Cross-Verification and validation of steady-state OPAL research reactor neutronic models using OpenMC and MCNP5 Codes: A foundation for advanced coupled simulations

Abstract

This study develops, verifies, and validates high-fidelity steady-state neutronic models of the OPAL research reactor using OpenMC and MCNP5. The models were developed based on a consistent methodology, utilizing identical input data, geometric modeling, and cross-section libraries, minimizing discrepancies from external factors, ensuring a solid foundation for subsequent code-to-code comparisons.

Verification and validation were conducted through comparisons with results from SERPENT and MCNP6, as well as experimental data. Our results showed strong agreement with the experimental data, including control rod worth calculations within 3% and axial peak factor differences averaging 2% for MCNP5 and 3% for OpenMC. Differences in isothermal temperature and void coefficients were approximately 1 pcm/°C and 7 pcm/%, respectively. Deviations from SERPENT and MCNP6 for few key parameters were within acceptable limits, consistent with reference studies, and attributed to variations in modeling, code differences, and Monte Carlo statistical uncertainties.

Finally, a comprehensive code-to-code comparison of key neutronic parameters, such as reactivity, flux distributions, kinetic parameters, and power distribution, showed excellent agreement between OpenMC and MCNP5, with relative differences under 1% for most parameters.

Overall, this study confirms the reliability of the developed models for simulating the OPAL reactor and establishes OpenMC as a viable alternative to MCNP for reactor physics simulations, laying the foundation for future coupling with thermal–hydraulic models.