The following video shows a demonstration of the decay of protactinium. The protactinium source is in a bottle just below the GM tube on the left hand side of the screen. Readings may be taken from the counter and corrected for background (around 6 counts every 10 seconds) and a decay curve plotted, from which the half-life may be calculated.

The readings are taken over ten second intervals with gaps of 2.5 seconds between each set of readings.