Nun, other activists face trial for breaching U.S. nuclear security By Preston Peeden KNOXVILLE, Tennessee (Reuters) - An elderly nun and two other environmental activists who broke into a supposedly secure facility that stores enriched uranium for nuclear bombs go on trial on Tuesday over the incident that embarrassed the U.S. government. Lawyers will present opening arguments in the case of the three activists charged with sabotage and destruction of government property after they cut through several fences in July to reach the heavily guarded Y-12 National Security Complex in Oak Ridge, Tennessee. They admitted to walking for two hours through the complex, which prosecutors described as the "Fort Knox" of U.S. nuclear installations, and spray-painted slogans and hammered on the walls of an enriched uranium facility. Fort Knox is a heavily guarded U.S. military base in Kentucky where gold reserves are stored. When a guard finally confronted the trio they offered him food and began singing. The activists - Michael Walli, 64, Greg Boertje-Obed, 57, and nun Melissa Kirby, 83 - were in a Tennessee federal court on Monday as a jury was selected from among more than 70 people. Walli wore a blue t-shirt that said "Ground the drones." The other two were not visible to journalists watching the proceedings on closed circuit television in a nearby courtroom. The breach embarrassed the U.S. government and sparked investigations by Congress and the Energy Department, which oversees nuclear facilities. An Energy Department inspector general report in August found "troubling displays of ineptitude" at the complex. Shortly after the incident, the top security official at the National Nuclear Security Agency and two other federal officials were reassigned. In addition, top officials at WSI, the international security company that provided security at Oak Ridge, were removed and officers were fired, demoted or suspended. Thomas D'Agostino, then the security agency administrator, said staff involved in the incident had been removed, cameras fixed, and patrolling and training improved. In January, the security agency named a new group to manage security at the site, Consolidated Nuclear Security LLC. The group replaced Babcock & Wilcox Co, which had contracted some of security work to WSI, a unit of G4S. Also that month D'Agostino stepped down, six months after the peace activists broke into Y-12. The agency said his departure had nothing to do with the breach. The Oak Ridge facility is the primary U.S. site for processing and storage of enriched uranium and one of the primary manufacturing facilities for the U.S. nuclear weapons program. Writing by Greg McCune; Editing by Steve Orlofsky and Mohammad Zargham