January 31, 2007 1896 Antoine Becquerel discovers radioactivity. 1942 Scientists at the University of Chicago create the first self-sustaining nuclear reaction. 1951 An experimental nuclear reactor in Arco, Idaho, produces enough electricity to power four light bulbs. 1954 The Atomic Energy Act authorizes development of nuclear energy for civilian use. 1957 First commercial nuclear-powered generating station is built in Shippingport, Pa. 1979 Mechanical failure and human error cause loss of coolant from the reactor core at the Three Mile Island power plant, near Middletown, Pa. 1986 Chernobyl disaster occurs in Ukraine, then part of the Soviet Union. Contamination from the radioactive fallout spreads to 58,000 square miles. 1996 Last nuclear plant in the U.S., Watts Bar-1, in Spring City, Tenn., comes online. 2003 Dominion Power and Exelon file applications to build nuclear facilities in Virginia and Illinois, respectively. The facilities would be the first new reactors since 1996.