Chemical Kinetic Uncertainty Quantification in Hydrogen Combustion Computational Fluid Dynamics Simulation for ENACCEF2 Experiment

Motegi, Kosuke; Matsumoto, Toshinori; Shiotsu, Hiroyuki

Proceedings of 21st International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-21) (Internet), 10 Pages, 2025/08

Core deformation reactivity with neutronics-thermal hydraulics-structural mechanics coupled analysis for FFTF LOFWOS Test #13

Doda, Norihiro; Kato, Shinya; Uwaba, Tomoyuki; Tanaka, Masaaki; Nakamine, Yoshiaki*; Igawa, Kenichi*; Iida, Masaki*

Proceedings of 21st International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-21) (Internet), 14 Pages, 2025/08

Accurate evaluation of reactivity feedback due to core deformation during power increases in sodium-cooled fast reactors requires comprehensive modeling of the interactions among neutronics, thermal-hydraulics, and core mechanics. To accurately consider these interactions, JAEA has developed an evaluation method that combines multiple analysis codes that model these phenomena in detail. In this study, the evaluation method was applied to the core analysis of the FFTF LOFWOS Test #13, and the analysis results of net reactivity were compared with the test results. The sensitivity analysis results of the core structural design parameters showed that the core bowing behavior has a significant effect on the temporal variation of net reactivity.

Experimental study of two-phase flow in a four-by-four unheated rod bundle for validation of thermal-hydraulics simulation codes

Muhammad, I.; Nagatake, Taku; Uesawa, Shinichiro; Ono, Ayako

Proceedings of 21st International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-21) (Internet), 12 Pages, 2025/08

This research aims to validate ACE-3D using data from a two-phase flow experiment. For this purpose, a two-phase flow experiment was conducted in a four-by-four unheated fuel assembly. In the experiment, the time-averaged void fraction distribution was measured using a wire mesh sensor system under high temperatures and high-pressure conditions. The experimental results were analyzed, and the data were visualized to understand better the behavior and characteristics of the two-phase flow in the fuel assembly. A two-phase flow data set is being developed, covering a wide range of experimental conditions, including higher-pressure regions, which can be used for validating thermal-hydraulic codes. Finally, the ACE-3D code was applied to the two-phase flow experiment. The calculation results were then compared to the experimental ones, and the issues were identified for improving ACE-3D in future simulations.