I've been rewatching HBO's fantastic Chernobyl series and I just came to the part where they send the divers to open the valves beneath the reactor to release the water below to prevent a thermal explosion that would open the remaining reactors and send radioactive material in all directions, as well as level much of the surrounding area. What would be the result if this mission failed and the sand-lava reaches the bubbling pools, causing the water to instantly evaporate and creating a massive thermal explosion and spreading more radiation in Eurasia?