Burn-up determination and accident testing of HTR-PM fuel elements irradiated in the HFR Petten

•7 INET HTR fuel elements irradiated in HFR Petten were sent to Karlsruhe for PIE.•The burn-up of these fuel elements was determined via gamma spectroscopy.•D-LOFC incidents were simulated in the KÜFA device in the JRC Hot Cells up to 1770°C.•Typical releases of Cs after the first test phase at 1620 °C were less than 2.5·10−5.•The release of Kr-85 was below the detection limits during the first heating phases.