Fission produces gases such as iodine-131 or Xenon-133 remain within the fuel rods, but if there were a major accident resulting in fuel failure, small amounts of the gases would be released in to the reactor coolant.
Fission produces gases such as iodine-131. Fission produces gases such as iodine-Xenon.133 remain within the fuel rods. Small amounts of the gases would be released in to the reactor coolant. There were a major accident. This major accident was resulting in fuel failure.