DOE OSTI2012
The AGR-1 irradiation test train consisted of six independently monitored capsules. All capsules contained twelve compacts in three stacks of four compacts each [Pope 2010]. Compact 6-1-1 was located in capsule 6, at the top of the test train. The compact was in stack 1 (one of the two stacks closest to the core) in position 1 (at the bottom of the 4 compact stack). Compact 6-1-1 was identified in the fabrication data package as LEU01-46T-Z32 [Hunn et al. 2006]. Details of the compact fabrication and measured properties can be found in that data package. The compact lot was made using TRISO-coated particles designated as AGR-1 Baseline fuel. These particles contained 19.7% enriched mixed uranium oxideuranium carbide (UCO) kernels with a O/U atomic ratio of ~1.36 and a C/U atomic ratio of ~0.33 [Pope 2010]. Details of the coated particle fabrication and measured properties can be found in the data package for the AGR-1 Baseline particles [Hunn and Lowden 2006]. The compact was irradiated at the INL Advanced Test Reactor (ATR) to an average calculated burn-up of 15.1% fissions per initial metal atom (FIMA) and an average calculated fast fluence of 3.0 x 10 25 n/m 2 [Sterbentz 2011] at a calculated volume averaged and time averaged temperature of approximately 1111°C [Hawkes 2012]. Capsules were disassembled and preliminary compact and graphite holder inspection was performed [Demkowicz et al. 2011]. Compact 6-1-1 was shipped to ORNL and post-irradiation examination (PIE) was performed according to examination plan PLN-3624 [Demkowicz 2010-2]. All the examination plan objectives listed below were completed except item 6, which was deleted due to limited funding. 1. Determine the inventory of fission products retained in the compact matrix, but not contained by the SiC and determine the number of exposed kernels or particles with defective SiC layers using the deconsolidation-leach-burn-leach method. 2. Gamma count all particles to quantify 137Cs inventory for comparison with calculated values and gamma spectrometric measurements made on the whole compact. Also, attempt to quantify the inventory of any other fission products for which gamma emissions are observed. 3. Characterize each particle based on the 137 Cs/ 144 Ce ratio to identify particles with low Cs retention that may be the result of a failed SiC coating. 4. Gamma count a subset of particles to determine the 110m Ag inventory for comparison with calculated values and gamma spectrometric measurements made on the whole compact. Also, attempt to quantify the inventory of other fission products observed. 5. Microscopically inspect selected particles to determine the condition of the kernels and coatings. This could include kernel migration, coating microstructures and defects, fission product attack of the SiC layer, and fission product migration in the coating layers. 6. Perform high temperature fission product release tests on a subset of particles in order to calibrate the collection efficiency of the Core Conduction Cooldown Test Facility (CCCTF) deposition cup for selected fission products. Gamma count particles before and after the heating test to quantify the released fission product fractions. 7. Archive remaining particles for later use. Compact 6-1-1 LBL began with compact deconsolidation in the Building 3525 hot cell, followed by two nitric acid leaches of the particles and matrix residue using a Soxhlet extraction apparatus. The matrix residue was then burned and the ash was leached twice with boiling nitric acid. The deconsolidated particles underwent an IMGA analysis to determine gamma-emitting isotope inventories for individual particles; the most conspicuous elements with reduced inventories, indicating fission product release, were silver and europium. During the IMGA analysis, particles with low silver were identified and a subset of these was set aside for materialography and x-ray. After the completion of the IMGA study, about 10% of the particles (421) were set aside as an archive and the remainder burned back and leached twice in the Soxhlet apparatus. Figure 1 shows a flow chart detailing the PIE of Compact 6-1-1.
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗