LLNL SCIENTISTS UNCOVER NEW CHEMISTRY IN NUCLEAR FALLOUT STUDY

Researchers at Lawrence Livermore National Laboratory (LLNL) have identified unexpected chemical interactions in the process by which nuclear fallout forms, findings that suggest current models may be missing key steps. The study, published in the journal Analytical Chemistry, examined how uranium, cerium, and caesium behave as they vaporise, react, and cool. The team used a plasma flow reactor to recreate conditions found inside a nuclear fireball. Their results indicate that the duration materials spend at high temperatures affects how volatile elements such as caesium become incorporated into particles.

The plasma flow reactor allowed scientists to introduce specific combinations of materials into a high-temperature plasma, where they were vaporised before passing through a temperature-controlled tube as they cooled. The researchers tested two distinct cooling scenarios, referred to as thermal histories, to observe how different conditions influenced particle formation. LLNL scientist Rakia Dhaoui stated that particles preserve a record of how they formed and that studying the process under controlled conditions replaces assumptions with measurements. Dhaoui added that the findings can improve the models used to interpret nuclear debris and support decision-making during nuclear incidents.

The research holds implications for safety assessments following both nuclear explosions and major reactor accidents. Fallout particles begin forming in the first fraction of a second after such an event, as superheated gases and plasma cool and condense into tiny solid matter. The study's authors argue that existing fallout models may overlook chemical interactions occurring during that condensation process. Improved models could assist scientists in reconstructing the sequence of events during a nuclear incident.