Mark Uhran, director of the international space station division at NASA headquarters in Washington, is leaving the agency July 27 to join the U.S. Department of Energy’s Oak Ridge National Laboratory in Tennessee.

“This has been a very difficult decision for me because my passion throughout the program’s long history has been to ensure that the space station be used in the most productive manner possible, and that it yield useful applications in science & technology worthy of the international investment,” Uhran, a long-time NASA manager, told colleagues in a July 13 email.

Uhran said his new position at Oak Ridge involves the International Thermonuclear Experiment Reactor, a global effort to construct a large-scale nuclear fusion reactor in France.