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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:0 Percentile:0.02(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

Reaction and alteration of mudstone with Ordinary Portland Cement and Low Alkali Cement pore fluids

Bateman, K.; Amano, Yuki; Kubota, Mitsuru*; Ouchi, Yuji*; Tachi, Yukio

Minerals (Internet), 11(6), p.588_1 - 588_19, 2021/06

 Times Cited Count:0 Percentile:0.04(Geochemistry & Geophysics)

Journal Articles

Restraint effect of coexisting nitrite ion in simulated high level liquid waste on releasing volatile ruthenium under boiling condition

Yoshida, Ryoichiro; Amano, Yuki; Yoshida, Naoki; Abe, Hitoshi

Journal of Nuclear Science and Technology, 58(2), p.145 - 150, 2021/02

 Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)

In the "evaporation and dryness due to the loss of cooling functions" which is one of the severe accidents at reprocessing plants in Japan, ruthenium (Ru) is possible to be released much more than other elements to the environment. This cause is considered that the volatile Ru compound can be released from high level liquid waste (HLLW) as gaseous compound in adding to the release by entrainment. It was expected that the release of the volatile Ru compound from the HLLW may be able to be restrained by coexisting nitrite ion because of its reduction power. To confirm the effect of nitrite ion on the release behavior of the volatile Ru compound, four experiments of heating the simulated HLLW (SHLLW) with setting the concentration of nitrite ion in the SHLLW as a parameter ware carried out. As a result, the release of the volatile Ru compound was seemed to be restrained by adding nitrite sodium as a source of nitrite ion under certain boiling condition. This result may contribute to improve source term analysis in the evaporation and dryness due to the loss of cooling functions.

Journal Articles

Consistent modelling of material weight loss and gas release due to pyrolysis and conducting benchmark tests of the model; A Case for glovebox panel materials such as polymethyl methacrylate

Ono, Takuya; Tashiro, Shinsuke; Amano, Yuki; Yoshida, Naoki; Yoshida, Ryoichiro; Abe, Hitoshi

PLOS ONE (Internet), 16(1), p.e0245303_1 - e0245303_16, 2021/01

 Times Cited Count:0 Percentile:0.01(Multidisciplinary Sciences)

It is necessary to consider how a glove box's confinement function will be lost when evaluating the amount of radioactive material leaking from a nuclear facility during a fire. In this study, we build a model that consistently explains the weight loss of glove box materials because of heat input from a flame and accompanying generation of the pyrolysis gas. The weight loss suggests thinning of the glove box housing, and the generation of pyrolysis gas suggests the possibility of fire spreading. The target was polymethyl methacrylate (PMMA), used as the glove box panel. Thermal gravimetric tests on PMMA determined the parameters to be substituted in the Arrhenius equation for predicting the weight loss in pyrolysis. The pyrolysis process of PMMA was divided into 3 stages with activation energies of 62 kJ/mol, 250 kJ/mol, and 265 kJ/mol. Furthermore, quantifying the gas composition revealed that the composition of the pyrolysis gas released from PMMA can be approximated as 100 percent methyl methacrylate. This result suggests that the released amount of methyl methacrylate can be estimated by the Arrhenius equation. To investigate the validity of such estimation, a sealed vessel test was performed. In this test, we observed increase of the number of gas molecules during the pyrolysis as internal pressure change of the vessel. The number of gas molecules was similar to that estimated from the Arrhenius equation, and indicated the validity of our method. Moreover, we also performed the same tests on bisphenol-A-polycarbonate (PC) for comparison. In case of PC, the number of gas molecules obtained in the vessel test was higher than the estimated value.

JAEA Reports

Effect of nitrogen oxides on decomposition behavior of gaseous ruthenium tetroxide

Yoshida, Naoki; Amano, Yuki; Ono, Takuya; Yoshida, Ryoichiro; Abe, Hitoshi

JAEA-Research 2020-014, 33 Pages, 2020/12

JAEA-Research-2020-014.pdf:3.66MB

Considering the boiling and drying accident of high-level liquid waste in fuel reprocessing plant, Ruthenium (Ru) is an important element. It is because Ru would form volatile compounds such as ruthenium tetroxide (RuO$$_{4}$$) and could be released into the environment with other coexisting gasses such as nitric oxides (NOx) such as nitric oxide (NO) and nitrogen dioxide (NO$$_{2}$$). To contribute to the safety evaluation of this accident, we experimentally evaluated the effect of NOx on the decomposition and chemical change behavior of the gaseous RuO$$_{4}$$ (RuO$$_{4}$$(g)). As a result, the RuO$$_{4}$$(g) decomposed over time under the atmospheric gasses with NO or NO$$_{2}$$, however, the decomposition rate was slower than the results of experiments without NOx. These results showed that the NOx stabilized RuO$$_{4}$$(g).

Journal Articles

Decomposition behavior of gaseous ruthenium tetroxide under atmospheric conditions assuming evaporation to dryness accident of high-level liquid waste

Yoshida, Naoki; Ono, Takuya; Yoshida, Ryoichiro; Amano, Yuki; Abe, Hitoshi

Journal of Nuclear Science and Technology, 57(11), p.1256 - 1264, 2020/11

 Times Cited Count:2 Percentile:66.08(Nuclear Science & Technology)

Emphasis has been placed on the behavior of ruthenium (Ru) in the evaporation to dryness accident due to the loss of cooling functions (EDLCF) of high-level liquid waste in fuel reprocessing plants. It is because Ru would form volatile compounds such as ruthenium tetroxide (RuO$$_{4}$$) and could be released into the environment with other coexisting gasses such as nitric acid (HNO$$_{3}$$), water (H$$_{2}$$O). To contribute to the safety evaluation of this accident, we experimentally evaluated the decomposition and chemical change behavior of the gaseous RuO$$_{4}$$ (RuO$$_{4}$$(g)) under the various atmospheric conditions: temperature and composition of coexisting gasses. As a result, the behavior of the RuO$$_{4}$$(g) was diverse depending on the atmospheric conditions. In the experiments with the dry air or H$$_{2}$$O vapor, decomposition of RuO$$_{4}$$(g) was observed. In the experiment with the mixed gas which containing HNO$$_{3}$$, almost no decomposition of the RuO$$_{4}$$(g) was observed, and chemical form of the RuO$$_{4}$$(g) was retained.

Journal Articles

Internal event level-1 PRA for sodium-cooled fast reactor considering safety measures of defense-in-depth level 1 to 3

Nishino, Hiroyuki; Kurisaka, Kenichi; Naruto, Kenichi*; Gondai, Yoji; Yamamoto, Masaya; Yamano, Hidemasa

Proceedings of Asian Symposium on Risk Assessment and Management 2020 (ASRAM 2020) (Internet), 12 Pages, 2020/11

The objective of this study is to evaluate the occurrence frequency of accident sequences which may lead to core damage if provisions in defense in depth (DiD) level 1 to 3 are the only safety measures. For this objective, the existing safety measures in this SFR are categorized into those for the DiD level 1-3 and those for the DiD level 4. The safety measures for the DiD level 1-3 are as follows; (1) main reactor shutdown system, (2) double boundary structure in the primary main and auxiliary cooling system and the reactor vessel, which maintain the reactor coolant level sufficient for coolant circulation in the primary main cooling system, (3) decay heat removal in a forced circulation mode. Accident sequences are categorized into typical SFR-specific groups and station blackout (SBO) in this study. The SFR-specific groups are unprotected loss of flow, unprotected transient over power, unprotected loss of heat sink, loss of reactor level, and protected loss of heat sink (PLOHS). The occurrence frequency of these accident sequence groups was quantified to identify major contributors. As the result, PLOHS excluding SBO was indicated as the dominant contribution of 80% or more in the all accident sequence groups and the annual occurrence frequency of the PLOHS was 1.0E-4 order of magnitude. For the PLOHS, loss of offsite power (LOOP) was indicated as major contribution of 30% in initiating events. In the accident sequences of the PLOHS initiated from LOOP, a dominant sequence was combination of common cause failure of primary pumps in the main cooling system and failure-to-start of the auxiliary cooling system after LOOP. The second dominant contribution (15% or more) in the all accident sequence groups is PLOHS in SBO (i.e., decay heat removal failure due to SBO). Each of the other accident sequence groups was 1%.

JAEA Reports

Hydrochemical investigation at the Mizunami Underground Research Laboratory; Compilation of groundwater chemistry data in the Mizunami Group and the Toki Granite (fiscal year 2019)

Fukuda, Kenji; Watanabe, Yusuke; Murakami, Hiroaki; Amano, Yuki; Aosai, Daisuke*; Hara, Naohiro*

JAEA-Data/Code 2020-012, 80 Pages, 2020/10

JAEA-Data-Code-2020-012.pdf:3.55MB

Japan Atomic Energy Agency has been investigating groundwater chemistry to understand the influence of excavation and maintenance of underground facilities as part of the Mizunami Underground Research Laboratory (MIU) Project in Mizunami, Gifu, Japan. In this report, we compiled data of groundwater chemistry and microbiology obtained at the MIU in the fiscal year 2019. In terms of ensuring traceability of data, basic information (e.g. sampling location, sampling time, sampling method and analytical method) and methodology for quality control are described.

Journal Articles

For better understanding of PRA; Guidance for better usage and application of PRA, 3; Consideration of external hazard in PRA

Takata, Takashi*; Yamano, Hidemasa; Narumiya, Yoshiyuki*

Nihon Genshiryoku Gakkai-Shi ATOMO$$Sigma$$, 62(8), p.448 - 451, 2020/08

This report describes risk analysis applicable to selection and evaluation of external hazards in risk assessment. Volcanic ash hazard evaluation is shown as one of hazard evaluations. The objective of the risk assessment is to secure and improve the safety of nuclear installation. This report also describes discussion on the process of response informed based on risk evaluation against external hazards.

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 2018

Yamano, Hidemasa; Takai, Toshihide; Furukawa, Tomohiro; Kikuchi, Shin; Emura, Yuki; Kamiyama, Kenji; Fukuyama, Hiroyuki*; Higashi, Hideo*; Nishi, Tsuyoshi*; Ota, Hiromichi*; et al.

Proceedings of 2020 International Conference on Nuclear Engineering (ICONE 2020) (Internet), 10 Pages, 2020/08

One of the key issues in a core disruptive accident (CDA) evaluation in sodium-cooled fast reactors is eutectic reactions between boron carbide (B$$_{4}$$C) and stainless steel (SS) as well as its relocation. Such behaviors have never been simulated in CDA numerical analyses in the past, therefore it is necessary to develop a physical model and incorporate the model into the CDA analysis code. This study focuses on B$$_{4}$$C-SS eutectic melting experiments, thermophysical property measurement of the eutectic melt, and physical model development for the eutectic melting reaction. The eutectic experiments involve the visualization experiments, eutectic reaction rate experiments and material analyses. The thermophysical properties are measured in a range from solid to liquid state. The physical model is developed for a severe accident computer code based on the measured data of the eutectic reaction rate and the physical properties. This paper describes the project overview and progress of experimental and analytical studies conducted until 2018. Specific results in this paper are boron concentration distributions of solidified B$$_{4}$$C-SS eutectic sample in the eutectic melting experiments, which would be used for the validation of the eutectic physical model implemented into the computer code.

JAEA Reports

Hydrochemical investigation at the Mizunami Underground Research Laboratory; Compilation of groundwater chemistry data in the Mizunami group and the Toki granite (fiscal year 2018)

Fukuda, Kenji; Watanabe, Yusuke; Murakami, Hiroaki; Amano, Yuki; Aosai, Daisuke*; Kumamoto, Yoshiharu*; Iwatsuki, Teruki

JAEA-Data/Code 2019-019, 74 Pages, 2020/03

JAEA-Data-Code-2019-019.pdf:3.53MB

Japan Atomic Energy Agency has been investigating groundwater chemistry to understand the influence of excavation and maintenance of underground facilities as part of the Mizunami Underground Research Laboratory (MIU) Project in Mizunami, Gifu, Japan. In this report, we compiled data of groundwater chemistry and microbiology obtained at the MIU in the fiscal year 2018. In terms of ensuring traceability of data, basic information (e.g. sampling location, sampling time, sampling method and analytical method) and methodology for quality control are described.

Journal Articles

Clades of huge phages from across Earth's ecosystems

Al-Shayeb, B.*; Sachdeva, R.*; Chen, L.-X.*; Ward, F.*; Munk, P.*; Devoto, A.*; Castelle, C. J.*; Olm, M. R.*; Bouma-Gregson, K.*; Amano, Yuki; et al.

Nature, 578(7795), p.425 - 431, 2020/02

 Times Cited Count:76 Percentile:99.64(Multidisciplinary Sciences)

Journal Articles

Rapid clogging of high-efficiency particulate air filters during in-cell solvent fires at reprocessing facilities

Ono, Takuya; Tashiro, Shinsuke; Amano, Yuki; Yoshida, Ryoichiro; Abe, Hitoshi

Nuclear Technology, 206(1), p.40 - 47, 2020/01

 Times Cited Count:1 Percentile:42.23(Nuclear Science & Technology)

Recent Japanese nuclear regulations have focused on the hazards of in-cell solvent fires at reprocessing facilities. In this work, a mixture of tributyl phosphate and dodecane-based solvents was burned to generate an aerosol composed of soot and unburned solvent that was then loaded onto a high-efficiency particulate air filter simulating the ventilation system of reprocessing facilities. A radical increase of differential pressure occurred in the filters during these tests after the dodecane burned out from the solvent in a phenomenon we named as rapid clogging, likely caused by the burnout of dodecane. This relationship provides valuable insight into the establishment of new regulations for reprocessing facilities. This work indicates that clogging of ventilation filters during solvent fires may occur more rapidly than previously estimated.

Journal Articles

Genetic survey of indigenous microbial eukaryotic communities, mainly fungi, in sedimentary rock matrices of deep terrestrial subsurface

Saito, Yoshimoto*; Hirano, Shinichi*; Nagaoka, Toru*; Amano, Yuki

Ecological Genetics and Genomics, 12, p.100042_1 - 100042_9, 2019/10

Culture-independent molecular techniques enable us to analyze microflora in various environments. Many uncultured prokaryotes have been detected by the molecular methods from extreme environments, including anaerobic, no light, high-pressure, and high temperature. Recently, microbial eukaryotes were also detected in deep-sea environments, suggesting that microbial eukaryotes can adapt to a wider range of environments than previously thought. Here, we performed a culture-independent analysis of eukaryotes from approximately -250 m depth in the Horonobe Underground Research Laboratory at Horonobe, Japan. Our results indicate that fungi are the dominant eukaryotic flora in deep sedimentary rocks of Horonobe. We detected a wide range of species, including Zygomycete, Basidiomycete, and Ascomycete fungi from the rocks. This study is the first report of eukaryotic diversity in deep subsurface sedimentary rocks.

Journal Articles

Thermophysical properties of molten stainless steel containing 5mass%B$$_{4}$$C

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

Nuclear Technology, 205(9), p.1154 - 1163, 2019/09

 Times Cited Count:13 Percentile:96.51(Nuclear Science & Technology)

An electromagnetic-levitation technique performed in a static magnetic field was used to measure the density, surface tension, normal spectral emissivity, heat capacity, and thermal conductivity of molten 316L stainless steel (SS316L) and SS316L that contained 5mass%B$$_{4}$$C. The addition of 5mass%B$$_{4}$$C to SS316L yielded reductions of 111 K, 6%, 19%, and 6% in the liquidus temperature, density, normal spectral emissivity, and thermal conductivity at the liquidus temperature of SS316L, respectively. The heat capacity increased by 5% with this addition. Although the 5mass%B$$_{4}$$C addition had no clear effect on the surface tension, sulfur dissolved in the SS316L resulted in a significant decrease in the surface tension.

Journal Articles

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

Yamano, Hidemasa; Takai, Toshihide; Furukawa, Tomohiro; Kikuchi, Shin; Emura, Yuki; Kamiyama, Kenji; Fukuyama, Hiroyuki*; Higashi, Hideo*; Nishi, Tsuyoshi*; Ota, Hiromichi*; et al.

Proceedings of International Nuclear Fuel Cycle Conference / Light Water Reactor Fuel Performance Conference (Global/Top Fuel 2019) (USB Flash Drive), p.418 - 427, 2019/09

Eutectic reactions between boron carbide (B$$_{4}$$C) and stainless steel (SS) as well as its relocation are one of the key issues in a core disruptive accident (CDA) evaluation in sodium-cooled fast reactors. Since such behaviors have never been simulated in CDA numerical analyses, it is necessary to develop a physical model and incorporate the model into the CDA analysis code. This study is focusing on B$$_{4}$$C-SS eutectic melting experiments, thermophysical property measurement of the eutectic melt, and physical model development for the eutectic melting reaction. The eutectic experiments involve the visualization experiments, eutectic reaction rate experiments and material analyses. The thermophysical properties are measured in the range from solid to liquid state. The physical model is developed for a severe accident computer code based on the measured data of the eutectic reaction rate and the physical properties. This paper describes the project overview and progress of experimental and analytical studies by 2017. Specific results in this paper is boron concentration distributions of solidified B$$_{4}$$C-SS eutectic sample in the eutectic melting experiments, which would be used for the validation of the eutectic physical model implemented into the computer code.

Journal Articles

Study on eutectic melting behavior of control rod materials in core disruptive accidents of sodium-cooled fast reactors, 3; Effect of B$$_{4}$$C addition on thermophysical properties of austenitic stainless steel in a liquid state

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

Proceedings of International Nuclear Fuel Cycle Conference / Light Water Reactor Fuel Performance Conference (Global/Top Fuel 2019) (USB Flash Drive), p.853 - 857, 2019/09

Thermophysical properties of molten mixture of 316L stainless steel (SS316L) and control-rod material (B$$_{4}$$C) are necessary for the development of computer simulation codes that describe core degradation mechanisms during severe accidents in nuclear power plants involving sodium-cooled fast reactors. The effect of B$$_{4}$$C addition to SS316L on the solidus and liquidus temperatures were first measured by differential scanning calorimetry. An electromagnetic levitation technique performed in a static magnetic field was used to measure the density, surface tension, normal spectral emissivity, specific heat capacity, and thermal conductivity of molten SS316L and SS316L containing B$$_{4}$$C. The effects of B$$_{4}$$C addition to SS316L on the thermophysical properties were studied up to 10 mass%.

Journal Articles

Analysis of chemical behavior of nitrogen oxide formed by thermal decomposition of FP nitrates in accident of evaporation to dryness by boiling of reprocessed high-level liquid waste

Yoshida, Kazuo; Tamaki, Hitoshi; Yoshida, Naoki; Yoshida, Ryoichiro; Amano, Yuki; Abe, Hitoshi

Nihon Genshiryoku Gakkai Wabun Rombunshi, 18(2), p.69 - 80, 2019/06

An accident of evaporation to dryness by boiling of high level liquid waste (HLLW) is postulated as one of the severe accidents at a fuel reprocessing plant. In this case, volatile radioactive materials, such as ruthenium (Ru) are released from the tanks with water and nitric-acid mixed vapor into atmosphere. In addition to this, nitrogen oxides are also released formed by the thermal decomposition of metal nitrates of fission products (FP) in HLLW. It has been observed experimentally that nitrogen oxide affects strongly to the transport behavior of Ru. Chemical reactions of nitrogen oxide with water and nitric acid are also recognized as the complex phenomena to undergo simultaneously in the vapor and liquid phases. An analysis method has been developed with coupling two types of computer codes to simulate not only thermo-hydraulic behavior but also chemical reactions in the flow paths of carrier gases. A simulation study has been also carried out with a typical facility building.

JAEA Reports

Hydrochemical investigation at the Mizunami Underground Research Laboratory; Compilation of groundwater chemistry data in the Mizunami group and the Toki granite (fiscal year 2017)

Fukuda, Kenji; Watanabe, Yusuke; Murakami, Hiroaki; Amano, Yuki; Hayashida, Kazuki*; Aosai, Daisuke*; Kumamoto, Yoshiharu*; Iwatsuki, Teruki

JAEA-Data/Code 2018-021, 76 Pages, 2019/03

JAEA-Data-Code-2018-021.pdf:3.78MB

Japan Atomic Energy Agency has been investigating groundwater chemistry to understand the influence of excavation and maintenance of underground facilities as part of the Mizunami Underground Research Laboratory (MIU) Project in Mizunami, Gifu, Japan. In this report, we compiled data of groundwater chemistry and microbiology obtained at the MIU in the fiscal year 2017. In terms of ensuring traceability of data, basic information (e.g. sampling location, sampling time, sampling method and analytical method) and methodology for quality control are described.

Journal Articles

Hydrogen-based metabolism as an ancestral trait in lineages sibling to the Cyanobacteria

Matheus Carnevali, P. B.*; Schulz, F.*; Castelle, C. J.*; Kantor, R. S.*; Shih, P. M.*; Sharon, I.*; Santini, J.*; Olm, M. R.*; Amano, Yuki; Thomas, B. C.*; et al.

Nature Communications (Internet), 10, p.463_1 - 463_15, 2019/01

 Times Cited Count:16 Percentile:82.78(Multidisciplinary Sciences)

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