Neutron monitoring systems including gamma thermometers and methods of calibrating nuclear instruments using gamma thermometers

摘要

A method of calibrating a nuclear instrument (920) using a gamma thermometer (924) may include: measuring, in the instrument (920), local neutron flux; generating, from the nuclear instrument (920), a first signal (S2) proportional to the local neutron flux; measuring, in the gamma thermometer (924), local gamma flux; generating, from the gamma thermometer (924), a second signal (S1) proportional to the local gamma flux; compensating the second signal (S1); and calibrating a gain of the nuclear instrument (920) based on the compensated second signal. Compensating the second signal (S1) may include: calculating selected yield fractions (± i ) for specific groups of delayed gamma sources; calculating time constants (Ä i ) for the specific groups of delayed gamma sources; calculating a third signal that corresponds to delayed local gamma flux based on the selected yield fractions (± i ) and time constants (Ä i ); and calculating the compensated second signal by subtracting the third signal from the second signal (S1). The specific groups may have decay time constants (Ä i ) greater than 5 x 10 -1 seconds and less than 5 x 10 5 seconds.