Investigation of Corrosion of Steel by Lead Bismuth Eutectic

A new research program has begun at UNLV in accelerator transmutation of waste. Lead Bismuth Eutectic (LBE) has been proposed for use in programs for accelerator transmutation of waste. The LBE acts both as a coolant and as a sputtering target. We have recently initiated a program to investigate the corrosion of steels by LBE. Corrosion products and chemical reactions will be identified using UNLV's facilities for SEM, XPS and XRD. The most recent experimental results will be reported. In proposed plans for accelerator transmutation of nuclear waste, Lead-Bismuth Eutectic (LBE) has been proposed for use in the transmuter, where it can serve two purposes: both as a coolant (removing heat from the nuclear waste) and as a spallation target (generating a neutron flux from the incident proton beam). The LBE circulates within stainless steel piping and containers. An absolutely critical question is whether LBE can be engineered to be compatible with the stainless steel walls that contain it with sufficient lifetime. The deleterious process is the corrosion of stainless steel that has been in intimate contact with LBE. It is known that the presence of small amounts of oxygen in such a system is beneficial in forming a passivation layer that inhibits corrosion. The Russians have 40 years of experience with LBE coolant loops in their Alpha-class nuclear submarines, and they have performed laboratory studies of the reactions of LBE with US steels. Los Alamos scientists have reviewed these studies, in which several US steels [316 (tube), 316L (rod), T-410 (rod) HT-9 (tube), and D-9 (tube) and one Russian steel EP823 rod)] were corrosion-tested. Los Alamos scientists are building and will operate a medium-scale LBE materials test loop (MTL). The UNLV program began in June 2001. In our preliminary studies, we have reexamined a number of the same steel samples previously examined by the Russians. At UNLV we have employed a Scanning Electron Microscope (SEM), in which a high voltage focussed electron beam strikes a solid sample, causing fluorescence in the x-ray spectral region. The x-rays are characteristic of the kind of atom. This instrument is capable of measuring elements from boron (Z=5) through uranium (Z=92), mapping the elemental analysis as a function of position. It does not reveal speciation; i.e., it does not provide information about the chemical species. This shows the presence of oxygen (from oxides) and their spatial distribution, with a spatial resolution of about a micron. A variety of steel samples have been examined both before and after exposure to LBE for varying lengths of time and varying temperatures.