Current status of accident tolerant fuel (ATF) development, 1; Overview of ATF development conducted under the technology development project for improving nuclear safety

Yamashita, Shinichiro

Nihon Genshiryoku Gakkai-Shi ATOMO, 65(4), p.233 - 237, 2023/04

https://doi.org/10.3327/jaesjb.65.4_233

In the wake of the accident at the Fukushima Daiichi Nuclear Power Plant (NPP) of TEPCO due to the Great East Japan Earthquake in 2011, interest in the early implementation of accident tolerant fuel (ATF) not only for many existing NPPs but also for future NPPs, which is expected to dramatically improve the safety of light water reactors, has increased globally, and research and development is currently underway in many countries around the world. In this article, an overview of domestic ATF technology development that has been carried out with the support of the Ministry of Economy, Trade and Industry since 2015, will be introduced.

NH generation; The Role of NO in the crevice corrosion repassivation of type 316L stainless steel

Aoyama, Takahito; Sugawara, Yu*; Muto, Izumi*; Hara, Nobuyoshi*

Journal of the Electrochemical Society, 166(10), p.C250 - C260, 2019/01

https://doi.org/10.1149/2.0501910jes

The role of NO in the repassivation of crevice corrosion of Type 316L stainless steel was investigated. In crevice corrosion tests, the solution was changed from 1 M NaCl to NaCl-NaNO. NO led to complete repassivation. Repassivation of the crevice corrosion was found to take place in two steps. In the first step, the estimated current density inside the crevice gradually decreased from ca. 5 mA cm to ca. 5 A cm. After that, the current density suddenly decreased to less than 0.1 A cm. From the potentiodynamic polarization in acidic solutions simulated inside the crevice (pH 0.2) and in situ observations of the crevice corrosion morphology, the first step was thought to be generated by the suppression of active dissolution by NO. It would appear that the generation of NH results in a pH increase and the further suppression of active dissolution, and then repassivation occurs.

Recontamination prevention technologies to prevent radioactive cesium from its runoff from not decontaminated forests to living areas

Nagasu, Ryosuke*; Tanabe, Daijiro*; Yokotsuka, Satoshi*; Kumazawa, Noriyuki*; Ajiki, Takaya*; Aizawa, Yusuke*; Naganawa, Hirochika; Nagano, Tetsushi; Yanase, Nobuyuki*; Mitamura, Hisayoshi*; et al.

Kankyo Joka Gijutsu, 17(2), p.58 - 61, 2018/03

A new technology to suppress cesium migration from forests has been developed collaboratively by Ibaraki University, Kumagai-gumi Co., Ltd. and its group company, Technos, and JAEA. The new technology utilizes polyelectrolytes (polymers with electric charges) and clay minerals to control Cs migration with the aid of natural forces such as rainfall and rainwater runoff. In Imitate-mura, Fukushima, verification tests of the new technology have been performed and its effect on controlling Cs migration from forests to grass farm adjoining the forests has been proven.

Grouting design, results and evaluation of a gallery at great depth in Mizunami Underground Research Laboratory

Tsuji, Masakuni*

Doboku Kuotari, Vol.190, p.51 - 74, 2016/05

Pre-excavation grouting of shafts and galleries has been conducted during the construction of Mizunami Underground Research Laboratory in the aspect of safe works and reducing the discharge treatment of the water inflow. The grouting methodology has been simultaneously studied and developed as there is less experience of grouting in low conductive rock with high water pressure, especially in Japan. After excavating GL.-500m gallery on the ventilation shaft side, a post-excavation grouting campaign was performed on a 16-meter section of the pre-grouted area. Three new options for the grouting design were adopted and found to be effective with sufficiently decreasing the water inflow into the gallery.

Experimental results of functional performance of a vacuum vessel pressure suppression system in ITER

Shibata, Mitsuhiko; Takase, Kazuyuki; Watanabe, Hironori; Akimoto, Hajime

Fusion Engineering and Design, 63-64, p.217 - 222, 2002/12

https://doi.org/10.1016/S0920-3796(02)00242-9

no abstracts in English

Experimental verification of effectiveness of integrated pressure suppression systems in fusion reactors during in-vessel loss of coolant events

Takase, Kazuyuki; Akimoto, Hajime

Nuclear Fusion, 41(12), p.1873 - 1883, 2001/12

https://doi.org/10.1088/0029-5515/41/12/315

no abstracts in English

The 3rd technological meeting of Tokai reprocessing plant

Maki, Akira; ; Taguchi, Katsuya; ; Shimizu, Ryo; Shoji, Kenji;

JNC TN8410 2001-012, 185 Pages, 2001/04

JNC-TN8410-2001-012.pdf:9.61MB

"The third technological meeting of Tokai Reprocessing plant (TRP)" was held in JNFL Rokkasyo site on March 14, 2001. The technical meetings have been held in the past two times. The first one was about the present status and future plan of the TRP and second one was about safety evaluation work on the TRP. At this time, the meeting focussed on the corrosion experrience, in-service inspection technology and future maintenance plan. The report contains the proceedings, transparancies and questionnaires of the meeting are contained.

Analysis on direct-contact condensation of vapor injected into a pressure suppression tank

Takase, Kazuyuki; Ose, Yasuo*; Suzuki, Takayuki*; Kunugi, Tomoaki*

Nihon Kikai Gakkai Kanto Shibu Yamanashi Koenkai (2001) Koen Rombunshu, p.197 - 198, 2001/00

no abstracts in English

Effect of magnetite as a corrosion product on the corrosion of carbon steel overpack

Taniguchi, Naoki; ; Kawasaki, Manabu*; Masugata, Tsuyoshi*

JNC TN8400 2001-001, 56 Pages, 2000/12

JNC-TN8400-2001-001.pdf:2.05MB

It is necessary to clear the effects of corrosion products on the corrosion life time of carbon steel overpack for geological isolation of high-level radioactive waste(HLW). Especially, it is important to understand the effects of magnetite because magnetite as a simulated corrosion product is reported to accelerate the corrosion rate of carbon steel. In this study, corrosion tests to reproduce the acceleration of corrosion due to magnetite was performed and the mechanism of the acceleration was investigated to evaluate the effects of magnetite as a corrosion product. Based on the results of experiments, following conclusions are obtained ; (1)Magnetite powder accelerates the corrosion rate of carbon steel. The main reaction of corrosion under the presence of magnetite is the reduction of Fe(III) in magnetite to Fe(II), but the reaction of hydrogen generation is also accelerated. The contribution of hydrogen generation reaction was estimated to be about 30% in the total corrosion reaction based on the experimental result of immersion test under the presence of magnetite. (2)Actual corrosion products containing magnetite generated by the corrosion of carbon steel protect the metal from the propagation of corrosion. The corrosion depth of carbon steel overpack due to magnetite was estimated to be about 1 mm based on the results of experiments. Even if the effect of magnetite is taken into the assessment of corrosion lifetime of overpack, total corrosion depth in 1000 years is estimated to be 33 mm, which is smaller than the corrosion allowance of 40 mm described in the second progress report on research and development for the geological disposal of HLM/ in Japan. It was concluded that the effect of magnetite on the corrosion life time of carbon steel overpack is negligible.

The Acceleration factor and inhibitor of the generation and growth of the cavity at high temperature; Computer simulation on growth of cavity

; Ueno, Fumiyoshi

JNC TN9400 2000-017, 10 Pages, 2000/03

JNC-TN9400-2000-017.pdf:0.58MB

lt is difficult to get hold the behave of growth of cavity which nucleates in grain boudaly in experimental observation. lt is considerd that numerical simulation is effective for the grasp of behave of cavity growth, because it is able to grasp the microscopic behavior of internal material whici is hardly observation. We examine the factor that the diffusive ratio and the stress etc., affected growth of cavity on grain boundary with numerical simulation using diffusive equation. As the result, a following knowledge was obtained. (1)With dominant of grain boundary diffusion, the shape of cavity transitions from quasi-equilibrium to crac-like. ln other hand, with dominant of surface diffusion, cavity grows up with initial shape. (2)With dominate of grain boundary diffusion, it accelerates the growth rate of the cavity near the tip by grain boundaly diffusion induced stressing perpendicular to gain boundary (3)With dominant of surface diffusion, the distribution of chemical potential is uniformity on cavity surface. ln other hand, with dominant of grain boundary diffusion compare to that of surface diffusion, the gradient of chemical potential is increased at the tip of cavity.