Fundamental study on seismic safety margin for seismic isolated structure using the laminated rubber bearings

Fukasawa, Tsuyoshi*; Miyagawa, Takayuki*; Uchita, Masato*; Yamamoto, Tomohiko; Miyazaki, Masashi; Okamura, Shigeki*; Fujita, Satoshi*

Nihon Kikai Gakkai Rombunshu (Internet), 87(898), p.21-00007_1 - 21-00007_17, 2021/06

https://doi.org/10.1299/transjsme.21-00007

This paper describes a fundamental study on the seismic safety margin for the isolated structure using laminated rubber bearings. The variation of the seismic response assumed in the isolated structure will occur under the superposition of "Variations in seismic response due to input ground motions" and "Error with design value accompanying manufacture of the isolation devices ". The seismic response analysis which allows to their conditions is important to assess the seismic safety margin for the isolated structure. This paper clarifies that the seismic safety margin of the isolated structure, which consists of rubber bearings, for Sodium-cooled Fast Reactor (SFR) is ensured against the basis ground motions of Japan Electric Association Guide 4601 (JEAG4601) and SFR through the seismic response analysis considering the variation factors of seismic response. In addition, a relationship between the seismic safety margin and the excess probability of linearity limits is discussed using the results of seismic response analysis.

Seismic evaluation for a large-sized reactor vessel targeting SFRs in Japan

Uchita, Masato*; Miyagawa, Takayuki*; Dozaki, Koji*; Chikazawa, Yoshitaka; Kubo, Shigenobu; Hayafune, Hiroki; Suzuno, Tetsuji*; Fukasawa, Tsuyoshi*; Kamishima, Yoshio*; Fujita, Satoshi*

Proceedings of 2018 International Congress on Advances in Nuclear Power Plants (ICAPP 2018) (CD-ROM), p.380 - 386, 2018/04

It is well-known that pool-type SFRs are the main streams recently in a field of Generation IV reactors. The pool-type encloses primary pumps and IHXs located around the core barrel in a main vessel. Consequently, the main vessel diameter trends to be larger than that of loop-types. From the viewpoint of commercialization in the future, a target of the vessel diameter and its weight including Sodium coolant will increase further. In this paper, the prospects are described in terms of seismic design and structural integrity for the thermal loadings to prevent buckling of the reactor vessel based on parameter studies with diameters of the vessel. In addition, the seismic isolation device which will be effective as a countermeasure is proposed in order to secure a margin against buckling of a large reactor vessel.

Study of the reaction Ca + Cm Lv at RIKEN-GARIS

Kaji, Daiya*; Morita, Kosuke*; Morimoto, Koji*; Haba, Hiromitsu*; Asai, Masato; Fujita, Kunihiro*; Gan, Z.*; Geissel, H.*; Hasebe, Hiroo*; Hofmann, S.*; et al.

Journal of the Physical Society of Japan, 86(3), p.034201_1 - 034201_7, 2017/03

https://doi.org/10.7566/JPSJ.86.034201

The fusion reaction of Ca + Cm Lv was studied using the gas-filled recoil-ion separator GARIS at RIKEN. A total of seven and spontaneous-fission decay chains were observed, which would originate from the reaction products of the element 116, Lv and Lv. Decay properties observed in the chains are in good agreement with the previously published ones. However, one of the chains showed a discrepancy, indicating the new spontaneous-fission branch in Cn or the production of the new isotope Lv.

Research on engineering technology in the full-scale demonstration of EBS and operation technology for HLW disposal; Research report in 2014 (Joint research)

Kobayashi, Masato*; Saito, Masahiko*; Iwatani, Takafumi*; Nakayama, Masashi; Tanai, Kenji; Fujita, Tomoo; Asano, Hidekazu*

JAEA-Research 2015-018, 14 Pages, 2015/12

JAEA-Research-2015-018.pdf:5.43MB

JAEA and RWMC concluded the letter of cooperation agreement on the research and development of radioactive waste disposal in April, 2005, and have been carrying out the collaboration work based on the agreement. JAEA have been carrying out the Horonobe URL Project which is intended for a sedimentary rock in the Horonobe town, Hokkaido, since 2001. In the project, geoscientific research and research and development on geological disposal technology are being promoted. Meanwhile, The Agency for Natural Resources and Energy, Ministry of Economy, Trade and Industry has been promoting construction of equipments for the full-scale demonstration of engineered barrier system and operation technology for high-level radioactive waste disposal since 2008, to enhance public's understanding to the geological disposal of HLW, e.g. using underground facility. RWMC received an order of the project in fiscal year 2014 continuing since fiscal year 2008. Since topics in this project are included in the Horonobe URL Project, JAEA carried out this project as collaboration work continuing since fiscal year 2008. This report summarizes the results of the research on engineering technology carried out in this collaboration work in fiscal year 2014.

Research on engineering technology in the full-scale demonstration of EBS and operation technology for HLW disposal; Research report in 2013 (Joint research)

Fujita, Tomoo; Tanai, Kenji; Nakayama, Masashi; Sawada, Sumiyuki*; Asano, Hidekazu*; Saito, Masahiko*; Yoshino, Osamu*; Kobayashi, Masato*

JAEA-Research 2014-031, 44 Pages, 2015/03

JAEA-Research-2014-031.pdf:16.11MB

Japan Atomic Energy Agency (JAEA) and Radioactive Waste Management Funding and Research Center (RWMC) concluded the letter of cooperation agreement on the research and development of radioactive waste disposal in April, 2005, and have been carrying out the collaboration work based on the agreement. JAEA have been carrying out the Horonobe Underground Research Laboratory (URL) Project which is intended for a sedimentary rock in the Horonobe town, Hokkaido, since 2001. In the project, geoscientific research and research and development on geological disposal technology are being promoted. Meanwhile, the government (the Agency for Natural Resources and Energy, Ministry of Economy, Trade and Industry) has been promoting construction of equipments for the full-scale demonstration of engineered barrier system (EBS) and operation technology for high-level radioactive waste (HLW) disposal since 2008, to enhance public's understanding to the geological disposal of HLW, e.g. using underground facility. RWMC received an order of the project in fiscal year 2012 (2011/2012) continuing since fiscal year 2008 (2008/2009). Since topics in this project are included in the Horonobe URL Project, JAEA carried out this project as collaboration work continuing since fiscal year 2008. This report summarizes the results of engineering technology carried out in this collaboration work in fiscal year 2013. In fiscal year 2013, emplacement tests using buffer material block for the vertical emplacement concept were carried out and visualization tests for water penetration in buffer material were carried out.

Temperature dependence of spin fluctuations in underdoped LaSrCuO

Sato, Kentaro*; Matsuura, Masato*; Fujita, Masaki*; Kajimoto, Ryoichi; Ji, S.*; Ikeuchi, Kazuhiko*; Nakamura, Mitsutaka; Inamura, Yasuhiro; Arai, Masatoshi; Enoki, Masanori*; et al.

JPS Conference Proceedings (Internet), 3, p.017010_1 - 017010_6, 2014/06

https://doi.org/10.7566/JPSCP.3.017010

Evaluation of fracture toughness of fine-grained isotropic graphites for HTGR

Yamada, Teruaki*; Matsushima, Yuki*; Kuroda, Masatoshi*; Sumita, Junya; Shibata, Taiju; Fujita, Ichiro*; Sawa, Kazuhiro

Nuclear Engineering and Design, 271, p.323 - 326, 2014/05

https://doi.org/10.1016/j.nucengdes.2013.11.055

In order to investigate the effects of the experimental methodology and the notch angle on the fracture toughness of the fine-grained isotropic nuclear graphites IG-110 and IG-430, the three-point-bending test, which has been recently proposed as the methodology to evaluate the fracture toughness of graphite for high temperature gas-cooled reactors (HTGRs), was performed using two types of the specimens with different notch angles. The results obtained in this study could be summarized as follows: (1) The values of the fracture toughness of IG-110 and IG-430 measured in this study were 0.890 MPa m and 1.031 MPa m, respectively. It was also found that the value of the fracture toughness of IG-110 was nearly equal to or smaller than the values obtained by the other method reported previously. (2) The values of the fracture toughness of the fine-grained isotropic graphites were not affected between the notch angles introduced by the incisive razor blade. (3) The ratio of the tensile strengths of IG-110 and IG-430 was estimated from Griffith Theory using the experimental data obtained in this study. The estimated strength ratio was in good agreement with the strength ratio obtained from the supplier's data.

Annual report on the environmental radiation monitoring around the Tokai Reprocessing Plant FY2012

Sumiya, Shuichi; Watanabe, Hitoshi; Miyagawa, Naoto; Nakano, Masanao; Nakada, Akira; Fujita, Hiroki; Takeyasu, Masanori; Isozaki, Tokuju; Morisawa, Masato; Mizutani, Tomoko; et al.

JAEA-Review 2013-056, 181 Pages, 2014/03

JAEA-Review-2013-056.pdf:6.22MB

Environmental radiation monitoring around the Tokai Reprocessing Plant has been performed by the Nuclear Fuel Cycle Engineering Laboratories, based on "Safety Regulations for the Reprocessing Plant of Japan Atomic Energy Agency, Chapter IV - Environmental Monitoring". This annual report presents the results of the environmental monitoring and the dose estimation to the hypothetical inhabitant due to the radioactivity discharged from the plant to the atmosphere and the sea during April 2012 to March 2013. In this report, some data include the influence of the accidental release from the Fukushima Daiichi Nuclear Power Plant of Tokyo Electric Power Co. in March 2011.

Evaluation of oxidation characteristics of fine-grained graphites (IG-110 and IG-430) for very high temperature reactor; Changes in density distribution and compressive strength caused by air-oxidation

Fujita, Ichiro*; Eto, Motokuni*; Osaki, Hirotaka; Shibata, Taiju; Sumita, Junya; Konishi, Takashi; Yamaji, Masatoshi; Kunimoto, Eiji

JAEA-Research 2013-004, 20 Pages, 2013/07

JAEA-Research-2013-004.pdf:2.4MB

Graphite components in HTGR and VHTR may be oxidized by impurities in coolant helium-gas even at normal operation, as well as by air at air-ingress accident. In this study, by air-oxidation test at 520-900C, oxidation characteristics of IG-110 and IG-430 graphites, and associated decrease in compressive strength were examined. The following results were obtained. (1) The activation energy of the air-oxidation for IG-430 is 176 kJ/mol being almost same as for IG-110, though the oxidation rate for IG-430 is less than a half of that for IG-110. (2) There are correlations between density change and decrease in compressive strength. Decrease in strength is the largest in case that the oxidation temperature is lower than 600 C where the homogenous oxidation occurs. (3) In the process of oxidation, amorphous binder regions are predominantly oxidized. It suggests that peeling-off of cokes grains is necessary to be considered for oxidation weight loss, as well as gasification.

Annual report on the environmental radiation monitoring around the Tokai Reprocessing Plant FY2011

Sumiya, Shuichi; Watanabe, Hitoshi; Nakano, Masanao; Takeyasu, Masanori; Nakada, Akira; Fujita, Hiroki; Isozaki, Tokuju; Morisawa, Masato; Mizutani, Tomoko; Nagaoka, Mika; et al.

JAEA-Review 2013-009, 195 Pages, 2013/06

JAEA-Review-2013-009.pdf:3.35MB

Environmental radiation monitoring around the Tokai Reprocessing Plant has been performed by the Nuclear Fuel Cycle Engineering Laboratories, based on "Safety Regulations for the Reprocessing Plant of Japan Atomic Energy Agency, Chapter IV - Environmental Monitoring". This annual report presents the results of the environmental monitoring and the dose estimation to the hypothetical inhabitant due to the radioactivity discharged from the plant to the atmosphere and the sea during April 2011 to March 2012. In this report, some data include the influence of the accidental release from the Fukushima Daiichi Nuclear Power Plant on Tokyo Electric Power Co. in March 2011.