ULSAN, South Korea (AP) - North Korea's weapons program is not the only nuclear headache for South Korea. The country's radioactive waste storage is filling up as its nuclear power industry burgeons, 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. South Korea is now the world's fifth-largest nuclear energy producer, operating 23 reactors. But unlike the rapid growth of its nuclear industry, its nuclear waste management plan has been moving at a snail's pace. A commission will be launched before this summer to start public discussion on the permanent storage of spent nuclear fuel rods, which must be locked away for tens of thousands of years.