Textbook discussions of a radioactive-series decay chain appear outside the normal realm of undergraduate lab experiments. This is due to the complexity of the necessary equipment and especially to the lack of availability of a suitable decay chain. Naturally occurring chains might be used, such as the buildup of ²²²Rn from an initially pure sample of ²²⁶Ra, but this adds greatly to the experimental complexity.

In our fluid flow model with bottles attached to force probes and interfaced to a computer, we now have simple but very versatile equipment that may be adjusted to any reasonable type of condition. It is now easy for us to simulate the various classes of conditions of series decay chains that are normally presented in textbooks.

With such simple equipment we believe that more undergraduate students should now have the pleasure of deriving expressions for at least the first three populations of a decay chain. The integrals involved are rather straightforward and the algebra is not cumbersome at all. This derivation is worth the effort because of the rich variety of experiments that may now be easily performed.

Many instructors may wish to use this experiment as a basis for statistical treatment of data. However, we were mainly interested in the overall qualitative agreement between theory and experimental data, and not in how close some value comes to its directly measurable amount. After all, this fluid flow from plastic water bottles through coffee stirrers is not exactly nuclear physics!