Bi-metallic, self powered, fixed incore detector, and method of calibrating same

A fixed incore detector apparatus, comprising:

• a neutron detector fixedly extending a length in a reactor core;
• a full length gamma ray detector adjacent to, electrically separate from and spatially congruent with said neutron detector;
• and
• segmented gamma ray detectors adjacent to and electrically separate from said neutron detector and positioned along the length.

A method of determining power distribution, comprising the steps of:

• (a) sampling an output signal from a neutron detector in a reactor core;
• (b) sampling an output signal from a gamma ray detector spatially congruent with, electrically separate from, and adjacent to said neutron detector;
• and
• (c) compensating the output signal of the gamma ray detector using the output signal of the neutron detector to thereby produce a power distribution signal.

A method of determining power distribution in a reactor, comprising the steps of:

• (a) sampling signals of spatially congruent, adjacent and electrically separate neutron and gamma ray sensitive detectors in the reactor;
• (b) compensating the neutron and gamma ray signals for prompt sources of signal error;
• (c) calculating first and second heat deposition rates for the neutron and gamma ray sensitive detectors, respectively;
• and
• (d) adjusting the compensated gamma ray signals to reflect power distribution of the reactor responsive to a difference between the first and second rates when the first rate has reached a steady state.