Tokyo, Japan

Japan is set to be nuclear power-free, for just the third time in more than four decades, and with no firm date for re-starting an energy source that has provided about 30 percent of electricity to the world's third-largest economy.

Kansai Electric Power 1,180 MW Ohi No.4 reactor is scheduled to be disconnected from the power grid late on Sunday and then shut for planned maintenance. It is the only one of Japan's 50 reactors in operation after the nuclear industry came to a virtual halt following the March 2011 Fukushima disaster.