[Cthulhu_]

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.

[shkkmo]

The xenon poisoning is why they took the control rods all the way out, but the runaway reaction was probably caused by the graphite tips on the ends of the control rods. As the control rods were scrammed these tips passed through areas of high neuton flux and caused a spike in power which probably caused the explosion.

There were a lot more factors at play in the chain, but the burnoff of the xenon wasn't itself the proximal cause of the explosion.