Membranes on solid supports offer an ideal format for imaging. Secondary ion mass spectrometry (SIMS) can be used to obtain composition information on membrane-associated components. Using the NanoSIMS50, images of composition variations in membrane domains can be obtained with a lateral resolution better than 100 nm. By suitable calibration, these variations in composition can be translated into a quantitative analysis of the membrane composition. Progress towards imaging small phase-separated lipid domains, membrane-associated proteins and natural biological membranes will be described.

Decontamination and decommissioning at the Savannah River Site have produced on-site disposals of low-level solid radioactive waste in the form of concrete rubble. In the case of a former tritium extraction facility, building demolition produced a significant volume of rubble embedded with tritium. The contaminated debris comprises a heterogeneous mixture of sizes, shapes, and internal tritium distributions. The rubble was disposed in long, shallow, unlined, earthen trenches, that were subsequently backfilled with excavated soil and exposed to normal infiltration. To forecast tritium flux to the water table, an unsteady dual porosity model was developed to describe vadose zone leaching and transport. Tritium was assumed to be released through unsteady, one-dimensional, molecular diffusion within concrete, while advective and diffusive transport occur in the surrounding backfill. Rubble size and shape variations were characterized through a combination of physical measurement and photographic image analysis. For simplicity, the characterization data were reduced to an approximately equivalent distribution of one-dimensional slab thicknesses for representation in the dual porosity formulation. Each size classification was simulated separately, and individual flux results were then blended in proportion to the thickness distribution to produce a composite flux. The fractional flux from concrete rubble was predicted to be roughly 40% …