Probing deformation behavior of a refractory high-entropy alloy using in situ 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 in situ 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.

幌延深地層研究計画; 令和5年度調査研究計画

中山 雅

JAEA-Review 2023-019, 70 Pages, 2023/11

JAEA-Review-2023-019.pdf:6.83MB

幌延深地層研究計画は、日本原子力研究開発機構が堆積岩を対象に北海道幌延町で実施しているプロジェクトである。令和5年度は、「令和2年度以降の幌延深地層研究計画」で示した、「実際の地質環境における人工バリアの適用性確認」、「処分概念オプションの実証」、「地殻変動に対する堆積岩の緩衝能力の検証」について、引き続き調査研究を行う。令和5年度に実施する主な調査研究は以下のとおりである。「実際の地質環境における人工バリアの適用性確認」では、国際共同研究DECOVALEX-2023において人工バリア性能確認試験を対象とした連成解析を行い、その結果について異なる解析コードによる解析結果との比較を通じて適用した解析コードの検証を行う。また、声問層に分布する割れ目を対象とした物質移行特性を評価するためのボーリング調査を継続する。「処分概念オプションの実証」では、搬送定置・回収技術の実証として、地下環境におけるコンクリートの劣化に関する試験および分析を継続する。また、閉鎖技術の実証として、350m調査坑道に新たに掘削する試験坑道の周辺を対象とした物理探査を行い、掘削直後における掘削損傷領域の割れ目の連続性や分布などの初期状態を把握するとともに、これまでに開発した物理探査技術の適用性を確認する。「地殻変動に対する堆積岩の緩衝能力の検証」では、過年度に実施した水圧擾乱試験の結果の解析や、岩石の強度・応力状態と断層/割れ目の水理学的連結性との関係に関する解析を継続する。地下施設の建設・維持管理では、掘削工事を再開し、350m調査坑道の拡張を行うとともに、深度500mに向けた立坑の掘削を開始する。国内外の資金や人材の活用に関する取り組みとして幌延国際共同プロジェクトを本格的に実施する。このプロジェクトでは、令和2年度以降の必須の課題のうち、「実際の地質環境における人工バリアの適用性確認」および「処分概念オプションの実証」に関わる3つのタスク(タスクA:物質移行試験、タスクB:処分技術の実証と体系化、タスクC:実規模の人工バリアシステム解体試験)を設定して調査研究を進める。

An Estimation method for an unknown covariance in cross-section adjustment based on unbiased and consistent estimator

丸山 修平; 遠藤 知弘*; 山本 章夫*

Journal of Nuclear Science and Technology, 60(11), p.1372 - 1385, 2023/11

https://doi.org/10.1080/00223131.2023.2203707

A new estimation method of an unknown covariance, which is defined by the difference between the true covariance (the population covariance) and a prior covariance assumed by an analyst, is proposed. The unknown covariance is estimated using an empirical covariance consistent with the observed data. To estimate the unknown covariance, an unbiased and consistent estimator in regression analysis has been incorporated into the conventional cross-section adjustment. This estimator does not require assumptions for the probability distribution of the observation data. The statistical properties of this estimator were numerically verified. In addition, the effectiveness of the proposed method was confirmed by another numerical test using actual integral experimental data. In the second numerical test, the modeling uncertainty (covariance) due to the deterministic analysis method was assumed to be unknown. The results showed that the proposed method could practically estimate the unknown covariance and adjusted cross-sections using only prior information on covariances.

Development of a DDA+PGA-combined non-destructive active interrogation system in "Active-N"

古高 和禎; 大図 章; 藤 暢輔

Nuclear Engineering and Technology, 55(11), p.4002 - 4018, 2023/11

https://doi.org/10.1016/j.net.2023.07.015

An integrated neutron interrogation system has been developed for non-destructive assay of highly radioactive special nuclear materials, to accumulate knowledge of the method through developing and using it. The system combines a differential die-away (DDA) measurement system for the quantification of nuclear materials and a prompt gamma-ray analysis (PGA) system for the detection of neutron poisons which disturb the DDA measurements; a common D-T neutron generator is used. A special care has been taken for the selection of materials to reduce the background gamma rays produced by the interrogation neutrons. A series of measurements were performed to test the basic performance of the system. The results show that the DDA system can quantify plutonium of as small as 20~mg and it is not affected by intense neutron background up to 4.2~TBq and gamma ray of 2.2~TBq. As a result of the designing of the combined system as a whole, the gamma-ray background counting rate at the PGA detector was reduced down to s even with the use of the D-T neutron generator. The test measurements show that the PGA system is capable of detecting less than 1~g of boron compound and about 100~g of gadolinium compound in~30 min. This research was implemented under the subsidy for nuclear security promotion of MEXT.

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.

Elucidation of solid particle interfacial phenomena in liquid sodium; Magnetic interactions on liquid metal and solid atoms at the solid interface

Tei, C.; 大高 雅彦; 桑原 大介*

Chemical Physics Letters, 829, p.140755_1 - 140755_6, 2023/10

https://doi.org/10.1016/j.cplett.2023.140755

固体金属粒子の界面に付着した液体ナトリウムの核磁気共鳴(NMR)信号を初めて検出することに成功した。本研究では、液体ナトリウムと液体ナトリウム中に浮遊する金属粒子との相互作用の違いによる緩和時間の違いを確認した。その結果、微小チタン粒子表面と液体金属ナトリウムは化学的ではなく物理的に相互作用していることが明らかとなった。

Review of JENDL/HE-2007 neutron-induced fission cross sections of uranium-235 and 238 above 200 MeV

深堀 智生

INDC(JPN)-210 (Internet), 5 Pages, 2023/10

U(n,f)の断面積値がENDF形式に正しく編集されておらず、間違った値がJENDL/HE-2007ファイルに格納・配布されている。JENDL/HE-2007ライブラリのU(n,f)断面積の高エネルギー部分は、FISCALコードの計算結果を使用して評価されている。このレポートでは、200MeV以上のJENDL/HE-2007ライブラリの正しいU(n,f)断面積値が示されている。

Measurement of mechanical behavior of B-enriched MgB wire using a pulsed neutron source

町屋 修太郎*; 長村 光造*; 菱沼 良光*; 谷口 博康*; Harjo, S.; 川崎 卓郎

Quantum Beam Science (Internet), 7(4), p.34_1 - 34_17, 2023/10

https://doi.org/10.3390/qubs7040034

Measuring the actual strain on the MgB filaments are of paramount importance, since tensile stress and strain diminish the critical current. In this study, the strain measurement using neutron diffraction during tensile loading was established. We fabricated a MgB wire enriched with boron-11, an isotope having a smaller neutron absorption cross- section than natural boron, and succeeded in obtaining changes in the lattice constant under tensile loading through Rietveld analysis.

Pd nanoparticles on the outer surface of microporous aluminosilicates for the direct alkylation of benzenes using alkanes

美崎 慧*; 三輪 寛子*; 伊藤 孝; 吉田 健文*; 長谷川 慎吾*; 中村 由紀奈*; 徳竹 駿太*; 高畠 萌*; 下村 浩一郎*; Chun, W.-J.*; et al.

ACS Catalysis, 13(18), p.12281 - 12287, 2023/09

https://doi.org/10.1021/acscatal.3c02309

The direct alkylation of benzenes with simple alkanes is one of the ideal processes for the production of alkylbenzenes. We demonstrated that Pd nanoparticles on the outer surface of H-ZSM-5 are efficient catalysts for direct alkylation. The reaction proceeds through the activation of an alkane on the acid sites present inside the zeolite pores. This process is followed by the nucleophilic addition of an arene to the activated alkane. The spillover of the abstracted hydrogen atoms from the acid sites to the Pd nanoparticles on the outer surface accelerates recombination to H. A maximum toluene conversion of 58.5% and selectivity of 95.6% for the alkylated products are achieved when toluene is reacted with -heptane. -selective alkylation is achieved, due to the effect of the pore size of H-ZSM-5. The SR study of muonium, a pseudo-isotope of hydrogen, in aluminosilicates suggested that the formation of atomic hydrogen is possible and its lifetime is in the sub-microsecond range or longer, which is long enough for chemical reactions.

Neutron capture cross-section measurement by mass spectrometry for Pb-204 irradiated in JRR-3

中村 詔司; 芝原 雄司*; 木村 敦; 遠藤 駿典; 静間 俊行*

Journal of Nuclear Science and Technology, 60(9), p.1133 - 1142, 2023/09

https://doi.org/10.1080/00223131.2023.2172088

近年、鉛冷却高速炉や加速器駆動システムの研究が進められており、Pb同位体の中性子捕獲断面積の高精度化が求められている。Pbは、天然存在比は小さいが中性子捕獲反応により長寿命放射性核種Pb(1730万年)を作るため、その重要性は高いと考えられる。しかし、原子炉を用いた通常の放射化法では、生成するPbからの放射線が弱いため測定するのが難しい。そこで、マススペクトロメトリーを適用した断面積測定を行った。本発表ではマススペクトロメトリーを適用したPbの中性子捕獲断面積測定について実験の詳細と得られた結果を報告する。