Leftovers from nuclear reactors contain the element neptunium. To safely store the waste, scientists need to know more about how to control neptunium’s chemistry. Knowing the stability of different oxidation states is central to chemical control. The +3 oxidation state is generally inaccessible in aqueous (water-based) solutions. Researchers devised an easy way to access neptunium in the +3 oxidation state. Using this method, the team discovered new neptunium properties. They also found out how neptunium’s stability in this oxidation state compares and contrasts with plutonium.