Research of Monte Carlo Laboratory
Monte Carlo Methods, Codes and Applications
Our laboratory is developing McCARD/G, a GPU-accelerated time-dependent Monte Carlo (TDMC) code designed for high-fidelity reactor transient simulations. Unlike the traditional history-based method, McCARD/G employs an event-based approach, defining neutron flights and collisions as events that can be executed in parallel on GPUs. This significantly enhances computational efficiency—achieving more than 200-fold speedups compared to CPU-based calculations—while maintaining the accuracy of the Monte Carlo method.
To further improve reliability and efficiency, McCARD/G incorporates delayed neutron precursor treatment, population control techniques, and a generalized lattice geometry module for complex reactor cores. These features enable accurate space–time neutron tracking and efficient geometry handling optimized for GPU architectures.
The code’s performance and accuracy have been validated through both C5G7-TD benchmark problems and experimental benchmarks at the Kyoto University Critical Assembly (KUCA), confirming strong agreement with reference results. Through this development, our laboratory is establishing a next-generation Monte Carlo framework that provides a robust tool for transient reactor analysis, safety validation, and advanced reactor core design.
* Representative Research Example :
Sang Hoon Jang and Hyung Jin Shim, “Advances for the time-dependent Monte Carlo neutron transport analysis in McCARD,” Nucl. Eng. Technol., vol. 55, 2712-2722 (2023).
Woo Kyoung Ko, Seong Jeong Jeong, Young In Kim, and Hyung Jin Shim, “Development of a GPU enhanced time-dependent Monte Carlo neutron transport version of McCARD,” EPJ Nuclear Sci. Technol., 10, 28 (2024).
Reactor Core Analysis
Our laboratory conducts extensive research on reactor core behavior to achieve precise understanding and contribute to safe and efficient reactor design. First, we focus on time-dependent Monte Carlo methods to accurately analyze core dynamics. This allows us to directly evaluate transient phenomena such as reactivity changes, power fluctuations, and temperature rise, while complementing and extending conventional point kinetics approaches. Such studies provide critical insights into high-fidelity predictions of reactor behavior under accident scenarios or operational transients.
In addition, we are developing integrated frameworks that couple neutronics and thermal-hydraulics to reflect the strong interplay between neutron transport and thermal feedback within the core. By linking Monte Carlo neutronics codes with subchannel-scale thermal-hydraulic solvers, we establish a comprehensive environment capable of realistically capturing nuclear–thermal interactions. This enables more accurate evaluations of power distribution shifts, fuel temperature feedback, and overall core safety margins, with direct applications to light water reactors and beyond.
Our research further extends to long-term burnup analysis by integrating depletion calculations with coupled neutronics–thermal-hydraulic frameworks. As fuel depletes, core characteristics such as reactivity, power distribution, and temperature profiles evolve in complex ways. To capture these effects, we perform fully coupled burnup analyses that account for both fuel composition changes and thermal feedback mechanisms. This provides realistic predictions of long-term operational characteristics, supporting optimized fuel management strategies and reliable core design.
Ultimately, these efforts aim to establish a robust foundation for both safety assurance and performance optimization of advanced nuclear systems. By encompassing time-dependent analyses, multiphysics coupling, and burnup evaluation, our research offers comprehensive methodologies that go beyond the limitations of conventional approaches. This integrated perspective not only advances the academic understanding of core physics but also provides practical tools for the design and validation of next-generation reactors.
Reactor Core Analysis
Our laboratory conducts comprehensive research on core design, the central element of nuclear reactors. The aim is to establish design methodologies that simultaneously achieve safety, efficiency, and sustainability in reactor operation.
In this area, we begin with detailed neutronic analyses to evaluate criticality, power distribution, reactivity characteristics, and fuel depletion behavior. Based on these evaluations, we explore designs that maximize fuel utilization and enable long-cycle operation. Coupled thermal-hydraulic analyses are also performed to assess cooling performance, temperature distributions, and safety margins under realistic operating conditions.
Ensuring safety and control capability is another key aspect of our research. We investigate ways to guarantee stable operation not only under normal conditions but also during transients, placing emphasis on inherent safety features and reliable control performance from the design stage.
Our studies also integrate fuel cycle management, multiphysics simulations, and optimization methods to enhance both practicality and economic viability, providing core concepts that meet the diverse requirements of next-generation reactors.
Ultimately, our core design research spans from the improvement of existing light water reactors to the development of advanced systems such as high-temperature gas-cooled reactors, small modular reactors, and innovative advanced reactors. Through these efforts, we aim to build a strong foundation for the safe application and future expansion of nuclear energy.
In addition, our laboratory has engaged in practical core design projects alongside advanced reactor studies. These include the BANDI-60 soluble-boron-free small modular reactor (SMR) core design for marine applications as well as the design of a research reactor core at the Moon-Moo Dae-Wang Science Research Institute. Through these activities, we have built up experience that spans from research reactors to commercial power plants and next-generation systems, thereby strengthening our comprehensive core design capabilities across a wide spectrum of nuclear applications.
* Representative Research Example :
Dokyun Kim and Hyung Jin Shim, “Equilibrium Core Design for 170MWe PWR-Type SMR Applying a Two-Batch Fuel Management Concept,” Transactions of the Korean Nuclear Society Spring Meeting, Jeju, May 18-19 (2023).
Kyoseong Song, Cheol Ho Pyeon, and Hyung Jin Shim. “Design of open-tank-in-pool-type educational critical assemblies using UO2 and U-7Mo fuels,” Annals of Nuclear Energy, 213, 111139 (2025).
Energy & Nuclear Policy
Our research area integrates engineering-based analysis with policy studies to provide scientifically grounded, quantitative insights for national energy strategies and the advancement of nuclear policy.
Using computational modeling, scenario analysis, and cost–benefit evaluation, we optimize Korea’s future energy portfolio and determine the appropriate share of nuclear power within it. Our work accounts for the integration of renewables, fossil fuels, and energy storage technologies to propose long-term, balanced energy mix strategies.
In parallel, we conduct policy-oriented studies on Korea’s nuclear industry and regulatory governance. This includes analyzing institutional and legal frameworks, developing industry growth roadmaps, assessing nuclear safety regulations, reviewing global regulatory trends, and evaluating the policy implications of advanced nuclear technologies such as SMRs and HTGRs. Through these efforts, we aim to deliver actionable roadmaps that link policy, technology, and industry, thereby strengthening the strategic role of nuclear energy in national policy.
* Representative Research Example :
Jisun Kim, Seul Ki Lim, Dokyun Kim, Hyung Jin Shim, “A Study on Roadmap for North Korea’s Denuclearization,” Transactions of the Korean Nuclear Society Spring Meeting, Jeju, Korea, May 23-24 (2019).
Ji Woong Park, Hyung Jin Shim, “Cost Assessment of 2030 Electricity Generation Mixes Changing the Nuclear Energy Proportion under South Korean Nationally Determined Contribution Target,” Transactions of the Korean Nuclear Society Spring Meeting, Jeju, May 19-20 (2022).
Machine Learning and AI for Reactor Physics
Our lab is pioneering next-generation reactor simulation tools by integrating artificial intelligence with reactor physics. We develop Physics-Informed Neural Network (PINN) models that solve the neutron diffusion equation to predict a reactor’s power distribution and criticality without relying on labeled data.
Our work has demonstrated that explicitly embedding physical formulas into the AI model, rather than relying on the network’s prediction alone, dramatically improves training stability, paving the way for more reliable AI-based analysis tools.
* Representative Research Example :
Jaeguk Lee, Hyung Jin Shim, “A CNN-Based Physics-Informed Neural Networks for Solving the Neutron Diffusion Equation,” M&C 2025 – International Conference on Mathematics & Computational Methods Applied to Nuclear Science & Engineering, Denver, CO, Apr. 27-30, 2025 (2025).