Complex sentence: Many of these reactors utilize highly enriched uranium (HEU), which the U.S. obtains all of its molybdenum (representing about half of global demand) from these aging nuclear reactors.
Split into simpler sentences: Many of these reactors utilize highly enriched uranium (HEU). The U.S. obtains all of its molybdenum (representing about half of global demand) from these aging nuclear reactors.