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Journal Articles

Validation practices of multi-physics core performance analysis in an advanced reactor design study

Doda, Norihiro; Kato, Shinya; Hamase, Erina; Kuwagaki, Kazuki; Kikuchi, Norihiro; Ohgama, Kazuya; Yoshimura, Kazuo; Yoshikawa, Ryuji; Yokoyama, Kenji; Uwaba, Tomoyuki; et al.

Proceedings of 20th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-20) (Internet), p.946 - 959, 2023/08

An innovative design system named ARKADIA is being developed to realize the design of advanced nuclear reactors as safe, economical, and sustainable carbon-free energy sources. This paper focuses on ARKADIA-Design for design studies as a part of ARKADIA and introduces representative verification methods for numerical analysis methods of the core design. ARKADIA-Design performs core performance analysis of sodium-cooled fast reactors using a multiphysics approach that combines neutronics, thermal-hydraulics, core mechanics, and fuel pin behavior analysis codes. To confirm the validity of these analysis codes, validation matrices are identified with reference to experimental data and reliable numerical analysis results. The analysis models in these codes and the representative practices for the validation matrices are described.

Journal Articles

Development of a design optimization framework for sodium-cooled fast reactors, 2; Development of optimization analysis control function

Doda, Norihiro; Nakamine, Yoshiaki*; Kuwagaki, Kazuki; Hamase, Erina; Kikuchi, Norihiro; Yoshimura, Kazuo; Matsushita, Kentaro; Tanaka, Masaaki

Keisan Kogaku Koenkai Rombunshu (CD-ROM), 28, 5 Pages, 2023/05

As a part of the development of the "Advanced Reactor Knowledge- and AI-aided Design Integration Approach through the whole plant lifecycle (ARKADIA)" to automatically optimize the life cycle of innovative nuclear reactors including fast reactors, ARKADIA-design is being developed to support the optimization of fast reactor in the conceptual design stage. ARKADIA-Design consists of three systems (Virtual plant Life System (VLS), Evaluation assistance and Application System (EAS), and Knowledge Management System (KMS)). A design optimization framework controls the connection between the three systems through the interfaces in each system. This paper reports on the development of an optimization analysis control function that performs design optimization analysis combining plant behavior analysis by VLS and optimization study by EAS.

Journal Articles

Applicability study of Bayesian optimization to neutronic design of a homogeneous two-region core

Kuwagaki, Kazuki; Yokoyama, Kenji

Proceedings of 30th International Conference on Nuclear Engineering (ICONE30) (Internet), 9 Pages, 2023/05

At the Japan Atomic Energy Agency (JAEA), a design support tool for advanced nuclear reactors is currently under development. This tool is called ARKADIA-Design, and is expected to support the integrated design evaluation of reactors from the viewpoints of safety, economy, and sustainability as a carbon-free energy source by utilizing the newest analysis/evaluation technologies such as AI technology, and the accumulated knowledge of fast reactor development. One development task of the ARKADIA-Design is to build a system that automatically identifies optimized design parameters by which an objective function specified by core performance is minimized (or maximized). In the present study, we set up a single objective optimization example problem with multiple constraints for a homogeneous two-region core, and showed that the optimal solution of this example problem can be automatically obtained by the Bayesian optimization method, which is a candidate optimization algorithm for the system. In addition, we also demonstrated how the system would assist the core design procedure in future, by indirectly solving a three-variable optimization problem of the core design. From these results and demonstrations, we confirmed that the system to be developed has the potential to be a useful support tool for the designers, enabling them to obtain optimal core designs efficiently.

Journal Articles

Investigation of optimization process for core design with integrated analysis between neutronics and plant dynamics

Hamase, Erina; Kuwagaki, Kazuki; Doda, Norihiro; Yokoyama, Kenji; Tanaka, Masaaki

Proceedings of 30th International Conference on Nuclear Engineering (ICONE30) (Internet), 10 Pages, 2023/05

To innovate a core design process, an optimization process for the core design has been developed as a part of the design optimization support tool named ARKADIA-Design. The core design optimization process is integrated by the core design analysis of neutronics, thermal-hydraulics, and fuel integrity and plant dynamics analysis with the Bayesian optimization (BO) algorithm. The optimization problem for design parameters with high core performance and inherent safety in ULOF event was solved by the integrated analysis between the neutronics and plant dynamics with the BO in a primary loop system including a core consisting of two-dimensional RZ cylindrical geometry. It was indicated that the optimization process could obtain an optimal solution.

Journal Articles

Applicability study of Bayesian optimization in core neutronic design using a toy model

Kuwagaki, Kazuki; Yokoyama, Kenji

Proceedings of International Conference on Physics of Reactors 2022 (PHYSOR 2022) (Internet), 10 Pages, 2022/05

In Japan Atomic Energy Agency (JAEA), an innovative design approach named ARKADIA (Advanced Reactor Knowledge- and AI-aided Design Integration Approach through the whole plant lifecycle) for the advanced nuclear reactors is currently under development. One of the tasks in ARKADIA is to build a system that automatically optimizes core and fuel designs by conducting core neutronic and thermal-hydraulic calculations, fuel integrity evaluations, and plant dynamic analyses. This system will be implemented to automatically find an optimal design that minimizes (or maximizes) objective function defined by a core performance, while varying the core and fuel design parameters such as fuel pin diameter, core height and diameter. In this study, as the first step of the system development, we focused only on core neutronic design and conducted a study of automatic optimization. As the optimization algorithm, Bayesian optimization (BO), which is an effective method for optimization problems with expensive computation cost of objective function, was selected. The applicability of BO was studied based on single- and two-objective optimization examples of core neutronic design in a toy model. As a result, in the former, it was confirmed that BO can obtain the optimal solution, which well matches the reference solution calculated by a brute force calculation, with a small number of required calculation executions. Its usability on core neutronic designs, where the computation cost per case is large, was confirmed. In the latter, it was shown that BO can obtain a pareto solutions-set that shows good agreement with the reference solution.

JAEA Reports

Integral benchmark test of JENDL-4.0 for U-233 systems with ICSBEP Handbook

Kuwagaki, Kazuki*; Nagaya, Yasunobu

JAEA-Data/Code 2017-007, 27 Pages, 2017/03

JAEA-Data-Code-2017-007.pdf:4.77MB
JAEA-Data-Code-2017-007-appendix(CD-ROM).zip:0.37MB

The integral benchmark test of JENDL-4.0 for U-233 systems using the continuous-energy Monte Carlo code MVP was conducted. The previous benchmark test was performed only for U-233 thermal solution and fast metallic systems in the ICSBEP handbook. In this study, MVP input files were prepared for uninvestigated benchmark problems in the handbook including compound thermal systems (mainly lattice systems) and integral benchmark test was performed. The prediction accuracy of JENDL-4.0 was evaluated for effective multiplication factors ($$k_mathrm{eff}$$'s) of the U-233 systems. As a result, a trend of underestimation was observed for all the categories of U-233 systems. In the benchmark test of ENDF/B-VII.1 for U-233 systems with the ICSBEP handbook, it is reported that a decreasing trend of calculated $$k_mathrm{eff}$$ values in association with a parameter ATFF (Above-Thermal Fission Fraction) is observed. The ATFF values were also calculated in this benchmark test of JENDL-4.0 and the same trend as ENDF/B-VII.1 was observed.

Oral presentation

Applicability study of Bayesian optimization in core neutronic design

Kuwagaki, Kazuki; Yokoyama, Kenji

no journal, , 

no abstracts in English

Oral presentation

Oral presentation

Development of core design optimization process towards design efficiency and reduction of excessive conservativeness; Setting of representative problem and investigation of core design optimization process

Hamase, Erina; Kuwagaki, Kazuki; Doda, Norihiro; Yokoyama, Kenji; Tanaka, Masaaki

no journal, , 

To improve efficiency and innovate the core design process by decreasing the excessive conservativeness using a function of the design optimization support tool named ARKADIA-Design, firstly, the optimization process that provides the core design specifications with high core performance and inherent safety in ULOF event has been developed. The objective function in the optimization problem is set with the indexes of core performance and thermal transient loads for the simplified loop model. The problem is solved by the coupled analysis between the core design analysis and plant dynamics analysis with Bayesian optimization (BO). It was indicated that the optimization process using the neutronics and plant dynamics analysis with BO in a single objective function could obtain the optimal solution.

Oral presentation

Study on design optimization of a homogeneous two-region core utilizing bayesian optimization

Kuwagaki, Kazuki; Yokoyama, Kenji

no journal, , 

no abstracts in English

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