Dual use is a term often used in politics and diplomacy to refer to technology which can be used for both peaceful and military means. It often refers to the proliferation of nuclear weapons, but that of bio-weapons is a major issue as well. Many types of nuclear reactors produce fissile material, such as plutonium, as a byproduct, which could be used in the development of a nuclear weapon. However, nuclear reactors can also be used for peaceful, civilian purposes, like providing electricity to a city. During the Cold War, the United States and Soviet Union spent billions of dollars developing rocket technology, which could carry humans into space.