Safety Test on Irradiated Compact 4-2-2

Post-irradiation examination (PIE) is in progress on coated particle fuel compacts from the first Advanced Gas Reactor (AGR) Fuel Development and Qualification irradiation experiment (AGR-1). The AGR-1 Post-Irradiation Examination Plan (INL/PLN-2828, Rev. 1) includes safety testing of the irradiated compacts in the Oak Ridge National Laboratory (ORNL) Core Conduction Cooldown Test Facility (CCCTF) and the Idaho National Laboratory (INL) Fuel Accident Condition Simulator (FACS) to evaluate the effect of elevated temperature on the fuel microstructure and fission product retention. Standard safety tests involve heating compacts to maximum temperatures of 1600, 1700, or 1800°C for typically 300 hours, where 1600°C is the expected maximum temperature during a high-temperature gascooled reactor (HTGR) depressurization conduction cooldown event, while 1700 and 1800°C explore the performance margin. The Compact 4-2-2 safety test was conducted using multiple hold temperatures from 1000–1600°C to investigate fission product retention at temperatures below 1600°C and during thermal cycling, with particular emphasis on silver retention behavior [INL/PLN-4714]. Previous tests produced unusual silver releases when temperatures were inadvertently or intentionally cycled between room temperature and 1600°C [ORNL/LTR-2012/396]; the Compact 4-2-2 test was designed to reproduce and explore these observations.