A senior official from the UN nuclear watchdog prepared Monday for a rare visit to North Korea for discussions on how the agency's inspectors would monitor and verify the shutdown of the Yongbyon nuclear reactor. Olli Heinonen, the International Atomic Energy Agency's deputy director general for safeguards, arrived in Beijing early Monday and was due to fly to Pyongyang Tuesday for a five-day visit, along with three colleagues. "Now we are going to go to negotiate the details: how to verify and make sure the reactors will be shut down at Yongbyon," Heinonen told reporters upon arrival at Beijing's International Airport. He said he was unsure whether he would have a chance to actually visit the Yongbyon site. North Korea, which expelled UN inspectors in late 2002, announced last week that it invited a "working-level delegation" to discuss procedures for shutting down the plutonium-producing facility. North Korea had pledged in February to shut down the Yongbyon reactor, its main processing facility.