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Journal Articles

Visualizing an ignition process of hydrogen jets containing sodium mist by high-speed imaging

Doi, Daisuke; Seino, Hiroshi; Miyahara, Shinya*; Uno, Masayoshi*

Journal of Nuclear Science and Technology, 56(6), p.521 - 532, 2019/06

Journal Articles

A Study on self-terminating behavior of sodium-concrete reaction

Kawaguchi, Munemichi; Doi, Daisuke; Seino, Hiroshi; Miyahara, Shinya

Journal of Nuclear Science and Technology, 53(12), p.2098 - 2107, 2016/12

 Times Cited Count:3 Percentile:42.29(Nuclear Science & Technology)

A sodium concrete reaction (SCR) is one of the important phenomena to cause the structural concrete ablation and the release of H$$_2$$ gas in the case of sever accident of sodium cooled fast reactors. In this study, the long-time SCR test had been carried out to investigate the self-termination mechanism. The results showed the SCR terminated even if the enough amount of Na remained on the concrete. The quantitative data were collected on the SCR terminating such as temperature and H$$_2$$ generation. The reaction products, which became the small solids in liquid Na were transferred with slurry state by generated H$$_2$$ bubbles. Though the Na transfers actively and ablated the concrete surface with the high H$$_2$$ generation rate, the mass exchange coefficient defined as $$E_p$$ decreased and the reaction products settled gradually with decreasing the H$$_2$$ generation rate. Therefore, the Na concentration decreased at the reaction front and resulted in the SCR terminating naturally.

Journal Articles

Experimental study and kinetic analysis on sodium oxide-silica reaction

Kikuchi, Shin; Koga, Nobuyoshi*; Seino, Hiroshi; Ohno, Shuji

Journal of Nuclear Science and Technology, 53(5), p.682 - 691, 2016/05

 Times Cited Count:2 Percentile:57.25(Nuclear Science & Technology)

In a sodium-cooled fast reactor (SFR), if considering hypothetical severe accidental condition such as the steel liner failure of structural concrete caused by intensive leakage of liquid sodium (Na) coolant, the liquid sodium-concrete reaction (SCR) may take place. The major consequences of SCR are hydrogen release, energy release and concrete ablation. Thus, it is important to understand the phenomenology of SCR. As a part of a series of studies on SCR, this study focused on the reaction between sodium oxide (Na$$_{2}$$O) and silica (SiO$$_{2}$$). Through thermoanalytical and X-ray diffraction measurements, it was revealed that Na$$_{2}$$O-SiO$$_{2}$$ reaction to form sodium orthosilicate (Na$$_{4}$$SiO$$_{4}$$) occurs at significantly lower temperature in comparison with Na-SiO$$_{2}$$ reaction.

Journal Articles

Kinetic study on liquid sodium-silica reaction for safety assessment of sodium-cooled fast reactor

Kikuchi, Shin; Koga, Nobuyoshi*; Seino, Hiroshi; Ohno, Shuji

Journal of Thermal Analysis and Calorimetry, 121(1), p.45 - 55, 2015/07

 Times Cited Count:4 Percentile:67.82(Thermodynamics)

In this study, the kinetic behavior of the sodium (Na)-silica (SiO2) reaction was investigated for an assessment method of reactivity/stability of siliceous concrete against the sodium-concrete reaction (SCR) by postulating a severe accidental condition in the sodium-cooled fast reactor (SFR). The reaction behavior was tracked using a differential scanning calorimetry (DSC) equipped with a videoscope for viewing the changes in the sample during the reaction. From detail kinetic analysis, it was revealed that the kinetic results determined from the kinetic data at the maximum reaction rate can be interpreted as is for the major reaction stage. In addition, the k value at a constant temperature calculated using the Arrhenius parameters determined by the simplified Kissinger method can be used for the reactivity/stability assessment of the siliceous concrete in view of the kinetics of the major reaction stage of the Na-SiO$$_{2}$$ reaction.

Journal Articles

Development of fast reactor containment safety analysis code, CONTAIN-LMR, 4; Applicability study of hydrogen combustion model

Doi, Daisuke; Ono, Isao*; Seino, Hiroshi

Proceedings of 23rd International Conference on Nuclear Engineering (ICONE-23) (DVD-ROM), 5 Pages, 2015/05

Journal Articles

Development of fast reactor containment safety analysis code, CONTAIN-LMR, 3; Improvement of sodium-concrete reaction model

Kawaguchi, Munemichi; Doi, Daisuke; Seino, Hiroshi; Miyahara, Shinya

Proceedings of 23rd International Conference on Nuclear Engineering (ICONE-23) (DVD-ROM), 6 Pages, 2015/05

CONTAIN-LMR code is an integrated analysis tool to predict the consequence of severe accident in a liquid metal fast reactor. A sodium-concrete reaction is one of the most important phenomena, and Sodium-Limestone Concrete Ablation Model (SLAM) has been installed into the original CONTAIN code. The SLAM treats chemical reaction kinetics between the sodium and the concrete compositions mechanistically, the application is limited to the limestone concrete. In order to apply SLAM to the siliceous concrete which is an ordinary structural concrete in Japan, the chemical reaction kinetics model has been improved. The improved model was validated to analyze a series of sodium-concrete experiments which were conducted in Japan Atomic Energy Agency. It has been found that relatively good agreement between calculation and experimental results is obtained and the CONTAIN-LMR code has been validated with regard to the sodium-concrete reaction phenomena.

Journal Articles

Development of fast reactor containment safety analysis code, CONTAIN-LMR, 5; Improvement of debris-concrete interaction model

Seino, Hiroshi; Kawaguchi, Munemichi; Izumi, Keitaro*

Proceedings of 23rd International Conference on Nuclear Engineering (ICONE-23) (DVD-ROM), 5 Pages, 2015/05

As a part of development of CONTAIN-LMR, CORCON and VANESA models for calculating the debris-concrete interaction (MCCI) have been improved taking into account the influence of soudium-pool existence. In this study, the following LMFR specific models in the code have been developed and improved: (1) chemical reaction in sodium pool, (2) aerosol decontamination in sodium pool, and (3) heat conduction in concrete. These models have been also confirmed and validated with experimental results. As a result, improved CORCON and VANESA can represent the MCCI behavior reasonably well. Further improvement and validation of CONTAIN-LMR will be continued in order to apply to the ex-vessel accident progression of LMFRs.

Journal Articles

Development of fast reactor containment safety analysis code, CONTAIN-LMR, 1; Outline of development project

Miyahara, Shinya; Seino, Hiroshi; Ohno, Shuji; Konishi, Kensuke

Proceedings of 23rd International Conference on Nuclear Engineering (ICONE-23) (DVD-ROM), 5 Pages, 2015/05

A CONTAIN-LMR code has been developed in JAEA for application to PRA of LMFRs since the original CONTAIN code had been introduced from SNL of U.S. in 1982. The code is a best-estimate, integrated analysis tool for predicting the physical, chemical and radiological conditions inside a containment building of LMFRs following a severe accident with reactor vessel melt-through. The code is also able to predict the source term to the environment in the accident. This code can treat many important phenomena consistently such as sodium fire, radioactive aerosol behavior, hydrogen burn, sodium-concrete reaction and core debris-concrete interaction occurred in the accident with inter-cell heat and mass flow under the multiple cell geometry. This paper describes the chronology of the code development in JAEA briefly as an introduction, and after that, the outline of computational models in the code, the examples of the code validation, and the future plan of the code application are described.

Journal Articles

Experimental study and kinetic analysis on sodium-concrete reaction in sodium-cooled fast reactor

Kikuchi, Shin; Seino, Hiroshi; Ohno, Shuji

Proceedings of 10th International Topical Meeting on Nuclear Thermal Hydraulics, Operation and Safety (NUTHOS-10) (USB Flash Drive), 13 Pages, 2014/12

For countermeasure against sodium leak, structural concrete is protected by steel liner in a sodium-cooled fast reactor. However, if considering severe accidental condition such as breach of steel liner by intensive sodium leak, the reaction of concrete with liquid sodium potentially may occur. The sodium-concrete reaction (SCR) may result in significant damage of structural concrete elements, the release of hydrogen and exothermic heat. Thus it is important to understand mechanism of SCR in terms of soundness of reactor structure. However, finding on the reaction kinetics is quite limited due to the experimental difficulty. In this study, kinetics of Na$$_{2}$$O-SiO$$_{2}$$ reaction as subsequent reaction was focused. Based on the measured results by DSC equipment, kinetic parameters such as activation energy and frequency factor were obtained by the laws of chemical kinetics. XRD analysis was also performed to identify the reaction products and to discuss possible overall reactions.

Journal Articles

Development of fast reactor containment safety analysis code, CONTAIN-LMR, 2; Validation study of sodium fire model in CONTAIN-LMR

Ohno, Shuji; Makino, Toru; Ono, Isao*; Seino, Hiroshi

Proceedings of 23rd International Conference on Nuclear Engineering (ICONE-23) (DVD-ROM), 5 Pages, 2014/05

The CONTAIN-LMR code is being developed in the Japan Atomic Energy Agency (JAEA) to utilize for the quantitative assessment of accident consequences considered in sodium-cooled fast reactor (SFR) plant. Out of various physical and chemical behaviors treated in the code, this paper describes sodium fire related study issues such as computational modeling and its validation activities with focusing on important evaluating targets. Sodium pool and spray fire model validation practices are presented through the numerical analyses of sodium leak and fire experiments performed in the SAPFIRE facility.

Journal Articles

Experimental study on sodium-concrete reaction mechanism in sodium-cooled fast reactor

Kikuchi, Shin; Seino, Hiroshi; Ohno, Shuji

Nippon Kikai Gakkai Rombunshu, B, 79(808), p.2650 - 2654, 2013/12

For countermeasure against sodium leak, structural concrete is protected by steel liner in a sodium-cooled fast reactor (SFR). However, if considering severe and unexpected accidental condition such as breach of steel liner by intensive sodium leak, the reaction with liquid sodium and concrete potentially may occur. For the purpose of elucidating the mechanism of the sodium-concrete reaction in SFRs, kinetic study of the sodium (Na)-silica (SiO$$_{2}$$) reaction has been carried out by Differential Scanning Calorimetry (DSC) technique. The Na-SiO$$_{2}$$ reaction temperaturewas identified from DSC curves. It was found that reactivity of Na-SiO$$_{2}$$ reaction is similar with the reaction between Na and aggregate of practical used concrete. Based on the measured reaction temperature, rate constant of Na-SiO$$_{2}$$ reaction was obtained. Thermal analysis results indicated that Na-SiO$$_{2}$$ reaction could occur under the elevated temperature in the timeframe of sodium-concrete reaction.

Journal Articles

Kinetic study of sodium-water surface reaction by differential thermal analysis

Kikuchi, Shin; Seino, Hiroshi; Kurihara, Akikazu; Ohshima, Hiroyuki

Journal of Power and Energy Systems (Internet), 7(2), p.79 - 93, 2013/06

For the purpose of elucidating the mechanism of the sodium-water surface reaction in a steam generator of sodium-cooled fast reactors, kinetic study of the sodium (Na)-sodium hydroxide (NaOH) reaction has been carried out by using Differential Thermal Analysis (DTA) technique. The parameters, including melting points of Na and NaOH, phase transition temperature of NaOH, Na-NaOH reaction temperature, and decomposition temperature of sodiumhydride (NaH) have been identified from DTA curves. Na, NaOH and Na$$_{2}$$O as major chemicalspecies were identified from the X-ray diffraction (XRD) analysis of the residues after the DTA experiment. It was inferred that Na$$_{2}$$O could be generated as a reaction product. Based on the measured reaction temperature, the rate constant of sodium monoxide (Na$$_{2}$$O) generation was obtained by the application of the laws of chemical kinetics. From the estimated rate constant, it was confirmed that Na$$_{2}$$O generation should be considered during the sodium-water reaction.

Journal Articles

Experimental study and kinetic analysis of sodium-water chemical reaction mechanism in steam generator of sodium-cooled fast reactor

Kikuchi, Shin; Seino, Hiroshi; Kurihara, Akikazu; Ohshima, Hiroyuki

Nippon Kikai Gakkai Rombunshu, B, 79(799), p.271 - 275, 2013/03

For the purpose of elucidating the mechanism of the sodium-water surface reaction in a steam generator of sodium-cooled fast reactors, kinetic study of the sodium (Na)-sodium hydroxide (NaOH) reaction has been carried out by using Differential Thermal Analysis (DTA) technique. It was reconfirmed that sodium monoxide (Na$$_{2}$$O) generation should be considered during the sodium-water reaction in spite of variation of volume fraction (Na:NaOH). Na, NaOH and Na$$_{2}$$O as major chemical species were identified from the X-ray diffraction (XRD) analysis of the residues after the DTA experiment. From XRD analysis, it seems that Na$$_{2}$$O is reaction product and reaction ratio is less than 100 percent.

Journal Articles

Combustion characteristics of generating hydrogen during sodium-concrete reaction

Seino, Hiroshi; Ohno, Shuji; Yamamoto, Ikuo*; Miyahara, Shinya

Proceedings of 8th Japan-Korea Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-8) (USB Flash Drive), 10 Pages, 2012/12

A hydrogen combustion experiment was conducted to simulate the sodium-concrete reaction under oxygen-existing conditions. As a result, it was found that hydrogen was burnt at the sodium pool surface because as sodium combustion heat played a role of the ignition energy, and the hydrogen combination ratio increased with the increase of the oxygen concentration in the atmosphere.

Journal Articles

Development of Level 2 PSA methodology for sodium-cooled fast reactors; Overview of evaluation technology development

Suzuki, Toru; Nakai, Ryodai; Kamiyama, Kenji; Seino, Hiroshi; Koyama, Kazuya*; Morita, Koji*

NEA/CSNI/R(2012)2, p.381 - 391, 2012/07

For the probabilistic safety assessment (PSA) of sodium-cooled fast reactors (SFRs), JAEA consolidated the analytical methodologies and technical basis for all phases/sequences to be evaluated in the Level 2 PSA. In addition to the existing computational codes such as SAS4A, SIMMER-III, DEBNET, ARGO and APPLOHS, JAEA newly developed MUTRAN and SIMMER-LT in order to evaluate the long term behaviors of the material-relocation in the degraded core. These tools enabled the systematic assessment for the in-vessel accident sequences. For the ex-vessel accident sequences, JAEA also improved CONTAIN/LMR taking into account the feature of SFRs and verified the analytical models utilizing the new experiments such as sodium-concrete reaction test. In addition, the technical basis for constructing event trees was compiled, in which the dominant factors having significant effects on the event progression were corresponded to the related experiments and analytical results.

Journal Articles

Kinetic study of sodium-water reaction phenomena by differential thermal analysis

Kikuchi, Shin; Seino, Hiroshi; Kurihara, Akikazu; Ohshima, Hiroyuki

Proceedings of 20th International Conference on Nuclear Engineering and the ASME 2012 Power Conference (ICONE-20 & POWER 2012) (DVD-ROM), 9 Pages, 2012/07

In this work, we studied the kinetics of Na-NaOH reaction as secondary surface reaction in the SWR by using DTA technique. Melting points of Na and NaOH, phase transition temperature of NaOH, Na-NaOH reaction temperature, and the decomposition temperature of NaH were identified from DTA curves. Na, NaOH, and Na$$_{2}$$O as major chemical species were identified from the XRD analysis of the residues after the DTA experiment. It was inferred that Na$$_{2}$$O could be generated as Na-NaOH reaction product. Based on the measured reaction temperature, the first-order Arrhenius type rate constant of Na$$_{2}$$O generation and these related kinetic parameters were obtained by the application of kinetic laws. According to this kinetic study, it was found that Na$$_{2}$$O generation should be considered during SWR.

Journal Articles

Development of level 2 PSA methodology for sodium-cooled fast reactors, 6; Development of technical basis in ex-vessel accident sequences

Ohno, Shuji; Seino, Hiroshi; Miyahara, Shinya

Proceedings of 8th International Topical Meeting on Nuclear Thermal-Hydraulics, Operation and Safety (NUTHOS-8) (CD-ROM), 12 Pages, 2010/10

This research has compiled technical basis which is necessary to carry out a probabilistic safety assessment (Level 2 PSA) for a sodium-cooled fast reactor. The accumulated technical information consists of experimental and analytical information which help ones to understand the loading to a containment vessel, as well as the existing information on dominant factors of important ex-vessel phenomena.

Journal Articles

Development of level 2 PSA methodology for sodium-cooled fast reactors, 1; Overview of evaluation technology development

Nakai, Ryodai; Suzuki, Toru; Kamiyama, Kenji; Seino, Hiroshi; Koyama, Kazuya*; Morita, Koji*

Proceedings of 8th International Topical Meeting on Nuclear Thermal-Hydraulics, Operation and Safety (NUTHOS-8) (CD-ROM), 12 Pages, 2010/10

The evaluation technology of Level-2 PSA for Sodium-Cooled Fast Reactors (SFRs) was established in order to systematically assess the core damage sequences. In addition to the existing computational tools for Level-2 PSA, the computational tools, MUTRAN and SIMMER-LT were developed for core material relocation phase. Also the analytical models, CORCON and VANESA, were improved based on newly performed experiments for the ex-vessel phase taking into account the feature of SFRs. The technical information was compiled as technical database used in the construction and quantification of level-2 PSA event trees for SFRs. The technical basis was established for the Level-2 PSA for SFRs.

Journal Articles

Development of severe accident evaluation technology (Level 2 PSA) for sodium-cooled fast reactors, 5; Identification of dominant factors in ex-vessel accident sequences

Ohno, Shuji; Seino, Hiroshi; Miyahara, Shinya

Proceedings of 2009 International Congress on Advances in Nuclear Power Plants (ICAPP '09) (CD-ROM), p.9110_1 - 9110_9, 2009/05

Typical ex-vessel accident sequences in the JSFR are discussed in this paper and dominant behaviors or factors in the sequences are investigated through parametric calculations using the CONTAIN/LMR code. Scenarios to be focused on are, (1) sodium vapor leakage from the reactor vessel and (2) sodium-concrete reaction, which are both to be considered in the LOHRS accident category and might be followed by an early containment failure due to the thermal effect of sodium combustion and hydrogen burning respectively. The calculated results clarify that the sodium vapor leak rate and the scale of sodium-concrete reaction are the important factors to dominate the ex-vessel accident progression. In addition, the results also provide the specific information such as pressure loading value to the containment and the timing of pressurization, which is indispensable as technical base in Level 2 PSA for developing event trees and for quantifying the accident consequences.

Journal Articles

Development of blow down and sodium-water reaction jet analysis codes; Validation by sodium-water reaction tests (SWAT-1R)

Seino, Hiroshi; Jitsu, Koji*; Kurihara, Akikazu; Ono, Isao*; Hamada, Hirotsugu

Proceedings of 13th International Conference on Nuclear Engineering (ICONE-13), 0 Pages, 2005/05

Blow down analysis code (LEAP-BLOW) and sodium-water reaction jet analysis code (LEAP-JET) have been developed to improve the evaluation accuracy on sodium-water reaction. The validation analyses by these codes were carried out using the data of SWAT-1R test. As the result, though there was a problem in the quantitative evaluation of LEAP-JET, it was possible to obtain the approximately appropriate results.

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