Safety assessment of radioactive waste repositories, regulatory development, dose assessment for residual contamination of soils and buildings, toxic materials risk assessment, and mixed waste issues. Systems analysis of mine closures and operational mine water balances. Over 100 publications on radioactive waste management and remediation.A frequent consultant to the International Atomic Energy Agency (IAEA), and has supported the governments of Azerbaijan, Belarus, Bulgaria, Egypt, Estonia, Japan, Malaysia, Moldova, Philippines, Poland, and Romania on IAEA missions on radioactive waste. Participant in numerous IAEA Coordinated Research Programs on radioactive waste management including NSARS, ISAM, ASAM, PRISM, and MODARIA.Currently leading performances assessments at Hanford, with activities supporting tank farm retrievals at WMA C, WMA A-AX, and WMA U, and Hanford Low-Level Burial Ground performance assessments. Recent project work in Slovenia, Finland, Korea, Sweden, South Africa, and Ukraine as well as USA projects to support Environmental Protection Agency (EPA), Electric Power Research Institute (EPRI), Department of Energy (DOE), and Nuclear Regulatory Commission (NRC) on a wide variety of radioactive waste disposal and radioactive contamination issues, including work on Yucca Mountain, and a number of sites for low-level waste. Technical input to regulatory rulemakings for high-level and low-level wastes, and for residual contamination from decommissioning.Past member of the National Research Council Committee on Cesium Processing Alternatives for High-Level Waste at the Savannah River Site. Former chair of Scientific Committee 87-3 for the National Council on Radiation Protection (NCRP) on safety assessment of radioactive waste disposal facilities, and a past member of NCRP Umbrella Scientific Committee 87 on Radioactive and Mixed Waste. In 2004, IAEA’s International Peer Review Team for the Australian National Repository. In 2019, international peer review of the Atomic Energy of Canada Limited Canadian Nuclear Laboratories safety case and assessment documents for the Near-Surface Disposal Facility.Specialties: Nuclear waste management regulationsSafety assessment