SEOUL: South Korea said on Wednesday it would oppose referral of North Korea to the UN Security Council despite a sharp escalation in the standoff over Pyongyang's nuclear ambitions. North Korea has shut down its only functioning nuclear reactor at Yongbyon, north of Pyongyang, and told a visiting US specialist that it planned to unload spent nuclear fuel from the plant and reprocess it into weapons-grade plutonium. A reactor must be shut down before nuclear fuel can be unloaded and sent for reprocessing. A senior North Korean diplomat at the United Nations, Han Song-Ryol, repeated the threat in an interview on Monday with a US newspaper, saying reprocessing would allow North Korea to "increase our deterrent," against the United States. Experts said reprocessing a full load of spent nuclear fuel from the reactor could double North Korea's nuclear arsenal.