The effects of the thickness of Zirconium liner on stress-strain behavior of monolithic fuel mini-plates during fabrication and irradiation processes were studied. Monolithic plate-type fuel elements is a new fuel form being developed for research and test reactors to achieve higher uranium densities which allows the use of low-enriched uranium fuel in reactor core. These fuel elements are comprised of a high density, low enrichment, U–Mo alloy based fuel foil encapsulated in a cladding material made of Aluminum. Early RERTR experiments indicated that the presence of an interaction layer between the fuel and cladding materials causes mechanical problems. To minimize the fuel/cladding interaction, employing a diffusion barrier between the cladding and the fuel materials was proposed. Current monolithic plate design employs a 0.025 mm thick, 99.8% pure annealed Zirconium diffusion barrier between the fuel foil (U10Mo) and the cladding materials (AL6061-O). To benchmark the irradiation performance, a number of plates were irradiated in the Advanced Test Reactor (ATR) with promising irradiation performance. To understand the effects of the thickness of the Zirconium diffusion barrier on the stress-strain behavior of the plates during fabrication, irradiation and shutdown stages, a representative plate from RERTR-12 experiments (Plate L1P7A0) was selected and simulated. Both fabrication and irradiation stages were considered. Simulations were repeated for various Zirconium thicknesses to understand the effects of the thickness of the diffusion barrier. Results of fabrication simulations indicated that Zirconium thickness has noticeable effects on foil’s stresses. Irradiation simulations revealed that the fabrication stresses of the foil would be relieved rapidly in the reactor. Results also showed that Zirconium thickness has little or no effects on irradiation and shutdown stresses.
Reactor Physics Methods and Preconceptual Core Design Analyses for Conversion of the Advanced Test Reactor to Low-Enriched Uranium Fuel Annual Report for Fiscal Year 2012