Analysis work on flush-out of plutonium and uranium for decommissioning of main plant in Tokai Reprocessing Plant

Sato, Hinata; Mori, Amami; Kuno, Sorato; Horigome, Kazushi; Goto, Yuichi; Yamamoto, Masahiko; Taguchi, Shigeo

JAEA-Technology 2024-011, 56 Pages, 2024/10

JAEA-Technology-2024-011.pdf:2.5MB

Flush-out, which recovers remaining nuclear materials in the process and transfer it to a highly radioactive liquid waste storage tank, has been performed at main plant of Tokai Reprocessing Plant. The flush-out has been composed from three steps: first step is to remove of spent fuel sheared powder, second step is to collect plutonium solution stored in the process, and third step is to convert uranium solution into uranium trioxide powder. The first step of flush-out activity has been completed in 2022. Second and third steps of flush-out have been completed from March 2023 to February 2024. Process control analysis has been performed for operation of the facility, and material accountancy analysis has been performed to control the accountancy of nuclear materials. In addition, related analytical work such as pretreatment for transporting inspection samples for safeguards analysis laboratories in IAEA has been also performed. This report describes results of analytical work performed in collections of plutonium and uranium solutions in second and third steps of the flush-out, including calibration of analytical equipment, waste generation, and education and training of analytical operator.

Study on actinide burning core concepts for the future phaseout of a fast reactor fuel cycle

Mori, Tetsuya; Naganuma, Masayuki; Oki, Shigeo

Nuclear Technology, 209(4), p.532 - 548, 2023/04

https://doi.org/10.1080/00295450.2022.2133514

This paper deals with a conceptual study on a plutonium (Pu) and minor actinide (MA) burning fast reactor core for the distant future phaseout of a fast-reactor fuel cycle after it is commercialized and used for a long time. This burning core aims to reduce the Pu and MA inventories contained in the fuel cycle through multiple recycling. A key point for the core design is the degradation of Pu and MA during multiple recycling. This degradation affects the core feasibility by increasing the sodium void reactivity and decreasing the absolute value of the Doppler constant. A feasible core concept was found by incorporating the following three factors to improve the reactivity coefficients: core flattening, fuel burnup reduction, and the use of silicon carbide (SiC) in the cladding and wrapper tubes. Notably, softening the neutron spectrum using the SiC structural material not only improved the reactivity coefficients but also indirectly mitigated the degradation of Pu and MA. Consequently, the designed core allowed for multiple recycling to continue until the Pu and MA reduced significantly, particularly by about 99% in a phaseout scenario starting from a fast-reactor fleet of 30-GWe nuclear power capacity. Fast reactors were found to have the potential to become self-contained energy systems that can minimize the inventories of Pu they produced themselves, as well as long-lived MA. Fast reactors can be among the important options for environmental burden reduction in the future.

Partial breakdown of translation symmetry at a structural quantum critical point associated with a ferroelectric soft mode

Ishii, Yui*; Yamamoto, Arisa*; Sato, Naoki*; Nambu, Yusuke*; Kawamura, Seiko; Murai, Naoki; Ohara, Koji*; Kawaguchi, Shogo*; Mori, Takao*; Mori, Shigeo*

Physical Review B, 106(13), p.134111_1 - 134111_7, 2022/10

https://doi.org/10.1103/PhysRevB.106.134111

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.

Quantifying the dislocation structures of additively manufactured Ti-6Al-4V alloys using X-ray diffraction line profile analysis

Yamanaka, Kenta*; Kuroda, Asumi*; Ito, Miyu*; Mori, Manami*; Bian, H.*; Shobu, Takahisa; Sato, Shigeo*; Chiba, Akihiko*

Additive Manufacturing, 37, p.101678_1 - 101678_12, 2021/01

https://doi.org/10.1016/j.addma.2020.101678

Status of study of long-term assessment of transport of radioactive contaminants in the environment of Fukushima (FY2018) (Translated document)

Nagao, Fumiya; Niizato, Tadafumi; Sasaki, Yoshito; Ito, Satomi; Watanabe, Takayoshi; Dohi, Terumi; Nakanishi, Takahiro; Sakuma, Kazuyuki; Hagiwara, Hiroki; Funaki, Hironori; et al.

JAEA-Research 2020-007, 249 Pages, 2020/10

JAEA-Research-2020-007.pdf:15.83MB

The accident of the Fukushima Daiichi Nuclear Power Station, Tokyo Electric Power Company Holdings, Inc. occurred due to the Great East Japan Earthquake, Sanriku offshore earthquake, of 9.0 magnitude and the accompanying tsunami. As a result, large amount of radioactive materials was released into the environment. Under these circumstances, Japan Atomic Energy Agency (JAEA) has been conducting "Long-term Assessment of Transport of Radioactive Contaminants in the Environment of Fukushima" concerning radioactive materials released in environment, especially migration behavior of radioactive cesium since November 2012. This report is a summary of the research results that have been obtained in environmental dynamics research conducted by JAEA in Fukushima Prefecture.

Status of study of long-term assessment of transport of radioactive contaminants in the environment of Fukushima (FY2018)

Nagao, Fumiya; Niizato, Tadafumi; Sasaki, Yoshito; Ito, Satomi; Watanabe, Takayoshi; Dohi, Terumi; Nakanishi, Takahiro; Sakuma, Kazuyuki; Hagiwara, Hiroki; Funaki, Hironori; et al.

JAEA-Research 2019-002, 235 Pages, 2019/08

JAEA-Research-2019-002.pdf:21.04MB

The accident of the Fukushima Daiichi Nuclear Power Station (hereinafter referred to 1F), Tokyo Electric Power Company Holdings, Inc. occurred due to the Great East Japan Earthquake, Sanriku offshore earthquake, of 9.0 magnitude and the accompanying tsunami. As a result, large amount of radioactive materials was released into the environment. Under these circumstances, JAEA has been conducting Long-term Environmental Dynamics Research concerning radioactive materials released in environment, especially migration behavior of radioactive cesium since November 2012. This report is a summary of the research results that have been obtained in environmental dynamics research conducted by JAEA in Fukushima Prefecture.

Presence of -martensite as an intermediate phase during the strain-induced transformation of SUS304 stainless steel

Hatano, Masaharu*; Kubota, Yoshiki*; Shobu, Takahisa; Mori, Shigeo*

Philosophical Magazine Letters, 96(6), p.220 - 227, 2016/06

https://doi.org/10.1080/09500839.2016.1190876

We have investigated the formation process of '-martensite from the -phase induced by external strain using synchrotron diffraction experiments, combined with Lorentz transmission electron microscopy (TEM) and high-resolution TEM observations. It is clearly demonstrated that -martensite with hexagonal symmetry appears as an intermediate structure during the plastic deformation of SUS304 stainless steel. In addition to stacking faults and dislocations, interfaces between the twin structures presumably play a key role in the formation of -martensite.

The Cause of corrosion occurred in a glove box filter casing and its repair technique

Mori, Eito; Yamamoto, Masahiko; Taguchi, Shigeo; Sato, Soichi; Kitao, Takahiko; Surugaya, Naoki

Nihon Hozen Gakkai Dai-11-Kai Gakujutsu Koenkai Yoshishu, p.132 - 138, 2014/07

The contamination of the radioactive material was observed on the filter casing surface of the glove box installed at the analytical laboratory in Tokai Reprocessing Plant. The cause of the contamination was investigated with visual inspection, penetrant testing and ultrasonic thickness measurement. It was found that a micro through-hole due to the corrosion of stainless-steel was generated in the glove box filter casing. The repair work of the filter casing was performed keeping the glove box negative pressure. The corrosion part of filter casing was replaced and newly fabricated casing was connected to the glove box with Tungsten Inert Gas welding method.

Magnetic properties of RFeO (R=Yb and Lu)

Yoshii, Kenji; Ikeda, Naoshi*; Fukuyama, Ryota*; Nagata, Tomoko*; Kambe, Takashi*; Yoneda, Yasuhiro; Fukuda, Tatsuo; Mori, Shigeo*

Solid State Communications, 173, p.34 - 37, 2013/11

https://doi.org/10.1016/j.ssc.2013.08.030

We have investigated the magnetic properties of RFeO (R=Yb and Lu), which belongs to the homologous family of electronic ferroelectric RFeO. Magnetization measurements show ferrimagnetic ordering at the Neel temperature (T) of about 270 K, which is slightly higher than that of RFeO (T about 230-250 K). Observation of spin glass and exchange bias shows a coexistence of ferromagnetic and antiferromagneticinteractions, similarly to RFeO. This situation gives rise to a complex magnetic change and a broad peak of magnetic entropy change. Some characteristics, such as refrigeration temperatures higher than in RFeO, seem to offer a possibility of this system to applications.