Physics-informed estimation of fracture resistance in irradiated aluminum alloys under cryogenic conditions for NTP-SMR application

As the development of nuclear thermal propulsion (NTP)–small modular reactor (SMR) systems and cryogenic nuclear facilities advances, there is an increasing demand for structural materials operating under combined cryogenic temperatures, mechanical loading, and irradiation environments. Under such conditions, the presence of crack-like defects and constrained deformation states renders fracture resistance the governing metric for structural integrity. Although aluminum alloys are widely used in nuclear components under cryogenic conditions, fracture resistance data under simultaneous cryogenic and irradiation conditions remain limited due to experimental constraints. In this study, a physics-informed framework is proposed to predict fracture resistance of AL6061 under NTP–SMR relevant irradiation and cryogenic conditions. Irradiation damage is quantified using an irradiation-induced porosity formulation incorporating physical correlations based on neutron fluence spectra. Temperature- and irradiation-dependent plasticity is described by an extended Gurson-type model, in which irradiation defects quantified by displacement per atom are treated through an additional evolution term. Damage parameters are calibrated through parametric analyses of notched specimens using Latin hypercube sampling. Crack growth analyses of compact tension specimens are performed to evaluate fracture resistance based on the J -integral, J_IC. The plane-strain fracture toughness K_IC converted from J_IC is adapted as a comparative reference to contextualize predicted degradation trends against available literature data. The proposed framework provides a transferable methodology for assessing fracture degradation trends in environments where standardized datasets remain limited.