STRUCTURE OF PWR PRIMARY CORROSION PRODUCTS

The composition and structure of ″crud″ dtaken from the fuel elements of various pressurized water reactors (PWR's) were determined by SEM (Scanning Electron Microscopy), EDAX (Energy dispersive X-ray Microanalysis), 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. Chromium also enters the inverse spinel lattice substitutionally to give a composition Cr//YNi//xFe//3//-//x//-//yO//4. Aluminum, when present, generally formed amorphous compounds with silicon in the loose crud.