Editing Subcritical reactor (section)

{{Short description|Device that achieves nuclear fission without triggering a chain reaction}}
A '''subcritical reactor''' is a [[nuclear fission]] [[nuclear reactor|reactor]] concept that produces fission without achieving [[Critical mass|criticality]]. Instead of sustaining a [[chain reaction]], a subcritical reactor uses additional [[neutron]]s from an outside source. There are two general classes of such devices. One uses neutrons provided by a [[nuclear fusion]] machine, a concept known as a [[Nuclear fusion–fission hybrid|fusion–fission hybrid]]. The other uses neutrons created through [[spallation]] of heavy nuclei by charged particles such as protons accelerated by a [[particle accelerator]], a concept known as an accelerator-driven system (ADS) or [[accelerator-driven sub-critical reactor]].