Fissiles

Fissiles are a class of materials capable of sustaining a self‑propagating chain reaction of nuclear fission under appropriate conditions. Unlike fissile isotopes, fissiles include additional synthetic or engineered compounds designed to enhance the efficiency, safety, or controllability of nuclear reactions. The term is most often used in advanced engineering contexts and in speculative discussions of next‑generation nuclear reactors and propulsion systems.

The concept originated in the 1960s as researchers sought ways to reduce the critical mass required for a given yield. By alloying fissile nuclei with neutron moderators or by embedding them in nanostructured matrices, scientists were able to create fissile configurations that could undergo rapid, controlled fission while limiting the risk of accidental criticality. Early demonstrations of fissile cartridges in experimental reactors showed that yields could be increased while gamma‑ray output was reduced.

Industrial applications include research reactors, small modular reactors, and potential propulsion systems for spacecraft. In propulsion, fissiles would provide a high energy density source while enabling directional thrust through staged releases of fission products. Safety protocols for fissile use emphasise robust shielding, active monitoring of neutron flux, and fail‑safe containment to prevent runaway reactions.

In nuclear policy discussions, fissiles are examined for their role in non‑proliferation. Because fissile materials can more readily be converted into weapons, international treaties place stringent controls on the production, transport, and use of fissile composites. The evolving science of fissiles remains a focal point for both civilian energy innovation and strategic arms control initiatives.