Design and operation of a pilot-irradiated fuel-assay gauge (LWBR Development Program)

An Irradiated Fuel Assay Gauge (IFAG) has been constructed and tested to demonstrate the feasibility of nondestructive assay of spent reactor fuel rods to a high degree of precision and accuracy. The IFAG uses the method of neutron interrogation and delayed neutron detection. The IFAG has been tested with 233UO2-ThO2 fuel. Several fuel rods which were irradiated in a test reactor for two to three years were assayed with the IFAG to a precision of 0.2% to 0.4%. These rods were also assayed by another nondestructive device, a lead slowing-down time spectrometer. One of the rods was also assayed slowing-down time spectrometer. One of the rods was also assayed destructively using chemical techniques. Good agreement was obtained among the different assay methods. The results demonstrated the successful operation of the IFAG. It is expected that a device based on the IFAG could be put into production for routine assay of spent fuel rods to an accuracy of 0.5% or better