Observed Changes in As-Fabricated U-10Mo Monolithic Fuel Microstructures After Irradiation in the Advanced Test Reactor

Abstract

A low-enriched uranium U-10Mo monolithic nuclear fuel is being developed by the Material Management and Minimization Program, earlier known as the Reduced Enrichment for Research and Test Reactors Program, for utilization in research and test reactors around the world that currently use high-enriched uranium fuels. As part of this program, reactor experiments are being performed in the Advanced Test Reactor. It must be demonstrated that this fuel type exhibits mechanical integrity, geometric stability, and predictable behavior to high powers and high fission densities in order for it to be a viable fuel for qualification. This paper provides an overview of the microstructures observed at different regions of interest in fuel plates before and after irradiation for fuel samples that have been tested. These fuel plates were fabricated using laboratory-scale fabrication methods. Observations regarding how microstructural changes during irradiation may impact fuel performance are discussed.

Prediction and Deformation Mechanism Analysis of High Porosity in U–10Mo Monolithic Fuels at High Burnup

“…The Mo-depleted zone near the U-10Mo/Zr interface has been observed in the microstructural analysis of the as-fabricated U-10Mo monolithic fuel plate [9,10], with the presence of the α−U phase. It is known that the fuels dominated by α−U easily trigger high fission gas swelling [9].…”

“…U-10Mo/Al monolithic fuel plates consist of U-10Mo fuel foil, Al alloy cladding and a Zr diffusion barrier layer, regarded as the most potential candidates for advanced research and test reactors due to their high uranium density and stable irradiation performance [5][6][7]. The post-irradiation examination indicates that the porosities near the U-Mo/Zr interface are higher than those of the other parts, with gradually expanding differences with the fission density [8][9][10]. In particular, a porosity of ~32% for the irradiated fuel plate L1P7A0 [8] appears near the fuel foil edge subjected to enhanced constraints, with a maximum of ~35% surrounding the U-Mo/Zr interface.…”

“…In particular, a porosity of ~32% for the irradiated fuel plate L1P7A0 [8] appears near the fuel foil edge subjected to enhanced constraints, with a maximum of ~35% surrounding the U-Mo/Zr interface. This high porosity results in mechanical property deterioration [11][12][13], becoming an important potential fracture mechanism of fuel foil [8][9][10].…”

Microstructural characterization of as-fabricated monolithic plates with boron carbide, aluminum boride, and zirconium boride burnable absorbers

“…The mathematical definitions of circularity (Circ), roundness (Rnd), and aspect ratio (AR) are defined in Eq. 1-3, respectively, where area is in units of µm 2 . Circularity is a measure of similarity to a perfect circle, the possible values of which span from zero to one.…”

“…The B4C acts as a burnable neutron absorber (BA) to suppress excess initial reactivity and to help control the power profile. The incorporation of BAs into the LEU fuel under development under the aLEU program would provide benefits similar to that of B4C in HEU fuel [1,2].…”