Fission Gas Release from Uranium-Zirconium Hydride Fuel During Heating to Melting

Fission gas release and fuel expansion of irradiated uranium-zirconium hydride fuel were measured during fuel heating to melting. The first indication of melting occurred at approximately the uranium-cladding eutectic temperature, whereas complete melting took place at the U metal melting point. Fission gas release began with the onset of uranium-cladding melting and gradually increased with rising temperature. Two sharp peaks in the fission gas release were observed corresponding to the events of uranium-zirconium eutectic melting and uranium melting. The fractional release was much higher than that measured previously for fuel without cladding at comparable temperatures.