 1986, large amounts of cesium-137 were released into the environment and transported to Western Europe by easterly winds.
Experts estimate that a total of 500 grams of cesium-137 fell over Germany at the time. That doesn't sound like much, and yet even the smallest amounts are dangerous. For example, in the years after the disaster, the mushrooms in Bavaria were so heavily contaminated with cesium-137 that they were unfit for human consumption.
To date, the cesium problem caused by Chernobyl has not entirely disappeared. Because cesium-137 has a half-life of 30 years. This means that after this period of time only half of the cesium atoms have disappeared because they have decayed. In 2016 there were still 250 grams of cesium-137 from Chernobyl in this country.
"Aha! Ten minutes of everyday knowledge" is WELT's knowledge podcast. Every Tuesday and Thursday we answer everyday questions from the field of science. Subscribe to the podcast on Spotify, Apple Podcasts, Deezer, Amazon Music, among others, or directly via RSS feed.