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論文

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

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 2000$$^{circ}$$C) in severe accidents. However, the study of SiC steam oxidation in conventional test facilities in water vapor atmospheres at temperatures above 1600$$^{circ}$$C 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.

論文

Oxidation kinetics of silicon carbide in steam at temperature range of 1400 to 1800$$^{circ}$$C studied by laser heating

Pham, V. H.; 永江 勇二; 倉田 正輝; Bottomley, D.; 古本 健一郎*

Journal of Nuclear Materials, 529, p.151939_1 - 151939_8, 2020/02

AA2019-0197.pdf:1.61MB

 被引用回数:2 パーセンタイル:62.87(Materials Science, Multidisciplinary)

As expected for accident tolerant fuels, investigation of steam oxidation for silicon carbide under the conditions beyond design basis accident scenarios is needed. Many studies focused on steam oxidation of SiC at temperatures up 1600$$^{circ}$$C have been conducted and reported in the literature. However, behavior of SiC in steam at temperatures above 1600$$^{circ}$$C still remains unclear. To complete this task, we have designed and manufactured a laser heating facility for steam oxidation at extreme temperatures. With the facility, we report the first results on the steam oxidation behavior of SiC at temperatures range of 1400-1800$$^{circ}$$C for short term exposure of 1-7 h under atmospheric pressure. Based on the mass change of SiC samples, parabolic oxidation rate and linear volatilization rate were calculated. The oxidation layer appears to be maintained at 1800$$^{circ}$$C in steam, but the bubble formation phenomenon suggests other volatilization reactions may limit its life.

論文

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 1600$$^{circ}$$C 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 1400-1800$$^{circ}$$C 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$$_{2}$$) 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$$^{-1}$$. 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 1800$$^{circ}$$C, a unique bubble formation on sample surface was recorded.

論文

Steam oxidation of silicon carbide at temperatures above 1600$$^{circ}$$C

Pham, V. H.; 永江 勇二; 倉田 正輝

Proceedings of Annual Topical Meeting on Reactor Fuel Performance (TopFuel 2018) (Internet), 6 Pages, 2018/10

High temperature interaction of chemical vapor deposition SiC with steam was investigated at 1700-1800$$^{circ}$$C for 0.1-3 h in a mixture of steam and argon gas containing 98% of steam at 1 atm. At the investigated conditions, although a dense oxide layer was observed on sample surface, significant mass loss of SiC occurred. Below 1700$$^{circ}$$C, the oxidation kinetics seems to follow the para-linear laws. The apparent activation calculated based on the data of this study is to be 370 kJ/mol. Rapid degradation and bubbling of SiC at 1800$$^{circ}$$C were observed after 1 h oxidation. This suggested that chemical interaction behaviours above 1700$$^{circ}$$C might be changed due to the liquefaction of silica.

論文

High temperature oxidation test of simulated BWR fuel bundle in steam-starved conditions

山崎 宰春; Pshenichnikov, A.; Pham, V. H.; 永江 勇二; 倉田 正輝; 徳島 二之*; 青見 雅樹*; 坂本 寛*

Proceedings of Annual Topical Meeting on Reactor Fuel Performance (TopFuel 2018) (Internet), 8 Pages, 2018/10

燃料集合体の酸化及び水素吸収はその後の事故進展挙動に影響を与えることから、PWR燃料集合体では、実効的な水蒸気流量としてg-H$$_{2}$$O/sec/rodという単位が導入されており、事故進展評価の重要なパラメータといて用いられている。一方BWRにおいては、燃料集合体の構成がPWRとは異なることにより、PWRで用いられている規格化された水蒸気流量ではチャンネルボックスの内外での酸化及び水素吸収の差が正確に評価できない。そのため、PWRで用いられているg-H$$_{2}$$O/sec/rodという規格化された水蒸気流量に代わる、適切な評価パラメータがBWRでも必要である。そこで、ジルカロイの水蒸気枯渇条件での酸化及び水素吸収データを取得するため、実機を模擬したBWRバンドル試験体を用いて高温酸化試験を行なった。BWRにおける水蒸気流量を規格化するため、水蒸気流路断面積を考慮したパラメータを検討した。

口頭

Interaction of zircaloy and molten mixture of stainless steel-B$$_{4}$$C at elevated temperatures

Pham, V. H.; 松浦 傑*; 南口 誠*; 永江 勇二; 倉田 正輝

no journal, , 

In this study, soaking experiments of Zry plates in molten SS-B$$_{4}$$C were conducted to investigate the recession rate of Zry plates in molten SS-B$$_{4}$$C at 1175-1225$$^{circ}$$C. The molten SS-B$$_{4}$$C mixture was prepared by heat-treatment at 1400$$^{circ}$$C for 12 h of a powder mixture containing 5 mol% B$$_{4}$$C and stainless steel. After decreasing temperature to the testing temperatures, Zry plates were soaked in the molten mixture for 0-60 min. After soaking tests, the Zry plates were pulled out of the molten mixture. The remaining thickness of Zry plates after the tests were measured by using optical microscope. To understand the influences of alloying elements in Zry and SS, three other sets of experiments (Zr plates in Fe-B$$_{4}$$C, Zr plates in SS-B$$_{4}$$C and Zry plates in Fe-B$$_{4}$$C) were also conducted. Results of the study indicated that the thickness of Zry plates decreased linearly with increase of soaking duration. The recession rate of Zry plates was increase with increase of testing temperatures. The value of apparent activation energy on the thickness recession rate of Zry plates was determined to be 333 kJ/mol. The alloying elements in SS showed a positive effect on suppression of Zry corrosion. In contrast, the alloying elements in Zry showed a negative effect on the process.

口頭

High-temperature interaction of silicon carbide with steam above 1600$$^{circ}$$C

Pham, V. H.; 永江 勇二; 倉田 正輝

no journal, , 

Silicon carbide (SiC) has recently attracted much attention as a potential material for accident tolerant fuel cladding. High-temperature interaction of SiC at temperature range below 1600$$^{circ}$$C has been studied by various authors. As expected for enhanced accident tolerant fuel cladding, high-temperature interaction of SiC must be also investigated at temperatures above 1600$$^{circ}$$C. In this study, we investigate high-temperature interaction of SiC in steam at temperature range of 1700$$sim$$1800$$^{circ}$$C using laser heating furnace. The oxidation kinetics is then studied based on the weight change and observation on cross-sectioned surface of tested sample using field emission scanning electron microscope. Off-gas measurement of hydrogen (H$$_{2}$$) and carbon monoxide (CO) generated during the test was also conducted via sensor gas chromatography.

口頭

Recession of ZrO$$_{2}$$ scale on fuel tube cladding by the melt of control rod assemble

中島 正太郎*; 松浦 傑*; 南口 誠*; 倉田 正輝; Pham, V. H.

no journal, , 

For a better understanding of the Fukushima-Daiichi Nuclear Power Plant accident, a reaction model of core melting process is very important. In this study, oxidized Zry plates were soaked into molten SS-B$$_{4}$$C mixture and heated into Ar gas at 1200$$^{circ}$$C. Recession of ZrO$$_{2}$$ scale was observed in the both cases. An oxygen solid solution region in the Zry sample was observed below ZrO$$_{2}$$ scale, although it was not observed in Zry oxidized at 600$$^{circ}$$C in high temperature steam conditions. When oxygen supply from the surrounding was halted, ZrO$$_{2}$$ scale can be reduced at high temperature such as 1200$$^{circ}$$C by oxygen dissolution into Zry inside.

口頭

Consideration for modeling of Zry oxidation and hydrogen uptake in steam-starved conditions

山崎 宰春; Pshenichnikov, A.; Pham, V. H.; 永江 勇二; 倉田 正輝

no journal, , 

燃料集合体の酸化及び水素吸収はその後の事故進展挙動に影響を与えることから、PWR燃料集合体では、実効的な水蒸気流量としてg-H$$_{2}$$O/sec/rodという1rodあたりの単位が導入されており、事故進展評価の重要なパラメータとして用いられている。一方BWRにおいては、燃料集合体の構成がPWRとは異なることにより、PWRで用いられている1rodあたりの水蒸気流量ではチャンネルボックスの内外での酸化及び水素吸収の差が正確に評価できない。そのため、PWRで用いられている規格化された水蒸気流量に代わる、適切な評価パラメータがBWRでも必要である。そこで、ジルカロイの水蒸気枯渇条件での酸化及び水素吸収データを取得するため、4本の燃料棒をチャンネルボックスで囲んだ試験体を用いて水蒸気枯渇条件にて高温酸化試験を行なった。BWRにおける水蒸気流量を規格化するため、水蒸気流路断面積を考慮したパラメータを検討した。

口頭

Advanced multi-scale modeling and experimental tests on fuel degradation in severe accident conditions, 1-5; Model of reaction between control rod and channel box

Pham, V. H.; 松浦 傑*; 中島 正太郎*; 永江 勇二; 倉田 正輝

no journal, , 

In this study, soaking experiments of pre-oxidized zry plates in molten mixture of stainless steel and 5 mol% boron carbide were conducted at 1200-1250$$^{circ}$$C. Thickness of oxide layer, ZrO$$_{2}$$ was measured before and after the soaking test to investigate the ZrO$$_{2}$$ thickness recession in the molten mixture. Results of the study indicated that the thickness recession of ZrO$$_{2}$$ was mainly caused by the diffusion of oxygen from oxide layer to metallic-Zr region.

口頭

ジルカロイ上に形成したZrO$$_{2}$$スケールにおける酸素供給が絶たれた際の減肉挙動

中島 正太郎*; 松浦 傑*; 南口 誠*; 倉田 正輝; Pham, V. H.

no journal, , 

沸騰型軽水炉(BWR)では、核燃料ペレット(UO$$_{2}$$)をZr合金(Zry)製被覆管で構成した燃料棒および炭化ホウ素(B$$_{4}$$C)製中性子吸収材料をステンレス鋼(SS)製管で構成された制御棒が隣接して格納されている。全電力喪失時においては、冷却水の供給停止によって核燃料が冷却されず、核燃料の温度が上昇し続けると、冷却水が蒸発して反応炉内が高温水蒸気環境となり、Zry中のZrと反応し燃料棒表面にZrO$$_{2}$$スケールを形成するとされている。また、制御棒を構成しているSSおよびB$$_{4}$$Cが共晶反応を起こし、液相が形成される。この液相が燃料被覆管と接触することで燃料被覆管が腐食され、核燃料の暴露に繋がったと考えられている。しかしながら、燃料棒表面に形成されたZrO$$_{2}$$スケールと液相の腐食プロセスの理解は十分にはされていないのが現状である。そこで本研究では、Ar雰囲気気流下においてZrO$$_{2}$$スケールを形成したZry板に熱処理を加えることで、液相化したSS-B$$_{4}$$Cに接触して水蒸気の供給が遮断された状況を熱力学的に模擬した実験を行い、シビアアクシデント時の腐食プロセスの解明を行った。

口頭

Steam oxidation of silicon carbide at high temperature up to 1800$$^{circ}$$C

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

no journal, , 

Silicon carbide has been considered as a potential candidate for fuel cladding. Many studies have been conducted to investigate the steam oxidation of SiC at temperatures below 1600$$^{circ}$$C. However, the steam oxidation behavior of SiC at temperatures above 1600$$^{circ}$$C remained unclear due to the lack of test facilities. In this study, we investigated the steam oxidation of SiC at temperatures ranging from 1400-1800$$^{circ}$$C using a newly developed laser heating facility.

口頭

Development of laser heating facility for steam oxidation at extreme temperatures

倉田 正輝; Pham, V. H.; 永江 勇二

no journal, , 

Since the disaster at Fukushima Daiichi Nuclear Power Plant, development of accident tolerant fuel to manage severe accidents has been proposed. As temperature of fuel rods could reach to temperatures above 2000$$^{circ}$$C during the accident, investigation of oxidation behavior at such temperatures for fuel claddings must be conducted. Nevertheless, there is no test facility capable for operating at such conditions. In this study, we developed a laser heating facility for steam oxidation of cladding materials at extreme temperatures. Main features of the facility are controlled environment, in situ observation, extreme fast heating and cooling rate and off gas analysis. As the heat is focused on the test sample only, the facility can be operated at temperatures above 2000$$^{circ}$$C. Preliminary tests have been conducted for monolithic SiC at 1400-1800$$^{circ}$$C for 1-7 h under 0.96 atm steam partial pressure. Results of the investigation showed that SiC underwent a mass loss which obeyed paralinear laws. Based on the mass change data, parabolic oxidation rate and linear volatilization rate of the process were obtained. The apparent activation energy of the oxidation process was calculated to be 96 kJmol $$^{-1}$$. Bubbling phenomenon was observed on SiC sample surface at 1800$$^{circ}$$C.

口頭

R&D for introducing silicon carbide materials to safety improvement of BWR's core, 5; Influence of steam flow rate on oxidation of SiC at high temperatures

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

no journal, , 

In this study, oxidation of SiC under various flow rates of steam was investigated at 1400$$^{circ}$$C using laser heating. Results of the investigation indicated that the mass evolution of SiC underwent a mass gain with 0.1 g/min of steam flow rate. Whereas, the mass evolution experienced a mass loss with 3 g/min of steam. Based on the data of mass change under the investigated conditions, the parabolic and linear rate constants were calculated and reported.

口頭

R&D for introducing silicon carbide materials to safety improvement of BWR's core, 7; Oxidation kinetics of SiC at 1400-1600$$^{circ}$$C under different steam flow rate

Pham, V. H.; 永江 勇二; 倉田 正輝; 石橋 良*

no journal, , 

Since the severe accident at Fukushima Daiichi Nuclear Power Plant, development of accident tolerant fuel claddings such SiC has been intensively discussed. However, application of SiC as fuel claddings has raised some concerns over its performance under severe accident conditions in steam. In this study, investigation of steam oxidation for SiC at 1400-1600$$^{circ}$$C under 0.1 and 3 g/min steam flow rate was performed using newly developed laser heating facility. Results of the investigation showed that the SiC experienced a mass gain behavior under 0.1 g/min steam flow rate. Whereas, it suffered a mass loss under 3 g/min steam flow rate. Based on the mass change data obtained in the investigation, reaction rate constants and activation energy of the process were calculated and reported.

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