Patent ID: 7349517

Claim:
A method of measuring a relative magnitude of the burnout of a fuel element in a reactor, the method comprising the steps of sequentially: a) transferring a fuel element from the reactor to a measuring position, b) subjecting the transferred fuel element at the position to a neutron flux, c) measuring with a first detector the total γ radiation emitted by the transferred fuel element; and thereafter d) if the radiation measured by the first detector exceeds a predetermined first limit, returning the transferred fuel element back to the reactor and e) if the radiation measured by the first detector does not exceed the first limit, measuring with a second detector a magnitude of high energy γ radiation above 1 MeV emitted by the transferred fuel element; and thereafter f) only if the radiation measured by the second detector exceeds a predetermined second limit, returning the transferred fuel element back to the reactor, the transferred fuel element not being returned to the reactor if the radiation measured by the second detector is below the second limit.