Using xenon as a fill gas in IFE chambers results in generating a large amount of radioactive xenon, iodine, and cesium isotopes. The cesium isotopes, 134Cs and 136Cs, and the iodine isotope, 126I, would produce a high level of off-site dose (62.13 rem) at the plant site boundary if they were released entirely to the environment during an accident. The xenon gas is pumped out of the chamber (recycled) during operation to remove unburned T2 and D2. Removing the Cs and I isotopes from the Xe gas during this recycling process will reduce the Cs and I inventories inside the chamber to negligible values. This process limited the off-site dose caused by the accidental release of Xe from the chamber of the SOMBRERO power plant to 29.9 mrem, which is less than the 1 rem no-evacuation limit. Using krypton, argon or neon as fill gases will result in producing lower levels of off-site dose than xenon.