12.112. The noble gas fission products such as xenon are inert chemi­cally. During irradiation, they are partially released from the ceramic oxide

fuel matrix and occupy grain boundary regions and whatever other free space is available within the fuel rod. Upon failure of the cladding and, in turn, the coolant system boundary, they would travel into the containment and be available for transport to the environment without acting chemi­cally. Although the transition during this time period by radioactive de­cay to other elements that may be reactive is a possibility, the effect is small in light of other process uncertainties and may be neglected in approximation-level analyses.