Miniature fission ionization chambers are widely used as in-core neutron detectors in nuclear reactors. The high neutron flux in the core imposes stringent requirements on their operational lifetime. This paper proposes a breeder fission ionization chamber by incorporating U-234 into the U-235 coating, enabling U-235 regeneration via the U-234 (n, γ)U-235 reaction as U-235 is consumed. A multi-physics coupled fission ionization chamber model was developed using Geant4 and Garfield++ to systematically investigate the effects of U-234/U-235 mixing patterns (layered/homogeneous) and U-234/U-235 ratios on detector sensitivity and lifetime characteristics. Simulation results show that: The optimal coating thickness is 5 μm, and the optimal mixing pattern is Radial Layered Type-II (U-235 layer encapsulating U-234). Detector sensitivity decreases monotonically with increasing U-234 proportion. A lifetime iterative model based on simulation data demonstrates that adding U-234 to the coating extends detector lifetime to varying degrees across 25 iterations. Higher U-234 proportions flatten the sensitivity-time curve, indicating improved stability. This study provides theoretical guidance for the engineering design of breeder fission ionization chambers.