Silicon Carbide High-Temperature Neutron Detectors for Reactor Instrumentation

Miniature neutron detectors have been constructed by positioning a ²³⁵U layer above the sensitive surface of a shallow-junction silicon carbide diode to act as a neutron conversion coating. A series of tests have been performed to verify the neutron detecting characteristics of ²³⁵U-coated SiC detectors operating in a reactor environment. The reactor neutron flux was varied between 10⁷ and 10¹¹ n/(cm² sec) to determine the linearity of response of the detector to changes in reactor power. The potential of the SiC neutron detector as a flux-mapping device was demonstrated by making axial traverses of the reactor core while holding the peak flux level constant at 10⁹ n/(cm² sec). The α-particle counting capabilities of these SiC diodes have been demonstrated to temperatures above 700° C (≈1300° F) and with integrated neutron fluxes greater than 6 × 10¹⁵ n/cm².