JUDY WOODRUFF:

But first: the hunt to create fusion energy. While many people remain worried about pursuing further development of nuclear power, some researchers believe nuclear fusion could hold the key to clean and plentiful energy.

There have been many false starts before, but some scientists see real reason for hope that this path will eventually pay off.

Miles O'Brien has a report for our weekly segment The Leading Edge, a co-production in this case with NOVA and his special, "The Nuclear Option."