Hecker discusses his visit with scientists at Yongbyon and government officials in Pyongyang from Feb. 12 to 16. Joel Wit, a former U.S. State Department official, and Keith Luse, a staffer for Sen. Richard Lugar, R-Indiana, accompanied him during a private visit that also involved discussions on formalizing health and educational exchanges between the North Korea and the U.S.

» Photo gallery of Siegfried Hecker's tour through the 5Mw Yongbyon Nuclear facility