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Journal Articles

Predictive modeling of a simple field matrix diffusion experiment addressing radionuclide transport in fractured rock. Is it so straightforward?

Soler, J. M.*; Neretnieks, I.*; Moreno, L.*; Liu, L.*; Meng, S.*; Svensson, U.*; Iraola, A.*; Ebrahimi, K.*; Trinchero, P.*; Molinero, J.*; et al.

Nuclear Technology, 208(6), p.1059 - 1073, 2022/06

 Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)

The SKB Task Force is an international forum on modelling of groundwater flow and solute transport in fractured rock. The WPDE experiments are matrix diffusion experiments in gneiss performed at the ONKALO underground facility in Finland. Synthetic groundwater containing several conservative and sorbing tracers was injected along a borehole interval. The objective of Task 9A was the predictive modelling of the tracer breakthrough curves from the WPDE experiments. Several teams, using different modelling approaches and codes, participated in this exercise. An important conclusion from this exercise is that the modelling results were very sensitive to the magnitude of dispersion in the borehole opening, which is related to the flow of water. Focusing on the tails of the breakthrough curves, which are more directly related to matrix diffusion and sorption, the results from the different teams were more comparable.

Journal Articles

Effects of fine-scale surface alterations on tracer retention in a fractured crystalline rock from the Grimsel Test Site

Tachi, Yukio; Ito, Tsuyoshi*; Akagi, Yosuke*; Sato, Hisao*; Martin, A. J.*

Water Resources Research, 54(11), p.9287 - 9305, 2018/11

 Times Cited Count:5 Percentile:37.45(Environmental Sciences)

Effects of fine-scale surface alterations on radionuclide migration in fractured crystalline rocks were investigated by a comprehensive approach coupling a series of laboratory tests, microscopic observations and modelling, using a single fractured granodiorite sample from the Grimsel Test Site, Switzerland. Laboratory tests including through-diffusion, batch sorption and flow-through tests using five tracers indicated that tracer retention was consistently in the sequence of HDO, Se, Cs, Ni, Eu, and as well as showing the existence of a diffusion-resistance layer near the fracture surface, cation excess and anion exclusion effects for diffusion. Microscale heterogeneities in structural properties around the fracture were clarified quantitatively by coupling X-ray CT and EPMA. A three layer model including weathered vermiculite, foliated mica and undisturbed matrix layers, and their properties such as porosity, sorption and diffusion parameters, could provide a reasonable interpretation for breakthrough curves and concentration distributions near fracture surface of all tracers, measured in flow-through tests.

JAEA Reports

Confirmation tests for Warm Pre-stress (WPS) effect in reactor pressure vessel steel (Contract research)

Chimi, Yasuhiro; Iwata, Keiko; Tobita, Toru; Otsu, Takuyo; Takamizawa, Hisashi; Yoshimoto, Kentaro*; Murakami, Takeshi*; Hanawa, Satoshi; Nishiyama, Yutaka

JAEA-Research 2017-018, 122 Pages, 2018/03

JAEA-Research-2017-018.pdf:44.03MB

Warm pre-stress (WPS) effect is a phenomenon that after applying a load at a high temperature fracture does not occur in unloading during cooling, and then the fracture toughness in reloading at a lower temperature increases effectively. Engineering evaluation models to predict an apparent fracture toughness in reloading are established using experimental data with linear elasticity. However, there is a lack of data on the WPS effect for the effects of specimen size and surface crack in elastic-plastic regime. In this study, fracture toughness tests were performed after applying load-temperature histories which simulate pressurized thermal shock transients to confirm the WPS effect. The experimental results of an apparent fracture toughness tend to be lower than the predictive results using the engineering evaluation models in the case of a high degree of plastic deformation in preloading. Considering the plastic component of preloading can refine the engineering evaluation models.

Journal Articles

Experimental and statistical study on fracture boundary of non-irradiated Zircaloy-4 cladding tube under LOCA conditions

Narukawa, Takafumi; Yamaguchi, Akira*; Jang, S.*; Amaya, Masaki

Journal of Nuclear Materials, 499, p.528 - 538, 2018/02

 Times Cited Count:5 Percentile:57.41(Materials Science, Multidisciplinary)

Journal Articles

Excavation damaged zone inferred by geophysical surveys on drift floor of Horonobe URL

Tokiwa, Tetsuya*; Aoyagi, Kazuhei; Fujita, Tomo

Rock Mechanics and Rock Engineering; From the Past to the Future (EUROCK 2016), p.901 - 906, 2016/07

Journal Articles

Modeling damage processes in laboratory tests at the Horonobe Underground Research Laboratory

Asahina, Daisuke*; Aoyagi, Kazuhei; Tsusaka, Kimikazu*; Houseworth, J.*; Birkholzer, J.*

Proceedings of 8th Asian Rock Mechanics Symposium (ARMS-8) (USB Flash Drive), 9 Pages, 2014/10

Journal Articles

Development of structural reliability evaluation method for aged piping considering uncertainty of seismic motions

Sugino, Hideharu*; Ito, Hiroto*; Onizawa, Kunio; Suzuki, Masahide

Nihon Genshiryoku Gakkai Wabun Rombunshi, 4(4), p.233 - 241, 2005/12

The purpose of this research is to establish the reliability evaluation method of aged nuclear power components for seismic events from a viewpoint of long-term use of the existing light water reactor nuclear power plants. For this purpose, we developed a piping failure probability evaluation code "PASCAL-SC" based on probabilistic fracture mechanics, and a probabilistic seismic hazard evaluation code "SHEAT-FM" for calculating the seismic occurrence probability of a plant site, paying attention to aging such as fatigue crack progress by the stress corrosion cracking and seismic load in primary coolant piping system. We proposed the reliability evaluation method of aged piping for seismic events by combination of these codes. Using this method, we evaluated the reliability of a weld line in the PLR(Primary Loop Recirculation system) piping of the BWR model plant for seismic events.

Journal Articles

Analytical study on biaxial strength of structural ceramics under tension-compression condition

Hanawa, Satoshi; Ishihara, Masahiro; Motohashi, Yoshinobu*

Key Engineering Materials, 297-300, p.40 - 46, 2005/11

no abstracts in English

Journal Articles

Study on brittle fracture model for multiaxial tensile stress

Hanawa, Satoshi; Ishihara, Masahiro; Motohashi, Yoshinobu*

Zairyo, 54(2), p.201 - 206, 2005/02

no abstracts in English

Journal Articles

Application of microstructure based brittle fracture model to biaxial strength of graphite materials

Hanawa, Satoshi; Ishihara, Masahiro; Shibata, Taiju

Transactions of 17th International Conference on Structural Mechanics in Reactor Technology (SMiRT-17) (CD-ROM), 6 Pages, 2003/08

From a viewpoint of advanced design method of graphite components, it is important to apply the realistic fracture model in the design method. The applicability of the microstructure based brittle fracture model under multiaxial stress condition was, therefore, investigated. The fracture model is possible to treat grain size as well as pore size with fracture mechanics approach taking account of the crystal structure of the graphite. The model was applied to the biaxial strength prediction of near isotropic nuclear graphite using grain/pore related microstructural parameters. Prediction results were compared with biaxial strength data obtained by simultaneous loadings of inner pressure and longitudinal load with thin-walled cylindrical specimen. From this study, it was found that the fracture model predicted fairly good not only mean strength but also strength distribution under biaxial stress condition, and it was concluded that the microstructure based brittle fracture model would be applicable as the advanced design method.

Journal Articles

Effect of interlaminar fracture on mechanical strength of C/C composites

Kojima, Takao; Tachibana, Yukio; Fujimoto, Nozomu; Ishihara, Masahiro

Proceedings of 8th Annual International Conference on Composites Engineering (ICCE/8), p.479 - 480, 2001/00

no abstracts in English

Journal Articles

Understanding of mechanical properties of graphite on the basis of mesoscopic microstructure (Review)

Ishihara, Masahiro; Shibata, Taiju; Takahashi, Tsuneo*; Baba, Shinichi; Hoshiya, Taiji

Proceedings of OECD/NEA 2nd Information Exchange Meeting on Basic Studies in the Field of High-temperature Engineering, p.225 - 241, 2001/00

no abstracts in English

Oral presentation

Effects of heterogeneity at fracture surface for tracer migration in a fractured crystalline rock from the Grimsel Test Site

Tachi, Yukio; Ito, Tsuyoshi; Akagi, Yosuke*; Sato, Hisao*; Martin, A. J.*

no journal, , 

The effects of heterogeneity at fracture surface on radionuclides migration in fractured crystalline rocks was investigated by laboratory migration experiments, microscopic observations and detailed modelling, using a single fractured granodiorite sample from the Grimsel Test Site (GTS), Switzerland. The tracer migration behaviors in fracture and matrix parts were evaluated by series of laboratory experiments including through-diffusion and flow-through experiments. Mineral distributions from fracture surface to matrix were evaluated by X-ray CT, and were validated by comparing the elemental mapping measured by EPMA. Based on the microscopic observations by X-ray CT and EPMA, the aperture and connectivity in fracture and minerals distribution near fracture surface were quantitatively evaluated. The heterogeneous multi-layered model assuming a weathered vermiculite zone, a foliated mica zone and rock matrix was possible to provide a reasonable interpretation for measured breakthrough curves of all tracers.

Oral presentation

Modeling the in-situ long-term sorption and diffusion experiment (LTDE-SD) at the Aspo Hard Rock Laboratory in Sweden; Scaling approach from laboratory to in-situ condition

Tachi, Yukio; Ito, Tsuyoshi; Gylling, B.*

no journal, , 

The in-situ long-term sorption and diffusion experiment (LTDE-SD) at the Aspo Hard Rock Laboratory in Sweden provides valuable dataset to test the scaling approach from laboratory to in-situ condition. The scaling approach developed in the in-situ Long-Term Diffusion (LTD) project at Grimsel Test Site in Switzerland was tested for the LTDE-SD results as part of the SKB Task Force on modeling of groundwater flow and transport of solutes in fractured crystalline rocks. Our modelling approach could account reasonably overall trends for sorption and diffusion of 10 radionuclides, and was then evaluated as being applicable for a wider range of radionuclides and for more complex fracture systems.

Oral presentation

Development and validation of a fracture model for the granite rocks at Mizunami Underground Research Laboratory, Japan

Elena, K.*; Teklu, H.*; Wang, Y.*; Iwatsuki, Teruki; Ozaki, Yusuke

no journal, , 

In this study, Discrete Fracture Network Model (DFN) is built based on the fracture data observed in the Mizunami Underground Research Laboratory. 297 fractures data with discharge is analyzed for the estimation of stochastic quantity under the assumption that those fractures are permeable and have an great impact on the hydraulic conductivity field. Both models of fracture and hydraulic conductivity around the Closure Test Drift at the depth of 500m are generated from derived stochastic models. The hydraulic model is input into the numerical simulation. The matching of calculated and observed inflow into research tunnel indicates the validity of generated model and modeling approach for fractured rock. These results are a part of results in Task C of Decovalex2019.

Oral presentation

PFM analysis code PASCAL-SP for aged piping; New probabilistic evaluation model of weld residual stress

Katsuyama, Jinya; Mano, Akihiro; Yamaguchi, Yoshihito; Li, Y.

no journal, , 

no abstracts in English

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