The civilized world has ended because of some super-plague. Maybe half a percent of the population survives. Thirty million people, spread across the entire world. Most of them in isolated, non-urban places. The human race will most likely survive, but there is going to be a lot of wandering about in the meantime.

It is during this period that a group of people has tasked themselves with saving these last, fleeting embers of the world. By safely turning off all of the nuclear power plants in the world.

Left to their own devices, the power plants would shut themselves down, but the core reactions would eventually cause the safety systems to breakdown. Radiation would leak, meltdowns would happen.

It would be very annoying to survive a biological holocaust just to die in a nuclear one.