Fuel morphology effects on the chemical form of iodine release from severely damaged fuel

Fission product release data for Xe, I, and Cs have been obtained from recent in-pile severe fuel damage experiments under simulated TMI-2 type accident conditions. Fresh fuel was trace-irradiated to a burnup level of 90 MWd/t just prior to testing to ensure the generation of both short- and long-lived fission product isotopes. The data indicate that for low-burnup fuel atomic I and Cs release is favored rather than molecular CsI. An a priori assumption of cesium-iodide (CsI) release from low-burnup fuel for risk analysis may therefore be inappropriate. (orig.)