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JAEA Reports

Compilation of previous studies on secondary effects induced by earthquake and fault activity (Contract research)

Goto, Akira; Murakami, Masaki*; Sakai, Ryutaro*; Terusawa, Shuji*; Sueoka, Shigeru

JAEA-Review 2020-003, 60 Pages, 2020/03

JAEA-Review-2020-003.pdf:4.43MB

One of the natural phenomena that may affect the geological disposal system are earthquake and fault activity. Fault displacement due to the earthquake and fault activity will be considered the direct effects. In addition to it, it is necessary to consider the secondary effects include secondary faults formed by the seismic fault activity as well as spring water and mud volcanoes that are generated by fluid movement attributed to the fault activity. This paper introduces previous studies performed focused on the hydraulic effects (spring water and mud volcanoes) and mechanical effects (secondary faults) in order to understand the effects of these secondary phenomena on the geological disposal system. We were able to collect 142 literatures from Japan and overseas by searching for related keywords in Japanese and English. As a result, we compiled case studies of each secondary impact. From the viewpoint of geological disposal, we extracted the following issues for future research and development. As for the sump water induced by earthquakes and faulting, accumulation of information related to its mechanism, affected area, and activity history is required. As for the mud volcanoes, reviewing of the mechanism of anomalous pore water pressure that causing the formation, also development of estimation technique are required. And for the secondary faults, accumulation of the detailed spatial distribution and reviewing of formation mechanism are required.

Journal Articles

Evaluation of influence of splay fault growth on groundwater flow around geological disposal system

Takai, Shizuka; Takeda, Seiji; Sakai, Ryutaro*; Shimada, Taro; Munakata, Masahiro; Tanaka, Tadao

Nihon Genshiryoku Gakkai Wabun Rombunshi, 16(1), p.34 - 48, 2017/03

In geological disposal, direct effect on geological repositories by active faults is avoided at a stage of site characterization; however, uncertainty remains for avoidance of faults derived from the active faults, which are concealed deep under the ground and difficult to detect in advance. In this research, the influence of growth of undetected splay faults on natural barrier in a geological disposal system, which will caused by attack of the faults in the future, was evaluated. We investigated examples of splay faults in Japan and set conditions for growth of splay faults. Furthermore, we assumed a disposal site composed of sedimentary rocks and made a hydrogeological model of growth of splay faults. We carried out groundwater flow analyses, changing parameters such as location and depth of repository and growth velocity of splay faults. The results indicate that main flow path from the repository is changed into upward flow along the splay fault due to its growth and the average velocity to the ground surface becomes one or two orders of magnitude higher than that before its growth. The results also suggest that the splay fault growth leads into the possibility of downward flow of oxidizing groundwater from ground surface area.

Journal Articles

Evaluation for influence of new volcanic eruption on geological disposal site

Shimada, Taro; Takeda, Seiji; Sakai, Ryutaro*; Takubo, Kazuya; Tanaka, Tadao

MRS Advances (Internet), 1(61), p.4081 - 4086, 2016/00

Volcanic eruption which may affect geological disposal system directly depends on the regional location in Japan. It is required that the disposal site should be located far from existing volcanos. However, there are regions where it is impossible to exclude the possibility of appearance of new volcanic activity on the site even if the site is located far from existing volcanos. In order to identify the influence of volcanic eruption at disposal site to public if it occurs public exposure doses were evaluated based on the two scenarios considering types of eruption at new volcanic activity in Japan. One is the exposure by tephra widespread by Strombolian eruption and deposited on the ground surface, including radionuclides from vitrified waste forms after a volcanic conduit penetrated disposal galleries. The other is that by waste forms appeared at the surface by Merapi type pyroclastic flow. Exposure doses of the residents living on the tephra do not exceed 1mSv/y even when the eruption occurs at 1,000 years after closure of disposal site. Dose rate for the volcanic researchers temporarily approaching waste forms becomes less than 1mSv/h when the eruption occurs 100,000 years after. It indicated that attention should be paid to the impact by Merapi type pyroclastic flow on researchers approaching waste forms appeared rather than that by Strombolian eruption on residents living on the tephra widespread.

Journal Articles

Production of $$^{88}$$Nb and $$^{170}$$Ta for chemical studies of element 105, Db, using the GARIS gas-jet system

Huang, M.*; Haba, Hiromitsu*; Murakami, Masashi*; Asai, Masato; Kaji, Daiya*; Kanaya, Jumpei*; Kasamatsu, Yoshitaka*; Kikunaga, Hidetoshi*; Kikutani, Yuki*; Komori, Yukiko*; et al.

Journal of Radioanalytical and Nuclear Chemistry, 304(2), p.845 - 849, 2015/05

 Times Cited Count:3 Percentile:32.14(Chemistry, Analytical)

A technique to utilize radioisotopes of Nb and Ta was developed for chemical studies of element 105, Db, by coupling a gas-jet transport system to the RIKEN gas-filled recoil ion separator (GARIS). The short-lived $$^{88}$$Nb and $$^{170}$$Ta were produced with nuclear reactions using a $$^{19}$$F beam whose energy was the same as that to produce $$^{262}$$Db. Then, they were separated with GARIS and extracted to a chemistry laboratory with the gas-jet transport system. By changing only magnetic field of GARIS and inserting an energy degrader and a shutter for recoil ions, we could deliver the $$^{88}$$Nb and $$^{170}$$Ta to a chemistry device for $$^{262}$$Db without changing other experimental conditions.

Journal Articles

Inter-atomic force constants of BaF$$_{2}$$ by diffuse neutron scattering measurement

Sakuma, Takashi*; Makhsun*; Sakai, Ryutaro*; Xianglian*; Takahashi, Haruyuki*; Basar, K.*; Igawa, Naoki; Danilkin, S. A.*

AIP Conference Proceedings 1656, p.020002_1 - 020002_4, 2015/04

 Times Cited Count:1 Percentile:51.16

Diffuse neutron scattering measurement on BaF$$_{2}$$ crystals was performed at 10 K and 295 K. Oscillatory form in the diffuse scattering intensity of BaF$$_{2}$$ was observed at 295 K. The correlation effects among thermal displacements of F-F atoms were obtained from the analysis of oscillatory diffuse scattering intensity. From the values of correlation effects and Debye-Waller temperature parameters, force constants among the first and second nearest neighboring atoms of BaF$$_{2}$$, were determined to be 4.40 and 2.30 eV/$AA$^{2}$$ at 295 K, respectively

Journal Articles

Production of $$^{262}$$Db in the $$^{248}$$Cm($$^{19}$$F,5$$n$$)$$^{262}$$Db reaction and decay properties of $$^{262}$$Db and $$^{258}$$Lr

Haba, Hiromitsu*; Huang, M.*; Kaji, Daiya*; Kanaya, Jumpei*; Kudo, Yuki*; Morimoto, Koji*; Morita, Kosuke*; Murakami, Masashi*; Ozeki, Kazutaka*; Sakai, Ryutaro*; et al.

Physical Review C, 89(2), p.024618_1 - 024618_11, 2014/02

 Times Cited Count:20 Percentile:81.46(Physics, Nuclear)

Journal Articles

Excitation functions for production of Rf isotopes in the $$^{248}$$Cm + $$^{18}$$O reaction

Murakami, Masashi*; Goto, Shinichi*; Murayama, Hirofumi*; Kojima, Takayuki*; Kudo, Hisaaki*; Kaji, Daiya*; Morimoto, Koji*; Haba, Hiromitsu*; Kudo, Yuki*; Sumita, Takayuki*; et al.

Physical Review C, 88(2), p.024618_1 - 024618_8, 2013/08

 Times Cited Count:12 Percentile:66.32(Physics, Nuclear)

Production cross sections of Rf isotopes in the $$^{248}$$Cm + $$^{18}$$O reaction were measured at the beam energy range of 88.2 to 101.3 MeV by use of a gas-filled recoil ion separator. The excitation functions of $$^{260}$$Rf, $$^{261a}$$Rf, and $$^{262}$$Rf were obtained together with those of spontaneously fissioning nuclides which have few-second half-lives and have been assigned to $$^{261b}$$Rf and a longer-lived state of $$^{262}$$Rf. The excitation function of few-second spontaneously fissioning nuclide exhibited the maximum cross section at the $$^{18}$$O beam energy of 94.8 MeV. The shape of the excitation function was almost the same as that of $$^{261a}$$Rf, whereas it was quite different from those of $$^{260}$$Rf and $$^{262}$$Rf. A few-second spontaneously fissioning nuclide previously reported as $$^{261b}$$Rf and $$^{262}$$Rf observed in$$^{248}$$Cm + $$^{18}$$O reaction was identified as $$^{261b}$$Rf.

JAEA Reports

Study on evaluation methodology for groundwater flow based on geochemical data, 2; Case study for Horonobe area (Contract research)

Sakai, Ryutaro; Takeda, Seiji; Munakata, Masahiro; Kimura, Hideo

JAEA-Research 2013-006, 18 Pages, 2013/07

JAEA-Research-2013-006.pdf:2.77MB

In the safety assessment for a geological disposal of radioactive waste, it is important to establish validation methods for deep groundwater flow to estimate radionuclide migration to human environment through groundwater flow. Costal sedimentary rocks in our country provide dominant fossil water formed during sub-seabed sedimentation and chemical compositions of the water mixed with meteoric water and fossil water depend on the initial fossil water composition and groundwater flow conditions. Analytical study on the effects of groundwater flow on the mixed water quality as a indicator of its Cl/$$delta$$$$^{18}$$O ratios was carried out in case of Horonobe district, where geochemical data is now being stored.

Journal Articles

New result in the production and decay of an isotope, $$^{278}$$113 of the 113th element

Morita, Kosuke*; Morimoto, Koji*; Kaji, Daiya*; Haba, Hiromitsu*; Ozeki, Kazutaka*; Kudo, Yuki*; Sumita, Takayuki*; Wakabayashi, Yasuo*; Yoneda, Akira*; Tanaka, Kengo*; et al.

Journal of the Physical Society of Japan, 81(10), p.103201_1 - 103201_4, 2012/10

 Times Cited Count:142 Percentile:97.35(Physics, Multidisciplinary)

An isotope of the 113th element, $$^{278}$$113, was produced in a nuclear reaction with a $$^{70}$$Zn beam on a $$^{209}$$Bi target. We observed six consecutive $$alpha$$ decays following the implantation of a heavy particle in nearly the same position in the semiconductor detector, in extremely low background condition. The fifth and sixth decays are fully consistent with the sequential decays of $$^{262}$$Db and $$^{258}$$Lr both in decay energies and decay times. This indicates that the present decay chain consisted of $$^{278}$$113, $$^{274}$$Rg (Z = 111), $$^{270}$$Mt (Z = 109), $$^{266}$$Bh (Z = 107), $$^{262}$$Db (Z = 105), and $$^{258}$$Lr (Z = 103) with firm connections. This result, together with previously reported results from 2004 and 2007, conclusively leads the unambiguous production and identification of the isotope $$^{278}$$113, of the 113th element.

Journal Articles

Inter-atomic force constants of Ag$$_{2}$$O from diffuse neutron scattering measurement

Wada, Tamotsu*; Sakuma, Takashi*; Sakai, Ryutaro*; Uehara, Hiroyuki*; Xianglian*; Takahashi, Haruyuki*; Kamishima, Osamu*; Igawa, Naoki; Danilkin, S. A.*

Solid State Ionics, 225, p.18 - 21, 2012/10

 Times Cited Count:6 Percentile:31.07(Chemistry, Physical)

Diffuse neutron scattering measurement on Ag$$_{2}$$O crystals was performed at 8 K and 295 K. The observed diffuse scattering intensities were analyzed by including the correlation effects among thermal displacements of atoms in Ag$$_{2}$$O. Using the values of correlation effects among neighboring atoms and the values of Debye-Waller temperature parameter, force constants among first, second and third nearest neighboring atoms have been evaluated.

JAEA Reports

Study on evaluation methodology for groundwater flow based on geochemical data; Case study for Horonobe area (Contract research)

Sakai, Ryutaro; Munakata, Masahiro; Kimura, Hideo

JAEA-Research 2011-054, 19 Pages, 2012/03

JAEA-Research-2011-054.pdf:2.07MB

In the safety assessment for a geological disposal of radioactive waste, it is important to establish validation methods for deep groundwater flow system to estimate radionuclide migration to human environment through groundwater flow. This study discussed the method which estimates groundwater mixing condition and groundwater flow process using principal component analysis (PCA) to groundwater chemistry and isotopic compositions, together with data of groundwater age and trace element in case of Horonobe area. The results show that hydrochemical system can be divided into two systems: (1) three deep groundwater mixing system at depths greater than 200 to 400 m, (2) mixing area of deep groundwater and surface water at depths less than 200 to 400 m. Groundwater in the deep aquifer is suggested to be discharged at surface through Omagari Fault.

Journal Articles

Production of $$^{265}$$Sg in the $$^{248}$$Cm($$^{22}$$Ne,5$$n$$)$$^{265}$$Sg reaction and decay properties of two isomeric states in $$^{265}$$Sg

Haba, Hiromitsu*; Kaji, Daiya*; Kudo, Yuki*; Morimoto, Koji*; Morita, Kosuke*; Ozeki, Kazutaka*; Sakai, Ryutaro*; Sumita, Takayuki*; Yoneda, Akira*; Kasamatsu, Yoshitaka*; et al.

Physical Review C, 85(2), p.024611_1 - 024611_11, 2012/02

 Times Cited Count:44 Percentile:91.13(Physics, Nuclear)

Two isomeric states in $$^{265}$$Sg, i.e, $$^{265}$$Sg$$^{a}$$ and $$^{265}$$Sg$$^{b}$$ were produced in the $$^{248}$$Cm($$^{22}$$Ne,5$$n$$) reaction. Decay properties of $$^{265}$$Sg$$^{a,b}$$ were investigated with a rotating-wheel apparatus for $$alpha$$ and spontaneous fission (SF) spectrometry under low background condition attained by a gas-jet transport system coupled to the RIKEN gas-filled recoil ion separator. Based on genetically correlated $$alpha$$-$$alpha$$ (-$$alpha$$) and $$alpha$$-SF decay chains, 18 and 24 events were assigned to $$^{265}$$Sg$$^{a}$$ and $$^{265}$$Sg$$^{b}$$, respectively. The half-life and $$alpha$$-particle energy of $$^{265}$$Sg$$^{a}$$ were measured to be $$8.5^{+2.6}_{-1.6}$$ s and $$8.84 pm 0.05$$ MeV, respectively, and those of $$^{265}$$Sg$$^{b}$$ were $$14.4^{+3.7}_{-2.5}$$ s and $$8.69 pm 0.05$$ MeV.

JAEA Reports

Study on validation method of regional groundwater flow model; Case study for Horonobe area and Niigata basin (Contract research)

Sakai, Ryutaro; Munakata, Masahiro; Kimura, Hideo; Ooka, Masao*; Seguchi, Mariko*

JAEA-Research 2011-029, 24 Pages, 2011/11

JAEA-Research-2011-029.pdf:3.67MB

In the safety assessment for a geological disposal of radioactive waste, it is important to establish validation methods for regional groundwater flow system to estimate radionuclide migration to human environment through groundwater flow. It is necessary to validate the groundwater flow property and flow boundary, as multi-groundwater systems including the different groundwater origins are possible to exist at deep underground. This results show that mixing analysis based on hydrochemical data and spatial plotting with hydrochemical data and thermal data are applicable to validate groundwater flow pattern and groundwater flow boundary in case of Horonobe area. It also demonstrates that mixing analysis based on hydrochemical data and spatial plotting with hydrological and hydrochemical data are applicable to validate the groundwater flow property and groundwater flow boundary in case of Nagaoka area.

JAEA Reports

Development of FEP database for geological and climatic disruptive events; Uplift, subsidence, earthquake activity, and climate change (Contract research)

Sakai, Ryutaro; Takeda, Seiji; Kimura, Hideo; Matsuba, Hisashi*

JAEA-Data/Code 2011-005, 107 Pages, 2011/06

JAEA-Data-Code-2011-005.pdf:2.74MB

In the safety assessment for a geological disposal of radioactive waste such as high-level radioactive waste, it is necessary to estimate the hydrological environmental changes affected by external factors such as long-termed earthquake activity and volcanic activity. Therefore it is important to perform the informations including a wide range of future processes and conditions of engineered barriers and geosphere in a systematic manner and to construct scenarios considering external factors. Generation of geological and climatic disruptive events such as earthquake activity, volcanic activity, uplift, subsidence, climatic change and sea-level change and propagation process of their impacts and their types are needed to be clarified in order to understand the phenomena of their influence on a disposal system in case of our country. Japan Atomic Energy Agency started to develop FEP database including the correlation of FEPs and FEP data sheet.

Journal Articles

Recharge evaluation of northern area in Hokkaido, Japan

Ikeda, Makoto; Munakata, Masahiro; Sakai, Ryutaro; Kimura, Hideo; Jia, H.*; Matsuba, Hisashi*

Nihon Chikasui Gakkai 2011-Nen Shunki Koenkai Koen Yoshi, p.86 - 91, 2011/05

no abstracts in English

JAEA Reports

Study on validation method of regional groundwater flow model; Case study for Boso peninsula

Sakai, Ryutaro; Munakata, Masahiro; Kimura, Hideo; Ichikawa, Yasuo*; Nakamura, Masaru*

JAEA-Research 2010-066, 20 Pages, 2011/03

JAEA-Research-2010-066.pdf:2.26MB

In the safety assessment for a geological disposal of radioactive waste, it is important to establish modelling methods and validation methods for regional groundwater flow system in the depth of 300$$sim$$1000m to estimate radionuclide migration to human environment through groundwater flow system. The study discussed application of data and assessment methods for model validation based on multiple indicators such as hydrology, groundwater chemistry, temperature and age of groundwater in case of the Boso Peninsula in Chiba Prefecture where a lot of in-situ data about groundwater was measured. This results show that existing hydrochemical and thermal data are applicable to explain freshwater and saltwater distribution and groundwater flow pattern in case of regional scale. It also indicates that gravitational groundwater is likely to flow into the deep part of fresh-saltwater interface based on the exist of Na-HCO$$_{3}$$ type water above fresh-saltwater interface mixed with meteoric water and that multiple indicators are applicable to evaluate groundwater flow property and groundwater flow boundary in case of site scale region.

Journal Articles

Force constants of Cu crystals from diffuse neutron scattering measurement

Sakuma, Takashi*; Mohapatra, S. R.*; Uehara, Hiroyuki*; Sakai, Ryutaro*; Xianglian*; Takahashi, Haruyuki*; Igawa, Naoki; Basar, K.*

Atom Indonesia, 36(3), p.121 - 124, 2010/12

Diffuse neutron scattering measurement on Cu crystals was performed at 10 K and 300 K and the observed diffuse scattering intensities were analyzed by including the correlation effects among thermal displacements of atoms in the theory. Using the values of correlation effects among neighboring atoms and the values of Debye-Waller temperature parameter, force constants among first, second and third nearest neighboring atoms had been evaluated. The estimated values of force constants among first, second and third nearest neighboring atoms of Cu were 5.58, 3.63 and 2.37 eV/${AA}$ $$^{2}$$ at 300 K, respectively. The relation between correlation effects and the inter-atomic distance is not depending much on the crystal binding types.

Journal Articles

Study of influence factors on hydraulic conductivity of sedimentary rocks

Sakai, Ryutaro; Munakata, Masahiro; Kimura, Hideo; Ooka, Masao*; Kameya, Hiroshi*; Hosoda, Koichi*

Dai-21-Kai Zenkoku Chishitsu Chosagyo Kyokai Rengokai "Gijutsu Foramu" Koenshu (CD-ROM), 2 Pages, 2010/11

no abstracts in English

Journal Articles

Recharge evaluation using distributed tank model

Ikeda, Makoto; Munakata, Masahiro; Sakai, Ryutaro; Fuchiwaki, Hirotaka; Kimura, Hideo; Matsuba, Hisashi*

Nihon Chikasui Gakkai 2010-Nen Shuki Koenkai Koen Yoshi, p.282 - 287, 2010/11

no abstracts in English

JAEA Reports

Study on uncertainty evaluation methodology related to hydrological parameter of regional groundwater flow analysis model

Sakai, Ryutaro; Munakata, Masahiro; Ooka, Masao*; Kameya, Hiroshi*

JAEA-Research 2009-038, 38 Pages, 2009/11

JAEA-Research-2009-038.pdf:8.87MB

In the safety assessment for a geological disposal of radioactive waste, it is important to develop a methodology and uncertainties of long-term estimation of regional groundwater flow system. The authors discussed the uncertainties of hydraulic conductivity as a significant hydrological parameter for regional groundwater flow analysis model. This study demonstrated that confining pressure change cased by uplift and subsidence and change of hydraulic gradients under the long-term geological and hydrological environmental change could possibly produce variations more than one order of magnitude in hydraulic conductivity of rock mass. It also clarified that the effect of water quality change on hydraulic conductivity is not negligible and that the replacement of fresh water and saline water cased by sea level change could predict to reduce hydraulic conductivities in rock mass 0.6 times from its present data in case of Horonobe site.

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