Placing an atomic energy source on the lunar surface is “not science fiction,” experts say, but does pose technical challenges.

Nuclear power on the moon is critical to the United States' space exploration and national security goals, and the U.S. government should "move quickly" to build reactors there before its terrestrial rivals, according to a directive issued by Transportation Secretary and acting NASA Administrator Sean Duffy, which was obtained by ABC News.

Is NASA going to put a nuclear reactor on the moon? Here's what Sean Duffy said about U.S. race against China in space and going to Mars.