There is a possibility that the first explosion (there were several) was nuclear-based and not steam-based [1] and produced radioactive plasma, but the plasma

There is a possibility that the first explosion (there were several) was nuclear-based and not steam-based [1] and produced radioactive plasma, but the plasma jets cut through both the bottom and top of the reactor. [1] https://www.tandfonline.com/doi/full/10.1080/00295450.2017.1384269 https://www.tandfonline.com/doi/full/10.1080/00295450.2017.1...