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, 10 Pages, 2025/00

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.

Estimation of long-term ex-vessel debris cooling behavior in Fukushima Daiichi Nuclear Power Plant unit 3

佐藤 一憲; 山路 哲史*; Li, X.*; 間所 寛

Mechanical Engineering Journal (Internet), 9(2), p.21-00436_1 - 21-00436_17, 2022/04

https://doi.org/10.1299/mej.21-00436

Interpretation for the two-week long Unit 3 ex-vessel debris cooling behavior was conducted based on the Fukushima-Daiichi Nuclear Power Plant (1F) data and the site data such as pressure, temperature, gamma ray level and live camera pictures. It was estimated that the debris relocated to the pedestal was in partial contact with liquid water for about initial two days. With the reduction of the sea water injection flowrate, the debris, existed mainly in the pedestal region, became "dry", in which the debris was only weakly cooled by vapor and this condition lasted for about four days until the increase of the sea water injection. During this dry period, the pedestal debris was heated up and it took further days to re-flood the heated up debris.

Evaluation of core material energy change during the in-vessel phase of Fukushima Daiichi Unit 3 based on observed pressure data utilizing GOTHIC code analysis

佐藤 一憲; 荒井 雄太*; 吉川 信治

Journal of Nuclear Science and Technology, 58(4), p.434 - 460, 2021/04

https://doi.org/10.1080/00223131.2020.1862718

The vapor formation within the reactor pressure vessel (RPV) is regarded to represent heat removal from core materials to the coolant, while the hydrogen generation within the RPV is regarded to represent heat generation by metal oxidation. Based on this understanding, the history of the vapor/hydrogen generation in the in-vessel phase of Fukushima Daiichi Nuclear Power Station Unit 3 was evaluated based on the comparison of the observed pressure data and the GOTHIC code analysis results. The resultant vapor/hydrogen generation histories were then converted to heat removal by coolant and heat generation by oxidation. The effects of the decay power and the heat transfer to the structures on the core material energy were also evaluated. The core materials are suggested to be significantly cooled by water within the RPV, especially when the core materials are relocated to the lower plenum.

Effect of quenching on molten core-concrete interaction product

北垣 徹; 池内 宏知; 矢野 公彦; Brissonneau, L.*; Tormos, B.*; Domenger, R.*; Roger, J.*; 鷲谷 忠博

Journal of Nuclear Science and Technology, 56(9-10), p.902 - 914, 2019/09

AA2018-0409.pdf:2.12MB

https://doi.org/10.1080/00223131.2019.1604272

Characterization of fuel debris is required to develop fuel debris removal tools. Especially, knowledge pertaining to the characteristics of molten core-concrete interaction (MCCI) product is needed because of the limited information available at present. The samples of a large-scale MCCI test performed under quenching conditions, VULCANO VW-U1, by CEA were analyzed to evaluate the characteristics of the surface of MCCI product generated just below the cooling water. As a result, the microstructure of the samples were found to be similar despite the different locations of the test sections. The Vickers hardness of each of the phases in these samples was higher than that of previously analyzed samples in another VULCANO test campaign, VBS-U4. From the comparison between analytical results of VULCANO MCCI test product, MCCI product generated under quenching condition is homogeneous and its hardness could be higher than that of the bulk MCCI product.

Thermodynamic evaluation of the solidification phase of molten core-concrete under estimated Fukushima Daiichi Nuclear Power Plant accident conditions

北垣 徹; 矢野 公彦; 荻野 英樹; 鷲谷 忠博

Journal of Nuclear Materials, 486, p.206 - 215, 2017/04

AA2016-0278.pdf:0.74MB

https://doi.org/10.1016/j.jnucmat.2017.01.032

The solidification phases of molten core-concrete under the estimated molten core-concrete interaction (MCCI) conditions in the Fukushima Daiichi Nuclear Power Plant Unit 1 were predicted using the thermodynamic equilibrium calculation tool in order to contribute toward the 1F decommissioning work and to understand the accident progression via the analytical results for the 1F MCCI products. We showed that most of the U and Zr in the molten core-concrete forms (U,Zr)O and (Zr,U)SiO, and the formation of other phases with these elements is limited. However, the formation of (Zr,U)SiO requires a relatively long time. Therefore, the formation of (Zr,U)SiO is limited under quenching conditions. The solidification phenomenon of the crust under quenching conditions and that of the molten pool under thermodynamic equilibrium conditions in the 1F MCCI progression are discussed.

Development of prediction technology of two-phase flow dynamics under earthquake acceleration, 16; Experimental and numerical study of pressure fluctuation effects on bubble motion

加藤 由幹; 吉田 啓之; 横山 諒太郎*; 金川 哲也*; 金子 暁子*; 文字 秀明*; 阿部 豊*

Proceedings of 23rd International Conference on Nuclear Engineering (ICONE-23) (DVD-ROM), 8 Pages, 2015/05

In this study, visualization experiment for the bubbly flow in a horizontal pipe excited by oscillation acceleration was performed to understand bubbly flow behavior under earthquake acceleration. Liquid pressure was also measured at upstream and downstream of the test section. In addition, to consider detailed effects of pressure gradient on bubble motion, numerical simulation of two-phase flow in horizontal pipe with vibration was performed by a detailed two-phase flow simulation code with an advanced interface tracking method: TPFIT. Based on observed images and calculated results, bubble velocity was evaluated. It was confirmed that the pressure gradient amplitude increased with the increase of the frequency of the table. In addition, it was observed that the bubble velocity amplitude also increases with the increase of the frequency of the table. It was concluded that the bubble motion was strongly affected by the pressure gradient in the test section.

Development of prediction technology of two-phase flow dynamics under earthquake acceleration

吉田 啓之; 永武 拓; 高瀬 和之; 金子 暁子*; 文字 秀明*; 阿部 豊*

Mechanical Engineering Journal (Internet), 1(4), p.TEP0025_1 - TEP0025_11, 2014/08

https://doi.org/10.1299/mej.2014tep0025

In this study, to develop the predictive technology of two-phase flow dynamics under earthquake acceleration, a detailed two-phase flow simulation code with an advanced interface tracking method TPFIT was expanded. In addition, the bubbly flow in a horizontal pipe excited by oscillation acceleration and under the fluctuation of the liquid flow was simulated by using the modified TPFIT. In the results, it was confirmed that the modified TPFIT can predict time dependent velocity distribution around the bubbles and shapes of bubbles qualitatively. The main cause of bubble deformation observed is large shear stress at the lower part of the bubble, and this large shear stress is induced by the velocity difference between the liquid phase and bubble. Moreover, we discussed about the difference between both effects of flow rate fluctuation and structure vibration on two-phase flow. In the results, bubble acceleration of the structure vibration case was larger than that of the flow rate fluctuation case. Finally, it was concluded that unsteady shear stress induced by vibration of the pipe wall was one of the main driving forces of bubble motion in structure vibration case.

Burnup importance function and its application to OECD/NEA/BUC phase II-A and II-C models

奥野 浩; 外池 幸太郎; 酒井 友宏*

Proceedings of International Conference on the New Frontiers of Nuclear Technology; Reactor Physics, Safety and High-Performance Computing (PHYSOR 2002) (CD-ROM), 8 Pages, 2002/10

燃焼の進展に伴い、軽水炉用燃料集合体の反応度は核分裂性核種の減損、特に軸方向中央部の減損により減少する。端部の反応度変化への重要性を描写するために、燃焼重要度関数を局所的な燃焼度変化の反応度減少への重みとして導入した。この関数をOECD/NEA/BUCのフェーズII-Aモデル(使用済PWR 燃料棒を表す)及び簡単化したフェーズII-Cモデル(局所的な燃焼変化による反応度変化を研究)に適用した。フェーズII-Aモデルへの適用は、端部の燃焼重要度が燃焼度あるいは冷却期間の増加に伴い増加することを明瞭に示した。異なる初期濃縮度での燃焼重要度を比較した。簡易化されたフェーズII-Cモデルへの適用の結果は、燃焼重要度関数が、平均燃焼度を一定にし燃焼度変化が最大・最小測定値の間であるという束縛条件下で最も反応度の高い燃焼分布を見い出すのに役立つことを示した。

Intraoperative boron neturon capture therapy for malignant gliomas; First clinical results of Tsukuba phase I/II trial using JAERI mixed thermal-epithermal beam

松村 明*; 山本 哲哉*; 柴田 靖*; 阿久津 博義*; 安田 貢*; 松下 明*; 中井 啓一*; 山田 隆*; 高野 晋吾*; 水谷 太郎*; et al.

Proceedings of 9th International Symposium on Neutron Capture Therapy for Cancer, p.29 - 30, 2000/10

1999年10月から新しいBNCT試験は術中BNCTの状態で混合熱-熱外ビームを用いてJRR-4医療照射設備で開始された。これまでに5名の患者はこの試験に参加した。最大表面B(n,)線量は第一グループにおいて正常脳内10.4Gyと計画され、重大な障害がなければ13Gyへ10%の線量増加を行う。すべての患者は明白な腫瘍の可能性となく、1~7ヶ月間の観察中であるが存命している。しかし過剰線量を受けた放射線損傷の1例がある。ほかには軽い脳神経障害が2例観察された(1例は脳神経麻痺、1例は構語障害)。純熱ビームモードと比較するとIOBNCTでのTMIの強い浸透度と2次線のために注意深く線量増加は計画されるべきである。(構語障害とは少し喋りづらい症状で、ろれつがまわりにくいようなものである。)

Japan-Australia co-operative program on research and development of technology for the management of high level radioactive wastes: Phase II (1990-1995)

馬場 恒孝; K.P.Hart*

JAERI-Tech 96-024, 67 Pages, 1996/05

JAERI-Tech-96-024.pdf:2.5MB

高レベル放射性廃棄物処理処分技術の研究開発における日豪の研究協力計画第二フェーズは1990年から5ヶ年計画として始められた。研究協力の主な活動は、長期耐久性に関する研究で、キュリウム添加シンロックの加速試験及び天然鉱物の特性を調べる試験であった。第二フェーズの研究協力計画の全般的な成果は、双方の担当者間ですばらしい協力関係を継続したことと、代替固化体としてのシンロックの潜在的な利点と限界について理解を深めたことである。同時に、キュリウム添加量の影響を明らかにする研究、ナチュラルアナログの研究及び廃棄物成分溶出の長期予測モデルの開発の必要性が認められた。