Sato, Tomonori; Hata, Kuniki; Kaji, Yoshiyuki; Ueno, Fumiyoshi; Inoue, Hiroyuki*; Taguchi, Mitsumasa*; Seito, Hajime*; Tada, Eiji*; Abe, Hiroshi*; Akiyama, Eiji*; et al.
JAEA-Review 2021-001, 123 Pages, 2021/06
In the implement of the decommissioning of Fukushima Daiichi Nuclear Power Station (1F), there are many problems to be solved. Specially, the mitigation of the aging degradation by the corrosion of the structural materials is important to implement the decommissioning safely and continuously. However, there are limited data for the environmental factors of corrosion in 1F, and the condition of 1F is continuously changing. So, the literature data for the water radiolysis and the corrosion under irradiation are listed as the database of corrosion under irradiation in this report. And the new obtained radiolysis and corrosion data, which have not been reported in the literature and will be required in the decommissioning of 1F, are reported.
Omori, Atsushi*; Akiyama, Eiji*; Abe, Hiroshi*; Hata, Kuniki; Sato, Tomonori; Kaji, Yoshiyuki; Inoue, Hiroyuki*; Taguchi, Mitsumasa*; Seito, Hajime*; Tada, Eiji*; et al.
Zairyo To Kankyo, 69(4), p.107 - 111, 2020/04
To evaluate the effect of oxidants, which are formed by radiolysis of water under gamma ray irradiation, on the corrosion of a carbon steel in humid environment, ozone was introduced as a model oxidant in to humidity-controlled air at 50C in a thermo-hygrostat chamber. Corrosion monitoring was performed by using an Atmospheric Corrosion Monitor-type (ACM) sensor consisting of a carbon steel anode and an Ag cathode. The output current of the ACM sensor was increased with the increase in relative humidity and it was obviously increased with the increase in the introduced ozone concentration at each relative humidity. The results indicate that ozone accelerates the corrosion of the carbon steel. The effect of ozone on the corrosion acceleration is attributed to the fast reduction reaction and fast dissolution reaction in to water compared to that of oxygen.
Yamashita, Susumu; Tada, Kenichi; Yoshida, Hiroyuki; Suyama, Kenya
Nihon Genshiryoku Gakkai Wabun Rombunshi, 17(3/4), p.99 - 105, 2018/12
In order to reveal melt relocation behaviors of core internals phenomenologically and to reduce the uncertainties of the melt relocation analysis in existing SA analysis codes, in JAEA, the numerical simulation code for melt relocation and accumulation behaviors based on computational fluid dynamics named JUPITER has been developed. In this paper, to consider the estimation method for fuel debris composition and its re-criticality, we performed the melt accumulating and spreading simulation to the pedestal region by JUPITER and also performed re-criticality analysis by Monte Carlo Codes for Neutron Transport Calculations based on Continuous Energy and Multi-group Methods (MVP) using detailed fuel debris composition data obtained by JUPITER. From the coupled analysis on fuel debris distribution by JUPITER and MVP, we had prospects for a detailed possibility of re-criticality of fuel debris with detailed fuel debris distribution.
Sakuma, Kazuyuki; Kitamura, Akihiro; Malins, A.; Kurikami, Hiroshi; Machida, Masahiko; Mori, Koji*; Tada, Kazuhiro*; Kobayashi, Takamaru*; Tawara, Yasuhiro*; Tosaka, Hiroyuki*
Journal of Environmental Radioactivity, 169-170, p.137 - 150, 2017/04
This paper describes watershed modeling of catchments surrounding the Fukushima Dai-ichi Nuclear Power Plant to understand radio-cesium redistribution by water flows and sediment transport. We extended our previously developed three-dimensional hydrogeological model of the catchments to calculate the migration of radio-cesium in both sediment-sorbed and dissolved forms. The simulations cover the entirety of 2013, including nine heavy rainfall events, as well as Typhoon Roke in September 2011. Typhoons Man-yi and Wipha were the strongest typhoons in 2013 and had the largest bearing on radio-cesium redistribution. The simulated Cs discharge quantities over the nine events in 2013 are in good agreement with field monitoring observations. Deposition mainly occurs on flood plains and points where the river beds broaden in the lower basins, and within dam reservoirs along the rivers. Differences in Cs discharge ratios between the five basins are explained by differences in the initial fallout distribution within the basins, the presence of dam reservoirs, and the input supply to watercourses. It is possible to use these simulation results to evaluate future radioactive material distributions in order to support remediation planning.
Tada, Hiroyuki*; Kumasaka, Hiroo*; Saito, Akira*; Nakaya, Atsushi*; Ishii, Takashi*; Fujita, Tomo; Sugita, Yutaka; Nakama, Shigeo; Sanada, Masanori*
Doboku Gakkai Rombunshu, F2 (Chika Kukan Kenkyu) (Internet), 73(1), p.11 - 28, 2017/03
This study examined the mechanical characteristics of rock segments and backfill materials and analyzed the stability of the drift that is supported by the rock segments and gravel backfill. The results confirmed the technical aspects of the formation of the rock segments and the effectiveness of the planned efforts to further reduce the amount of cement used.
Kitamura, Akihiro; Kurikami, Hiroshi; Sakuma, Kazuyuki; Malins, A.; Okumura, Masahiko; Machida, Masahiko; Mori, Koji*; Tada, Kazuhiro*; Tawara, Yasuhiro*; Kobayashi, Takamaru*; et al.
Earth Surface Processes and Landforms, 41(12), p.1708 - 1726, 2016/09
Sediment erosion and transport processes that are considered to be important in predicting the future radioactive material distribution through sediment-sorbed form in Fukushima Prefecture are simulated. Since large portion of the sediment is considered to be supplied into the rivers, it is important to trace their migration process in terms of each river basin. We choose five river basins, namely the Odaka, the Ukedo, the Maeda, the Kuma, and the Tomioka, from north to south, because of their importance in contamination aspects and prediction studies. The results are summarized as comprehensive dataset of sediment migration for particular river basins in typical typhoon events that account for the most of annual soil erosion. Detail calculations implemented for the amount of sediment supplied in to the river, deposited on river and dam beds, and exported to the ocean.
Ozaki, Yusuke; Matsui, Hiroya; Kuwabara, Kazumichi; Tada, Hiroyuki*; Sakurai, Hideyuki*; Kumasaka, Hiroo*; Goke, Mitsuo*; Kobayashi, Shinji*
JAEA-Research 2016-007, 125 Pages, 2016/06
In Mizunami Underground Research Laboratory (MIU), the stress analysis of fractured rock have been performed with crack tensor model. In MIU, a reflooding test is performed at 500m stage. In this study, stress analysis of rock during submerging process of the tunnel is performed by using crack tensor model. The deformation of the rock under different water levels in the tunnel is simulated. The stress condition by high pressure due to inflow of groundwater into tunnel is also estimated. These simulation are performed under assumption that groundwater does not permeate into rock for the estimation of maximum pressure acting on the rock. The stress analysis with consideration of permeation of groundwater into rock is also conducted for the estimation of stress condition after the diffusion of water pressure in tunnel. The results of these analyses lead the conclusion that the pressure of the rock reaches the groundwater pressure near the face of tunnel when the tunnel is submerged.
Takayama, Yusuke; Sato, Toshinori; Sanada, Hiroyuki; Tada, Hiroyuki*; Kumasaka, Hiroo*; Fukuda, Tsuyoshi*; Kobayashi, Shinji*
JAEA-Research 2015-003, 102 Pages, 2015/07
In the rock mechanical study in the Mizunami Underground Research Laboratory Project, the development of the evaluation method for the excavation damaged zone due to excavation of shafts and research galleries is one of the important issues. In this study, three-dimensional excavation analysis is conducted. Crack tensor used in these analysis were measured using the data collected in wall surface observation in study tunnels such as the horizontal tunnels to a depth of 500 m. The results of analysis were compared with existing measurements at a depth of 500 m obtained using in-situ strain meters. The excavation analysis using crack tensor and initial stress obtained from the Phase I and Phase II were carried out to examine the influence of crack tensor and initial stress on the results of analysis.
Sanada, Hiroyuki; Sato, Toshinori; Tanno, Takeo*; Hikima, Ryoichi*; Tada, Hiroyuki*; Kumasaka, Hiroo*; Ishii, Takashi*; Sakurai, Hideyuki*
JAEA-Research 2014-006, 124 Pages, 2014/06
Japan Atomic Energy Agency has been implementing the Mizunami Underground Research Laboratory (MIU) Project in order to develop the comprehensive investigation techniques for the geological environment and the engineering techniques to construct a deep underground laboratory in crystalline rock. In the rock mechanical study in the MIU Project, the development of the evaluation method for the excavation damaged zone due to excavation of shafts and research galleries is one of the important issues. In this report, crack tensor was calculated using the tunnel wall mapping and rock mechanical test results in the shaft and research galleries in the MIU. Two dimension excavation analysis was conducted at the Ventilation Shaft and GL -500 m Sub Stage using the calculated crack tensor at GL -500 m. Based on calculated crack tensor at GL 500 m, validation of the crack tensor at GL -500 m estimated during Phase I was verified. Relative error of crack tensor was calculated in order to examine variation of relative error to the scale of observation areas.
Sanada, Hiroyuki; Hikima, Ryoichi; Tanno, Takeo; Sato, Toshinori; Goke, Mitsuo*; Tada, Hiroyuki*; Kumasaka, Hiroo*
Proceedings of ITA-AITES World Tunnel Congress 2013 (WTC 2013)/39th General Assembly, p.855 - 860, 2013/05
Japan Atomic Energy Agency (JAEA) has been implementing the Mizunami Underground Research Laboratory (MIU) Project for the R&D of geological disposal of High-level Radioactive Waste (HLW) in granite. The MIU Project has been divided into three overlapping phases: Surface-based Investigation Phase (Phase I), Construction Phase (Phase II), and Operation Phase (Phase III). In this paper, FEM analysis using crack tensor theory at the MIU was carried out in order to estimate deformation around the horizontal tunnel for investigations and construction during Phase III, and to confirm the validity of FEM analysis results including parameter settings using fracture information from the vertical borehole drilled during Phase I. The relationship between statistical observations on tunnel walls and pilot boreholes was used to estimate the crack tensor for the investigated area. FEM analysis in this work described the increase of stress in concrete liners due to decrease of Young's Modulus compared to Phase I. Since investigations during Phase II could effectively detected high angle fractures, which couldn't be satisfactorily detected during Phase I, the crack tensor was improved using the Phase II results. Predictions and applicability of the analysis method are to be confirmed with in situ experiments during Phase III.
Tada, Hiroyuki*; Kumasaka, Hiroo*; Saito, Akira*; Nakaya, Atsushi*; Ishii, Takashi*; Sanada, Masanori; Noguchi, Akira*; Kishi, Hirokazu*; Nakama, Shigeo; Fujita, Tomo
Dai-13-Kai Iwa No Rikigaku Kokunai Shimpojiumu Koen Rombunshu (CD-ROM), p.133 - 138, 2013/01
The authors have been developing methods for constructing tunnels using the minimum quantities of cement-type support materials in high-level radioactive waste disposal facilities and advancing research and development about the technical formation of rock segment using low alkaline mortar. In this study, the mechanical characteristic values concerning the rock segment and backfill materials were examined. The stability analysis of tunnel supported by the rock segment and backfilling with gravel were performed. Technical formation and effectiveness of the alternative supports planned for further reduction in cement influence was confirmed from a study result above-mentioned.
Tanno, Takeo; Sato, Toshinori; Sanada, Hiroyuki; Hikima, Ryoichi; Matsui, Hiroya; Tada, Hiroyuki*; Goke, Mitsuo*; Kumasaka, Hiroo*; Ishii, Takashi*
JAEA-Research 2012-002, 86 Pages, 2012/03
The Crack tensor model which is a kind of equivalent continuum model has been studied in rock mechanical investigation in the MIU. The fractured rock mass is modeled as the elastic continuum model with the crack tensor. In this study, crack tensor based on the geological observation in the MIU project was calculated, and REV (Representative Elementary Volume) in the shafts and research galleries was studied based on the relative error of the crack tensor. The correlation between the crack density, the trace length of crack and the trace of crack tensor and the rock mass classification was also studied.
Tanno, Takeo; Sato, Toshinori; Matsui, Hiroya; Sanada, Hiroyuki; Kumasaka, Hiroo*; Tada, Hiroyuki*
Dai-41-Kai Gamban Rikigaku Ni Kansuru Shimpojiumu Koenshu (CD-ROM), p.185 - 190, 2012/01
The Japan Atomic Energy Agency (JAEA) is conducting the MIzunami Underground research laboratory (MIU) project in order to develop comprehensive geological investigation and engineering techniques for deep underground applications (e.g. geological disposal of HLW). This modelling study has a two-fold objective, to contribute to the evaluation of the mechanical stability of shaft and research drifts, and to plan the future studies. A crack tensor model, a method of an equivalent continuum model, has been studied at the MIU. In this study, the relationship between the estimated crack tensor parameters and the rock mass classification was revealed.
Hayashi, Katsuhiko; Noguchi, Akira; Kishi, Hirokazu; Kabayashi, Yasushi*; Nakama, Shigeo; Fujita, Tomo; Naito, Morimasa; Tada, Hiroyuki*; Kumasaka, Hiroo*; Goke, Mitsuo*; et al.
JAEA-Research 2010-057, 101 Pages, 2011/03
Cement-type materials that are used for supports or grouting at high-level radioactive waste disposal facilities leach into the groundwater and create a highly alkaline environment. Of concern in highly alkaline environments are the alteration of bentonite used as buffers or backfill materials, and of surrounding rock mass, and the increased uncertainty regarding the provision of performance of the disposal system over a long period of time. In this study, to reduce the quantity of cement-type materials that cause highly alkaline environments, technical feasibility of the support structure including the materials which considered the long-term performance of the HLW disposal system are discussed by using knowledge and technology accumulated in JAEA and Shimizu Construction. Moreover, based on the results, the problems remained in the application to the future HLW disposal institution are summarized.
Matsui, Hiroya; Tanno, Takeo; Hirano, Toru*; Goke, Mitsuo*; Kumasaka, Hiroo*; Tada, Hiroyuki*; Ishii, Takashi*
JAEA-Research 2010-043, 87 Pages, 2010/12
The results are as follows (1) For the ventilation shaft at GL-350m, the crack tensor deformation analysis based on FY2004 work's results showed the calculated displacement was smaller than the measured displacement. A geometrical parameters of fractures in FY2004 work's result was different from one based on geological observation in the shaft. Therefore, the crack tensor of FY2004 work's results seems to be underestimated. (2) Large discontinuities with NE strike and high dipping observed in a shaft were major reason for the difference of crack tensors determined by borehole investigation from surface and geological observations in a shaft. Therefore, the crack tensor for pilot borehole investigation in a shaft was calculated as well and compared with each results. It was found that the fabric tensor is similar with it of geological observation and the vale was medium. (3) The crack tensor around GL-500m was estimated by relation of statistical quantities for fractures between GL-300m and GL-500m. Consequently, the deformation analysis based on the estimated crack tensor showed an increase in convergence and stress in the support system compared to FY2004 work's results.
Kitada, Kazuya*; Kobune, Masafumi*; Adachi, Wataru*; Yazawa, Tetsuo*; Saito, Hiroyuki; Aoki, Katsutoshi; Mizuki, Junichiro; Ishikawa, Kenya*; Hiranaga, Yoshiomi*; Cho, Yasuo*
Chemistry Letters, 37(5), p.560 - 561, 2008/05
Seno, Yasuhiro; Nakama, Shigeo; Sato, Toshinori*; Goke, Mitsuo*; Tada, Hiroyuki*; Sakurai, Hideyuki*
JAEA-Research 2007-081, 120 Pages, 2008/01
A 3D Crack Tensor Model analysis was carried out to predict the rock mass behavior of the complex (articulated) section at -500 m. Properties were chosen based on the Rock Mechanics Model constructed in the Surface-based Investigation Phase (Phase I). The Virtual Fracture Model was applied to analyze the change the hydraulic conductivity.
Goke, Mitsuo*; Tada, Hiroyuki*; Seno, Yasuhiro; Nakama, Shigeo; Sato, Toshinori
Tonneru Kogaku Rombunshu, 16, p.35 - 45, 2006/11
no abstracts in English
Sato, Toshinori; Mikake, Shinichiro; Nakama, Shigeo; Seno, Yasuhiro; Mori, Takayuki*; Iwano, Keita*; Goke, Mitsuo*; Tada, Hiroyuki*
Proceedings of 7th International Conference on Analysis of Discontinuous Deformations (ICADD-7) (CD-ROM), p.245 - 256, 2005/12
Two one-thousand meter deep shafts and research galleries at several levels will be excavated in granite for the Mizunami Underground Research Laboratory (MIU) project. Research on the deep geological environment in this project will provide the basis for Research and Development on geological disposal of high-level radioactive waste. The site of MIU project is located in Mizunami, Gifu, in the central part of the main island of Japan. By July 2003, entrances to the shafts were constructed, and excavation of lower part of shaft entrance was started in March 2004. Current status (September 2005) of construction is excavation of the shafts to a depth of 150 m has been done. Mechanical investigations including hydraulic fracturing test and laboratory tests on core samples were performed, and numerical analysis using continuous model and discontinuous model; MBC (Micro-mechanics based continuum model), Crack tensor model and FRACOD (fracture propagation code), were also performed to predict mechanical stability of openings and support systems, and rock mass behavior around openings. In this analysis EDZ (Excavation Damaged Zone) due to blasting and excavation step were considered in same cases. This paper describes the current status of Mizunami Underground Research Laboratory for crystalline rock and the results of prediction for rock mass behavior around the deep underground openings using some analytical methods. Measurements during shaft sinking and future plan of investigations in the URL are also describes in this paper.
Goke, Mitsuo*; Horita, Masakuni*; Tada, Hiroyuki*
JNC TJ7400 2004-007, 102 Pages, 2004/02
Tono Geoscience Center (TGC), Japan Nuclear Cycle Development Institute (JNC) conducts the Mizunami Underground Research Laboratory (MIU) project in order to develop the comprehensive investigation techniques for the geological environment and the engineering techniques in the deep underground application. The purposes of this work were to contribute to the rock mechanical modeling for MIU project. We proposed an analytical method of modeling of excavation damaged zone. The crack tensor analytical model was applied to analyze the rock stress in consideration of the existence of excavation damaged zone as a research drift and a shaft were excavated. The virtual fracture model was applied to the hydraulic conductivity change analysis.The results are as follows:1) As compared with analytical result without excavation damaged zone, the crack tensor stress analysis in consideration of excavation damaged zone showed that the convergence of a shaft and a drift increased and the maximum value of principal stress decreased, while the safety factor distribution was almost changeless.2) As compared with analytical result without excavation damaged zone, the hydraulic conductivity change analysis in consideration of excavation damaged zone showed the maximum increase rate of hydraulic conductivity increased remarkably.3) As the stiffness decreased in excavation damaged zone, the convergence of a shaft and a drift increased, the maximum value of principal stress decreased, and the maximum increase rate of hydraulic conductivity increased. Especially, in analytical case supposed that new cracks parallel to perimeter of a drift broke out in excavation damaged zone, the maximum increase rate of hydraulic conductivity was up to 5000 times.4) As the stiffness of rock mass decreased by taking into the existence of excavation damaged zone, the convergence reduction effect increased, and the stress in support parts increased.