Abstract: When monitoring the period of a nuclear reactor, a signal representing the reactor power is generated and compared with a reference signal. When a difference between the power signal and the reference signal is detected, the level of the reference signal is changed at a predetermined rate independent of the magnitude of said difference in a direction to reduce said difference. Hereby the reference signal is brought to follow the power signal as long as the latter does not change faster than said predetermined rate of change for the reference signal. At least one warning level signal is generated, the level of which being equal to the instant level of the reference signal multiplied by a predetermined factor greater than one. The power signal is compared also with this warning level signal, and a warning signal is generated when the level of the power signal becomes equal to or exceeds the level of said warning level signal.

Abstract: The present invention provides a self-powered neutron detector in which the net contribution of current generated by external gamma radiation is largely equal to zero. A self-powered neutron detector comprises a centralized emitter core, an insulator surrounding the core, an electrically conductive collector surrounding the insulator, and a conduit connected to the emitter core and the collector for withdrawal of generated gamma current. A layer is positioned between the emitter core and the insulator which consists of a material having a high atomic number, a low neutron activation cross section, and a thickness of at most about 5 microns.