One group of terrorism experts believes criminals and terrorists could, would, and probably will use nuclear terrorism at some point either to threaten or to cause mass destruction. Possible scenarios of access to nuclear weapons are the theft of a nuclear bomb; the theft of weapons-grade, fissionable material for the construction of a homemade bomb; the theft and dispersal of radioactive plutonium particles into the air; and attacks on nuclear power plants. Each of these scenarios must overcome significant security obstacles. If mass casualties were a prime objective of terrorists, nerve gas is more easily accessible than nuclear weaponry. Terrorism authorities who do not believe a terrorist nuclear threat is a serious risk cite the lack of serious incidents in a nuclear age now over 40 years old. 3 references.