Researchers at Lawrence Livermore National Laboratory have used a plasma flow reactor to recreate conditions inside a nuclear fireball. Their experiments show that cooling rates and thermal history significantly influence how radioactive particles form, particularly for volatile elements like cesium.
The team vaporized combinations of uranium, cerium, and cesium in a controlled high-temperature plasma. They then tracked particle formation under two different cooling scenarios to observe changes in chemistry and composition. Rakia Dhaoui, an LLNL scientist and study author, noted that longer exposure to high temperatures allows cesium to mix more extensively with the other elements. Uranium and cerium condensed earlier, serving as benchmarks, while cesium behaved differently based on thermal conditions. The findings indicate that many existing fallout models treat materials independently and may miss key chemical interactions. The study was published in Analytical Chemistry in 2026. Researchers plan to test more realistic material mixtures to refine models used for interpreting nuclear debris and supporting safety assessments.