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論文

Microstructural evolution of intermetallic phase precipitates in Cr-coated zirconium alloy cladding in high-temperature steam oxidation up to 1400$$^{circ}$$C

Mohamad, A. B.; 根本 義之; 古本 健一郎*; 岡田 裕史*; 佐藤 大樹*

Corrosion Science, 224, p.111540_1 - 111540_15, 2023/11

The steam oxidation test on the Cr-coated Zry cladding was studied up to 1400$$^{circ}$$C to understand the oxidation behavior under the accidental conditions. The double-sided oxidation test study showed that Cr coating can protect Zry cladding at 1200$$^{circ}$$C within 5 min. Cr coating has a protective effect on the Zry cladding up to 1200$$^{circ}$$C in a steam environment. However, in the oxidation test up to 1200$$^{circ}$$C/30 min and 1300$$^{circ}$$C/5 min, Cr coating can no longer protect Zry cladding. Furthermore, at 1300$$^{circ}$$C, the intermetallic phase of the Zr(Cr, Fe)$$_{2}$$ phase that precipitated within the Zry substrate formed as globule microstructures with Fe enrichment. In addition, the transition of the intermetallic phase within the Zry substrate from the solid to the pre-liquid and liquid phases was observed, where it was determined at 1350$$^{circ}$$C/60 min and 1400$$^{circ}$$C/30 min within the ZrO$$_{2}$$ phase (outer side region). The oxidation of the Zr(Cr, Fe)$$_{2}$$ interlayer was also determined in this study, where it resulted in the formation of the oxide phase of Cr, Zr, and Fe. It is worth mentioning that further experiments, such as mechanical testing and modeling, should be considered to support the degradation of the Cr-coated Zry cladding mainly when the liquid phase of the intermetallic phase is obtained for beyond design-basis accident environment.

論文

Effects of azimuthal temperature distribution and rod internal gas energy on ballooning deformation and rupture opening formation of a 17 $$times$$ 17 type PWR fuel cladding tube under LOCA-simulated burst conditions

古本 健一郎; 宇田川 豊

Journal of Nuclear Science and Technology, 60(5), p.500 - 511, 2023/05

 被引用回数:0 パーセンタイル:0.01(Nuclear Science & Technology)

In order to contribute to better modeling and evaluation of fuel fragmentation, relocation, and dispersal expected under loss of coolant accident (LOCA) conditions, LOCA-simulated cladding burst experiments were performed on as-received nonirradiated 17 $$times$$ 17 type Zircaloy-4 cladding specimens that were internally pressurized. The experiments were designed to terminate at burst occurrence to focus on ballooning and rupture opening formation and to investigate the effects of various factors. The postburst cladding hoop strain decreased with the increase in azimuthal temperature distribution (ATD) of the cladding, as found previously. The rupture opening size increased with the increase in ATD and the increase in energy of the pressurized gas stored inside the pressure boundary of the test sample system. Comparison with the existing database, which included tests on irradiated rods containing fuel pellets, suggested that formation of the rupture opening was influenced by the characteristic behavior of high burnup fuels, such as limited gas migration in the cladding tube due to fuel-cladding bonding and interaction of the ejected fuel fragments with the cladding tube.

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:12 パーセンタイル:86.84(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

The Applicability of SiC-SiC fuel cladding to conventional PWR power plant

古本 健一郎*; 渡部 清一*; 山本 晃久*; 手島 英行*; 山下 真一郎; 齋藤 裕明; 白数 訓子

Proceedings of 2017 Water Reactor Fuel Performance Meeting (WRFPM 2017) (USB Flash Drive), 10 Pages, 2017/09

2015年以降、三菱原子燃料(MNF)は、日本原子力研究開発機構(JAEA)が経済産業省からの受託事業で実施している日本の事故耐性燃料の研究開発プロジェクトに加わった。このプログラムにおいて、MNFは、現行の沸騰水型軽水炉(PWR)において炭化ケイ素複合材料(SiC)を被覆管として導入した場合の影響を評価することを担当している。本論文では、既存のPWRに対してSiCを被覆管として用いる場合の適用性に関する評価結果を報告する。既存PWRへのSiC被覆管の適用性評価として、SiC複合材を用いた場合の解析評価と炉外試験の両方を実施した。解析評価では、三菱独自の燃料設計コードとJAEAが開発した燃料ふるまいコードを用いた。なお、これらのコードは、SiC複合材被覆管を用いた燃料のふるまいを評価するために改良が施されている。一方、炉外試験としては、SiC複合材サンプルの熱伝導度測定とオートクレーブを用いた腐食試験を実施した。合わせて、設計基準事故を模擬した条件下でのSiC複合材の性能評価が行えるようにするために、新たに試験装置も開発した。

口頭

安全性向上に資する新型燃料の既存軽水炉への導入に向けた研究開発,4; PWR用SiC複合材料

手島 英行*; 渡部 清一*; 古本 健一郎*; 桐村 一生*; 山越 義規*; 井岡 郁夫; 山下 真一郎; 加治 芳行

no journal, , 

事故耐性燃料の被覆管材料として有力な材料の一つであるSiC複合材の主な課題として、(1)材料・照射特性の把握、(2)燃料特性の成立性評価、(3)事故時安全性への影響評価、が挙げられる。本研究では、上述した1$$sim$$3の課題解決を目的として、SiC複合材被覆管を用いた炉外試験及び照射試験、燃料ふるまい・炉心特性及び事故時安全性の評価手法の開発並びに解析評価を計画・実施している。

口頭

事故耐性燃料としてのSiC複合材被覆管の既設PWRへの適用性に関する評価,2; 運転時の燃料ふるまい評価

古本 健一郎*; 手島 英行*; 渡部 清一*; 山本 晃久*; 白数 訓子; 齋藤 裕明; 山下 真一郎

no journal, , 

高温における水との反応熱および水素発生が少ないSiC複合材は事故耐性燃料被覆管として有力な材料の一つである。しかし、従来の被覆管材料であるZr合金と較べて基本的な材料物性が異なるだけでなく、SiC複合材に特有の照射挙動が存在する。そのため、SiC複合材被覆管燃料棒の運転時の炉内ふるまいは、それらを考慮して解析評価する必要がある。

口頭

事故耐性燃料としてのSiC複合材被覆管の既設PWRへの適用性に関する評価,3; 設計基準事故評価における安全性に関する評価

渡部 清一*; 手島 英行*; 古本 健一郎*; 片山 正晶*; 山下 真一郎

no journal, , 

SiC複合材は高温での安定性に優れ、反応熱や水素発生がほとんどないことから、シビアアクシデントを抑制しうる事故耐性燃料被覆管として有力な材料の一つである。しかし、DBA発生時におけるSiC複合材の挙動に関する知見は少ない。そこで本研究では、DBA発生時の挙動を評価するための試験装置を開発し、SiC複合材被覆管(SiC被覆管)を用いてモックアップ試験を実施した。

口頭

安全性向上に資する新型燃料の既存軽水炉への導入に向けた研究開発,4; PWR用SiC複合材料

渡部 清一*; 佐藤 大樹*; 古本 健一郎*; 村上 望*; 山下 真一郎; 深堀 智生

no journal, , 

事故耐性燃料の被覆管材料として有力な材料の一つであるSiC複合材の主な課題として、(1)材料・照射特性の把握、(2)燃料設計の成立性評価、(3)事故時安全性への影響評価が挙げられる。本研究では、上述した(1)$$sim$$(3)の課題解決を目的として、SiC被覆管を用いた炉外試験及び照射試験、燃料ふるまい・炉心特性及び事故時安全性の評価手法の開発並びに解析評価を計画・実施している。

口頭

事故耐性燃料としてのSiC複合材被覆管の既設PWRへの適用性に関する評価,5; 炉心・燃料特性への影響評価

村上 望*; 桐村 一生*; 山路 和也*; 左藤 大介*; 渡部 清一*; 佐藤 大樹*; 古本 健一郎*; 山下 真一郎; 深堀 智生

no journal, , 

SiC被覆管は従来の被覆管材に比べ熱伝導率が低く、また、燃料健全性の観点から燃焼を通じペレットと被覆管の接触を防止するよう間隙を大きくする必要があり、この結果燃料温度が上昇し反応度停止余裕に影響する。対策として燃料棒細径化及び中空ペレットを採用した場合の炉心・燃料特性への影響を検討した。

口頭

事故耐性燃料としてのSiC複合材被覆管の既設PWRへの適用性に関する評価,6; 機械特性試験

古本 健一郎*; 佐藤 大樹*; 渡部 清一*; 山下 真一郎; 深堀 智生

no journal, , 

既設PWR燃料にSiC被覆管を適用した燃料棒の健全性評価において、被覆管応力の評価が重要である。また、SiC複合材の機械特性には異方性があるため、軸・周方向それぞれの機械特性を把握することが必要である。しかし、SiC複合材の脆性的挙動のため、特に周方向の機械特性を調べることが技術的に難しい。そこで本研究では、SiC被覆管サンプルを用いて、近年Zr基合金管材を対象として開発された周方向機械特性試験であるA-EDC試験を実施し、SiC被覆管の周方向機械特性の取得を試みた。

口頭

事故耐性燃料としてのSiC複合材被覆管の既設PWRへの適用性に関する評価,7; LOCA模擬試験

佐藤 大樹*; 渡部 清一*; 小宮山 大輔*; 古本 健一郎*; 岡本 倫明*; 大和 正明*; 山下 真一郎; 深堀 智生

no journal, , 

SiC被覆管は、既設PWRのLOCA時に想定される高温環境において、高耐食性及び高強度を示すことが期待されているが、LOCA時を模擬して取得されたSiC被覆管の挙動データは少ない。そこで、SiC被覆管用にLOCA模擬試験装置を製作して試験を実施し、SiC被覆管のLOCA時挙動を調査した。

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

The Behavior of Cr-coated Zry cladding under high-temperature steam oxidation

Mohamad, A. B.; 古本 健一郎; 根本 義之; 井岡 郁夫; 佐藤 大樹*; 岡田 裕史*; 山下 真一郎; 逢坂 正彦

no journal, , 

Chromium (Cr) coated zirconium (Zr) based alloy cladding is the promising material for a near term accident tolerant fuel (ATF). Cr-coated Zr based cladding was fabricated by sputtering technique and HT oxidation tests were conducted up to different high temperatures (1100$$^{circ}$$C to 1400$$^{circ}$$C). The present work aims to investigate the metallography of Cr-coated Zr cladding after HT steam test. The result showed Cr$$_{2}$$O$$_{3}$$ layers were formed as a protective oxide layer at the outmost layer for all samples. However, Cr-Zr-Fe phases were observed In particular, the main phases observed in the cross-sectional area were Cr$$_{2}$$O$$_{3}$$, Cr, ZrO$$_{2}$$, Cr-Zr, and Zr situated from outer to inner of the sample after HT test. The details of the microstructure and mechanism of these samples will be discussed in the presentation.

口頭

Transition of the Zr(Cr, Fe)$$_{2}$$ intermetallic phase up to the eutectic temperature

Mohamad, A. B.; 根本 義之; 古本 健一郎*; 岡田 裕史*; 佐藤 大樹*

no journal, , 

The development of Accident Tolerant Fuel (ATF) had been started by conducting the investigation on new concepts to improve the safety of Light Water Reactors (LWRs). It is well known that the Cr coating on Zry cladding has shown an improvement in behavior under accident conditions and normal operation. In the Cr-Zr system, the eutectic phase of ZrCr$$_{2}$$ is present at 1332$$^{circ}$$C and forms as intermetallic compounds. There is still lack of data on the evolution of the intermetallic phase when the oxidation temperature reaches the eutectic temperature of Cr-Zr. Therefore, the purpose of this study will be to understand the solid-to-liquid phase transition of Zr(Cr, Fe)$$_{2}$$. High temperature oxidation tests were performed in a steam atmosphere to the target temperature (i.e., 1100$$^{circ}$$C, 1200$$^{circ}$$C, 1300$$^{circ}$$C, 1350$$^{circ}$$C, and 1400$$^{circ}$$C) for different exposure times of 5, 30, and 60 min. From the tests, the transition of Zr(Cr, Fe)$$_{2}$$ that formed at the Cr-Zr interface and also that precipitated in the Zry cladding were studied with varied oxidation time and temperatures. The microstructural evolution of the intermetallic phase was observed in the Zr substrate within the progress of the oxidation of Cr-coated Zry. A dendritic structure was observed at 1400$$^{circ}$$C, indicating the formation of the Zr(Cr, Fe)$$_{2}$$ liquid phase when the oxidation temperature is above the eutectic temperature.

口頭

The Transition of protective coating to no-longer protective coating of Cr-coated Zry cladding in high temperature steam oxidation

Mohamad, A. B.; 根本 義之; 古本 健一郎*; 岡田 裕史*; 佐藤 大樹*

no journal, , 

The development of Accident Tolerant Fuel (ATF) started with the investigation of new concepts to improve the safety of Light Water Reactors (LWR). It is well known that the Cr coating on Zry cladding has shown improved behaviour under accident conditions and in normal operation. However, many questions remain about the oxidation behaviour of Cr-coated Zry cladding as it approaches the Cr-Zr eutectic temperature. In the present study, the steam oxidation tests were carried out under different oxidation conditions in order to understand the oxidation behaviour of the Cr-coated material mainly above the eutectic temperature. The results obtained showed that the Cr coating can protect the Zry substrate at 1100$$^{circ}$$C to 1200$$^{circ}$$C/5min. However, at 1200$$^{circ}$$C/30min, the Cr coating no longer protected the Zry substrate. This is due to the formation of Zr at the Cr grain boundary where it becomes a short path for O diffusion and reacts with the Zry substrate.

口頭

Oxidation behavior of Cr-coated Zry cladding in steam environments

Mohamad, A. B.; 根本 義之; 古本 健一郎*; 岡田 裕史*; 佐藤 大樹*

no journal, , 

It is widely recognized that the Cr coating on Zry cladding has shown an improvement in the behavior under accident conditions and normal operation. Many research groups around the world have conducted the high-temperature oxidation and LOCA tests on Cr-coated Zry under accident conditions and explained the degradation phenomena from these tests. Although many literatures have revealed the mechanism and phenomena of the degradation of the Cr-coated, there is still a lack of data on the Zr-Cr-Fe phase or intermetallic phase behavior when the temperature reaches and exceeds the eutectic temperature of Zr-Cr (1332$$^{circ}$$C). In the present study, a high temperature steam oxidation test is carried out from 1100 to 1400$$^{circ}$$C in order to understand the behavior of Cr-coated Zry as it approaches the eutectic temperature. Fromelectron probe microanalysis, the Fe enrichment of the Zr(Cr,Fe)$$_{2}$$ phase is identified for the sample tested at 1300$$^{circ}$$C. In addition, the liquid formation of the Zr(Cr,Fe)$$_{2}$$ phase is observed at 1300$$^{circ}$$C.

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