Evidence of tellurium iodide compounds in a power-ramped irradiated UO2 fuel rod

The existence of tellurium iodide compounds was evidenced in power-ramped UO2 irradiated fuel by means of post-test SIMS analysis that showed both volatile fission product releases from the pellet centre and precipitates composed of these volatile fission products on the fuel periphery. Thermodynamic calculations confirmed the stability of TeIx gaseous phases in equilibrium with irradiated UO2. Both the experimental and theoretical results offer a strong incentive to consider TeIx compounds for stress corrosion cracking (SCC) of the cladding during a power ramp instead of CsI since TeIx compounds are more corrosive to Zircaloy cladding than CsI.