fissionfusion

Fissionfusion, often written fission–fusion, is a term used to describe systems that combine fission and fusion processes within a single device or concept. The term appears in discussions of both weapons technology and proposed nuclear energy concepts. In general, it denotes arrangements in which a fission reaction and a fusion reaction interact to produce energy more efficiently than either could alone.

In thermonuclear weapons, a fission device serves as the primary that creates the extreme conditions for a secondary fusion stage; the energy produced by fusion can then be augmented by fission in surrounding material, a configuration sometimes described as fission–fusion–fission. This architecture enables very large yields and has been the subject of historical development, although public details are limited and tightly controlled.

In fusion–fission hybrids intended for civilian use, fusion reactions provide energetic neutrons that drive fission in a surrounding blanket of fertile or fissile material. Such hybrids aim to improve fuel utilization, enable burning of certain long-lived wastes, or enhance neutron economy. Realistic implementation faces substantial technical challenges, including achieving sustained fusion power, materials that withstand intense neutron bombardment, and economic viability.

Historically, the concept emerged during the development of thermonuclear weapons in the mid-20th century, and later research has explored hybrid reactors as a potential complement to conventional fission or future fusion power. At present, no commercial fission–fusion devices exist, and most work remains at conceptual or experimental stages in specialized programs.

See also: thermonuclear weapon, fusion power, nuclear waste transmutation.