Measurement of reactor tube cladding thickness by x-ray fluorescence spectrometry

An x-ray fluorescence spectrometer was designed and fabricated which nondestructively determines the thickness of aluminum cladding at small suspected thin spots in the inner or outer surface of actinide reactor tubes. The analysis method is based on the difference in absorption of actinide L/sub ..cap alpha../ and L/sub ..beta../ fluorescent x-rays in passing through the cladding. Calibration plots of the logarithm of the L/sub ..beta..//L/sub ..cap alpha../ x-ray intensity ratio versus cladding thickness are linear to at least 40 mils for U-Al, U/sub 3/O/sub 8/-Al, and PuO/sub 2/-Al substrates. Accuracy and precision of the experimentally determined cladding thickness and evaluated for both uranium and plutonium substrates. Experimental thickness data are reported for 618 quality assurance analyses on six Mark 41 PuO/sub 2/-Al target tubes. An x-ray fluorescence cladding thickness monitor operated with a computer-controlled fluoroscope holds considerable promise for quality assurance because (1) a permanent record of cladding thickness for each reactor tube would be provided and (2) the cladding integrity of each tube would be assured before irradiation in the reactor