Nuclear fission is currently considered the cleanes way to generate electrical power due to it not producing carbon dioxide or similar byproducts…
However there is a big problem with these power plants due to the way these generators work. Let me Explain.
In these power plants power is generated by inserting fuelrods of usually Uranium-235 into water. The fission then gets started by “shooting” neutrons at the uranium thus converting it into the radioactive and unstable Uranium-236. This Uranium-236 decomposes into smaller atoms for example Krypton and Barium, as well as additional neutrons that start new reactions themselves resulting in a chain reaction. If this process would not be regulated by a so called “Medium” absorbing some neutrons and hereby controlling reaction speed and temperature of the system it would come to a meltdown. In most modern reactors the water not only functions as a way to convert the energy of the fission to electricity via steampower but also as a medium, but never the only medium, since the water vapor absorbs less neutrons per volume, what was one of the reasons for the nuclear meltdown at the Tschernobyl.
All this does not seem so bad, however the byproducts of this reaction (for example the Barium) are highly radioactive and give off dangerous levels of radiation while in the process of decaing to other elements that are radioactive themselves. The speed of this process is described by the so called “Half-life” – the time it takes for half the atoms in a batch to decay to another element with another Half-life.
For example the Half-life of Barium-141, a byproduct of nuclear fission, is 18 minutes and a few seconds. That doesn’t seem so bad but keep in mind after these 18 minutes it will take another 18 minutes for another half of the not yet decayed haft to decay and so on. And it doesn’t stop there, the Baruium decays to form Lanthanum-141 that itself has a Half-life of roughly 5 hours and 30 minutes.
So the big problem is the huge amount of radiation released by this decay process that lasts for a very long time and we still dont know how to get rid of this waste.