P30 Gas content measurements of irradiated coated particles using the PGA system*

The Postirradiation Gas Analyzer (PGA) system has the capability of quantitatively measuring fission and reactive gases that are contained in irradiated HTGR fuel particles. Irradiation experience has shown that pyrocarbon coatings may become permeable to fission gases due to fast neutron damage while still remaining mechanically intact /1,2/. The reference HTGR fissile particle is a UC2 kernel surrounded by a porous pyrocarbon layer, a dense isotropic pyrocarbon layer, a SiC layer, and another layer of dense isotropic pyrocarbon - a "so-called" Triso particle design. The reference HTGR fertile particle is a Th02 kernel surrounded by a porous pyrocarbon layer and a layer of dense isotropic pyrocarbon - a "so-called" Biso particle design. The combined function of these various layers is to contain the fission products produced during