Differential pressure rise event for filters of HTTR primary helium gas circulators, 1; Investigation of differential pressure rise event

Nemoto, Takahiro; Arakawa, Ryoki; Kawakami, Satoru; Nagasumi, Satoru; Yokoyama, Keisuke; Watanabe, Masashi; Onishi, Takashi; Kawamoto, Taiki; Furusawa, Takayuki; Inoi, Hiroyuki; et al.

JAEA-Technology 2023-005, 33 Pages, 2023/05

JAEA-Technology-2023-005.pdf:5.25MB

During shut down of the HTTR (High Temperature engineering Test Reactor) RS-14 cycle, an increasing trend of filter differential pressure for the helium gas circulator was observed. In order to investigate this phenomenon, the blower of the primary helium purification system was disassembled and inspected. As a result, it is clear that the silicon oil mist entered into the primary coolant due to the deterioration of the charcoal filter performance. The replacement and further investigation of the filter are planning to prevent the reoccurrence of the same phenomenon in the future.

Analysis of the radioactivity concentrations in radioactive waste generated from JRR-3, JRR-4 and JRTF facilities

Tobita, Minoru*; Konda, Miki; Omori, Takeshi*; Nabatame, Tsutomu*; Onizawa, Takashi*; Kurosawa, Katsuaki*; Haraga, Tomoko; Aono, Ryuji; Mitsukai, Akina; Tsuchida, Daiki; et al.

JAEA-Data/Code 2022-007, 40 Pages, 2022/11

JAEA-Data-Code-2022-007.pdf:1.99MB

Radioactive wastes generated from nuclear research facilities in Japan Atomic Energy Agency are planning to be buried in the near surface disposal field. Therefore, it is required to establish the method to evaluate the radioactivity concentrations of radioactive wastes until the beginning of disposal. In order to contribute to this work, we collected and analyzed concrete, ash, ceramic and brick samples generated from JRR-3, JRR4 and JRTF facilities. In this report, we summarized the radioactivity concentrations of 24 radionuclides (H, C, Cl, Ca, Co, Ni, Sr, Nb, Tc, Ag, I, Cs, Ba, Eu, Eu, Ho, U, U, Pu, Pu, Pu, Am, Am, Cm) which were obtained from radiochemical analysis of the samples in fiscal years 2020-2021.

Identification of carbon in glassy cesium-bearing microparticles using electron microscopy and formation mechanisms of the microparticles

Hidaka, Akihide

Nuclear Technology, 208(2), p.318 - 334, 2022/02

https://doi.org/10.1080/00295450.2021.1929767

The author previously proposed that the Cs bearing microparticle (Type A) may have been formed by melting and atomization of glass fibers (GF) of the HEPA filter in the SGTS due to flame and blast during the hydrogen explosion in Unit 3. If this hypothesis is correct, the Type A could contain or accompany carbon (C), that ignites spontaneously above 623 K, because of the limited time to be heated up, inclusion of C in the binder applied on the GF surface and closely located charcoal filter. As the previous studies did not focus on C, the present analyses were performed with EPMA whether the Type A contains C. The results showed that the Type A contained C originating from the binder, and non-spherical particles accompanied by the Type A and the film surrounding the Type A contained more C, which is thought to originate from the charcoal filter. These results cannot be explained by the other mechanisms proposed so far, and can be explained consistently by the author proposed hypothesis.

Development of technology for rapid analysis of strontium-90 with low isotopic abundance using laser resonance ionization (Contract research); FY2018 Center of World Intelligence Project for Nuclear Science/Technology and Human Resource Development

Collaborative Laboratories for Advanced Decommissioning Science; The University of Tokyo*

JAEA-Review 2019-027, 70 Pages, 2020/01

JAEA-Review-2019-027.pdf:5.18MB

JAEA/CLADS, had been conducting the Center of World Intelligence Project for Nuclear Science/Technology and Human Resource Development (hereafter referred to "the Project") in FY2018. The Project aims to contribute to solving problems in nuclear energy field represented by the decommissioning of the Fukushima Daiichi Nuclear Power Station, Tokyo Electric Power Company Holdings, Inc. For this purpose, intelligence was collected from all over the world, and basic research and human resource development were promoted by closely integrating/collaborating knowledge and experiences in various fields beyond the barrier of conventional organizations and research fields. The sponsor of the Project was moved from the Ministry of Education, Culture, Sports, Science and Technology to JAEA since the newly adopted proposals in FY2018. On this occasion, JAEA constructed a new research system where JAEA-academia collaboration is reinforced and medium-to-long term research/development and human resource development contributing to the decommissioning are stably and consecutively implemented. Among the adopted proposals in FY2018, this report summarizes the research results of the "Development of Technology for Rapid Analysis of Strontium-90 with Low Isotopic Abundance Using Laser Resonance Ionization". In this study, we will develop a rapid analysis technique for strontium-90 using diode laser-based resonance ionization with elemental and isotopic selectivity. Strontium-90 is one of the major difficult-to-measure nuclides released into the environment due to the accident at Tokyo Electric Power Company (TEPCO)'s Fukushima Daiichi Nuclear Power Station. Our method is particularly intended for real samples which contain high concentrations of strontium stable isotopes such as marine samples.

HEPA filter clogging and volatile material release under solvent fire accident in fuel reprocessing facility

Ono, Takuya; Watanabe, Koji; Tashiro, Shinsuke; Amano, Yuki; Abe, Hitoshi

Proceedings of 25th International Conference on Nuclear Engineering (ICONE-25) (CD-ROM), 7 Pages, 2017/07

After the Fukushima-Daiichi accident, countermeasures against the severe accident are newly required as regulatory items for nuclear facilities. Organic solvent fire in cell was defined as one of the accidents in the fuel reprocessing plant. When the solvent burns, aerosols including soot are released. The substances clog HEPA filters in the ventilation system and their breakthrough may happen because of differential pressure rising. Moreover, the fire can also release volatile radioactive gaseous species, which can pass through HEPA filters. These phenomena are important for evaluation of confinement capability of the facility and public exposure. We have investigated, in relating to the clogging behavior, release behavior of aerosols as well as of volatile materials from burnt solvent. In the presentation, we will report experimental data and evaluation results obtained from recent research.

Generation method of underwater landmarks for ocean observation

Takahashi, Satoru*; Nota, Yoshiki*; Matsuda, Asahi*; Kawabata, Kuniaki; Suzuki, Tsuyoshi*; Takemura, Fumiaki*; Ogasawara, Kei*; Kaneko, Shunichi*

Journal of Signal Processing, 21(1), p.15 - 24, 2017/01

https://doi.org/10.2299/jsp.21.15

In recent years, many researchers try to observe the state of the global environment from marine information for the understanding of the global environment change. First, we introduce the recording system of underwater environment which is made by the authors. By using this system, we want to observe the change of global environment from the coral bleaching. In this paper, especially, we propose the generation method of underwater landmark which is used to measure the position of robot of oceanographic observation based on the dynamic image processing. In here, underwater landmark means the feature point in underwater image.

Development of an altitude maintenance system for underwater robots using laser beams

Taba, Ryo*; Takemura, Fumiaki*; Tansuriyavong, S.*; Kawabata, Kuniaki; Sagara, Shinichi*; Ogasawara, Kei*

Proceedings of 21st International Symposium on Artificial Life and Robotics (AROB 21st 2016) and 1st International Symposium on BioComplexity (ISBC-1) (Internet), p.395 - 399, 2016/01

Numerical simulation of two-phase flow behavior in venturi scrubber by interface tracking method

Yoshida, Hiroyuki; Horiguchi, Naoki; Abe, Yutaka*

Proceedings of 2015 US-Japan Seminar on Two-Phase Flow Dynamics, 10 Pages, 2015/05

Relationship between self-priming and hydraulic behavior in venturi scrubber

Horiguchi, Naoki; Yoshida, Hiroyuki; Kaneko, Akiko*; Abe, Yutaka*

Mechanical Engineering Journal (Internet), 1(4), p.TEP0026_1 - TEP0026_11, 2014/08

https://doi.org/10.1299/mej.2014tep0026

Positive and negative ion sources for magnetic fusion

Hemsworth, R. S.*; Inoue, Takashi

IEEE Transactions on Plasma Science, 33(6), p.1799 - 1813, 2005/12

https://doi.org/10.1109/TPS.2005.860090

The positive or negative ion sources which form the primary components of neutral beam injection systems used in magnetic fusion have to meet simultaneously several demanding requirements. This paper describes the underlying physics of modern positive ion sources, which provide the required high proton fraction (90%) and high current density (2 kA/m) at a low source pressure (0.4 Pa) with a high electrical efficiency and uniformity across the accelerator grids. The development of negative ion sources, which are required if high energy neutral beams are to be produced, is explained. The paper reports that negative ion sources have achieved many of the parameters required of sources for the neutral beam injectors of future fusion devices and reactors, 200 A/m of D at low pressure, 0.3 Pa, with low co-extracted electron content. The development needed to meet all the requiremens of future systems is briefly discussed.