Background With the continuous development of nuclear power technology, reactor design has put forward higher requirements for the accuracy, efficiency and multi-functionality of nuclear computing software. The current mainstream Monte Carlo software has deficiencies in the balance between reactor radiation shielding design and nuclear design calibration, which restricts the critical simulation efficiency of the reactor core. Therefore, CNPRI has specifically developed the 3D Monte Carlo software LARCH 1.0 to meet the actual needs of nuclear power engineering design.

Purpose This study aims to optimize the particle energy search mechanism in Monte Carlo simulation and address the pain point of low efficiency in traditional search methods; thereby based on the optimized search method, the delta-tracking algorithm is further improved to enhance the efficiency of core critical calculation and provide efficient and accurate calculation support for reactor design.

Method During the development of the LARCH software, the core technological innovation lies in the adoption of a unified energy grid design to replace the traditional binary search and logarithmic search methods. Through the standardization and unification of the energy grid, the number of searches in the particle energy matching process is reduced, and the time consumption of a single search is shortened. Based on the unified energy grid technology, we further developed and optimized the delta-tracking algorithm to achieve the improvement of computing efficiency. By designing a targeted numerical verification scheme, the LARCH 1.0 software and the traditional Monte-Carlo software were compared and tested in reactor problem simulations.

Results The optimized technical solution has achieved remarkable results. The search method based on the unified energy grid has significantly reduced the time cost of particle energy search compared with the traditional method. Based on this, the optimized delta-tracking algorithm has increased the critical computing efficiency of the Monte-Carlo software core by approximately 25%.

Conclusions The unified energy grid method and the optimized delta-tracking algorithm adopted by the LARCH 1.0 3D Monte-Carlo software provide an effective technical path for the efficiency improvement of the Monte Carlo software and significantly enhance the critical calculation efficiency of the reactor core. The application potential of this software indicates that it can provide more efficient and reliable numerical simulation tools for reactor design. More extensive engineering verification and functional iterations will be further carried out subsequently.