neutronsand

Neutronsand is a fictional or hypothetical material described as a sand-like aggregate that contains free neutrons embedded within a granular matrix. It is not a real substance, and its existence is limited to thought experiments and science fiction contexts, where neutron-rich media serve as plot devices.

In imagined models, neutronsand comprises ordinary sand (silica-based grains) with nano- or micro-scale porosity that is either able to trap neutrons or to be continuously replenished by an external neutron source, such as a reactor or spallation facility. Free neutrons decay with a half-life of about 14.7 minutes, so timing and supply are central concerns.

Potential properties in speculative depictions include elevated energy density, unique neutron scattering behavior, and the possibility of transient energy release. However, any real-world material would undergo nuclear activation, producing radioactive isotopes and heat. Handling neutronsand would require significant shielding and radiological controls, making practical use highly problematic.

Feasibility is constrained by fundamental physics: free neutrons cannot be indefinitely confined in a solid without an external source, and continuous replenishment would be essential. No experimental realization exists, and discussions remain within theoretical or fictional domains rather than established science.

In fiction and academic thought experiments, neutronsand is used to explore neutron economy, shielding limits, and the challenges of maintaining a neutron-rich medium. See also: neutron sources, nuclear shielding, neutron moderation.