Deokjung Lee

This paper presents a comprehensive neutronic simulation of the new sodium-cooled fast reactor (SFR) benchmark based on the extended Start-Up Tests of the China Experimental Fast Reactor. This extended phase evaluates three-dimensional (3D) full-core calculations across seven distinct work packages. Three packages incorporate empirical measurement data: burnup, deep penetration, and neutron dynamics (transient), while the remaining four rely on the simulation results provided by participants from different institutions: neutron spectrum, group constants, kinetic parameters, and spatial reactivity distribution. Simulations were performed primarily using the high-fidelity Monte Carlo transport code MCS. To ensure reproducibility, all modeling input variables, simulation procedures, and more detailed results are compiled within the supplementary data. This work establishes a high-fidelity reference for future SFR computer code validation as well as advanced research and development.

I. Recent advancements in accident-tolerant fuel (ATF) research have aimed to enhance the safety and efficiency of nuclear power plants, particularly in commercial pressurized water reactors (PWRs)...

I. The method of characteristics (MOC) has been widely used for high-fidelity light water reactor (LWR) core analyses in recent decades, offering a competitive alternative to Monte Carlo methods in...

Background Hornet is introduced as a GPU-optimized nuclear data processing code designed to accelerate neutron cross-section handling and A Compact ENDF (ACE) file sampling for incident neutron data and thermal scattering laws. Hornet supports continuous-energy Monte Carlo applications and is Monte Carlo–agnostic, making it versatile for academic use and easy integration into various Monte Carlo frameworks. Methods Hornet is implemented in CUDA C++ using an object-oriented design to take full advantage of Graphical Processing Unit (GPU) parallelism. Verification was conducted through both standalone tests and integration with GPU-optimized REActor Physics Monte Carlo (GREAPMC) – an in-house Graphical Processing Unit (GPU) Monte Carlo code – across standard benchmark simulations, including International Atomic Energy Agency (IAEA) INDC (USA)-107 pin-cell and Mosteller benchmarks. Performance and precision were assessed by comparing Hornet’s output against that of Monte Carlo Simulation (MCS), an in-house CPU-based high-fidelity Monte Carlo code. Results Across all benchmark scenarios, Hornet matched MCS in accuracy, delivering Root Mean Square (RMS) power differences below 0.1% in pin-by-pin power distribution within an OPR1000 fuel assembly. Remarkable tracking rate enhancements were also observed compared to MCS. Hornet’s ability to maintain continuous-energy treatment on GPU hardware was demonstrated with precise modeling of bound and free thermal scattering effects. Conclusions Hornet enables robust and efficient GPU-based continuous-energy nuclear data processing, producing high-precision results on par with CPU-based Monte Carlo codes. Its object-oriented CUDA C++ architecture ensures maintainability and adaptability. Tested extensively with GREAPMC, Hornet proves to be a powerful tool for modern nuclear analysis and reactor design. Planned enhancements such as support for photo-atomic ACE file processing will broaden its applicability further.

A calculation technique computing the adjoint flux of perturbed system is developed for the exact perturbation theory in Monte Carlo transport. By using a correlated sampling and iterated fission probability methods together, the adjoint flux of perturbed system is calculated during a forward Mote Carlo simulation of an unperturbed system. In the perturbation-included iterated fission probability method, no additional particle simulation is required to compute the adjoint flux of perturbed system. The exact perturbation method is implemented in the Monte Carlo code MCS. The results of perturbation method for k -eigenvalue change are compared against differential operator sampling, adjoint-weighted perturbation, and direct perturbation methods for the Godiva benchmark and PLUS7 fuel assembly.