>>14278281K I read up on this, it's a VVER-1000/320 model reactor, it's a pressurized water moderated reactor design with a thermal output of 3 GW and a negative void coefficient (no Chenobyl explosions), and there are 6 of them at this power plant.
Reactors produce about 5% of their full power heat load through decay heat, which doesn't shut off after fission stops, so immediately after reactor shutdown each core will be producing 150 megawatts of heat. Over the next few days this heat output will drop, since it's coming from short lived fission products, but it's still going to require a serious amount of cooling. The VVER-1000 has really big pressure header tanks mostly full of coolant water, but in the event of an emergency where all exterior cooling is removed they would likely need to vent the primary heat transfer loop to atmospheric pressure then pump in lake water. It's much better to ruin the entire reaction vessel with lake sediments than it is to let the cores melt down.
I would hope that the entire facility has already scrammed the reactors the moment they were attacked, and hopefully beforehand, but they're still likely managing almost all of that 150 MW of thermal decay power output per core right now (for the facility that's a total of 900 megawatts of heat). I would say that at worst we are looking at a Fukushima level whoopsie, not a chernobyl level uh-oh.
