James D. Landry

Superconducting magnetometer for quality control of nuclear fuel rods

A superconducting magnetometer is used to assay gadolinium in uranium dioxide nucear fuel rods. Less than 10 percent by weight gadolinium is present in solid solution in the fluorite phase to provide power flattening and to extend the time between refueling of nuclear reactors. The magnetometer is part of an automated rod scanner which provides quality inspection of more than 50 000 fuel rods per year. The magnetometer can resolve a single out‐of‐specification gadolinia pellet (10 g of UO2 with a maximum of 10% Gd) with as much as 0.2 percent by weight ferromagnetic impurity. The measurement techniques considered during development of the scanner were neutron methods, x‐ray fluorescence spectroscopy, modulated‐field magnetometry, and moving sample magnetometry. The latter technique was applied by moving the fuel rod at speeds of about 5 cm/sec through two regions of different static magnetic field in excess of 20 000 oersteds. Each region contains a sampling coil which detects changes in magnetization wit...