There is a certain limit of the linear heat generating rate below which power variations are safe for the PCI, because the deviation between clad creep and pellet swelling remains within the permitted frame, and thus the fuel and cladding can adapt to the new power level (IAEA, 2010a). According to the last survey made by IAEA, only a limited number of PCI-related failures have been observed recently in PWR fuel, while PCI is still the second cause of cladding failures for BWR fuel (IAEA, 2010a). An additional mitigation method currently under development is the adoption of advanced fuel with a reduced release rate of fission products with burn-up.