Spent Fuel Monitor for Nuclear Safeguards

A monitor has been designed to detect the absence of a fuel bundle from its position in a storage basket. In addition, a signal is obtained which can be compared with the recorded irradiation and storage history of the fuel. The detectors are silicon diodes mounted in an array of lead collimators to view each bundle in a 4 × 4 array. Test results are presented which show that the absence of a bundle can be reliably detected. For spent bundles removed from the reactor at the same time, the output currents from the signal diodes are linearly related to the irradiation of the fuel.