An investigation of the failure modes in U-10Mo monolithic fuel irradiated to high burnup

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

“…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. This high porosity results in mechanical property deterioration [11][12][13], becoming an important potential fracture mechanism of fuel foil [8][9][10].…”

“…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].…”

“…According to the fuel skeleton creep-influenced volume growth model for U-10Mo fuels [19], it is understandable that the bubble volume growth could be strengthened by the augmented irradiation creep rate coefficient of the Mo-depleted zone, due to its enhanced creep deformation ability [15,17]. The measured porosity values of the irradiated fuel plate L1P7A0 [8] cannot be predicted by the available fission gas swelling models [19][20][21], and the predictions under high burnup levels would be much lower than the experimental data near the fuel foil edge due to the cladding constraint-induced high hydrostatic pressure. As a result, the high porosity phenomena of U-Mo fuel foil under deep burnup would have some other influencing factors.…”

“…As a result, the high porosity phenomena of U-Mo fuel foil under deep burnup would have some other influencing factors. The post-irradiation examination [8] demonstrates that the solid fission product Neodymium (Nd) intruded into the fission gas bubbles is proposed as the driver of fission bubble interconnection under deep burnup. The intrusion of solid fission products into the bubbles occupies the volume of fission gas atoms, leading to higher bubble pressures and possibly inducing additional bubble growth [19].…”