Kind of impressive thinking how much energy that is considering all the control rods are in place and this is the residual heat, just a tiny percentage of what it puts out when operating normally.
What I can’t figure out is how they keep things from cracking and breaking when you start dumping cold sea water on something that hot, the contractions in size alone must have a lot of very close tolerance equipment moving all over the place.
I suspect that is part of the issue. Can’t just turn the fill pipe on and blast it with a few thousand gallons of cold seawater. Probably have to sneak up on it. Yes, impressive amount of heat left in the core.
It is not only residual heat. There is some natural radioactive decay of the materials going on. I am told this is on the order of 5-8% of the plant output, at least immediately after a shut-down. It probably reduces a little once you get past a few half-lives of the shorter-lived isotopes.