I literally just finished listening to the latest on NPR: once the electricity for pumping the coolant went out, they went to their first back-up system, generators. They didn't work.
They're now on their second back-up system, batteries, with a life of about 8 hours.
After that the choices get uncomfortably difficult.
I'm hopefully certain that it will never come to this, but the words "Three Mile Island" and "Chernobyl" were uttered a few times during the report.