I had not, but TIL about xenon poisoning and that it was a major contributing factor in the Chernobyl accident (the tl;dr is they did a test where they reduced the fission rate; there was a buildup of Xenon 135 because of that, which caused the reaction to not start back up as fast as the operators thought it should. They removed the control rods almost completely, and when the Xenon stopped doing its thing they had a runaway reaction on their hands.