It was nuclear, but IRL the power wouldn’t last more than a few days. Even if the authorities had enough time to sever the local area from the grid, the plant would likely be shut down before it was abandoned (granted we’ve idea if the plant in Dawn was abandoned; given the events of Land of the dead there’s a good chance it wasn’t).
Not in the gas station I worked at. I can’t imagine a situtation (well, other than the apocalypse) when we’d ever need to. Then again it was part of a corporate chain; not a mom & pop. Anything more complicated than putting new receipt paper in or checking for a skimmer we called the hotline to have maintence sent out.