How do scientists know how much radioactivity there will be?
The pattern of ingrowth varies according to the relative length of the half-lives of the original radionuclide and its decay products. Under certain conditions, decay products undergo transformation at the same rate they are produced. When this occurs, radioactive equilibrium is said to exist. Whether equilibrium occurs depends on the relative lengths of the half-live of radionuclides and their decay products. Using equations that account for half-lives, the rate of ingrowth, whether equilibrium occurs, the original amount of radionuclide, and the steps in its decay chain, scientists can estimate the amount of activity that will be present at various points.
