Steam oxidation of silicon carbide at high temperatures for the application as accident tolerant fuel cladding, an overview

Pham, V. H.; 倉田 正輝; Steinbrueck, M.*

Thermo (Internet), 1(2), p.151 - 167, 2021/09

https://doi.org/10.3390/thermo1020011

Since the nuclear accident at Fukushima Daiichi Nuclear Power Station in 2011, a considerable number of studies have been conducted to develop accident tolerant fuel (ATF) claddings for safety enhancement of light water reactors. Among many potential ATF claddings, silicon carbide is one of the most promising candidates with many superior features suitable for nuclear applications. In spite of many potential benefits of SiC cladding, there are some concerns over the oxidation/corrosion resistance of the cladding, especially at extreme temperatures (up to 2000C) in severe accidents. However, the study of SiC steam oxidation in conventional test facilities in water vapor atmospheres at temperatures above 1600C is very challenging. In recent years, several efforts have been made to modify existing or to develop new advanced test facilities to perform material oxidation tests in steam environments typical of severe accident conditions. In this article, the authors outline the features of SiC oxidation/corrosion at high temperatures, as well as the developments of advanced test facilities in their laboratories, and, finally, give some of the current advances in understanding based on recent data obtained from those advanced test facilities.

Oxidation of silicon carbide in steam studied by laser heating

Pham, V. H.; 永江 勇二; 倉田 正輝; 古本 健一郎*; 佐藤 寿樹*; 石橋 良*; 山下 真一郎

Proceedings of International Nuclear Fuel Cycle Conference / Light Water Reactor Fuel Performance Conference (Global/Top Fuel 2019) (USB Flash Drive), p.670 - 674, 2019/09

Silicon carbide (SiC) has recently attracted much attention as a potential material for accident tolerant fuel cladding. To investigate the performance of SiC in severe accident conditions, study of steam oxidation at high temperatures is necessary. However, the study focusing on steam oxidation of SiC at temperatures above 1600C is still certainly limited due to lack of test facilities. With the extreme oxidation/corrosion environment in steam at high temperatures, current refractory materials such as alumina and zirconia would not survive during the tests. Application of laser heating technique could be a great solution for this problem. Using laser heating technique, we can localize the heat and focus them on the test sample only. In this study, we developed a laser heating facility to investigate high-temperature oxidation of SiC in steam at temperature range of 1400-1800C for 1-7 h. The oxidation kinetics is then being studied based on the weight gain and observation on cross-sectioned surface of tested sample using field emission scanning electron microscope. Off-gas measurement of hydrogen (H) and carbon monoxide (CO) generated during the test is also being conducted via a sensor gas chromatography. Current results showed that the SiC sample experienced a mass loss process which obeyed paralinear laws. Parabolic oxidation rate constant and linear volatilization rate constant of the process were calculated from the mass change of the samples. The apparent activation energy of the parabolic oxidation process was calculated to be 85 kJ.mol. The data of the study also indicated that the mass change of SiC under the investigated conditions reached to its steady stage where hydrogen generation became stable. Above 1800C, a unique bubble formation on sample surface was recorded.

Improvements in drill-core headspace gas analysis for samples from microbially active depths

宮川 和也; 奥村 文章*

Geofluids, 2018, p.2436814_1 - 2436814_11, 2018/10

https://doi.org/10.1155/2018/2436814

地下深部の炭化水素ガスの濃度組成や同位体組成を調べる事により、炭化水素ガスの起源や長期的な流体移動に関する知見が得られる。地上からのボーリング孔を用いてガス採取を行う場合によく用いられる方法として、ボーリングのカッティングスあるいはコアに吸着したガスをサンプル容器のヘッドスペースに追い出して分析する方法がある。しかしながら、この方法により得られた結果は、しばしば大きなばらつきを示す。本研究では、上述の手法により採取・分析した結果を、地下施設を利用して得られた結果と比較し、ばらつきの原因が試料の採取・保管方法に起因することを明らかにし、正しい値を得るための要点を指摘した。

Corrosion test of HTGR graphite with SiC coating

Chikhray, Y.*; Kulsartov, T.*; Shestakov, V.*; Kenzhina, I.*; Askerbekov, S.*; 角田 淳弥; 植田 祥平; 柴田 大受; 坂場 成昭; Abdullin, Kh.*; et al.

Proceedings of 8th International Topical Meeting on High Temperature Reactor Technology (HTR 2016) (CD-ROM), p.572 - 577, 2016/11

高温ガス炉(HTGR)に用いられる黒鉛について、耐腐食性を有するSiC被覆の適用は重要な課題である。本研究は、高密度のIG-110黒鉛にSiCを傾斜被覆した材料について、1673Kまでの温度で蒸気との化学反応の結果を示したものである。100Paの蒸気との反応に関する実験では、SiC酸化のパッシブ反応により表面にSiO膜が形成されることを確認した。また、1Paの蒸気とのアクティブ反応では、表面に様々なカーボン複合材が形成されることを確認した。

The Effect of crystal textures on the anodic oxidization of zirconium in a boiling nitric acid solution

加藤 千明; 石島 暖大; 上野 文義; 山本 正弘

Journal of Nuclear Science and Technology, 53(9), p.1371 - 1379, 2016/09

AA2015-0626.pdf:1.2MB

https://doi.org/10.1080/00223131.2015.1110506

硝酸水溶液でジルコニウムの応力腐食割れに関して、ジルコニウムの陽極酸化に及ぼす結晶配向の影響を調査した。酸化ジルコニウム膜の成長挙動は、脱不動態化電位(1.47V vs. SSE)で、劇的に変化した。1.5Vでは、酸化皮膜は速く成長し、その平均皮膜厚さは電荷量に比例して増加した。酸化皮膜は周期的な3乗則に従った成長挙動を示した。周期的な3乗則に従った成長挙動への遷移前では、酸化皮膜の成長挙動に結晶配向の影響を及ぼさなかった。しかし、皮膜成長の遷移後は、酸化皮膜の平均皮膜厚さと厚い酸化皮膜の下に生じたき裂は結晶配向の影響を受けた。(0002)面が配向している圧延面では、その平均皮膜厚さは減少し、皮膜内のき裂により皮膜の剥離が生じた。(0002)面に垂直面である圧延方向面では、厚い酸化皮膜の下には、圧延方向に深く進展したき裂が観察された。き裂は酸化物層の中をジルコニウム母材の(0002)面に沿って進展した。酸化物層は、ひも状の酸化ジルコニウムとジルコニウム水素化物からなり、ひも状の酸化ジルコニウムは、単斜晶ZrOに加えて斜方晶ZrOを含んでいた。外部応力が無い条件でき裂が発生・進展した機構の1つの仮定として、(0002)面に析出した水素化物の酸化と、その後に生じる斜方晶ZrOから単斜晶ZrOへの相変態がその原因の一つと考えられた。

Activation and control of visible single defects in 4H-, 6H-, and 3C-SiC by oxidation

Lohrmann, A.*; Castelletto, S.*; Klein, J. R.*; 大島 武; Bosi, M.*; Negri, M.*; Lau, D. W. M.*; Gibson, B. C.*; Prawer, S.*; McCallum, J. C.*; et al.

Applied Physics Letters, 108(2), p.021107_1 - 021107_4, 2016/01

https://doi.org/10.1063/1.4939906

Creation and characterisation of single photon emitters near the surface of 4H- and 6H-silicon carbide bulk substrates and 3C-SiC epitaxially grown on silicon substrates were investigated. These single photon emitters can be created and stabilized by thermal annealing in an oxygen atmosphere at temperatures above 550 C. Hydrofluoric acid (HF) treatment is shown to effectively annihilate the emission from defects and to restore an optically clean surface. However, the emission from the defects can be obtained after re-oxidation above 550 C. By measuring using standard confocal microscopy techniques, the excited state lifetimes for the emitters are found to be in the nanosecond regime in all three polytypes, and the emission dipoles are aligned with the lattice.

Upgrade in catalytic activity of hydrophobic platinum catalysts by irradiation with electron beams

岩井 保則

Fusion Engineering and Design, 98-99, p.1796 - 1799, 2015/10

https://doi.org/10.1016/j.fusengdes.2015.03.024

疎水性白金触媒は水蒸気-水素間水素同位体交換反応やトリチウム酸化の用途にて核融合分野で広く使用されている。疎水性触媒の触媒活性は空気中の水蒸気や水ミストのほかに燃焼反応により生成する水にもほとんど影響されない特徴を持つ。一般的に疎水性触媒は多孔性の疎水性高分子に白金を担持することで作成される。日本はスチレンジビニルベンゼンを疎水性高分子とした疎水性白金触媒をトリチウム水処理システムに採用してきた実績を有する。システム規模低減のためには触媒活性の可能な限りの向上が必要である。二種類の疎水性白金触媒を電子線で照射した場合のトリチウム酸化性能の変化を精査した。両方の触媒とも線量の増加とともに疎水性触媒の触媒活性は向上し、500から1000kGyにて総括反応速度係数はピーク値を示し、それ以降の線量では徐々に低下することを見出した。総括反応速度係数のピーク値は未照射の6倍の値を示した。スチレンジビニルベンゼンは放射線に対する耐久性が強く、この程度の線量では機械的強度に影響はなく、簡易に触媒活性を向上可能な有力な方法であることを見出した。

Corrigendum to "Si 2p and O 1s photoemission from oxidized Si(001) surfaces depending on translational kinetic energy of incident O molecules"

寺岡 有殿; 吉越 章隆

Applied Surface Science, 343, P. 212, 2015/07

https://doi.org/10.1016/j.apsusc.2015.02.146

We have performed experiments on surface chemical reactions using a supersonic O molecular beam and O gas. Translational kinetic energy values of the O molecules have been estimated by calculations. I had made a mistake in the calculations. We had calculated the translational kinetic energy with gas constant R = 1.13410 eV/K. However, R = 8.61710 eV/K is correct. Consequently, the correct translational kinetic energy values can be obtained by multiplying those in the published article by a factor of 0.76. Even if they are corrected, conclusions and the points of arguments are as they are except the translational kinetic energy values themselves.

Corrigendum to "Commissioning of surface chemistry end-station in BL23SU of SPring-8" [Appl. Surf. Sci. 169-170 (2001) 738-741]

寺岡 有殿; 吉越 章隆

Applied Surface Science, 339, P. 158, 2015/06

https://doi.org/10.1016/j.apsusc.2015.02.144

We have performed experiments on surface chemical reactions using a supersonic O molecular beam. Translational kinetic energy values of the O molecules have been estimated by calculations. I had made a mistake in the calculations. We had calculated the translational kinetic energy with gas constant R = 1.13410 eV/K. However, R = 8.61710 eV/K is correct. Consequently, the correct translational kinetic energy values can be obtained by multiplying those in the published article by a factor of 0.76. Even if they are corrected, conclusions and the points of arguments are as they are except the translational kinetic energy values themselves.

Erratum; Precise control of Si(001) initial oxidation by translational kinetic energy of O molecules

寺岡 有殿; 吉越 章隆

Japanese Journal of Applied Physics, 54(3), P. 039204_1, 2015/03

https://doi.org/10.7567/JJAP.54.039204

We have performed experiments on surface chemical reactions using a supersonic O molecular beam and O gas. Translational kinetic energy values of the O molecules have been estimated by calculations. We have noticed a mistake in the calculations. We had calculated the translational kinetic energy with gas constant = 1.13410 eV/K. However, = 8.61710 eV/K is correct. Consequently, the correct translational kinetic energy values can be obtained by multiplying those in the published article by a factor of 0.76. Even if they are corrected, conclusions and the points of arguments are as they are except the translational kinetic energy values themselves.