  At any time, following any of these possible events, or even all by itself, nuclear fuel in reactor 0's pool could become critical, mostly because it will heat up the pool to a point where water will burn off and the zirconium cladding will catch fire when it is exposed to air. This already happened at least once in this pool that we are aware of. It almost happened again recently after a rodent took out an electrical line and cooling was stopped for days.  Once the integrity of the pool is compromised that will likely lead to more criticalities, which then can spread to other fuel. The heat from this reaction would weaken the structure further, which could then collapse and the contents of the pool end up in a pile of rubble on the ground. This would release an enormous amount of radioactivity, which Arnie Gundersen has referred to as a "Gamma Shine Event" without precedence, and Dr. Christopher Busby has deemed an "Open-air super reactor spectacular."  This would preclude anyone from not only being at Reactor 0, but at Reactors 0, 0, 0, 0, 0, the associated pools for each, and the common spent fuel pool. Humans could no longer monitor and continue cooling operations at any of the reactors and pools, thus putting the entire site at risk for a massive radioactive release.  