This paper evaluates the neutronic feasibility and multi-physics safety of a hybrid Accident Tolerant Fuel (ATF) assembly in a VVER-1000 reactor. The proposed design strategically employs standard UO2 within the inner core and a high-density U3Si2 matrix in the peripheral pins to take advantage of inter-assembly thermalization for cycle length extension. Coupled evaluations were performed using OpenMC continuous-energy Monte Carlo transport and OpenFOAM steady-state conjugate heat transfer Computational Fluid Dynamics (CFD). The hybrid assembly meets the target of extending the depletion cycle to 540 days through the rapid breeding of peripheral Pu-239. Although this configuration induces intensely localized radial power peaking (399.18 W/cm3), the superior metallic thermal conductivity of U3Si2 (>15.0 W/m⋅K) completely eliminates the thermal penalty. OpenFOAM simulations of the ATF pins demonstrate that the peak centerline temperatures are reduced by 50 K compared to the interior of the UO2 core (690 K vs. 740 K), yielding a drastic reduction in localized sensible stored energy. Neutronic safety is strictly preserved, maintaining deeply negative Fuel and Moderator Temperature Coefficients (−1.895 pcm/K and −36.533 pcm/K) alongside a robust B4C Control Rod Worth (65,323.56 pcm). These results demonstrate that the hybrid ATF assembly fundamentally improves LOCA coping times while enhancing the overall economics of the reactor.