Problems of cladding:

The problems of cladding collapse concluding from fuel densification and cladding creep have occurred mostly along with unpressurized fuel rods in PWRs. To decrease the cladding creep sufficiently to avoid the establishment of fuel column gaps and following tubing collapse, the following methods have been successful: pressurizing the fuel rods along with helium to pressures of 200 psig to 400 psig; and increasing fuel pellet density through sintering (bonded mass of metal particles partially and shaped fused through pressure and heating below the melting point) a material within a manner leading to a higher initial density and a stabilized pore microstructure.