AGR-3/4 TRISO Fuel Compact Ceramography

Abstract

The combined third and fourth irradiation in the Advanced Gas Reactor (AGR) program (AGR-3/4) contained tristructural isotropic (TRISO)-coated particle fuel and designed-to-fail (DTF) fuel particles. The DTF particles were only coated with highly anisotropic pyrocarbon (PyC) so they would purposely fail during the AGR-3/4 irradiation and provide a source of fission products for measurement. Frickey performed materialographic preparation of the irradiated and unirradiated fuel compacts. This included designing and fabricating the mounts, grinding, and polishing the mounts at the Hot Fuel Examination Facility at Idaho National Laboratory. Cassie Anderson-Thueson assisted in the mounting, grinding, polishing, and optical microscopy work. John Stanek and Francine Rice assisted in the mount design and provided valuable input to sample preparation and microscopy processes leading to acquisition of the images included in this report. Fuel burnup and fast neutron fluence were calculated by Dr. Jim Sterbentz. Fuel temperatures and temperature variations were calculated by Grant Hawkes.

Status of Modifications to the AGR-3/4 Fission Product Transport Model

“…Destructive sampling of selected IRs and ORs has produced radial fission product concentration profiles for both gamma-emitting nuclides and Sr-90. In some cases, rings were sampled at multiple axial locations (Stempien 2021). These are represented by square ■ or star ☆ markers.…”

“…The experiment consisted of fuel compacts containing TRISO-coated driver-fuel particles similar to AGR-1 baseline fuel (Collin 2015a;Hunn and Lowden 2007;Hunn et al 2014) and designed-to-fail (DTF) particles that are designed to release fission products during irradiation to migrate through the surrounding cylindrical rings of graphitic matrix and nuclear-grade graphite. Following irradiation, PIE measurements of the fission inventories and spatial distributions (axially and radially) within AGR-3/4 samples (primarily the graphite rings and compacts) were completed (Harp, Stempien, and Demkowicz 2020;Stempien 2021;Stempien et al 2018). These data will be used to support refinement of fission product transport models and HTGR source-term analyses.…”

“…The total inventories of the SRs were determined via burn-leach (Stempien et al 2018). Azimuthally-averaged radial concentration profiles were obtained for 90 Sr via destructive sampling of portions of IRs and ORs (Stempien 2021). Total 90 Sr inventories for these rings have been estimated (Stempien 2021), but are not shown here.…”

“…Azimuthally-averaged radial concentration profiles were obtained for 90 Sr via destructive sampling of portions of IRs and ORs (Stempien 2021). Total 90 Sr inventories for these rings have been estimated (Stempien 2021), but are not shown here. Strontium concentrations from R-DLBL of the compacts are consistent with radial outward diffusion, though the IR and ORs exhibit increased concentrations at their edges.…”

“…The calculated time-averaged axial variation in temperature was less than 177℃ for the compacts, 54℃ for the IR, and 24℃ for the OR. The IR and OR of Capsule 3 were subjected to destructive physical sampling to generate radial fission product concentration profiles (Stempien 2021). These data points are included here using star and square symbols in the following plots.…”