Assessment of Iodine Gas Decontamination in Sodium Pool for Advanced Reactors

Following fuel damage events in oxide-fuel sodium-cooled fast reactors, iodine gas that is released from failed fuel may be retained within the sodium pool during bubble transport. To explore this phenomenon, which can be important for accurate source term assessments, data were collected from past experimentation and used for model validation. The data considered for validation included various parametric conditions regarding the sodium pool and injected gas mixture. According to the assessment, modeling bubble transport utilizing bubble sizes estimated from past experimentation tends to underestimate iodine removal. When considering bubble breakup during bubble rise through the sodium pool, the bubble size can be corrected based on the bubble size–rise velocity correlation. With this approach, the predictability of iodine removal is improved, which highlights the impact of small bubble sizes, which promotes mass transfer through the enlarged surface area to volume ratio. According to the assessment, the approach is expected to provide a reasonable approach for simulating iodine gas behavior in sodium-cooled fast reactors with oxide fuel, and the phenomenon could also be potentially applied to other reactive gases expected to be released during fuel damage events.