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Journal Articles

Investigating eutectic behavior and material relocation in B$$_{4}$$C-stainless steel composites using the improved MPS method

Ahmed, Z.*; Wu, S.*; Sharma, A.*; Kumar, R.*; Yamano, Hidemasa; Pellegrini, M.*; Yokoyama, Ryo*; Okamoto, Koji*

International Journal of Heat and Mass Transfer, 250, p.127343_1 - 127343_17, 2025/11

 Times Cited Count:0

Journal Articles

Radiation heating effects on B$$_{4}$$C-SS eutectic melting and its relocation behaviour

Ahmed, Z.*; Sharma, A. K.*; Pellegrini, M.*; Yamano, Hidemasa; Okamoto, Koji*

Arabian Journal for Science and Engineering, 50(5), p.3361 - 3371, 2025/03

 Times Cited Count:1 Percentile:0.00(Multidisciplinary Sciences)

Journal Articles

A Preliminary study for boron mixing effect on severe accident scenario in sodium-cooled fast reactor

Yamano, Hidemasa; Morita, Koji*

Proceedings of 13th Korea-Japan Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS13) (Internet), 9 Pages, 2024/11

Journal Articles

France-Japan collaboration on severe accident studies in sodium-cooled fast reactors, 3; Thermodynamic, Kinetic, and Thermophysical Studies of Core Material Mixture

Yamano, Hidemasa; Emura, Yuki; Takai, Toshihide; Kubo, Shigenobu; Quaini, A.*; Fossati, P.*; Delacroix, J.*; Journeau, C.*

Proceedings of International Conference on Nuclear Fuel Cycle (GLOBAL2024) (Internet), 4 Pages, 2024/10

This report mainly introduces trends in fast reactor development in Japan in addition to introducing overseas development trends for major developing countries. The paper describes major severe accident study results focusing on kinetics of interaction in core material mixtures, physical properties of core material mixtures, high temperature thermodynamic data for the uranium oxide (UO$$_{2}$$)-iron (Fe)-boron carbide (B$$_{4}$$C) system, experimental studies on B$$_{4}$$C-stainless steel (SS) kinetics and B$$_{4}$$C-SS eutectic material relocation (freezing), and B$$_{4}$$C-SS eutectic and kinetics models for severe accident code systems,

Journal Articles

Study on eutectic melting behavior of control rod materials in severe accidents of sodium-cooled fast reactors, 2; Modeling of multi-phase eutectic reaction behavior

Morita, Koji*; Yamano, Hidemasa

Proceedings of 14th International Topical Meeting on Nuclear Reactor Thermal-Hydraulics, Operation, and Safety (NTHOS-14) (Internet), 12 Pages, 2024/08

This paper describes the generalized model developed for these eutectic reactions between boron carbide (B$$_{4}$$C) and stainless steel (SS) as well as for the reactions that occur between eutectic reaction products in the solid and liquid states and SS or B$$_{4}$$C. We also describe the thermophysical property model based on thermophysical property data.

Journal Articles

Study on eutectic melting behavior of control rod materials in severe accidents of sodium-cooled fast reactors, 1; Project overview and progress until 2022

Yamano, Hidemasa; Takai, Toshihide; Emura, Yuki; Fukuyama, Hiroyuki*; Higashi, Hideo*; Nishi, Tsuyoshi*; Morita, Koji*; Nakamura, Kinya*; Ahmed, Z.*; Pellegrini, M.*

Proceedings of 14th International Topical Meeting on Nuclear Reactor Thermal-Hydraulics, Operation, and Safety (NTHOS-14) (Internet), 12 Pages, 2024/08

This paper describes the project overview and progress of experimental and analytical studies conducted until 2022. A specific result in this paper is to obtain first experimental data of B$$_{4}$$C-SS eutectic freezing.

Journal Articles

Study on eutectic melting behavior of control rod materials in severe accidents of sodium-cooled fast reactors, 4; Analyzing Eutectic Melting and Relocation Dynamics in B$$_{4}$$C-stainless steel using the Moving Particle Semi-Implicit (MPS) Method

Ahmed, Z.*; Wu, S.*; Pellegrini, M.*; Okamoto, Koji*; Sharma, A.*; Yamano, Hidemasa

Proceedings of 14th International Topical Meeting on Nuclear Reactor Thermal-Hydraulics, Operation, and Safety (NTHOS-14) (Internet), 14 Pages, 2024/08

The analysis show that once eutectic reaction occurs, the boron diffuses into the stainless steel (SS) wall. Melting initiates at the B$$_{4}$$C and SS interface, with melt flow following SS cladding penetration. Also, we observed that as temperature rises, a proportional increase in the boron concentration within the melt. The updated MPS method indicated a computational capability of the eutectic reaction model used to effectively analyze control rod eutectic reactions, simulating severe accidents, and its subsequent relocation to understand the effect of B$$_{4}$$C ingress into the core.

Journal Articles

Application of the GIF safety design criteria and safety design guidelines on natural circulation capability to next generation sodium-cooled fast reactor in Japan

Yamano, Hidemasa; Futagami, Satoshi; Higurashi, Koichi*

Proceedings of 14th International Topical Meeting on Nuclear Reactor Thermal-Hydraulics, Operation, and Safety (NTHOS-14) (Internet), 12 Pages, 2024/08

This paper describes the application of safety design criteria (SDC) and safety design guidelines (SDG) developed in the Generation-IV International Forum on the natural circulation of sodium to sodium-cooled fast reactors (SFRs) recently designed in Japan.

Journal Articles

Study on the difference between B$$_{4}$$C powder and B$$_{4}$$C pellet regarding the eutectic reaction with stainless steel

Hong, Z.*; Ahmed, Z.*; Pellegrini, M.*; Yamano, Hidemasa; Erkan, N.*; Sharma, A. K.*; Okamoto, Koji*

Progress in Nuclear Energy, 171, p.105160_1 - 105160_13, 2024/06

 Times Cited Count:6 Percentile:91.70(Nuclear Science & Technology)

In this study, it is found that the eutectic reaction between B$$_{4}$$C powder and stainless steel (SS) is considerably more rapid than that between the B$$_{4}$$C pellet and SS. The derived reaction rate constant values for powder and pellet cases are consistently based on the reference values. Also, a composition analysis using SEM/EDS was conducted for the detailed microstructures of the powder and pellet samples. In the powder case, only one thick layer is found as the reaction layer consisting of (Fe, Cr)B precipitate, including B$$_{4}$$C powder. In the pellet case, two layers are found in the reaction layer.

Journal Articles

Eutectic melting and relocation behavior of B$$_{4}$$C pellet-stainless steel under radiative heating

Ahmed, Z.*; Sharma, A. K.*; Pellegrini, M.*; Yamano, Hidemasa; Kano, Sho*; Okamoto, Koji*

Ceramics International, 50(10), p.17665 - 17680, 2024/05

 Times Cited Count:3 Percentile:51.99(Materials Science, Ceramics)

In this study, we identified two distinct failure mechanisms: the separation of stainless steel from the B$$_{4}$$C pellet, resulting in the formation of a later melting drop, and the fracture of the B$$_{4}$$C pellet into multiple pieces, possibly due to thermal stress. The visualization technique and thermal interfacial resistance analysis precisely captured the eutectic temperature.

Journal Articles

Visualization experiments of radiation heating on the eutectic reaction between B$$_{4}$$C-SS and its relocation behavior

Ahmed, Z.*; Sharma, A. K.*; Pellegrini, M.*; Yamano, Hidemasa; Okamoto, Koji*

Proceedings of Saudi International Conference On Nuclear Power Engineering (SCOPE2023) (Internet), 8 Pages, 2023/11

In this study, the eutectic behavior and subsequent melt structure of boron migration are observed by a quantitative and high-resolution visualization method using radiative heating. Experiments were conducted using B4C pellet and powder within SS tubes, replicating the actual control rod design in the temperature range of 1150$$^{circ}$$C to 1372$$^{circ}$$C to study long-duration melting and relocation behavior. The visualization technique accurately identified the time of eutectic melting onset and the related temperature, pointing out different values for the pellet and the powder cases.

Journal Articles

Preliminary analysis of severe accident in sodium-cooled fast reactor using eutectic reaction model of boron-carbide control-rod material

Yamano, Hidemasa; Morita, Koji*

Proceedings of 20th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-20) (Internet), p.4295 - 4308, 2023/08

This study applied the SIMMER-IV code with the newly developed model to a preliminary SA analysis of the SFR. The analysis results show that the eutectic reaction is caused by the contact between the liquid SS and the broken B$$_{4}$$C pellets which are released to the coolant channel after the failure of cladding which is melted by the mixture of liquid SS and fuel particles coming from the neighboring fuel assemblies. The liquid eutectic material formed by the reaction moves from the control assembly to the neighboring fuel assemblies. The lower density of the eutectic melt than molten SS drives the upward motion of the eutectic in the molten core pool. This analysis indicated that the SIMMER-IV code using the eutectic reaction model has successfully simulated the eutectic reaction and the relocation of the eutectic melt as well as the reactivity transient behavior caused by the molten core material relocation.

Journal Articles

A Quantitative method of eutectic reaction study between boron carbide and stainless steel

Hong, Z.*; Pellegrini, M.*; Erkan, N.*; Liao, H.*; Yang, H.*; Yamano, Hidemasa; Okamoto, Koji*

Annals of Nuclear Energy, 180, p.109462_1 - 109462_9, 2023/01

 Times Cited Count:3 Percentile:41.50(Nuclear Science & Technology)

A series of experiments were conducted using B$$_{4}$$C material and SUS304 tubes as a simulant of the real control rods. Reaction rate constant data in the 1450K-1500K range were obtained, and are consistent with the reference values. The reaction layer microstructure observation and the associated chemical composition analysis were also carried onto the experiment samples.

Journal Articles

Normal spectral emissivity, specific heat capacity, and thermal conductivity of type 316 austenitic stainless steel containing up to 10 mass% B$$_{4}$$C in a liquid state

Fukuyama, Hiroyuki*; Higashi, Hideo*; Yamano, Hidemasa

Journal of Nuclear Materials, 568, p.153865_1 - 153865_12, 2022/09

 Times Cited Count:12 Percentile:88.44(Materials Science, Multidisciplinary)

The normal spectral emissivity, specific heat capacity and thermal conductivity of type 316 austenitic stainless steel (SS) containing boron carbide (B$$_{4}$$C) in a liquid state were experimentally measured over the composition range of SS-$$x$$ mass% B$$_{4}$$C (up to 10%) and wide temperature ranges using an electromagnetic levitator in a static magnetic field. The normal spectral emissivity and specific heat capacity were almost constant against temperature for all SS-B$$_{4}$$C melts, and the thermal conductivities of the melts had a negligible or small positive temperature dependence. The B$$_{4}$$C-content dependence of each property at 1800 K had a different tendency across the eutectic composition (around 3 mass% B$$_{4}$$C) of the SS-B$$_{4}$$C pseudo-binary system.

Journal Articles

Preliminary analysis of core disruptive accident in sodium-cooled fast reactor using eutectic reaction model of boron-carbide control-rod material

Yamano, Hidemasa; Morita, Koji*

Nihon Kikai Gakkai 2022-Nendo Nenji Taikai Koen Rombunshu (Internet), 5 Pages, 2022/09

It is necessary to simulate a eutectic melting reaction and relocation behavior of boron carbide (B4C) as a control rod material and stainless steel (SS) during a core disruptive accident (CDA) in an advanced large-scale sodium-cooled fast reactor (SFR) designed in Japan. A physical model simulating the eutectic reaction and relocation of the eutectic melt was developed to incorporate into the fast reactor severe accident analysis code SIMMER-IV for the CDA numerical analysis of SFRs. This study applied the SIMMER-IV code with the newly developed model to the CDA analysis of the SFR. This analysis indicated that the SIMMER-IV code using the eutectic reaction model has successfully simulated the eutectic reaction and the upward motion of the eutectic melt in the molten core pool as well as the reactivity transient behavior caused by the molten core material relocation.

Journal Articles

Study on eutectic melting behavior of control rod materials in core disruptive accidents of sodium-cooled fast reactors, 1; Project overview and progress until 2020

Yamano, Hidemasa; Takai, Toshihide; Emura, Yuki; Fukuyama, Hiroyuki*; Higashi, Hideo*; Nishi, Tsuyoshi*; Ota, Hiromichi*; Morita, Koji*; Nakamura, Kinya*; Fukai, Hirofumi*; et al.

Proceedings of 13th International Topical Meeting on Nuclear Reactor Thermal-Hydraulics, Operation and Safety (NUTHOS-13) (Internet), 12 Pages, 2022/09

This paper describes the project overview and progress of experimental and analytical studies conducted until 2020. Specific results in this paper are the measurement of the eutectic reaction rates and the validation of physical model describing the eutectic reaction in the analysis code through the numerical analysis of the B$$_{4}$$C-SS eutectic reaction rate experiments in which a B$$_{4}$$C pellet was placed in a SS crucible.

Journal Articles

Preliminary application of eutectic reaction model on boron carbide and stainless steel to severe accident simulation of sodium-cooled fast reactors

Yamano, Hidemasa; Morita, Koji*

Proceedings of 19th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-19) (Internet), 16 Pages, 2022/03

For a severe accident (SA) simulation of sodium-cooled fast reactors, a eutectic reaction model between boron carbide (B$$_{4}$$C) and stainless steel (SS) has been developed to be incorporated into the SA simulation codes: SIMMER-III/IV. To confirm the applicability of SIMMER-IV involving the eutectic reaction model to reactor simulations, this study has preliminarily applied this code with the newly developed physical model to a SA simulation of a large-scale SFR designed in Japan. The simulation results show that the eutectic reaction is caused by the contact between the liquid SS and the broken B$$_{4}$$C pellets which are released to the coolant channel after the failure of cladding which is melted by the mixture of liquid SS and fuel particles coming from the neighboring fuel assemblies. The liquid eutectic material formed by the reaction stayed in the control assembly and the neighboring fuel assemblies. This preliminary simulation shows that the spreading area of B$$_{4}$$C-SS eutectic formation is limited within this calculation time.

Journal Articles

Effect of B$$_{4}$$C absorber material on melt progression and chemical forms of iodine or cesium under severe accident conditions

Hidaka, Akihide

Insights Concerning the Fukushima Daiichi Nuclear Accident, Vol.4; Endeavors by Scientists, p.341 - 356, 2021/10

Journal Articles

Effect of B$$_{4}$$C addition on the solidus and liquidus temperatures, density and surface tension of type 316 austenitic stainless steel in the liquid state

Fukuyama, Hiroyuki*; Higashi, Hideo*; Yamano, Hidemasa

Journal of Nuclear Materials, 554, p.153100_1 - 153100_11, 2021/10

 Times Cited Count:16 Percentile:86.09(Materials Science, Multidisciplinary)

The effects of B$$_{4}$$C addition on the solidus and liquidus temperatures of type 316 austenitic stainless steel (SS), and on the density and surface tension of molten SS, were experimentally studied. The solidus temperature of SS-x mass% B$$_{4}$$C (from 0 to 10) monotonically decreased from 1666 to 1307 K with B$$_{4}$$C addition. The liquidus temperature had a minimum at around 2.5 mass% B$$_{4}$$C, and increased with further B$$_{4}$$C addition up to 10 mass%. The density and surface tension of molten SS-x mass %B$$_{4}$$C were successfully measured over a wide temperature range (including an undercooling region) via an electromagnetic-levitation technique. The density of each sample decreased linearly with temperature. The density also monotonically decreased with B$$_{4}$$C content. Although the addition of B$$_{4}$$C had no clear effect on the surface tension of SS-x mass %B$$_{4}$$C, sulfur dissolved in SS316L caused a significant decrease in the surface tension.

Journal Articles

Viscosities of molten B$$_{4}$$C-stainless steel alloys

Nishi, Tsuyoshi*; Sato, Rika*; Ota, Hiromichi*; Kokubo, Hiroki*; Yamano, Hidemasa

Journal of Nuclear Materials, 552, p.153002_1 - 153002_7, 2021/08

 Times Cited Count:8 Percentile:61.36(Materials Science, Multidisciplinary)

Determining high precision viscosities of molten B$$_{4}$$C-stainless steel (B$$_{4}$$C-SS) alloys is essential for the core disruptive accident analyses of sodium-cooled fast reactors and for analysis of severe accidents in boiling water reactors (BWR) as appeared in Fukushima Daiichi. However, there are no data on the high precision viscosities of molten B$$_{4}$$C-SS alloys due to experimental difficulties. In this study, the viscosities of molten SS (Type 316L), 2.5mass%B$$_{4}$$C-SS, 5.0mass%B$$_{4}$$C-SS, and 7.0mass%B$$_{4}$$C-SS alloys were measured using the oscillating crucible method in temperature ranges of 1693-1793 K, 1613-1793 K, 1613-1793 K, and 1713-1793 K, respectively. The viscosity was observed to increase as the B$$_{4}$$C concentration increased from 0 to 7.0 mass%. Using the experimental data of the molten 2.5mass%B$$_{4}$$C-SS and 5.0mass%B$$_{4}$$C-SS and 7.0mass%B$$_{4}$$C-SS in the temperature range of 1713-1793 K, the equation for the viscosity of molten B$$_{4}$$C-SS alloys was determined, and the measurement error of the viscosity of molten B$$_{4}$$C-SS alloys is less than $$pm$$8%.

124 (Records 1-20 displayed on this page)