After North Korea agreed to disable its nuclear reactor for aids from the United States, South Korea, China, Russia, and Japan during six parties talk in 2007, they began to take the first of three phases, which is to close down Yongbyun nuclear power plant. This article stated that they already implemented 8 out of 11 steps to disable such facilities. As North Korea getting closer to shut down its main nuclear reactor, South Korea suggested that they are willing to buy "unused rods" in Yongbyun to use it as South Korea energy source. This article also noted that Japan has not been committed with the nuclear agreement as they reject to aid North Korea until they show significant improvement on disablement of nuclear weapons.
South Korea's decision on buying North Korea's "unused rods" is surely a non-zero-sum trade. South Korea can benefit not only from energy they would receive but also stimulate the North Korea's process on disablement. North Korea can benefit from it as they wouldn't have to throw away their "work" for nothing. Furthermore, this also could be very good for U.S or other anti-terrorist country because there were several accusations that North Korea support terrorist groups and those unused rods may have put on hands of those terrorists.