Benchmark analysis of SPERT III E-core critical experiments using the STREAM neutronics code

This study delivers a high-fidelity neutronic analysis of the SPERT III E-Core, a pressurized-water experimental reactor designed to probe fundamental transient behavior during reactivity-initiated accidents (RIAs). Using the advanced 3D transport code STREAM, we construct a detailed full-core representation—including fuel assemblies, cruciform transient control rods, control rod followers, and flux suppressors, to simulate both steady-state operation and rapid power excursions. Eigenvalue predictions at cold and hot zero-power conditions agree with measurements within 400 pcm, while simulated RIA responses, including reactivity evolution, peak power, and energy release, remain within 10 % of experimental observations. These results demonstrate that STREAM reliably captures fast transient dynamics in complex reactor configurations. Beyond validating a modern deterministic tool against historically important pulse-reactor experiments, this work establishes a foundation for next-generation transient modeling, supporting enhanced safety assessment, performance optimization, and informed regulatory decision-making in advanced reactor systems.