The head of the U.S. National Nuclear Security Administration announced on Friday he would step down on Jan. 18.
Thomas D'Agostino has led the semiautonomous branch of the Energy Department for the past 5 1/2 years. He will be replaced on an acting basis by Neile Miller, who has served as NNSA principal deputy administrator since August 2010.
The nuclear agency was established in 2000 to manage key national security efforts, including oversight of the DOE nuclear arms complex and organizing nuclear nonproliferation projects around the world.
D'Agostino spent 36 years in federal service, in recent years working concurrently as NNSA chief and DOE undersecretary for nuclear security.
During his tenure "we have eliminated or secured hundreds of nuclear weapons worth of nuclear materials," Energy Secretary Steven Chu said in prepared comments. "We have reduced the number of deployed warheads to the lowest level since the 1950s -- an approximate reduction of 85 percent from the darkest days of the Cold War -- while successfully maintaining the safety, security, and effectiveness of a shrinking stockpile."
The organization and its component parts, including nuclear research sites in several states, have faced troubles in recent years. Most recently, there have been questions about the spiraling costs of some projects and renewed security concerns after several peace protesters were able to enter a protected area that houses highly enriched uranium at the Y-12 site in Tennessee.
The situation led lawmakers to press for NNSA reforms. Representative Michael Turner (R-Ohio) called for limiting Energy Department oversight of the agency as a means of addressing spiking expenses. His measure failed to survive as a component of defense authorization legislation the House approved this week.
"I'd like to thank Tom D'Agostino for his service to the nation over the past 30 years, including over five years as administrator of the National Nuclear Security Administration," Turner said in a prepared statement. "I have always respected Tom's service to this nation, including during several very difficult years as administrator."