Radioactive waste from spent fuel rods, old nuclear weapons, and radioactive pharmaceuticals is like a two-year old at a birthday party. It has astonishing energy, gets into everything, and wreaks havoc with its environment if you leave it unattended. If we tremble before the terrible twos, how can we control radioactive waste?
Both kids and radioactive material need supervision. Like a child, an energetic radioactive molecule will become less energetic as it ages. Certain materials, like those used in radioactive medicines, have only low-level radioactivity and will decay in only a few days or months. This type of radioactive waste can be stored under strict supervision until its radioactivity has decayed and it can be disposed of as any other solid waste.
Like a two year old, radioactive waste can get into everything: water, soil, plants and animals. One way to control it is to trap it in ceramic-type materials so that it can't escape into the environment. Hopefully, by the time the ceramic breaks down, the radioactivity will have decayed and will no longer pose a threat.
Whether encased in ceramic or not, materials with a long life, (like weapons-grade plutonium and reactor-core uranium), can't be supervised for the thousands of years it will take to decay. We hope that if we store it in stable geological formations, it will sit undisturbed for thousands of years. However, if the ceramics or storage containers become corroded, the radioactive waste might leak before it has decayed. Nuclear waste can't be stored and forgotten: it presents problems for future generations because the dangers of the waste can be minimized, but not completely eliminated.