Measurement of effective Sr diffusion coefficients in IG-110 graphite

Abstract Radionuclide transport and release from operating HTGR cores during normal and off-normal operations carries the possibility of increased exposure risk to reactor personnel as well as radionuclide release to the surrounding environment in the event of a depressurization accident. Diffusion is one of the primary processes by which this radionuclide transport takes place. 90Sr is one of several fission products which is commonly investigated within the context of high-temperature gas-cooled reactors due to its low volatility and ability to migrate through intact TRISO fuel particles. Effective diffusion coefficients for strontium in unirradiated IG-110 graphite have been experimentally determined over the temperature range 1773 K – 1973 K using a time-release method coupled to an inductively-coupled plasma mass spectrometer. The results of this work are: D S r , I G − 110 = ( 1.7 × 10 − 1 m 2 / s ) e x p ( − 3.46 × 10 5 J / m o l R T )