Self Powered Neutron Detector (SPND) is a neutron detector used in nuclear fission reactors. It is a compact device extensively used worldwide for mapping of neutron flux, helping the reactor-operators in maintaining the neutron economy. It gives a direct current signal proportional to the incident flux of neutrons, due to production of negative beta particles or Compton electrons in the heart of the device.
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Self Powered Neutron Detector (SPND) Wikipedia(Text) CC BY-SA