Hybrid two-step method for higher-order modes calculation: a novel approach to advance nuclear reactor technology
The NEAL (Nuclear Energy & Applications Laboratory) team at University of South China develops HARMONY2.0 code with hybrid two-step method, enabling efficient higher-order modes calculation for complex core geometries and energy spectra
image: In the traditional two-step method, the homogenization group constants of the fuel assembly are calculated using the assumption of reflective boundary conditions. In the hybrid two-step method used in HARMONY 2.0, the homogenization group constants are calculated based on the “real” boundary conditions with OpenMC.
Credit: Er-Pin Zhang
The NEAL team at the University of South China has made new progress in the field of nuclear reactor numerical computation. They have developed a MC-deterministic hybrid two-step method for efficient higher-order modes calculation in nuclear reactors, providing an innovative technical approach for reactor physics analysis. The related research has been published in the journal: Nuclear Science and Techniques.
Innovative Hybrid Two-Step Strategy
Traditional deterministic methods for higher-order modes calculation suffer from limited adaptability to complex geometries and energy spectra, while MC approaches face low computational efficiency and excessive memory consumption. To address these challenges, the research team combined the strengths of both methods:
Step 1: The Monte Carlo code OpenMC is employed to generate homogenized multi-group constants, ensuring precise treatment of complex geometries and arbitrary energy spectra.
Step 2: The Implicitly Restarted Arnoldi Method (IRAM) is used to solve the diffusion equation, preserving the higher-order modes calculation capability of HARMONY1.0 while avoiding the geometric/spectral limitations of deterministic methods.
Parallel Computing Acceleration
Event-driven parallelization & domain decomposition method (based on OpenMP) was implemented to optimize the iterative computation process for large-scale higher-order modes problems, significantly improving the efficiency of solving prompt α and λ modes.
Validation with Complex Geometries
Successful calculation of λ-mdoes in the Hoogenboom and ATR reactor, prompt α modes in the MUSE-4 experimental facility verifies the validity of the method.
Broad Application Prospects
Higher-order mode calculations have been widely applied in reactor physics, particularly for core reactivity measurements, online monitoring. The hybrid two-step method provides a novel computational strategy for reactor analysis. Moreover, the efficient high-order modes calculation tools also provide a effective research basis for the development of core reactivity measurements, online monitoring, thus contributing to the development of nuclear reactor technology.
“Our team is currently conducting further research based on the HARMONY2.0 code,” said Professor Jin-Sen Xie, the corresponding author of the study. “We remain committed to advancing this work to deliver useful scientific outcomes for nuclear reactor technology.”
The complete study is accessible via DOI: 10.1007/s41365-024-01619-7
Nuclear Science and Techniques (NST) is a peer-reviewed international journal sponsored by the Shanghai Institute of Applied Physics, Chinese Academy of Sciences. The journal publishes high-quality research across a broad range of nuclear science disciplines, including nuclear physics, nuclear energy, accelerator physics, and nuclear electronics. Its Editor-in-Chief is the renowned physicist, Professor Yu-Gang Ma.