Read More North and South Korea exchange machine gun fire  A permanent solution remains elusive, with experts dismissing as unrealistic hopes that Seoul will be able to revise a 40-year-old nuclear agreement with Washington so it can reprocess spent fuel.  U.S. and South Korean government officials declined to comment on the issue.  Reprocessing is a costly and technologically challenging solution that has fallen out of favor in Britain, France and elsewhere.  It is also diplomatically thorny given concerns about nuclear proliferation, especially on the Korean peninsula, where North Korea is trying to develop nuclear weapons.  A medium-term, safer solution could be to store spent fuel in metal and concrete-covered dry casks, which could hold it for up to 100 years. Building casks for the country's existing spent fuel would cost up to $2.6 billion, according to Reuters calculations based on industry figures.  Read MoreNorth Korea leader Kim is still in charge, has leg injury  But persuading people to live next to such facilities would be a huge task in an Indiana-sized country with a population of 50 million, with many already bitter about the presence of reactors.  "As a resident, we are concerned as we live near such dangerous materials," said a woman who runs a sushi restaurant 10 kilometers (6 miles) from the country's oldest nuclear reactor near the southeast coast. She did not give her name.  "It is hard to know the situation at the reactor as we usually learn of any developments via media reports."  Underlining the difficulty authorities face winning over the public is the case of a new site to store low- and medium-level radioactive waste such as contaminated clothing and tools. The facility, in the southeastern city of Gyeongju, is yet to open after years of delay as opponents questioned its safety.  In Samcheok, another southeastern city, 85 percent of nearly 29,000 participants in a non-binding ballot last Thursday voted against plans to launch a new reactor, emphasizing anti-nuclear sentiment in the country.
South Korea has around 70 percent of its used fuel stacked in temporary storage pools, with some sites due to fill by the end of 2016.