Specifications for benchmark analyses of transient thermal-hydraulics in reactor vessel and primary heat transport system during decay heat removal operation

Kobayashi, Jun; Tanaka, Masaaki; Hamase, Erina; Ezure, Toshiki

JAEA-Data/Code 2025-009, 74 Pages, 2025/08

JAEA-Data-Code-2025-009.pdf:4.7MB

In a sodium-cooled fast reactor, a diversified auxiliary cooling system to remove decay heat from the core is required to enhance its safety. The decay heat removal systems (DHRSs) include a direct reactor auxiliary cooling system (DRACS) with a heat exchanger in the upper plenum (UP) of the reactor vessel (RV), a primary reactor auxiliary cooling system (PRACS) with a heat exchanger in the primary heat transport system (PHTS), an intermediate reactor auxiliary cooling system (IRACS) with a heat exchanger in the secondary heat transport system (SHTS), a heat removal system which employs a steam generator, and a reactor vessel auxiliary cooling system (RVACS) that effects cooling from outside the RV. In the operation of the DRACS with a dipped-type direct heat exchanger (D-DHX) installed in the UP of the RV (UP-RV), the thermal interaction, called core-plenum interaction (CPI), regarding the thermal-hydraulic phenomena in the UP-RV and the core is observed. The CPI includes the penetration flow of the sodium at a low temperature from the D-DHX into the core assemblies, the flow in the gap between assemblies, and the radial heat transfer through sodium in the gap. On the other hand, in the operation of the PRACS or IRACS, where the flowrate in the PHTS is maintained, the core coolability is affected by plant operating conditions. Two transient tests conducted at the PLANDTL-DHX sodium test facility in Japan Atomic Energy Agency were provided to develop an appropriate numerical analysis model for prediction of transient thermal-hydraulics in the DHRSs, the core, and the PHTS. In this document, the geometry information of the RV and the PHTS, including the heat exchangers for the DHRS, and the measured flowrate and temperature transients at each inlet of the intermediate heat exchanger (IHX) on the SHTS side and DHRS were specified as the boundary conditions for the benchmark analyses.

Development of gas entrainment evaluation method in the hot plenum of sodium-cooled fast reactor

Ezure, Toshiki; Matsushita, Kentaro; Sasaki, Keisuke; Tanaka, Masaaki

Dai-29-Kai Doryoku, Enerugi Gijutsu Shimpojiumu Yokoshu (Internet), 5 Pages, 2025/06

In the design of the pool-type demonstration sodium-cooled fast reactor (demonstration reactor), the prevention of gas entrainment in the hot plenum of the reactor vessel is one of important issues to be addressed in the conceptual design of demonstration reactor. Related to this problem, the authors have been developing an evaluation approach combining the analysis method of entrained gas-transport in the primary circuit, SYRENA, and the gas entrainment evaluation method, StreamViewer, at the free surface in the hot plenum of the demonstration reactor. In this study, a development plan of StreamViewer is presented toward application to the evaluation of the demonstration reactor design. Furthermore, an overview of scaled model water experiment of the pool-type demonstration reactor to obtain the validation date for StreamViewer is also presented.

Application study of adaptive mesh refinement method on unsteady wake vortex analysis

Alzahrani, H.*; Matsushita, Kentaro; Sakai, Takaaki*; Ezure, Toshiki; Tanaka, Masaaki

Nuclear Technology, 13 Pages, 2025/06

https://doi.org/10.1080/00295450.2025.2472582

Development of evaluation method for cover gas entrainment by vortices generated at free surface in upper plenum of sodium-cooled fast reactor is required, and an evaluation method by predicting vortices from flow velocity distribution obtained by CFD analysis is developed. In this study, Adaptive Mesh Refinement (AMR) method is examined to improve efficiency of CFD analysis. Initial mesh was refined with two indexes: the first index (Index-1) is when the second invariant of velocity gradient tensor, Q, is negative and the second one (Index-2) is pressure gradient index added to Index-1. As a result of applying AMR method to unsteady vortices system with a flat plate and performing transient analyses with refined meshes, the result of pressure distribution and velocity around the flat plate in mesh using Index-2 was similar to the result of all refined mesh. It was also confirmed that vortices generation and growth was better simulated by refining meshes around separation area.

Nuclear power propulsion system for nuclear ship "Mutsu" and technical reference

Tanaka, Kei*; Kudo, Toshihiro

Marine Engineering, 60(2), p.21 - 26, 2025/04

no abstracts in English

Structural behaviors of lead zirconate titanate-based ferroelectric ceramics during pyroelectric-power generation cycles

Kawasaki, Takuro; Fukuda, Tatsuo; Yamanaka, Satoru*; Murayama, Ichiro*; Kato, Takanori*; Baba, Masaaki*; Hashimoto, Hideki*; Harjo, S.; Aizawa, Kazuya; Tanaka, Hirohisa*; et al.

Journal of Applied Physics, 137(9), p.094101_1 - 094101_7, 2025/03

https://doi.org/10.1063/5.0243081

Surface and interfacial aggregation states in thin films of a polystyrene/polyrotaxane blend

Taguchi, Miki*; Miyata, Noboru*; Miyazaki, Tsukasa*; Aoki, Hiroyuki; Ozawa, Satoru*; Hasegawa, Ryuichi*; Morimitsu, Yuma*; Kawaguchi, Daisuke*; Yamamoto, Satoru*; Tanaka, Keiji*

Polymer Journal, 7 Pages, 2025/03

https://doi.org/10.1038/s41428-025-01030-y

Development of gas entrainment evaluation model based on distribution of pressure along vortex center line; Application to a gas entrainment experiment with traveling vortices in an open water channel flow?

Matsushita, Kentaro; Ezure, Toshiki; Tanaka, Masaaki; Imai, Yasutomo*; Fujisaki, Tatsuya*; Sakai, Takaaki*

Nuclear Engineering and Design, 432, p.113785_1 - 113785_16, 2025/02

https://doi.org/10.1016/j.nucengdes.2024.113785

Establishing an evaluation method for the gas entrainment (GE) of argon cover gas due to surface vortices is required in terms of safety design of sodium-cooled fast reactors. To modify the evaluation model in an in-house evaluation tool for GE, StreamViewer, a modified evaluation model on the pressure distribution along the vortex center line (PVL model) was proposed to identify the vortex center lines by connecting continuous vortex center points from the suction port to the surface and evaluate gas core length based on the balance between the hydrostatic pressure and the pressure decrease distribution along the vortex center line. PVL model was applied the three-dimensional numerical analysis results for the experiments where a plate induced unsteady traveling vortices in the open channel flow. Consequently, the GE evaluation using StreamViewer with PVL model could reproduce the relation between the inlet flow velocity and the gas core length in the unsteady vortex flow experiments.

Neutron reflectometry study on the interfacial layer of epoxy resin to improve adhesion strength

Liu, Y.*; Miyata, Noboru*; Miyazaki, Tsukasa*; Shundo, Atsuomi*; Kawaguchi, Daisuke*; Tanaka, Keiji*; Aoki, Hiroyuki

ACS Applied Materials & Interfaces, 8 Pages, 2025/00

http://doi.org/10.1021/acsami.5c07863

Development of HCl-free solid-phase extraction combined with ICP-MS/MS for rapid assessment of difficult-to-measure radionuclides, 3; Measurement of Se concentration in concrete rubble

Banjarnahor, I. M.; Do, V. K.; Furuse, Takahiro; Ota, Yuki; Tanaka, Kosuke

Journal of Radioanalytical and Nuclear Chemistry, 10 Pages, 2025/00

https://doi.org/10.1007/s10967-025-10143-w

Developing an online composition prediction for an HI-I-HO system using deep neural network

Tanaka, Nobuyuki; Takegami, Hiroaki; Noguchi, Hiroki; Kamiji, Yu; Myagmarjav, O.; Ono, Masato; Sugimoto, Chihiro

Chemical Engineering Science, 299, p.120479_1 - 120479_11, 2024/11

https://doi.org/10.1016/j.ces.2024.120479

We developed a deep neural network method to predict the composition of the iodine-sulfur process of thermochemical water-splitting hydrogen production using measurable properties. Unlike conventional titration analysis, this approach allows a quick understanding of fluid composition, providing essential information for controlling operating conditions. This study focused on the HI-I-HO three-component system within the IS process. Using Gibbs phase rule, the DNN model was constructed using online measurable parameters, such as temperature, pressure, and density, as input conditions. The model was trained with experimental data, and the structural parameters were tuned. Composition prediction using actual trend data demonstrated good correlation with titration analysis measurements. Furthermore, the local interpretable model-agnostic explanations method was incorporated to gain insights into the significance of input parameters for compositions from the DNN model, providing valuable information on crucial parameters for effective composition control.