Lead isotopes, also called lead isotopes are a group of radioactive elements that were originally used to track the position of ships in the ocean. Today, such elements are used to track radioactive fallout from nuclear disasters such as the Chernobyl accident in 1986 and Fukushima disaster in 2011.
In the year and a half since Fukushima, nuclear power in Japan has been reduced to a level not seen since WWII. And as we’ve learned from the Japanese earthquake and tsunami, the radiation levels in Chernobyl are still way higher than they were in the days when the bomb was used to kill two million people.
The isotopes that fuel nuclear fission are usually radioactive when they’re used, but they quickly decay to almost nothing—this is called “half-life.” So if you have one isotope, you’re likelier to have another one. If you’re just unlucky enough to be exposed to a nuclear bomb, you’re still going to have a long half-life.
So the isotopes are essentially like the nuclear fuel of the bomb. The more radioactive the isotope is, the longer it takes to decay into nothing. The isotopes used in Chernobyl were pretty much all carbon-14, which is a long-lived isotope and is easily stored inside of a nuclear weapon. So the fact that Chernobyl had higher levels of carbon-14 than Hiroshima was just a coincidence.
The problem is that the longer the isotopes decay, the more radioactive they become. And they become more and more radioactive as you go farther away from the explosion. The farther you get from the explosion, the more radioactive it becomes. So the very definition of a nuclear war makes it impossible for people to leave Chernobyl, where the most radioactive isotope is one-third of the bomb’s radius.
The radiation levels in Chernobyl are a bit higher than Hiroshima because the Chernobyl explosion was far larger and spread a lot of radioactive material around a lot more. The radioactive isotopes in Hiroshima are spread a lot more uniformly, making them a bit less dangerous. But still, there is a wide enough radioactive zone left that there’s no way to leave.
The Russians say that an isotope of uranium the size of one-tenth of the bomb radius is used in the Chernobyl disaster. The Chernobyl disaster was the world’s most powerful nuclear explosion, so it is difficult for a nuclear physicist to explain how the isotope was found on the ground. The Russians were so confident about its presence that they sent a team of scientists to look for it, and they found the isotope.
But there are still no leads on where it came from. The Russians think that the whole world is contaminated with the isotope, but they cannot explain how it got there or how it got into the hands of the Soviets.
The Russians are convinced that they have found the source, but so far they have not offered a satisfactory explanation. The best they can come up with is that the isotope was found in a very small quantity and that it’s been hiding in the environment for a while.
They may be right about that, but that doesn’t prove anything. It just means that whatever it is, it’s not in a location that the Russians would have access to.