福島第一原子力発電所2号機原子炉格納容器貫通部X-6内の堆積物の分析

米山 海; 二田 郁子; 田中 康之; 小高 典康; 菊池 里玖; 坂野 琢真; 古瀬 貴広; 佐藤 宗一; 三本木 満; 田中 康介

JAEA-Technology 2025-008, 44 Pages, 2025/12

JAEA-Technology-2025-008.pdf:4.3MB

東京電力ホールディングス株式会社福島第一原子力発電所(1F)の廃炉に向け、原子炉建屋格納容器内部の調査が行われている。燃料デブリの取出しや建屋解体の作業を安全に進めるためには、汚染状況を把握し、作業の計画や作業者の被ばくを管理する必要がある。本件は、2号機原子炉格納容器貫通部X-6(X-6ペネ)内の堆積物について、含まれる元素、放射性核種濃度、核種組成を把握することを目的に分析を実施した。本分析の対象試料は、スミヤろ紙に付着したX-6ペネ内部の堆積物である。堆積物に含まれる核種の把握、また、元素や元素の共存の様子を把握するため、非破壊分析として線スペクトル分析、蛍光X線(XRF)分析、走査型電子顕微鏡-エネルギー分散型X線(SEM-EDX)分析を実施した。さらに、堆積物に含まれる放射性核種やその組成を詳細に明らかにするために、堆積物を硝酸及びフッ化水素酸で溶解し、溶解液中の核種、Sr-90及び核種の放射能分析を実施した。得られた結果を、2020年にX-6ペネ内の異なる場所で採取された堆積物の分析結果と比較した。非破壊での線スペクトル分析では、Co-60、Sb-125、Cs-134、Cs-137、Eu-154、Eu-155及びAm-241が検出された。XRF分析では、格納容器内の構造物由来と考えられるFeが主要な元素として検出され、そのほか燃料や燃料被覆管に由来すると考えられる微量のU及びZrが検出された。SEMEDX分析の結果では、堆積物の主要な元素としてOとFeが検出されたことに加え、Uを含む粒子が観察され、UとともにFe、Si、Cr、Ni、Zrが検出された。これらの結果は2020年採取試料と同様の傾向であった。放射能分析では、非破壊測定で検出された核種(Co-60、Sb-125、Cs-134、Cs-137、Eu-154、Eu-155)に加えて、Sr-90、Pu-238、Pu-239+240、Am-241、Cm-244、U-235、U-238の定量値を得た。これらの結果をもとに、1F事故に由来する汚染の主要な線放出核種であるCs-137を基準とした放射能比を算出した。さらに、U-238に対する放射能比についても算出し、ORIGENによる2号機の燃料組成の計算値と比較した。

熱化学水素製造法ISプロセスのためのヨウ化水素濃縮用イオン交換膜の開発

田中 伸幸; 澤田 真一*; 越川 博*; 八巻 徹也*

Material Stage, 25(6), p.76 - 80, 2025/09

熱化学水素製造法ISプロセスの熱効率の向上を行う膜技術の開発が進められており、HI-I-HO (HIx)溶液のHI濃縮のため、カチオン交換膜を用いた電解電気透析法(EED)が適用されている。カチオン交換膜に対して、放射線グラフト重合法を用いることにより、イオン導電性を向上し、消費エネルギーを大幅に削減した。さらに、グラフト鎖に架橋を導入し、膜の膨潤を抑制することで、H選択性を向上させ、イオン導電率との両立を実現した。現在では、膨潤抑制効果がさらに期待できるイオン飛跡グラフト重合法を用いて、イオン交換膜の性能向上を進めている。

U(VI) adsorption on mudstone in the presence of carbonate; Batch experiments, modeling, cryo-TRLFS and PARAFAC analysis

Mei, H.; 青柳 登; 斉藤 拓巳*; 田中 万也; 杉浦 佑樹; 舘 幸男

Applied Clay Science, 276, p.107944_1 - 107944_8, 2025/07

https://doi.org/10.1016/j.clay.2025.107944

Dissolved inorganic carbon (DIC) existing in groundwaters near geological disposal site may affect the migration and fate of released radionuclides (e.g., uranium (U)). However, it is still unclear how DIC affects the sorption of U(VI) on mudstone, a potential choice for host rock formation barriers, and the characteristics of U(VI) adsorption species. In view of this, adsorption of U(VI) on mudstone as a function of pH or the DIC level was investigated through batch adsorption experiments, component additivity (CA) modeling, and parallel factor (PARAFAC) analysis of cryogenic time-resolved laser fluorescence spectroscopy (cryo-TRLFS). The inhibition effect of DIC on adsorption of U(VI) was implied from the batch experimental results. The CA model considering montmorillonite and illite as the main phases responsible for adsorption reflected the variation trend but underestimated the experimental data. Three components were decomposed from the PARAFAC analysis of the cryo-TRLFS data of mudstone and adsorption samples. Based on the spectral shapes, lifetimes, and variation trends, two components were assigned to the intrinsic U(VI) species in the mudstone matrix and the third component to a ternary uranyl-carbonate surface species. The obtained results imply a significant influence of the DIC level on retention and fate of U(VI), which needs to be considered in safety assessment of potential deep geological disposal schemes.

Neutron reflectometry study on the interfacial layer of epoxy resin to improve adhesion strength

Liu, Y.*; 宮田 登*; 宮崎 司*; 春藤 淳臣*; 川口 大輔*; 田中 敬二*; 青木 裕之

ACS Applied Materials & Interfaces, 17(25), p.37311 - 37318, 2025/06

http://doi.org/10.1021/acsami.5c07863

The performance of structural adhesives is strongly influenced by the interfacial structure between the adhesive and adherend. In this study, we developed a nanometric stable interfacial layer derived from an epoxy resin system containing excess hardener. This layer, formed on solid substrates, exhibited excellent structural stability, even after extensive solvent washing. Neutron reflectometry (NR) was employed to investigate its structure under both dry and humid conditions, revealing a robust and well-defined interface that suppressed moisture accumulation at the adherend interface. FT-IR spectroscopy confirmed an excess of unreacted amino groups in the adsorbed layer, enabling further curing reactions with freshly applied epoxy resin. Re-coating experiments demonstrated that the adsorbed layer remained intact after thermal curing, suggesting strong interfacial compatibility. Notably, the presence of the adsorbed layer led to a significant enhancement in adhesive performance. Lap shear tests showed that the adhesion strength of the epoxy resin nearly doubled when the adsorbed layer was introduced at the interface. This approach does not rely on external coupling agents or primers, but instead utilizes a homologous material system to tailor interfacial properties through molecular-level design. The strategy presented here offers a practical and scalable method for improving adhesion in epoxy systems. By directly engineering the adhesive interface using components intrinsic to the epoxy formulation, this method enables reliable and enhanced bonding performance without altering the bulk material.

Development of HCl-free solid-phase extraction combined with ICP-MS/MS for rapid assessment of difficult-to-measure radionuclides, 3; Measurement of Se concentration in concrete rubble

Banjarnahor, I. M.; Do, V.-K.; 古瀬 貴広; 太田 祐貴; 田中 康介

Journal of Radioanalytical and Nuclear Chemistry, 334(7), p.4997 - 5006, 2025/05

https://doi.org/10.1007/s10967-025-10143-w

Se has been conventionally measured via radiometry. However, measuring Se this way is difficult due to its low specific radioactivity. Moreover, the measurement is time-consuming and susceptible to the radioactive interferences from highly radioactive nuclides (Sr, Cs, etc.) coexisting in the samples. ICP-MS/MS is widely known as a powerful technique to quantify difficult-to-measure radionuclides, which can effectively eliminate the interferences using a collision/reaction cell. In this research, a novel HCl-free chemical separation method was developed for separating Se from concrete matrices, followed by the selective measurement of Se concentration via ICP-MS/MS. Se was purified by stepwise chemical separation using anion exchange resin and activated alumina. The separation condition was optimized and evaluated. The chemical recovery of 85% was achieved. Se concentration was determined via ICP-MS/MS at m/z = 79 using ammonia gas as the reaction gas, and possible interferences such as those from the Br isobar and argon gas were effectively mitigated. A method limit of detection of 0.1 Bq g was achieved for the concrete rubble samples, making it a reliable tool for determining Se concentrations in concrete rubble collected from the Fukushima Daiichi Nuclear Power Station.

Development of corrosion-stable dual-Si-layered membranes for hydrogen production via thermochemical iodine-sulfur process

Myagmarjav, O.; 田中 伸幸; 野口 弘喜; 上地 優; 小野 正人; 野村 幹弘*; 竹上 弘彰

Progress in Nuclear Science and Technology (Internet), 7, p.235 - 242, 2025/03

https://doi.org/10.15669/pnst.7.235

Hydrogen plays an important role in the transition to clean energy and the achievement of net-zero emissions. Thermochemical iodine-sulfur (IS) process, which uses nuclear heat to decompose water, is considered the most prospective method for producing large amounts of hydrogen without emitting carbon dioxide. The IS process consists of three coupled chemical reactions (Bunsen reaction, sulfuric acid decomposition, and hydrogen iodide decomposition). A major challenge for the practical application of the IS process is the efficient separation of hydrogen from the mixed corrosive gas of hydrogen iodide and iodine generated during hydrogen iodide decomposition (2HI H + I). A membrane that can efficiently separate H while treating this corrosive HI gas has not yet been developed. In this study, a membrane with high separation performance and corrosion stability was developed by fabricating a three-layer structure consisting of a base -alumina support tube, a middle silica layer and a top H-selective silica layer. By selecting the dipping time and CVD time, which are critical to the properties of the resulting silica layers, the prepared membrane showed high separation performance. For instance, the H/SF selectivity varied between 1622 and 1671 in the temperature range of 30-200 C. The result suggests that the developed membranes had no defects, especially existence of pinholes. HI stability tests also showed that these membrane were stable in corrosive environments.

Construction of a Compton camera-equipped robotic system capable of moving autonomously towards the radiation source

佐藤 優樹; 角藤 壮*; 田中 孝幸*; 嶋野 寛之*

European Physical Journal; Special Topics, 10 Pages, 2025/00

https://doi.org/10.1140/epjs/s11734-025-01483-5

In decommissioning the Fukushima Daiichi Nuclear Power Station, understanding the distribution of radioactive substances is crucial to developing detailed decontamination plans and minimizing worker exposure. In this study, an autonomous mobile radiation source detection system based on a mecanum wheel robot equipped with a Compton camera was constructed. The Compton camera visualizes the radiation source, and software embedded in the robot system reads the results to recognize the radiation source and move the robot toward it. If the robot's depth camera detects an obstacle while moving, it changes direction, visualizes the radiation source again using the Compton camera, and repeats moving the robot toward the radiation source. Furthermore, two demonstration tests were conducted in the laboratory using a Cs radiation source to confirm that the robot can reach it where there are obstacles or a narrow region. We have also summarized issues that must be identified to apply this system to actual decommissioning sites.

Developing an online composition prediction for an HI-I-HO system using deep neural network

田中 伸幸; 竹上 弘彰; 野口 弘喜; 上地 優; Myagmarjav, O.; 小野 正人; 杉本 千紘

Chemical Engineering Science, 299, p.120479_1 - 120479_11, 2024/11

https://doi.org/10.1016/j.ces.2024.120479

熱化学水素製造法ISプロセスでは、溶液組成を制御して安定な運転を行うため、溶液組成を把握することが求められる。本研究では、深層ニューラルネットワークモデルによる機械学習を用いて、計測可能な物性値から組成をオンラインで予測する手法を開発した。本手法は、従来のサンプリングによる滴定分析と比べて、迅速に溶液組成に関する情報を取得することが出来る。ISプロセスで主要な溶液組成であるHI-I-HO系において、温度、圧力、溶液密度の測定値から組成を予測できるモデルを作成し、トレンドデータから組成を推定可能であることを示した。また、得られたモデルを解析することで、組成制御に効果的な運転パラメータを明らかにした。

Effect of neutron beam properties on dose distributions in a water phantom for boron neutron capture therapy

石川 諒尚; 田中 浩基*; 中村 哲志*; 熊田 博明*; 櫻井 良憲*; 渡辺 賢一*; 吉橋 幸子*; 棚上 裕生*; 瓜谷 章*; 鬼柳 善明*

Journal of Radiation Research (Internet), 65(6), p.765 - 775, 2024/11

https://doi.org/10.1093/jrr/rrae076

From the viewpoints of the advantage depths (ADs), peak tumor dose, and skin dose, we evaluated the effect of neutron beam properties, namely, the ratio between thermal and epithermal neutron fluxes (thermal/epithermal ratio), fast neutron component, and -ray component on the dose distribution. Several parameter surveys were conducted with respect to the beam properties of neutron sources for boron neutron capture therapy assuming boronophenylalanine as the boron agent using our dose calculation tool, called SiDE. The ADs decreased by 3% at a thermal/epithermal ratio of 20% - 30% compared with the current recommendation of . The skin dose increased with the increasing thermal/epithermal ratio, reaching a restricted value of 14 Gy-eq at a thermal/epithermal ratio of . The fast neutron component was modified using two different models, namely, the "linear model," in which the fast neutron intensity decreases log-linearly with the increasing neutron energy, and the "moderator thickness (MT) model," in which the fast neutron component is varied by adjusting the moderator thickness in a virtual beam shaping assembly. Although a higher fast neutron component indicated a higher skin dose, the increment was at a fast neutron component of Gy cm for both models. Furthermore, in the MT model, the epithermal neutron intensity was higher at a fast neutron component of Gy cm compared with the current recommendation of Gy cm. The -ray component also caused no significant disadvantages up to several times larger compared with the current recommendation.

Validation study on SFR core bowing codes using Joyo ex-core experiment data; Multiple duct bowing benchmark

Wozniak, N.*; Shemon, E.*; Feng, B.*; 大釜 和也; 堂田 哲広; 上羽 智之; 二神 敏; 田中 正暁; 山野 秀将; 太田 宏一*; et al.

Proceedings of International Conference on Nuclear Fuel Cycle (GLOBAL2024) (Internet), 4 Pages, 2024/10

ナトリウム冷却高速炉の安全評価の精度向上のため、炉心変形による反応度を現実的に評価する手法の開発が必要である。炉心を構成する集合体の熱湾曲解析モデルの妥当性を確認することを目的に、「常陽」燃料集合体の複数ダクトの熱湾曲試験を対象としたベンチマーク解析を日米共同で実施した。解析結果と試験結果の比較から、両国の炉心湾曲コードは単列ダクトの熱湾曲を合理的に予測できることがわかった。