Analysis of deposits inside the reactor at Fukushima Daiichi Nuclear Power Station in JFY2021; The Subsidy program of "Project of Decommissioning and Contaminated Water Management (Development of Analysis and Estimation Technology for Characterization of Fuel Debris)" starting FY2021

Ikeuchi, Hirotomo; Sasaki, Shinji; Onishi, Takashi; Nakayoshi, Akira; Arai, Yoichi; Sato, Takumi; Ohgi, Hiroshi; Sekio, Yoshihiro; Yamaguchi, Yukako; Morishita, Kazuki; et al.

JAEA-Data/Code 2023-005, 418 Pages, 2023/12

JAEA-Data-Code-2023-005-01.pdf:24.59MB
JAEA-Data-Code-2023-005-02.pdf:32.18MB

For safe and steady decommissioning of Tokyo Electric Power Company Holdings' Fukushima Daiichi Nuclear Power Station (1F), information concerning composition and physical/chemical properties of fuel debris generated in the reactors should be estimated and provided to other projects conducting the decommissioning work including the retrieval of fuel debris and the subsequent storage. For this purpose, in FY2021, samples of contaminants (the wiped smear samples and the deposits) obtained through the internal investigation of the 1F Unit 2 were analyzed to clarify the components and to characterize the micro-particles containing uranium originated from fuel (U-bearing particles) in detail. This report summarized the results of analyses performed in FY2021, including the microscopic analysis by SEM and TEM, radiation analysis, and elemental analysis by ICP-MS, as a database for evaluating the main features of each sample and the probable formation mechanism of the U-bearing particles.

Study on eutectic melting behavior of control rod materials in core disruptive accidents of sodium-cooled fast reactors; Project overview and progress until JFY2022

Yamano, Hidemasa; Takai, Toshihide; Emura, Yuki; Fukuyama, Hiroyuki*; Nishi, Tsuyoshi*; Morita, Koji*; Nakamura, Kinya*; Pellegrini, M.*

Nihon Kikai Gakkai 2023-Nendo Nenji Taikai Koen Rombunshu (Internet), 5 Pages, 2023/09

A research project has been conducting thermophysical property measurement of a eutectic melt, eutectic melting reaction and relocation experiments, eutectic reaction mechanism investigation, and physical model development on the eutectic melting reaction for reactor application analysis in order to simulate the eutectic melting reaction and relocation behavior of boron carbide as a control rod material and stainless steel during a core disruptive accident in an advanced sodium-cooled fast reactor designed in Japan. This paper describes the project overview and progress until JFY2022.

Reaction of Np, Am, and Cm ions with CO and O in a reaction cell in triple quadrupole inductively coupled plasma mass spectrometry

Kazama, Hiroyuki; Konashi, Kenji*; Suzuki, Tatsuya*; Koyama, Shinichi; Maeda, Koji; Sekio, Yoshihiro; Onishi, Takashi; Abe, Chikage*; Shikamori, Yasuyuki*; Nagai, Yasuyoshi*

Journal of Analytical Atomic Spectrometry, 38(8), p.1676 - 1681, 2023/07

https://doi.org/10.1039/D3JA00136A

Development of technologies for enhanced analysis accuracy of fuel debris; Summary results of the 2020 fiscal year (Subsidy program for the project of decommissioning and contaminated water management)

Ikeuchi, Hirotomo; Koyama, Shinichi; Osaka, Masahiko; Takano, Masahide; Nakamura, Satoshi; Onozawa, Atsushi; Sasaki, Shinji; Onishi, Takashi; Maeda, Koji; Kirishima, Akira*; et al.

JAEA-Technology 2022-021, 224 Pages, 2022/10

JAEA-Technology-2022-021.pdf:12.32MB

A set of technology, including acid dissolving, has to be established for the analysis of content of elements/nuclides in the fuel debris samples. In this project, a blind test was performed for the purpose of clarifying the current level of analytical accuracy and establishing the alternative methods in case that the insoluble residue remains. Overall composition of the simulated fuel debris (homogenized powder having a specific composition) were quantitatively determined in the four analytical institutions in Japan by using their own dissolving and analytical techniques. The merit and drawback for each technique were then evaluated, based on which a tentative flow of the analyses of fuel debris was constructed.

Study on eutectic melting behavior of control rod materials in core disruptive accidents of sodium-cooled fast reactors, 1; Project overview and progress until 2020

Yamano, Hidemasa; Takai, Toshihide; Emura, Yuki; Fukuyama, Hiroyuki*; Higashi, Hideo*; Nishi, Tsuyoshi*; Ota, Hiromichi*; Morita, Koji*; Nakamura, Kinya*; Fukai, Hirofumi*; et al.

Proceedings of 13th International Topical Meeting on Nuclear Reactor Thermal-Hydraulics, Operation and Safety (NUTHOS-13) (Internet), 12 Pages, 2022/09

This paper describes the project overview and progress of experimental and analytical studies conducted until 2020. Specific results in this paper are the measurement of the eutectic reaction rates and the validation of physical model describing the eutectic reaction in the analysis code through the numerical analysis of the BC-SS eutectic reaction rate experiments in which a BC pellet was placed in a SS crucible.

Sodium-cooled Fast Reactors

Ohshima, Hiroyuki; Morishita, Masaki*; Aizawa, Kosuke; Ando, Masanori; Ashida, Takashi; Chikazawa, Yoshitaka; Doda, Norihiro; Enuma, Yasuhiro; Ezure, Toshiki; Fukano, Yoshitaka; et al.

Sodium-cooled Fast Reactors; JSME Series in Thermal and Nuclear Power Generation, Vol.3, 631 Pages, 2022/07

https://shop.elsevier.com/books/sodium-cooled-fast-reactors/morishita/978-0-12-824076-2

This book is a collection of the past experience of design, construction, and operation of two reactors, the latest knowledge and technology for SFR designs, and the future prospects of SFR development in Japan. It is intended to provide the perspective and the relevant knowledge to enable readers to become more familiar with SFR technology.

Newly found fault outcrops of the Tsuruga fault in the Mihama Town, Fukui Prefecture, Japan

Tateishi, Ryo*; Shimada, Koji; Iwamori, Akiyuki*; Wada, Shinya*; Seno, Shotaro*; Nagata, Ken*

Chishitsugaku Zasshi (Internet), 128(1), p.63 - 64, 2022/04

https://doi.org/10.5575/geosoc.2022.0007

The Tsuruga Fault is an active right-lateral strike-slip fault that is about 20 km in length and distributed in the northeast-southwest direction from the eastern part of Tsuruga City to the southern part of Mihama Town, Fukui Prefecture. The Tsuruga fault borders the Jurassic accretionary complex (mixed rock) and the late Cretaceous granite around the Oritodani area in the Shinjo district of Mihama-cho. Lateral bendings of valleys along the fault in this area are clear geomorphological signatures of fault activity. We briefly report newly found multiple fault outcrops at these bending points with photos of them. This research is the result of joint research by Kansai Electric Power Company, University of Toyama, and JAEA.

Structural investigation of borosilicate glasses by using XAFS measurement in Soft X-ray region (Joint research)

Nagai, Takayuki; Okamoto, Yoshihiro; Yamagishi, Hirona*; Ota, Toshiaki*; Kojima, Kazuo*; Inose, Takehiko*; Sato, Seiichi*; Hatakeyama, Kiyoshi*

JAEA-Research 2021-010, 62 Pages, 2022/01

JAEA-Research-2021-010.pdf:6.05MB

The local structure of glass-forming elements and waste elements in borosilicate glasses varies with its chemical composition. In this study, borosilicate glass frit and simulated waste glass samples were prepared and the local structure and chemical state regarding boron(B), oxygen(O), silicon(Si) and waste elements of iron(Fe), cesium(Cs) were estimated by using XAFS measurement in soft X-ray region. Following results were obtained by XAFS measurements of prepared glass frit and simulated waste glass samples: (1) The effect of NaO concentration on B-O coordination structure is greater than that of the waste elements concentration. (2) The height of pre-edge by O K-edge spectrum depends on the concentration of first transition elements such as Fe in glass samples. Following results were obtained by XAFS measurements of simulated waste glass samples after immersion test to investigate the long chemical stability. (1) A new compound was formed on the sample surface after the immersion test, and changes in the surface state were confirmed by Raman spectroscopy. (2) Cs on the sample surface after immersion test dissolves into the leaching solution. The Si K-edge XANES spectra of borosilicate glass frits and simulated waste glass samples included lanthanides oxide were measured, and following was confirmed. (1) As the NaO concentration increases in borosilicate glass frit, the K-edge peak of Si shifts to the low energy side. (2) The peak height of the K-edge of Si differs depending on the kind of lanthanide.

Study on eutectic melting behavior of control rod materials in core disruptive accidents of sodium-cooled fast reactors, 1; Project overview and progress until 2019

Yamano, Hidemasa; Takai, Toshihide; Furukawa, Tomohiro; Kikuchi, Shin; Emura, Yuki; Kamiyama, Kenji; Fukuyama, Hiroyuki*; Higashi, Hideo*; Nishi, Tsuyoshi*; Ota, Hiromichi*; et al.

Proceedings of 28th International Conference on Nuclear Engineering (ICONE 28) (Internet), 11 Pages, 2021/08

https://doi.org/10.1115/ICONE28-63301

One of the key issues in a core disruptive accident (CDA) evaluation in sodium-cooled fast reactors is eutectic reactions between boron carbide (BC) and stainless steel (SS) as well as its relocation. Such behaviors have never been simulated in CDA numerical analyses in the past, therefore it is necessary to develop a physical model and incorporate the model into the CDA analysis code. This study focuses on BC-SS eutectic melting experiments, thermophysical property measurement of the eutectic melt, and physical model development for the eutectic melting reaction. The eutectic experiments involve the visualization experiments, eutectic reaction rate experiments and material analyses. The thermophysical properties are measured in a range from solid to liquid state. The physical model is developed for a CDA computer code based on the measured data of the eutectic reaction rate and the physical properties. This paper describes the project overview and progress of experimental and analytical studies conducted until 2019. Specific results in this paper are the validation of physical model describing BC-SS eutectic reaction in the CDA analysis code, SIMMER-III, through the numerical analysis of the BC-SS eutectic melting experiments in which a BC block was placed in a SS pool.

Discrimination between active and non-active faults based on the chemical composition of fault gouge; An Attempt using linear discriminant analysis

Tateishi, Ryo*; Shimada, Koji; Shimizu, Mayuko; Ueki, Tadamasa*; Niwa, Masakazu; Sueoka, Shigeru; Ishimaru, Tsuneari

Oyo Chishitsu, 62(2), p.104 - 112, 2021/06

AA2020-0092.pdf:4.61MB

https://doi.org/10.5110/jjseg.62.104

We attempted to discriminate between active and non-active faults by linear discriminant analysis using the chemical composition data of fault gouges in Japan, and then examined the elements that represent the difference between them and better discriminants. As a result, the multiple discriminants obtained could discriminate between them with high probability. In addition, the generalization performance of these discriminants is discussed, and the discriminants that can be expected to have high discriminant performance for unknown samples are presented. Also, from the combination of elements common to these discriminants, we narrowed down the number of elements that represent the difference between active and non-active faults to 6, and showed that the combination of TiO and Sr contributing the most to the discrimination. The method applied in this study is an innovative one that can discriminate the activity by chemical analysis of fault rocks that are universally present in the bedrock.