Space weather benchmarks on Japanese society

Ishii, Mamoru*; Shiota, Daiko*; Tao, Chihiro*; Ebihara, Yusuke*; Fujiwara, Hitoshi*; Ishii, Takako*; Ichimoto, Kiyoshi*; Kataoka, Ryuho*; Koga, Kiyokazu*; Kubo, Yuki*; et al.

Earth, Planets and Space (Internet), 73(1), p.108_1 - 108_20, 2021/12

https://doi.org/10.1186/s40623-021-01420-5

We surveyed the relationship between the scale of space weather events and their occurrence rate in Japan and we discussed the social impact of these phenomena during the Project for Solar-Terrestrial Environment Prediction (PSTEP). The information was compiled for domestic users of space weather forecasts for appropriate preparedness against space weather disasters. This paper gives a comprehensive summary of the survey, focusing on the fields of electricity, satellite operations, communication and broadcasting, satellite positioning usage, aviation, human space activity, and daily life on the Earth's surface, using the cutting-edge knowledge of space weather. Quantitative estimations of the economic impact of space weather events on electricity and aviation are also given.

Dynamic PRA of flooding-initiated accident scenarios using THALES2-RAPID

Kubo, Kotaro; Zheng, X.; Tanaka, Yoichi; Tamaki, Hitoshi; Sugiyama, Tomoyuki; Jang, S.*; Takata, Takashi*; Yamaguchi, Akira*

Proceedings of 30th European Safety and Reliability Conference and 15th Probabilistic Safety Assessment and Management Conference (ESREL 2020 and PSAM-15) (Internet), p.2279 - 2286, 2020/11

https://www.rpsonline.com.sg/proceedings/esrel2020/pdf/4717.pdf

Probabilistic risk assessment (PRA) is one of the methods used to assess the risks associated with large and complex systems. When the risk of an external event is evaluated using conventional PRA, a particular limitation is the difficulty in considering the timing at which nuclear power plant structures, systems, and components fail. To overcome this limitation, we coupled thermal-hydraulic and external-event simulations using Risk Assessment with Plant Interactive Dynamics (RAPID). Internal flooding was chosen as the representative external event, and a pressurized water reactor plant model was used. Equations based on Bernoulli's theorem were applied to flooding propagation in the turbine building. In the analysis, uncertainties were taken into account, including the flow rate of the flood water source and the failure criteria for the mitigation systems. In terms of recovery action, isolation of the flood water source by the operator and drainage using a pump were modeled based on several assumptions. The results indicate that the isolation action became more effective when combined with drainage.

Preheat effect on titanium plate fabricated by sputter-free selective laser melting in vacuum

Sato, Yuji*; Tsukamoto, Masahiro*; Shobu, Takahisa; Yamashita, Yoshihiro*; Yamagata, Shuto*; Nishi, Takaya*; Higashino, Ritsuko*; Okubo, Tomomasa*; Nakano, Hitoshi*; Abe, Nobuyuki*

Applied Physics A, 124(4), p.288_1 - 288_6, 2018/04

https://doi.org/10.1007/s00339-018-1712-4

The dynamics of titanium (Ti) melted by laser irradiation was investigated in a synchrotron radiation experiment. As an indicator of wettability, the contact angle between a selective laser melting (SLM) baseplate and the molten Ti was measured by synchrotron X-rays at 30 keV during laser irradiation. As the baseplate temperature increased, the contact angle decreased, down to 28 degrees at a baseplate temperature of 500C. Based on this result, the influence of wettability of a Ti plate fabricated by SLM in a vacuum was investigated. It was revealed that the improvement of wettability by preheating suppressed sputtering generation, and a surface having a small surface roughness was fabricated by SLM in a vacuum.

Possible singlet-triplet transition of ESR in the kagome-lattice antiferromagnet

Sakai, Toru; Hijii, Keigo*; Okubo, Susumu*; Ota, Hitoshi*; Nakano, Hiroki*; Miyashita, Seiji*

Applied Magnetic Resonance, 46(9), p.997 - 1002, 2015/09

https://doi.org/10.1007/s00723-015-0652-9

The S=1/2 kagome-lattice antiferromagnet is investigated by the numerical diagonalization of 18-spin finite-size cluster. The matrix elements proportional to the intensity of the singlet-triplet ESR transition are calculated in the presence of the Dzyaloshinsky-Moriya interaction. Some angle-dependent selection rules is also proposed.

Development of hydrophobic platinum catalyst for the effective collection of tritium in fusion plants

Iwai, Yasunori; Kubo, Hitoshi*; Oshima, Yusuke*

Isotope News, (736), p.12 - 17, 2015/08

http://www.jrias.or.jp/books/pdf/201508_TENBO_IWAI.pdf

We have successfully developed a new hydrophobic platinum catalyst for collecting tritium at nuclear fusion reactors. Catalysts used to collect tritium are called hydrophobic precious metal catalysts. In Japan, hydrophobic precious metal catalysts manufactured from polymers have been used for heavy water refinement.However, this catalyst has issues related to embrittlement to radiation and thermal stability. These technological issues needed to be solved to allow for its application to nuclear fusion reactors requiring further enrichment from highly-concentrated tritiated water. We developed a new method of manufacturing catalysts involving hydrophobic processing with an inorganic substance base. As a result, previous technological issues were able to be solved with the development of a catalyst that exhibited no performance degradation in response to radiation application of 530kGy, a standard for radiation resistance, and maintenance of thermal stability at over 600C, which is much higher than the 70C temperature that is normally used. The catalyst created with this method was also confirmed to have achieved the world's highest exchange efficiency, equivalent to 1.3 times the previously most powerful efficiency. The application of this catalyst to the liquid phase catalytic exchange process is expected to overcome significant technological hurdles with regards to improving the reliability and efficiency of systems for collecting tritium from tritiated water.

Hydrophobic Pt catalyst for combustion of hydrogen isotopes at low temperatures

Iwai, Yasunori; Kubo, Hitoshi*; Sato, Katsumi; Oshima, Yusuke*; Noguchi, Hiroshi*; Taniuchi, Junichi*

Proceedings of 7th Tokyo Conference on Advanced Catalytic Science and Technology (TOCAT-7) (USB Flash Drive), 2 Pages, 2014/06

Hydrophobic platinum catalysts have been developed especially for combustion of hydrogen isotopes released in a nuclear facility. A new type of hydrophobic hydrogen combustion catalyst commercially named TKK-KNOITS catalyst is hardly susceptible to water mist and water vapor in the atmosphere and water produced by hydrogen combustion. It is capable of maintaining the activity even at relatively low temperatures. The TKK-KNOITS catalyst is superior to other previous hydrophobic catalysts in applicability to wide range of hydrogen concentration from very thin to dense. The catalyst which carrier is composed of inorganic oxide has thermal stability up to 873 K.

Room-temperature reactor packed with hydrophobic catalysts for the oxidation of hydrogen isotopes released in a nuclear facility

Iwai, Yasunori; Sato, Katsumi; Taniuchi, Junichi*; Noguchi, Hiroshi*; Kubo, Hitoshi*; Harada, Nobuo*; Oshima, Yusuke*; Yamanishi, Toshihiko

Journal of Nuclear Science and Technology, 48(8), p.1184 - 1192, 2011/08

https://doi.org/10.3327/jnst.48.1184

The inorganic-based hydrophobic Pt-catalyst named H1P has been developed especially for efficient oxidation of a tracer level of tritium in the ambient temperature range even in the presence of saturated water vapor. The overall reaction rate constant for H1P catalyst in the ambient temperature range was considerably larger than that for traditionally applied Pt/AlO catalyst. Moreover, the decrease in reaction rate for H1P in the presence of saturated water vapor compared with in the absence of water vapor was slight due to its excellence in hydrophobic performance. Oxidation reaction on the catalyst surface is the rate-controlling step in the ambient temperature range and diffusion in a catalyst substratum above 313 K due to its fine porosity. The overall reaction rate constant in the ambient temperature range was dependent on the space velocity and hydrogen concentration in carrier.

Development of a computer tool to support scenario analysis for safety assessment of HLW geological disposal

Makino, Hitoshi; Kawamura, Makoto; Wakasugi, Keiichiro; Okubo, Hiroo*; Takase, Hiroyasu*

JAEA-Data/Code 2007-005, 67 Pages, 2007/02

JAEA-Data-Code-2007-005.pdf:6.66MB

In this study, based on an improvement method for treatment of FEP interaction a computer tool to support scenario analysis by specialists of performance assessment has been developed. Anticipated effects of this tool are to improve efficiency of complex and time consuming scenario analysis work and to reduce possibility of human errors in this work. This tool also enables to describe interactions among a vast number of FEP's and the related information as interaction matrix, and analysis those interactions from a variety of perspectives.

Development of decommissioning management system (10); Improvement of evaluation accuracy and simplification of input work

Kondo, Hitoshi; Miyazaki, Hitoshi*; Okubo, Toshiyuki

JNC TN9410 2005-009, 32 Pages, 2005/03

JNC-TN9410-2005-009.pdf:4.62MB

When the plan of Decommissioning such as nuclear fuel cycle facilities and small-scale research reactor is settled on, it is necessary to optimize the index concerning the decommissioning (such as the cost, the waste and the term of works. etc) by selecting the technology and the process appropriately. In Waste Management section, the development of the Decommissioning Management System (DECMAN) which can calculate these decommissioning indexes from the facilities data and the dismantlement technique automatically is advanced. This report describes the problem found in 2003 and the solution concerning the operation and the evaluation technique.

Development of chemical decontamination method for old Waste Treatment Facility

Fukuda, Seiji; Kondo, Hitoshi; Okubo, Toshiyuki

JNC TN9410 2004-010, 56 Pages, 2004/03

JNC-TN9410-2004-010.pdf:1.53MB

The Old Waste Treatment Facility of JOYO(0ld JWTF), operation of which stopped in 1995, is scheduled to be dismantled starting in 2010. In order to reduce worker's radiation exposure, it is necessary to reduce radiation dose rate of the main equipments by system chemical decontamination before dismantling. In thjs research, the decontamination solutions were selected in view of reduction of consequential waste amount and expense of treatment of decontamination waste. We evaluated decontamination factor (DF) in test with contaminated samples (Hot test). Moreover we performed a conceptual design of the decontamination system using the decontamination solution that obtained the highest DF in hot test. The solution selected in hot test did not achieve the target DF to all equipments. For some equipment more aggressive solutions, which dissolve contaminants and base metal, would be needed, however using these solutions would tend to increase consequential waste amount and expense of treatment of decontamination waste. Therefore, we evaluated the dissolution rate of these solutions for stainless steels in test with non-contaminated samples (Cold test). The main result of obtaining through the hot test and the cold test is shown below.(1)By alternating immersions in sodium hydroxide solution and nitric acid, the highest DF was obtained. (Maximum of DF=10.7, 80 deg-C). (2)The decontamination system is composed of two decontamination solution tanks, a washing water tank, a pump that supplies decontamination solutions and washing water, and filters for removing contaminants. (3)The test samples were immersed in various solutions (HN03 + HF, HCl, H2S04) for 24 hours at room temperature. As a result, it was confirmed that the dissolution rate of HN03 + HF is remarkably large compared with other solutions (7.43 micro-m/day).