Irradiation Behavior of Cored U₃Si Fuel Elements

Zircaloy-clad specimens of U₃Si have been irradiated in pressurized water at rod powers of 480 to 565 W per centimeter of length to burnups of ≈ 5500 MWd/tU. The rate of swelling of the U₃Si, which is rapid during the early part of the irradiation, appears to decrease with increasing burnup. The increase in external diameter was much less for these fuel elements than for earlier ones. The improvement is attributed to the provision of a central void which became filled by the U₃Si during irradiation.