External Neutron Drive for Subcritical Reactors

Graphite-moderated thermal-spectrum subcritical reactors with a long diffusion path from neutron birth to absorption can be driven effectively from a neutron production target outside of the core, in contrast to the commonly accepted view that subcritical power reactors must have the source at the reactor center. Advantages of the external target include (a) elimination of the capital cost of a heavy magnet suspended above the reactor core, (b) elimination of safety concerns related to beam-induced damage from power failure in the magnet, (c) avoiding the disruption of the core to accommodate the neutron target, (d) the elimination of difficulties of access and removal of the target or fuel from the core owing to the magnet, and (e) the elimination of power peaking around the target and related high fuel burnup and materials damage concerns. There are also gains from driving a single reactor with two external targets instead of one.