AGR-1 Compact 5-3-1 Post-Irradiation Examination Results

Abstract

Destructive post-irradiation examination was performed on Advanced Gas Reactor (AGR)-1 fuel Compact 5-3-1, which was irradiated to a final compact-average burnup of 16.93% fissions per initial metal atom and a time-average, volume-average temperature of 1040°C. Analysis of this compact focused on characterizing the extent of fission product release from the particles, examining particles to determine the condition of the kernels and coating layers, and experimentally verifying the fuel burnup. Work included deconsolidation of the compact and leach-burn-leach analysis, visual inspection and gamma counting of individual particles, measurement of isotopic inventories in the fuel by mass spectrometry and subsequent burnup calculations, analyzing the fission product inventory in the kernels and coating fragments separately in a small number of particles, metallurgical preparation of selected particles, and examination of particle cross-sections with optical microscopy. Deconsolidation-leach-burn-leach (DLBL) analysis revealed no particles with failed tristructural isotropic or failed silicon carbide (SiC) layers (as indicated by a very low uranium inventory in all of the leach solutions). The DLBL data also provided information on the inventory of fission products retained in the compact outside of the SiC layers. The total fraction of the predicted Ag-110m inventory in the DLBL solutions was 9.07 × 10-3 , indicating significant release from the particles and retention in the compact matrix or outer pyrolytic carbon during irradiation. Cesium inventory was very low; the fraction of the compact inventory in the DLBL solutions was 2.45 × 10-6 and 6.46 × 10-6 for Cs-134 and Cs-137, respectively. Cerium and europium were found at levels greater than the equivalent inventory in one particle, and strontium levels were almost as high, indicating the release of small quantities through intact SiC. The data also revealed that the Pd-105 inventory in the compact outside of SiC was approximately 0.5% of the predicted compact inventory, indicating release through intact coatings and retention in the matrix or outer pyrolytic carbon at nearly the same level as silver. Jeffrey Berg (technical direction and data analysis of deconsolidation-leach-burn-leach results), Dr. Jeffrey Giglio and Daniel Cummings (inductively coupled plasma-mass spectroscopy experiments and data analysis), Brian Storms (particle gamma counting and Sr-90 analysis), and Brian Frickey and Cad Christensen (preparation of ceramographic mounts).

AGR-1 Post Irradiation Examination Final Report

“…The use of this local burnup monitor is best illustrated by Figure 9 in Harp et al 2014. Determination of burnup from mass spectrometry data first involved dissolution of a small number of kernels from each compact examined. The method used to dissolve the actinides and fission products from the kernels for burnup analysis is described in the individual compact reports (Demkowicz et al , 2015b(Demkowicz et al , 2015c(Demkowicz et al , 2015d. Significant effort was put into optimizing the dissolution methodology to ensure full Pu recovery along with recovering U, the lanthanide fission products, and other minor actinides.…”

“…A large number of particles from 15 different AGR-1 compacts have been analyzed microscopically to statistically study changes in kernel and coating morphology induced by irradiation. This includes characterization of almost 1000 particles in cross sections of six fuel compacts, where internal features of each particle were exposed at a single random depth (Ploger et al 2012a, Hunn, Savage, and Kehn 2012, and over 300 loose particles randomly selected from three compacts that were mounted in planar arrays and examined at multiple elevations for enhanced perspective (Demkowicz et al 2015a, Demkowicz et al 2015c, Demkowicz et al 2015d, Bower et al 2015. Based on these studies, characteristic particle morphologies have been identified, and particles were classified according to these morphological types to obtain statistics on particle behavior.…”

“…Further details on characterization of particles in full compact cross sections are presented in Ploger et al 2012a andPloger et al 2014. Details of results from particle ensembles examined in cross section at multiple polish planes can be found in Demkowicz et al 2015c, Demkowicz et al 2015d, Bower et al 2015. Additional observations on particle morphology evolution based on examination of cross sections with optical microscopy and x-ray analysis can be found in the individual compact PIE reports (see Table 23).…”

Advanced Electron Microscopy and Micro analytical technique development and application for Irradiated TRISO Coated Particles from the AGR-1 Experiment

“…Fraction of retained Ag-110m inventory in 56 of the 72 AGR-1 fuel compacts after irradiation. Data are plotted as a function of vertical position in the experiment (top of the experiment at the left) and by stack number (Demkowicz et al, 2015a).…”

“…An expanded dataset from TRISO-coated particles from Compacts 6-3-2, 5-3-1, 5-2-3, 4-1-1, 1-3-1, and 4-3-3 are reported and compared. Generally, particles from each compact were selected to represent a low and high-Ag-retention particle (details of the selection criteria are described by Demkowicz et al, 2015a). Unfortunately, in the case of Compact 6-3-2 (i.e., the Baseline fuel-type compact), the low-retention particle (AGR1-632-030) was over-polished during sample preparation and important SiC-IPyC interface features were lost.…”