PACKED STORAGE: South Korea's radioactive waste storage is filling up, but what South Korea sees as its best solution — reprocessing the spent fuel so it can be used again — faces stiff opposition from its U.S. ally.

NUCLEAR PROBLEM: South Korea It is now the world's fifth-largest nuclear energy producer, operating 23 reactors. A commission will be launched before this summer to start public discussion on permanent storage of spent nuclear fuel rods.

THE TREATY: Nuclear technology was originally transferred from the U.S. under a 1973 treaty that governs how its East Asian ally uses nuclear technology and explicitly bars reprocessing.