A Preliminary Carbon-Footprint Comparison of Low-Activity Radioactive Waste Immobilization Techniques

From the 1940s through the 1980s, the Hanford Nuclear Site produced plutonium and accumulated 212,000 cubic meters of mixed radioactive and hazardous chemical waste in 177 aging underground tanks. After removing strontium, cesium, and transuranics, much of this waste could be classified as “Low Activity Waste” (LAW). In late 2025, the Direct Feed LAW facility began vitrification, mixing liquid waste with molten glass at 1150 °C and decomposing many hazardous chemicals. The present assessment compares the carbon footprints of two methods for immobilizing supernatant liquids and diluted saltcake: grouting with cement, slag, and fly ash and vitrification in glass. This study considers CO2e emissions from process inputs, electricity use, and the manufacturing and transportation of containers and canisters for immobilized LAW. Because vitrifying saltcake produces significant secondary waste, it should be minimized. Instead, saltcake could be grouted, as at the Savannah River Site. Additionally, the U.S. Department of Energy should avoid shipping liquid waste off-site and, when possible, opt for rail transport to reduce Hanford’s carbon footprint. From a sustainability standpoint, immobilizing Hanford’s waste reduces the risk of contaminating the Columbia River, groundwater, and soil.