The CANDU core discharge monitor (VIFC) is a typical unattended monitoring system operating in an inaccessible area. It detects irradiated fuel upon discharge from the core face of a CANDU reactor.

Both neutron (normal on power discharge signal) and γ ray intensities are continuously monitored. The inspector is able to review a summary file against the operator declaration and identify any unusual movement associated with fuel bundle discharge. The review software tool validates irradiated fuel discharges both when the reactor is on power and when it is shut down. Because of the linear increase in background signal, the system can also track the operating power level of the reactor.

(Source: IAEA Safeguards Techniques and Equipment)