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Journal Articles

A Scaling approach for retention properties of crystalline rock; Case study of the in-situ long-term sorption and diffusion experiment (LTDE-SD) at the $"A$sp$"o$ Hard Rock Laboratory in Sweden

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

Water Resources Research, 57(11), 20 Pages, 2021/11

This paper focuses on the scaling approach for sorption and diffusion parameters from laboratory to in-situ conditions using the dataset of LTDE-SD experiment performed at the $"A$sp$"o$ HRL. The near-surface heterogeneities at both fracture surface and rock matrix could be evaluated by conceptual model with high porosity and diffusivity, and sorption capacity, and their gradual change at the near-surface zones. The modelling results for non-sorbing Cl-36 and weak-sorbing Na-22 could validate the model concept and the parameter estimation of porosity and diffusivity, by considering the disturbed zone of 5 mm thickness with gradual parameter changes. The De values of these cationic and anionic tracers showed typical cation excess and anion exclusion effects. The modelling results for high sorbing tracers (Cs-137, Ra-226, Ni-63 and Np-237) with different sorption mechanism could confirm the validity of the scaling approaches of Kd values as a function of particle size and their relation to the near-surface disturbances.

Journal Articles

Application of probabilistic fracture mechanics to reactor pressure vessel using PASCAL4 code

Lu, K.; Katsuyama, Jinya; Li, Y.; Yoshimura, Shinobu*

Journal of Pressure Vessel Technology, 143(2), p.021505_1 - 021505_8, 2021/04

 Times Cited Count:0 Percentile:0(Engineering, Mechanical)

Journal Articles

Permeability measurement for macro-fractured Horonobe mudstone

Kamata, Kento*; Nara, Yoshitaka*; Matsui, Hiroya; Ozaki, Yusuke

Dai-15-Kai Iwa No Rikigaku Kokunai Shimpojiumu Koen Rombunshu (Internet), p.205 - 209, 2021/01

When considering the projects such as radioactive waste disposal, it is important to evaluate the confinement performance of underground substances in rock mass. However, the change in permeability of macro-fractured mudstone has not been sufficiently studied. Therefore, in this study, we investigated its effect on permeability by introducing a macro-fracture into a cylindrical specimen of mudstone distributed in the Horonobe area, Hokkaido. First, the hydraulic conductivity was measured by subjecting a specimen with a macro-fracture introduced by a brazilian test to a falling head permeability test. After that, it was compared with the hydraulic conductivity of the intact specimen measured by the transient pulse method. As a result, it was confirmed that the hydraulic conductivity was increased by about one order due to the introduction of macro-fracture. The increase rate of hydraulic conductivity obtained from the results of this research was smaller than that of previous researches using granite and basalt.

Journal Articles

Poroelastic hydraulic-response of fractured mudstone to excavation in the Horonobe URL; As an indicator of fracture hydraulic-disconnectivity

Ozaki, Yusuke; Ishii, Eiichi; Sugawara, Kentaro*

Extended abstract of International Conference on Coupled Processes in Fractured Geological Media; Observation, Modeling, and Application (CouFrac 2020) (Internet), 4 Pages, 2020/11

We perform the numerical simulation of the response of hydraulic head observed in HDB-6 during the excavation of the Horonobe URL to verify the existence of low effective permeable domain in the subsurface. The low permeable domain as an intact rock due to the low hydraulic fracture connectivity is estimated to exist in the deep domain while the permeability of the shallow domain is relatively high due to the hydraulic fracture connectivity there. Our simulation shows that the observed hydraulic head is affected by the Mandel-Cryer effect due to the hydrogeological structure and the effect for the duration of over years requires the low permeability as an intact rock in the deep domain. These results verify the existence of the low effective permeable domain in the deep subsurface estimated by the previous study.

JAEA Reports

Review and evaluation on the surface area of vitrified products of high-level waste; Surface area increase factors due to fracturing and their bases for the performance assessment of geological disposal

Igarashi, Hiroshi

JAEA-Review 2020-006, 261 Pages, 2020/09

JAEA-Review-2020-006.pdf:4.42MB

A literature review was conducted on the increase in surface area of vitrified products of HLW due to the fracturing caused by cooling during glass pouring process and by mechanical impact, from the perspective of a parameter of the radionuclide release model in the performance assessment of geological disposal system studied overseas. The review was focused on the value of surface area increase factor set as a parameter in the model, the experimental work to evaluate an increase in surface area, and how the parameters on surface area were determined based on the experimental results. The surface area obtained from the experiments executed in Japan was also discussed in comparison with the overseas studies. On the basis of the investigation, the effects of various conditions on the surface area were studied, such as a diameter of vitrified product, cooling condition during and after the glass pouring, impact on vitrified products during their handling, environment after the closure of disposal facility, and others. The causes of fracturing are associated with the phenomena or events in the waste management process such as production, transport, storage, and disposal. The surface area increase factors set in the nuclide release model of the glass and their bases were reviewed. In addition, the measured values and the experimental methods for surface increase factors published so far were compared. Accordingly, the methods for measuring surface area as the bases were identified for these factors set in the models. The causes of fracturing and features of these factors were studied with respect to the relation with the waste management process. The results from the review and assessment can contribute to the expanding the knowledge for the conservative and realistic application of these factors to performance assessment, and to the developing and upgrading of safety case as a consequence.

Journal Articles

Constraint effect on fracture mechanics evaluation for an under-clad crack in a reactor pressure vessel steel

Shimodaira, Masaki; Tobita, Toru; Takamizawa, Hisashi; Katsuyama, Jinya; Hanawa, Satoshi

Proceedings of ASME 2020 Pressure Vessels and Piping Conference (PVP 2020) (Internet), 7 Pages, 2020/08

In JEAC 4206 which prescribes the methodology for assessing the structural integrity of reactor pressure vessels (RPVs), an under-clad crack (UCC) at the inner surface of RPV is postulated, and it is required that the fracture toughness of RPV steels is higher than stress intensity factor for at the crack tip during the pressurized thermal shock event. In the present study, to investigate the effect of cladding on the fracture toughness, we performed three-point bending fracture toughness tests and finite element analyses (FEAs) for an RPV steel containing an UCC or a surface crack, and the constraint effect for UCC was also discussed. As the result, we found that the fracture toughness for UCC was considerably higher than that for surface crack. On the other hand, the FEAs showed that the cladding decreased the constraint effect for UCC.

Journal Articles

Extension of PASCAL4 code for probabilistic fracture mechanics analysis of reactor pressure vessel in boiling water reactor

Lu, K.; Katsuyama, Jinya; Li, Y.

Proceedings of ASME 2020 Pressure Vessels and Piping Conference (PVP 2020) (Internet), 10 Pages, 2020/08

Journal Articles

Four-point-bend tests on high-burnup advanced fuel cladding tubes after exposure to simulated LOCA conditions

Narukawa, Takafumi; Amaya, Masaki

Journal of Nuclear Science and Technology, 57(7), p.782 - 791, 2020/07

 Times Cited Count:2 Percentile:62.87(Nuclear Science & Technology)

Journal Articles

Recent verification activities on probabilistic fracture mechanics analysis code PASCAL4 for reactor pressure vessel

Lu, K.; Katsuyama, Jinya; Li, Y.; Miyamoto, Yuhei*; Hirota, Takatoshi*; Itabashi, Yu*; Nagai, Masaki*; Suzuki, Masahide*; Kanto, Yasuhiro*

Mechanical Engineering Journal (Internet), 7(3), p.19-00573_1 - 19-00573_14, 2020/06

Journal Articles

Improvements on evaluation functions of a probabilistic fracture mechanics analysis code for reactor pressure vessels

Lu, K.; Katsuyama, Jinya; Li, Y.

Journal of Pressure Vessel Technology, 142(2), p.021208_1 - 021208_11, 2020/04

 Times Cited Count:3 Percentile:65.8(Engineering, Mechanical)

Journal Articles

Guideline on probabilistic fracture mechanics analysis for Japanese reactor pressure vessels

Katsuyama, Jinya; Osakabe, Kazuya*; Uno, Shumpei*; Li, Y.; Yoshimura, Shinobu*

Journal of Pressure Vessel Technology, 142(2), p.021205_1 - 021205_10, 2020/04

 Times Cited Count:1 Percentile:31.67(Engineering, Mechanical)

no abstracts in English

JAEA Reports

Visualization of fractures in an excavation damaged zone in the Horonobe Underground Research Laboratory, 2 (Joint research)

Aoyagi, Kazuhei; Chen, Y.*; Ishii, Eiichi; Sakurai, Akitaka; Miyara, Nobukatsu; Ishida, Tsuyoshi*

JAEA-Research 2019-011, 50 Pages, 2020/03

JAEA-Research-2019-011.pdf:3.48MB

In this research, we performed the resin injection experiment at the 350 m Gallery of Horonobe Underground Research Laboratory in order to identify the distribution of fractures induced around the gallery owing to excavation. We also observed the rock cores obtained around the resin injection borehole under ultraviolet light. As a result, the extent of the development of EDZ fracture was 0.9 m from the gallery wall. In the depth within 0.4 m from the gallery wall, the density of the EDZ fracture is higher than the depth more than 0.4 m from the gallery wall. As a result of the analysis on the fracture aperture by image processing, the fractures with a large aperture (1.02 mm in maximum) were observed within 0.3 m from the gallery wall, while the maximum aperture was 0.19 mm in the depth more than 0.3 m from the gallery wall.

Journal Articles

Fracture limit of high-burnup advanced fuel cladding tubes under loss-of-coolant accident conditions

Narukawa, Takafumi; Amaya, Masaki

Journal of Nuclear Science and Technology, 57(1), p.68 - 78, 2020/01

 Times Cited Count:1 Percentile:23.13(Nuclear Science & Technology)

Journal Articles

Permeability measurement for macro-fractured granite using water including clay

Nara, Yoshitaka*; Kato, Masaji*; Sato, Tsutomu*; Kono, Masanori*; Sato, Toshinori

Proceedings of 5th ISRM Young Scholars' Symposium on Rock Mechanics and International Symposium on Rock Engineering for Innovative Future (YSRM 2019 and REIF 2019) (USB Flash Drive), 6 Pages, 2019/12

It is important to understand the long-term migration of radionuclides considering carious rock engineering projects such as the geological disposal of radioactive wastes. The network of fractures and pores in a rock mass can play important roles as the pathway of the fluid flow of rock. Usually groundwater contains fine-grained minerals such as clays. It is probable that the accumulation of the fine-grained minerals occurs in a fracture if the groundwater flows in a fracture in a rock. In this study, we have conducted the permeability measurement using water including clays. Specifically, we used a macro-fractured granite as a rock sample, and investigated the change of the permeability under the flow of the water including clays. It was shown that the hydraulic conductivity decreased with elapsed time.

Journal Articles

Visualization of fractures induced around the gallery wall in Horonobe Underground Research Laboratory

Aoyagi, Kazuhei; Chen, Y.*; Ishii, Eiichi; Sakurai, Akitaka; Ishida, Tsuyoshi*

Proceedings of 5th ISRM Young Scholars' Symposium on Rock Mechanics and International Symposium on Rock Engineering for Innovative Future (YSRM 2019 and REIF 2019) (USB Flash Drive), 6 Pages, 2019/12

In the excavation of a repository for high-level radioactive waste (HLW) disposal, it is important to understand the hydro-mechanical characteristics of the Excavation Damaged Zone (EDZ) induced around the gallery because EDZ can lead to the migration pathway of radionuclides. Thus, we performed the resin injection experiment at the 350 m gallery of Horonobe Underground Research Laboratory in Japan to investigate the characteristics of fractures induced around the gallery wall in excavation. In the experiment, we developed a low viscosity resin mixed with a fluorescent substance and injected to the borehole drilled about 1 m in length. After the experiment, we overcored around the injection borehole. The observation on the cut surface of the overcore under ultraviolet light revealed that the fractures were distributed within 0.8 m from the gallery wall. Fractures are interconnected each other in particular within 0.25 m from the niche wall. Furthermore, fractures with large aperture (about 1.0 mm) were developed in that region. These observed results will be fundamental information for understanding of the fracturing process in the EDZ.

Journal Articles

Behavior of high-burnup advanced LWR fuel cladding tubes under LOCA conditions

Narukawa, Takafumi; Amaya, Masaki

Proceedings of International Nuclear Fuel Cycle Conference / Light Water Reactor Fuel Performance Conference (Global/Top Fuel 2019) (USB Flash Drive), p.912 - 921, 2019/09

Journal Articles

Enhancement of permeability activated by supercritical fluid flow through granite

Nohara, Tsuyoshi; Uno, Masaoki*; Tsuchiya, Noriyoshi*

Geofluids, 2019, p.6053815_1 - 6053815_16, 2019/08

 Times Cited Count:1 Percentile:0.02(Geochemistry & Geophysics)

Amphibole-plagioclase thermometry was applied to estimate the temperature of a glassy vein as approximately 700. The results of observations of the rock core revealed that of supercritical fluid flow was microfracture filling with hornblende and plagioclase. The current high permeability was recognized to be microfracture network. A high-angle fracture of chlorite filling in combination with an open fracture was recognized as characteristics of a high-permeability type.

Journal Articles

Application of probabilistic fracture mechanics methodology for Japanese reactor pressure vessels using PASCAL4

Lu, K.; Katsuyama, Jinya; Li, Y.; Yoshimura, Shinobu*

Proceedings of 2019 ASME Pressure Vessels and Piping Conference (PVP 2019) (Internet), 9 Pages, 2019/07

Journal Articles

Effect of coolant water temperature of ECCS on failure probability of RPV

Katsuyama, Jinya; Masaki, Koichi; Lu, K.; Watanabe, Tadashi*; Li, Y.

Proceedings of 2019 ASME Pressure Vessels and Piping Conference (PVP 2019) (Internet), 7 Pages, 2019/07

For reactor pressure vessel (RPV) of pressurized water reactor, temperature of coolant water in emergency core cooling system (ECCS) may have influence on the structural integrity of RPV during pressurized thermal shock (PTS) events. Focusing on a mitigation measure to raise the coolant water temperature of ECCS for aged RPVs in order to reduce the effect of thermal shock due to PTS events, we performed thermal hydraulic analyses and probabilistic fracture mechanics analyses by using RELAP5 and PASCAL4, respectively. From the analysis results, it was shown that the failure probability of RPV was dramatically reduced when the coolant temperature in accumulator as well as high and low pressure injection systems (HPI/LPI) was raised, although raising the coolant temperature of HPI/LPI only did not cause reduction in the failure probability.

153 (Records 1-20 displayed on this page)