Accurate modeling of atomic masses with reliable uncertainty quantification is essential for understanding heavy-element production in astrophysical environments. This remains challenging because uncertainties arise not only from model parameters but also from structural limitations, often leading to underestimation when extrapolating beyond known nuclei. Here, we introduce SPICE, a probabilistic nuclear mass model that uses local Bayesian averaging to emulate mixing between low-lying nuclear configurations within a shell-model-inspired framework. By incorporating configurations associated with excitations across harmonic-oscillator and spin-orbit major shells, the model achieves root-mean-square deviations of about 500 keV with only 10-13 parameters. Our results show that local configuration mixing improves predictive accuracy and provides insight into evolving shell structure in neutron- and proton-rich regions, with potential extensions to include configuration mixing effects from non-orthogonal configurations.

Nuclear physical inputs are critical for predicting the abundance of r-process elements. Extensive sensitivity studies have recently been performed to gauge the impact of the individual properties of nuclei on the r-process. In this work, we investigate the impact of the large uncertainties in the theoretical predictions of the masses of neutron-rich Sn isotopes and the location of the neutron drip line on the abundance of r-process abundances. The uncertainties in the predicted r-process abundances are obtained through large-scale network calculations by simultaneously varying the masses and reaction rates of Sn within the predicted mass uncertainties. The calculations use a generally indicative astrophysical trajectory of neutron-star mergers and are based on three different mass models. The results indicate that the large uncertainty in the location of the neutron drip line for Sn can significantly and asymmetrically affect the predicted abundances of nuclei after the second peak, in particular around A=140−155, sometimes accompanied by a delayed freeze-out.