First, I have for you a graphical representation of the difference in energy radioactive energy between like amounts of Potassium-40 (as in a banana) and Cesium-137:
Using a standard American Football field as a unit of measure (100 yards, or about 91 ½ meters), if a human hair’s thickness represents the energy in a unit of Potassium 40, take the graphic below, which represents 18 rows of 60 football fields:
Think of the thickness of that human hair (0.001 mm) representing the energy of Potassium 40, stand in the end zone of a football field and place the hair underneath the goal post. Now imagine all the pictured football fields end-to-end (all 1080 of them, representing 108,000 yards).
THAT’s roughly how much more energy Cesium-137 has than Potassium-40. Again, 100 Billion times more energy.
However, if you can imagine that it could, it does get much worse than that: The graphic above does not take into account the daughter product of Cesium-137’s decay, which is Barium-137; the graphic only accounts for the Beta radiation of Potassium-40 & Cesium-137, not the Gamma resulting from Barium-137.
The specific activity of Barium-137 is 540 million Curies/gram ¬– on top of Cs-137’s 88 Ci/g solely from beta decay – as compared to Potassium-40’s; put that in your banana and smoke it.