Thermoelectric-powered heat pipe-cooled nuclear reactors, characterized by their sunlight-independent operation, long operational lifespan, and high reliability, have emerged as a critical focus in deep space exploration research. To address the thermal management challenges of spaceborne nuclear reactor systems, this study develops a comprehensive thermal analysis model for radiators and establishes a generalized design framework tailored for heat pipe-cooled space reactors. The proposed framework supports the design of radiators across diverse configurations, laying a foundation for future deep-space missions. The framework that enables rapid structural design and temperature field simulations of radiators is implemented via C++ programming language. Validation against Fluent confirms the tool’s accuracy. A case study demonstrates its application to the design and optimization of a radiator for a 10 kWe thermoelectric-conversion heat pipe-cooled space reactor. Results demonstrate that among various fin dimension schemes, the configuration with uniform heat dissipation power per fin yields the optimal design performance.