This interests Washington because light-water reactors produce far less plutonium than graphite technology.
"These light-water reactors are simply not on the table."
He said "the right moment to consider" helping the North build a light-water nuclear reactor was after it gave up all of its weapons programs.
It is also intent on eventually receiving a new light-water nuclear reactor and help with its electricity needs in the meantime.
Officials said the plan to build light-water reactors could be scrapped.
They will be light-water reactors, in which ordinary water is used to moderate the nuclear reaction.
Washington favors the change because light-water reactors yield less plutonium.
Perhaps light-water reactors would have prevailed in any event.
North Korea was promised two light-water reactors to end its nuclear arms program in a 1994 deal reached with the Clinton administration.
"A light-water reactor cannot be used for developing nuclear weapons," he said during the tour.
