Interaction of solute manganese and nickel atoms with dislocation loops in iron-based alloys irradiated with 2.8 MeV Fe ions at 400 C

Nguyen, B. V. C.*; 村上 健太*; Chena, L.*; Phongsakorn, P. T.*; Chen, X.*; 橋本 貴司; Hwang, T.*; 古澤 彰憲; 鈴木 達也*

Nuclear Materials and Energy (Internet), 39, p.101639_1 - 101639_9, 2024/06

https://doi.org/10.1016/j.nme.2024.101639

In reactor pressure vessel materials, the formation of Mn- and Ni-rich nanoclusters is a major cause of neutron irradiation embrittlement. The segregation of these solute atoms into dislocation loops has attracted attention as a mechanism to accelerate solute clustering. In this study, the behaviors of solute Mn and Ni atoms in Fe-0.6wt.%Ni, Fe-1.4wt.%Mn, and Fe-1.4wt.%Mn-0.6wt.%Ni alloys irradiated at 400 C up to 3 dpa were analyzed using three-dimensional atom probe tomography. Solute atom clusters were observed in all materials, and their shapes were spherical, flat, and torus in FeNi, FeMn, and FeMnNi, respectively. In ternary alloy FeMnNi, Mn and Ni atoms were concentrated in the sample in the form of arcs, and the orientation of the plane containing the arcs was estimated by comparing field desorption images. The size, number density, and orientation of this structure were found to be in good agreement with those of both types of dislocation loops, namely, b = 1/2 111 and b = 100, identified in a previous study using the same material. The positions of Ni and Mn enrichment did not fully overlap. Ni atoms tended to be concentrated more in the inner part of the loop than the Mn atoms. Mn atoms were enriched only in the vicinity of the dislocation loops, whereas Ni atoms showed a higher concentration inside the dislocation loops than in the bulk.

Determination of Sr in highly radioactive aqueous samples via conversion to a kinetically stable 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid complex followed by concentration-separation-fractionation based on capillary electrophoresis-liquid scintillation

大内 和希; 原賀 智子; 廣瀬 和生*; 黒澤 結香*; 佐藤 義行; 渋川 雅美*; 齋藤 伸吾*

Analytica Chimica Acta, 1298, p.342399_1 - 342399_7, 2024/04

https://doi.org/10.1016/j.aca.2024.342399

従来の高線量試料分析法では被ばくリスクが高く、大量の二次放射性廃棄物が発生することから、放射線放出量を低減できる迅速な分析法が強く望まれている。このニーズに取り組むため、我々は液体シンチレーションカウンティングと2点検出によるキャピラリー過渡的等速電気泳動(ctITP)を組み合わせたSr定量法を開発した。これは、1,4,7,10-テトラアザシクロドデカン-1,4,7,10-テトラ酢酸(DOTA)-Sr錯体を1回の操作で分離・分画する方法である。高線量の放射性試料をマイクロリットルレベルで取り扱うことができ、従来のイオン交換法よりも大幅に高速であるこの方法により、実高線量廃棄物中のSrを選択的に定量した。ctITPにおける濃縮・分離の成功は、Sr-DOTA錯体が解離不活性であることに起因する。

Probing deformation behavior of a refractory high-entropy alloy using neutron diffraction

Zhou, Y.*; Song, W.*; Zhang, F.*; Wu, Y.*; Lei, Z.*; Jiao, M.*; Zhang, X.*; Dong, J.*; Zhang, Y.*; Yang, M.*; et al.

Journal of Alloys and Compounds, 971, p.172635_1 - 172635_7, 2024/01

https://doi.org/10.1016/j.jallcom.2023.172635

The grain orientation-dependent lattice strain evolution of a (TiZrHfNb) refractory high-entropy alloy (HEA) during tensile loading has been investigated using neutron diffraction. The equivalent strain-hardening rate of each of the primary -oriented grain families was found to be relatively low, manifesting the macroscopically weak work-hardening ability of such a body-centered cubic (BCC)-structured HEA. This finding is indicative of a dislocation planar slip mode that is confined in a few single-slip planes and leads to in-plane softening by high pile-up stresses.

Oxidation and embrittlement behavior of FeCrAl-ODS cladding tube under loss-of-coolant accident conditions

成川 隆文; 近藤 啓悦; 藤村 由希; 垣内 一雄; 宇田川 豊; 根本 義之

Journal of Nuclear Materials, 587, p.154736_1 - 154736_8, 2023/12

https://doi.org/10.1016/j.jnucmat.2023.154736

To evaluate the oxidation and embrittlement behavior of an oxide-dispersion-strengthened FeCrAl (FeCrAl-ODS) cladding tube under loss-of-coolant accident (LOCA) conditions, we conducted isothermal oxidation and ring-compression tests on unirradiated, stress-relieved FeCrAl-ODS cladding tube specimens. Further, we discussed the loss of coolable geometry of the reactor core loaded with the FeCrAl-ODS cladding tubes under LOCA conditions, using data from the ring-compression tests in this study and the integral thermal shock tests from our previous study. The results reveal that oxidation kinetics of the FeCrAl-ODS cladding tube at 1523 K is four orders of magnitude lower than that of a conventional Zircaloy cladding tube, which highlights the exceptional oxidation resistance of the FeCrAl-ODS cladding tube. The breakaway oxidation of the FeCrAl-ODS cladding tube was observed at 1623 K for durations equal to or exceeding 6 h, and melting was observed at 1723 K. The ring-compression and the integral thermal shock tests indicate that, depending on the oxidation time, the ductile to brittle transition threshold - as determined by the ring-compression test - exists between 1623 K and 1723 K. Meanwhile, the fracture threshold - established through the integral thermal shock test - falls between 1573 K and 1673 K. Therefore, taking a conservative approach based on available data, the fracture and non-fracture results from the integral thermal shock tests can define the lower and upper boundaries of the threshold for the loss of coolable geometry of the reactor core during a LOCA.

Predictive and inverse modeling of a radionuclide diffusion experiment in crystalline rock at ONKALO (Finland)

Soler, J. M.*; Keklinen, P.*; Pulkkanen, V.-M.*; Moreno, L.*; Iraola, A.*; Trinchero, P.*; Hokr, M.*; ha, J.*; Havlov, V.*; Trpkoov, D.*; et al.

Nuclear Technology, 209(11), p.1765 - 1784, 2023/11

https://doi.org/10.1080/00295450.2023.2209234

The REPRO-TDE test was performed at a depth of about 400 m in the ONKALO underground research facility in Finland. Synthetic groundwater containing radionuclide tracers (HTO, Cl-36, Na-22, Ba-133, Cs-134) was circulated for about four years in a packed-off interval of the injection borehole. Tracer activities were additionally monitored in two observation boreholes. The test was the subject of a modelling exercise by the SKB GWFTS Task Force. Eleven teams participated in the exercise, using different model concepts and approaches. Predictive model calculations were based on laboratory-based information concerning porosities, diffusion coefficients and sorption partition coefficients. After the experimental results were made available, the teams were able to revise their models to reproduce the observations. General conclusions from these back-analysis calculations include the need for reduced effective diffusion coefficients for Cl-36 compared to those applicable to HTO (anion exclusion), the need to implement weaker sorption for Na-22, compared to results from laboratory batch-sorption experiments, and the observation of large differences between the theoretical initial concentrations for the strongly-sorbing Ba-133 and Cs-134 and the first measured values a few hours after tracer injection. Different teams applied different concepts, concerning mainly the implementation of isotropic vs. anisotropic diffusion, or the possible existence of Borehole Disturbed Zones around the different boreholes. The role of microstructure was also addressed in two of the models.

Hierarchical Bayesian modeling to quantify fracture limit uncertainty of high-burnup advanced fuel cladding tubes under loss-of-coolant accident conditions

成川 隆文; 濱口 修輔*; 高田 孝*; 宇田川 豊

Nuclear Engineering and Design, 411, p.112443_1 - 112443_12, 2023/09

https://doi.org/10.1016/j.nucengdes.2023.112443

For realizing a highly reliable fracture limit evaluation of fuel cladding tubes during loss-of-coolant accidents (LOCAs) in light-water reactors, we developed a method to quantify the fracture limit uncertainty of high-burnup advanced fuel cladding tubes. This method employs a hierarchical Bayesian model that can quantify uncertainty even with limited experimental data. The fracture limit uncertainty was quantified as a probability using the amount of oxidation (Equivalent cladding reacted: ECR) and the initial hydrogen concentration (the hydrogen concentration in the fuel cladding tubes before the LOCA-simulated tests) as explanatory variables. We divided the regression coefficients of this model into a hierarchical structure with an overall average term common to all types of fuel cladding tubes and a term representing differences among various types of fuel cladding tubes. This hierarchical structure enabled us to quantify the fracture limit uncertainty through the effective use of prior knowledge and data, even for high-burnup advanced fuel cladding tubes with a small number of data points. The fracture limits representing a 5% fracture probability with 95% confidence of the high-burnup advanced fuel cladding tubes evaluated by the hierarchical Bayesian model were higher than 15% ECR for the initial hydrogen concentrations of up to 700-900 wtppm and restraint loads below 535 N. These fracture limits were comparable to the limit of the unirradiated Zircaloy-4 cladding tube, indicating that the burnup extension and use of the advanced fuel cladding tubes do not significantly lower the fracture limit of fuel cladding tubes. Further, we proposed a method to reduce the fracture limit uncertainty by using non-binary data, instead of the binary data, depending on the condition of the fuel cladding tube specimens after performing the LOCA-simulated test, thereby increasing the amount of information in the data.

中性子回折によるハイエントロピー合金の変形挙動のその場観察

Harjo, S.

日本結晶学会誌, 65(3), p.178 - 182, 2023/08

https://doi.org/10.5940/jcrsj.65.178

Observations of deformation behavior of high entropy alloys using neutron diffraction measurements during deformation at various temperatures are reviewed. Neutrons are used to investigate stresses and crystallographic microstructures inside engineering materials, taking advantage of their large penetrating power and the ability to see the arrangement of atoms by diffraction methods. The important structural details of high entropy alloys such as internal stresses, phase conditions, dislocations, texture etc. are discussed in relation to the deformation conditions. Some highlights are introduced: (a) Cooperative deformation in CrMnFeCoNi alloy at ultralow temperatures, (b) Stacking fault energies in CrFeCoNi and CrCoNi alloys, and (c) Load redistribution in eutectic high entropy alloy AlCoCrFeNi during high temperature deformation.

X-ray free electron laser observation of ultrafast lattice behaviour under femtosecond laser-driven shock compression in iron

佐野 智一*; 松田 智己*; 廣瀬 明夫*; 寺井 智之*; 掛下 智之*; 犬伏 雄一*; 佐藤 孝弘*; 矢橋 牧名*; 菖蒲 敬久; 他22名*

Scientific Reports (Internet), 13, p.13796_1 - 13796_10, 2023/08

https://doi.org/10.1038/s41598-023-40283-6

Over the past century, understanding the nature of shock compression of condensed matter has been a major topic. About 20 years ago, a femtosecond laser emerged as a new shock-driver. Unlike conventional shock waves, a femtosecond laser driven shock wave creates unique microstructures in materials. Therefore, the properties of this shock wave may be different from those of conventional shock waves. However, the lattice behaviour under femtosecond laser-driven shock compression has never been elucidated. Here we report the ultrafast lattice behaviour in iron shocked by direct irradiation of a femtosecond laser pulse, diagnosed using X-ray free electron laser diffraction. We found that the initial compression state caused by the femtosecond laser driven shock wave is the same as that caused by conventional shock waves. We also found, for the first time experimentally, the temporal deviation of peaks of stress and strain waves predicted theoretically. Furthermore, the existence of a plastic wave peak between the stress and strain wave peaks is a new finding that has not been predicted even theoretically. Our findings will open up new avenues for designing novel materials that combine strength and toughness in a trade-off relationship.

Improvement in the elution performance of an N,N,N',N-tetraoctyl diglycolamide impregnated extraction chromatography adsorbent using neodymium via micro-particle-induced X-ray emission analysis

高畠 容子; 渡部 創; 新井 剛*; 佐藤 隆博*; 柴田 淳広

Applied Radiation and Isotopes, 196, p.110783_1 - 110783_5, 2023/06

https://doi.org/10.1016/j.apradiso.2023.110783

An adsorbent used for the recovery of trivalent minor actinides (MA(III); Am and Cm) from high level liquid waste generated from reprocessing of spent nuclear fuel was subjected to micro-PIXE analysis to improve its elution performance. The experimental adsorbent comprised SiO particles, a polymer coating, and an TODGA. The particles to be analyzed were subjected to Nd adsorption and an elution operation, but Nd in the adsorbent was found to be uniformly distributed. This might have been caused by individual differences in the amount of impregnated TODGA. The remaining Nd species were not localized to a specific part of the adsorbent after the adsorption operation. Some Nd elements were retained in the adsorbent after elution, probably because of the poor diffusion of the mobile phase inside the adsorbent. An adsorbent having a different microstructure from the first was then evaluated, and rapid elution was observed on new adsorbent along micro-PIXE analysis

再処理施設の高レベル廃液蒸発乾固事故のソースターム解析手法の整備

吉田 一雄; 玉置 等史; 桧山 美奈*

JAEA-Research 2023-001, 26 Pages, 2023/05

JAEA-Research-2023-001.pdf:1.61MB

再処理施設の過酷事故の一つである高レベル放射性廃液貯槽の冷却機能喪失による蒸発乾固事故では、沸騰により廃液貯槽から発生する硝酸-水混合蒸気とともにルテニウム(Ru)の揮発性の化学種が放出される。このためリスク評価の観点からは、Ruの定量的な放出量の評価が重要な課題である。再処理施設のリスク評価の精度向上に資するため、計算プログラムを用いて当該事故時でのソースタームを解析的に評価する手法の整備を進めている。提案する解析手法では、まず廃液貯槽の沸騰をSHAWEDで模擬する。模擬結果の蒸気発生量等を境界条件としてMELCORにより施設内の蒸気等の流れに沿って各区画内の熱流動状態を模擬する。さらに各区画内の熱流動状態を境界条件としてSCHERNを用いてRuを含む硝酸、NO等の化学挙動を模擬し、施設外への放射性物質の移行量(ソースターム)を求める。本報では、仮想の実規模施設での当該事故を想定して、これら3つの計算プログラム間でのデータの授受を含めて解析事例を示す。