Apparently one of the big issues facing nuclear power plants is keeping the reactors cool, and this is a factor regardless of age/design. From articles I've read, plants are required to have 8 hours of battery backup for cooling, but there's concern that this may be inadequate. I won't be surprised to see additions/modifications made to plants in the US as result of seeing how difficult it is to contain a plant after a sustained outage. Any number of severe weather events, earthquakes, operator accidents, etc could impact a plant, requiring emergency cooling for weeks/months on end until a complete shutdown could occur.
