OK, figure electricity has been around for 140 or so years: mankind has survived longer without electricity than with. Why do you need a car, a plane, a ship, or the internet if you are the last person alive on Earth? If you get sick or injured, well again, it will be just like before modern medicine existed. Mankind has lived longer without than with. If you're near a city, having a pharmacy to break into for a supply of penicillin would greatly help. Grabbing a generator for electricity would be nice, but gasoline goes bad over time. You'd eventually run out of usable gasoline, maybe in as little as 6 months. Unmaintained dams would be a bigger concern for me than failing nuclear power plants. There are many dams around the US just for flood control. One local river is only 750ft wide, but before flood control, the floods were 7 miles wide. The Mississippi River flood of 1927 put 27,000 square miles of land under 30ft of water. The real question is: if you were truly the last person alive on the planet, how long would you want to survive? When do you think isolation psychosis would kick in for you? The species ends with you, no matter what.