Abstract: A self-powered neutron detector comprises a tubular collector, a tubular emitter surrounding this collector, and a tubular collector surrounding this emitter, with electrical insulation between the emitter and the two collectors. The collectors are electrically interconnected. This arrangement produces a detector suitable for external instrumentation on the outside of the pressure vessel of a reactor, for instance, a pressurized-water reactor.

Abstract: A self-powered neutron detector has a neutron-sensitive emitter, a collector enclosing this emitter and insulation between these two components. When irradiated by neutrons, the emitter generates Compton electrons so that a current is produced between the emitter and electrode and which may be used with a current-measuring device to provide a readout. The emitter is enclosed and electrically connected with a metal which is substantially neutron-insensitive so that the detector provides a substantially true and prompt signal accurately reflecting the neutron flux density received by the detector.

Abstract: A nuclear reactor has a reactor core and is provided with means for determining the flux density in this core, including flux detectors located in the core at fixed positions and flux probes which are movable in the core through a range of positions. Means are provided for causing the movable flux probes to go into operation automatically when the fixed flux detectors are actuated by flux densities of predetermined values.