UN inspectors visited a nuclear reactor Monday being built in central Iran that has been off-limits since April, the official Islamic Republic News Agency reported. "The team visited the 40-megawatt research reactor in Arak," IRNA quoted an unnamed official as saying. "The inspection took some 5 hours." The report did not provide additional details. Experts from the UN's nuclear watchdog have said access to the reactor is critical to their review of Teheran's overall nuclear activities.