Structure of PWR Primary Corrosion Products

Abstract The composition and structure of “erud” taken from the fuel elements of various pressurized water reactors (PWR's) were determined by SEM, EDAX, X-ray analysis, infrared spectroscopy, and thermomagnetic analysis. The samples were taken from reactors varying in materials of construction from all stainless steel to mainly Inconel 600 and Zircaloy fuel cladding. It is shown that crud is essentially a nickel ferrite (NixFe3–xO4) with 0.45 < x < 0.75. Calibration of the lattice parameter versus x allows convenient determination of the main constituents of crud samples. Chromium also enters the inverse spinel lattice substitutionally to give a composition CryNixFe3–x–yO4. Aluminum, when present, generally formed amorphous compounds with silicon in the loose crud.