Nuclear reactors, medical equipment and uranium enrichment plants for reactors or nuclear weapons present a salad of radioactive materials in their tailings.
There are some of them, with very low half-life, but with a large emission of energy and radiation in a short time. These are more dangerous than those with a very long half-life, but emit little energy and radiation per unit time. They are less dangerous, but they last an eternity.
The necessary procedure is to condition and dispose of these wastes properly so that they do not contaminate the environment and do not affect human health.