Fuel “failure” refers to a situation when the cladding has been breached and radioactive material leaks from the fuel pellet into the reactor coolant water. The materials most likely to leak through a cladding breach are fission-product gases and volatile elements, notably:
- Krypton (Kr)
- Xenon (Xe)
- Iodine (I)
- Caesium (Cs)
Fuel leaks do not present a significant risk to plant safety, but they have a major impact on reactor operations and potentially on plant economics.