Evaluation study of fault activity on Shionohira and Kuruma Faults located at the border of Fukushima and Ibaraki Prefecture, Japan

Aoki, Kazuhiro; Imai, Hirotaro; Seshimo, Kazuyoshi; Kimura, Megumi; Kirita, Fumio; Nakanishi, Ryuji

JAEA-Research 2024-005, 177 Pages, 2024/10

JAEA-Research-2024-005.pdf:12.02MB

This study presents a method for evaluating displacements on active faults that lack clear markers of fault offset. The method uses geological surveys, core studies, and chemical analyses along with hydraulic and mechanical tests. We applied this method to three test sites along the Shionohira Fault (Shionohira and Betto sites) and the Kuruma Fault (Minakamikita site). Laboratory friction tests on the fault gouge using a variable-speed, rotating shear friction apparatus were conducted. The samples from the Shionohira and Betto sites showed velocity weakening or strengthening, but no velocity dependence was observed at the Minakamikita site. A small-scale test to induce fault slip was conducted using the SIMFIP method. At the Shionohira site, fault slip can be modeled as a Coulomb rupture and shows a frictional dependence on slip velocity. On the other hand, at the Minakamikita site, a complex response using multiple fractures and slip planes was observed. Based on the water pressure response, the hydraulic properties of the area between the faults were evaluated. The transmissivity and specific storage are larger at Shionohira than at Minakamikita. Fault slip data such as shear plane attitude or shear sense were obtained from core samples and stress inversion analysis was performed. We attempted to elucidate the history of the movement and stress that formed the fracture zone. The results reconstructed five activity stages at Shionohira site and two stages at Minakamikita site. As shown in this report, the frictional properties, fault rupture mode, hydraulic properties and the history of fault motion were found to be different between the Shionohira and Kuruma sites. However, the results are based on a few locational data, so case studies at other sites and more applications to other faults should be considered to improve the reliability of the evaluation.

Evaluating the effectiveness of a geostatistical approach with groundwater flow modeling for three-dimensional estimation of a contaminant plume

Takai, Shizuka; Shimada, Taro; Takeda, Seiji; Koike, Katsuaki*

Journal of Contaminant Hydrology, 251, p.104097_1 - 104097_12, 2022/12

https://doi.org/10.1016/j.jconhyd.2022.104097

When assessing the risk from an underground environment that is contaminated by radioactive nuclides and hazardous chemicals and planning for remediation, the contaminant plume distribution and the associated uncertainty from measured data should be estimated accurately. While the release history of the contaminant plume may be unknown, the extent of the plume caused by a known source and the associated uncertainty can be calculated inversely from the concentration data using a geostatistical method that accounts for the temporal correlation of its release history and groundwater flow modeling. However, the preceding geostatistical approaches have three drawbacks: (1) no applications of the three-dimensional plume estimation in real situations, (2) no constraints for the estimation of the plume distribution, which can yield negative concentration and large uncertainties, and (3) few applications to actual cases with multiple contaminants. To address these problems, the non-negativity constraint using Gibbs sampling was incorporated into the geostatistical method with groundwater flow modeling for contaminant plume estimation. This method was then tested on groundwater contamination in the Gloucester landfill in Ontario, Canada. The method was applied to three water soluble organic contaminants: 1,4-dioxane, tetrahydrofuran, and diethyl ether. The effectiveness of the proposed method was verified by the general agreement of the calculated plume distributions of the three contaminants with concentration data from 66 points in 1982 (linear correlation coefficient of about 0.7). In particular, the reproduced large spill of organic contaminants of 1,4-dioxane in 1978 was more accurate than the result of preceding minimum relative entropy-based studies. The same peak also appeared in the tetrahydrofuran and diethyl ether distributions approximately within the range of the retardation factor derived from the fraction of organic carbon.

Application of data assimilation in groundwater hydrology; Characterization of hydraulic heterogeneity of hydrogeological structure based on in-situ data

Onoe, Hironori

Keisan Kogaku, 24(1), p.3851 - 3854, 2019/01

In this study, inverse analysis using observed data of pumping test was carried for confirmation of the applicability of inverse analysis method of groundwater flow based on in-situ data. Target of this inverse analysis was spatial distribution of hydrogeological heterogeneity of the fault. Inverse analysis had been applied to the area around the Mizunami Underground Research Laboratory, which is constructed by the Japan Atomic Energy Agency in order to construct scientific and technological basis for geological disposal of High-level Radioactive Waste. As a result of this study, the estimated results of inverse analysis are consistent with previous study result, and it was concluded that inverse analysis using hydraulic response due to pumping test is effective for hydrogeological characterization in deep underground.

Development of a back analysis method for the estimation of in situ stress based on the measured convergence in the Horonobe Underground Research Laboratory

Aoyagi, Kazuhei; Kamemura, Katsumi*; Nago, Makito*; Sugawara, Kentaro*; Matsubara, Makoto*

Proceedings of ITA-AITES World Tunnel Congress 2017 (WTC 2017) (USB Flash Drive), 10 Pages, 2017/06

An in situ stress state is one of the important factors in the design of deep underground facility of high-level radioactive waste disposal repository. This study establishes a practical and effective method for estimating in situ stress state on the basis of the measured convergence during gallery excavation. The convergence was measured in various directions of the loop gallery at 350m depth of the Horonobe Underground Research Laboratory; this allows determination of the stress state corresponding to the rock mass deformation behavior in an approximately 120 m* 200 m area. To estimate in situ stress state around that area, a back analysis method considering the existence of faults and fractures around the gallery was developed. The analyzed results showed a good agreement with the trend of in situ stress state estimated from hydraulic fracturing method.

Evaluation of mechanical properties and microstructure in ion-irradiated surface layer

Naoe, Takashi*; Futakawa, Masatoshi; Naito, Akira*; Kogawa, Hiroyuki; Ikeda, Yujiro; Motohashi, Yoshinobu*

JSME International Journal, Series A, 48(4), p.280 - 285, 2005/10

Target vessel materials used in spallation neutron source will be exposed to proton and neutron irradiation and mercury immersion environments. In order to evaluate the surface degradation of the vessel candidate materials due to such environment, the triple-ion beam irradiation taking the spallation reaction into account and mercury immersion tests were carried out. Mechanical properties of the gradient surface layer ware evaluated by the inverse analysis with multi-layer model that considers distribution of surface characteristic was applied to the load and depth curves measured by using the instrumented indentation machine. Transmission electron microscopic observations ware performed to evaluate the changes of microstructure in irradiated surface layer using focused ion-beam cut micro-specimen. It was confirmed that the ductility loss is enhanced by the irradiation and mercury immersion, and simulated stress and strain curves of the ion-irradiated surface layer ware adequately in good agreement with the curves of experimental equivalent neutron-irradiated material.

Mechanical characterization of austenitic stainless steel ion irradiated under external stress

Ioka, Ikuo; Futakawa, Masatoshi; Naito, Akira; Nanjo, Yoshiyasu*; Kiuchi, Kiyoshi; Naoe, Takashi*

Journal of Nuclear Materials, 329-333(Part2), p.1142 - 1146, 2004/08

https://doi.org/10.1016/j.jnucmat.2004.04.038

no abstracts in English

Relationship between tensile curve and indentation load-depth curve for a Ni-base alloy with microstructures by cold work and aging

Yamamoto, Junichiro*; Futakawa, Masatoshi; Kurata, Yuji; Naoe, Takashi*

Nihon Kikai Gakkai Kanto Shibu Ibaraki Koenkai (2002) Koen Rombunshu, p.1 - 2, 2002/09

no abstracts in English

None

; Saegusa, Hiromitsu

JNC TY7400 2000-004, 62 Pages, 2000/05

JNC-TY7400-2000-004.pdf:1.45MB

None

Amounts of particulate radionuclides and their reaction constants in radionuclide migration test using undisturbed samples of aerated sandy soil layers

Ogawa, Hiromichi; Takebe, Shinichi;

JAERI-Research 94-002, 12 Pages, 1994/07

JAERI-Research-94-002.pdf:0.61MB

no abstracts in English

Material properties degradation of radiation shielding lead glasses by laser irradiation

Wakui, Takashi; Yamasaki, Kazuhiko*; Futakawa, Masatoshi

no journal, , 

Pulsed Nd:YAG laser was irradiated to two radiation shielding glasses with the different lead content and a lead-free glass. Although no irradiation damage of the lead-free glass was visually confirmed in the laser irradiation condition of this study, the irradiation damage in the lead glasses could be recognized and the lead glass with the high lead content tends to cause the higher irradiation damage. Vickers hardness, elastic modulus and fracture toughness were evaluated by indentation technique with a Vickers indenter were 82-75%, 90-80% and 71-65% of the lead-free glass, respectively. The yield stresses evaluated by the inverse analysis using Kalman's filter based on load-depth curve obtained by the indentation technique with a spherical indenter were 87-67% of the lead-free glass. The yield stress of the irradiation damage area of the lead glass with the low lead content decreased to 74% of unirradiated area.