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JAEA Reports

Development of technique for acquiring fracture void structure data for a single fracture and acquisition of hydraulic/mass transport properties in a fracture

Sato, Hisashi*; Sawada, Atsushi; Takayama, Yusuke

JAEA-Research 2020-012, 37 Pages, 2020/11


In the safety assessment of the geological disposal of high-level radioactive waste, it is important to fully understand the permeability and mass transport properties of actual fractures when setting parameters for permeability and mass transport properties of fractures. Permeability and mass transport properties of a fracture are affected by the void structure of the fracture. Therefore, it is necessary not only to conduct a hydraulic test but also to evaluate hydraulic properties based on the void structure of the fracture. Therefore, the purpose of this study is to develop a technique to acquire a three-dimensional void structure of a fracture from fracture surface shape data, and to obtain a dataset of three- dimensional void structure data and hydraulic data of the fracture. Specifically, we made a transparent replica sample of fracture and measure the fracture surface shape data in the exact coordinates. The three-dimensional void structure data was constituted from fracture surface shape data in the same coordinates. In addition, we conducted a permeability test and tracer test for the same sample to obtain a permeability and mass transport properties of the fracture. To assess the validity of the acquired data, we compared it with the apertures evaluated based on different methods. As a result, the average aperture from the fracture void structure was almost same as the average aperture acquired by different methods, from the above that the test result was validated.

JAEA Reports

Technical design of the pressure-resistant chamber for open inspections of the storage containers of nuclear fuel materials

Marufuji, Takato; Sato, Takumi; Ito, Hideaki; Suzuki, Hisashi; Fujishima, Tadatsune; Nakano, Tomoyuki

JAEA-Technology 2019-006, 22 Pages, 2019/05


Radioactive contamination incident occurred at Plutonium Fuel Research Facility (PFRF) in Oarai Research and Development Institute, Japan Atomic Energy Agency on June 6, 2017. During inspection work of storage container containing nuclear fuel materials, the PVC bag packaging in the storage container ruptured when a worker opened the lid in the hood, and a part of contents was spattered over the room. The cause of the increase of internal pressure of the storage container was gas generation by alpha radiolysis of the epoxy resin mixed with nuclear fuel materials. Opening inspection of about 70 similar containers stored in PFRF has been planned to confirm the condition of the contents and to stabilize the stored materials containing organic compounds. For safe and reliable open inspection of the storage containers with high internal pressure in the glove box, it is necessary to develop a pressure-resistant chamber in which the storage containers are opened and the contents are inspected under gastight condition. This report summarizes the concerns and countermeasures of the chamber design and the design results of the chamber.

Journal Articles

Progress report of Japanese simulation research projects using the high-performance computer system Helios in the International Fusion Energy Research Centre

Ishizawa, Akihiro*; Idomura, Yasuhiro; Imadera, Kenji*; Kasuya, Naohiro*; Kanno, Ryutaro*; Satake, Shinsuke*; Tatsuno, Tomoya*; Nakata, Motoki*; Nunami, Masanori*; Maeyama, Shinya*; et al.

Purazuma, Kaku Yugo Gakkai-Shi, 92(3), p.157 - 210, 2016/03

The high-performance computer system Helios which is located at The Computational Simulation Centre (CSC) in The International Fusion Energy Research Centre (IFERC) started its operation in January 2012 under the Broader Approach (BA) agreement between Japan and the EU. The Helios system has been used for magnetised fusion related simulation studies in the EU and Japan and has kept high average usage rate. As a result, the Helios system has contributed to many research products in a wide range of research areas from core plasma physics to reactor material and reactor engineering. This project review gives a short catalogue of domestic simulation research projects. First, we outline the IFERC-CSC project. After that, shown are objectives of the research projects, numerical schemes used in simulation codes, obtained results and necessary computations in future.

Journal Articles

Vertical and lateral transport of particulate radiocesium off Fukushima

Otosaka, Shigeyoshi; Nakanishi, Takahiro; Suzuki, Takashi; Sato, Yuhi; Narita, Hisashi*

Environmental Science & Technology, 48(21), p.12595 - 12602, 2014/11

 Times Cited Count:20 Percentile:60.12(Engineering, Environmental)

From August 2011 to July 2013, a sediment trap was deployed at 100 km east of the Fukushima Daiichi Nuclear Power Plant and sinking particles were collected. Sinking flux of $$^{137}$$Cs decreased over time with seasonal fluctuation. The $$^{137}$$Cs fluxes were mainly affected by two principal modes. One was a rapid sinking of radiocesium-bound particles (moderate mode). This mode was dominant especially in the early post-accident stage, and was presumed to establish the distribution of radiocesium in the offshore seabed. Another was the secondary transport of particles attributed to turbulence near the seabed and was observed in winter (turbulence mode). Although the latter process would not drastically change the distribution of sedimentary radiocesium, attention should be paid as this key process redistributing the accident-derived radiocesium may cumulatively affect the long-term distribution.

Journal Articles

R&D status on water cooled ceramic breeder blanket technology

Enoeda, Mikio; Tanigawa, Hisashi; Hirose, Takanori; Nakajima, Motoki; Sato, Satoshi; Ochiai, Kentaro; Konno, Chikara; Kawamura, Yoshinori; Hayashi, Takumi; Yamanishi, Toshihiko; et al.

Fusion Engineering and Design, 89(7-8), p.1131 - 1136, 2014/10

 Times Cited Count:17 Percentile:84.87(Nuclear Science & Technology)

The development of a Water Cooled Ceramic Breeder (WCCB) Test Blanket Module (TBM) is being performed as one of the most important steps toward DEMO blanket in Japan. Regarding the fabrication technology development using F82H, the fabrication of a real scale mockup of the back wall of TBM was completed. Also the assembling of the complete box structure of the TBM mockup and planning of the pressurization testing was studied. The development of advanced breeder and multiplier pebbles for higher chemical stability was performed for future DEMO blanket application. From the view point of TBM test result evaluation and DEMO blanket performance design, the development of the blanket tritium simulation technology, investigation of the TBM neutronics measurement technology and the evaluation of tritium production and recovery test using D-T neutron in the Fusion Neutronics Source (FNS) facility has been performed.

Journal Articles

Gamma-ray dose analysis for ITER JA WCCB-TBM

Sato, Satoshi; Tanigawa, Hisashi; Hirose, Takanori; Enoeda, Mikio; Ochiai, Kentaro; Konno, Chikara

Fusion Engineering and Design, 89(9-10), p.1984 - 1988, 2014/10

 Times Cited Count:1 Percentile:10.7(Nuclear Science & Technology)

In order to evaluate nuclear properties of the ITER JA WCCB-TBM (Water Cooled Ceramic Breeder Test Blanket Module) and ensure that the design conforms to the nuclear regulation for licensing, nuclear analyses have been performed for the WCCB-TBM including flame, shield, pipe-forest, bio-shield and AEU (Ancillary Equipment Unit). Nuclear analyses are performed with the Monte Carlo code MCNP5.14, activation code ACT-4 and Fusion Evaluated Nuclear Data Library FENDL-2.1. MCNP geometry input data of the TBM is created from CAD data with the automatic conversion code GEOMIT, and other geometry input data is created by manually. By adopting the dog-leg gaps, decay $$gamma$$-ray dose rate can be drastically reduced and hands-on access is possible for shield. Detailed calculation results will be presented in this symposium.

Journal Articles

Characterization and storage of radioactive zeolite waste

Yamagishi, Isao; Nagaishi, Ryuji; Kato, Chiaki; Morita, Keisuke; Terada, Atsuhiko; Kamiji, Yu; Hino, Ryutaro; Sato, Hiroyuki; Nishihara, Kenji; Tsubata, Yasuhiro; et al.

Journal of Nuclear Science and Technology, 51(7-8), p.1044 - 1053, 2014/07

 Times Cited Count:9 Percentile:65.28(Nuclear Science & Technology)

For safe storage of zeolite wastes generated by treatment of radioactive saline water at the Fukushima Daiichi Nuclear Power Station, properties of the Herschelite adsorbent were studied and its adsorption vessel was evaluated for hydrogen production and corrosion. Hydrogen production depends on its water level and dissolved species because hydrogen is oxidized by radicals in water. It is possible to evaluate hydrogen production rate in Herschelite submerged in seawater or pure water by taking into account of the depth effect of the water. The reference vessel of decay heat 504 W with or without residual pure water was evaluated for the hydrogen concentration by thermal hydraulic analysis using obtained fundamental properties. Maximum hydrogen concentration was below the lower explosive limit (4 %). The steady-state corrosion potential of a stainless steel 316L increased with absorbed dose rate but its increase was repressed by the presence of Herschelite. At 750 Gy/h and $$<$$60$$^{circ}$$C which were values evaluated at the bottom of the vessel of 504 W, the localized corrosion of SUS316L contacted with Herschelite would not immediately occur under 20,000 ppm of Cl$$^{-}$$ concentration.

Journal Articles

The Proposals relevant to seepage flow simulation in rockmass around tunnel under unsaturated condition; Method for estimating unsaturated seepage parameters of stones and setting of boundary condition on tunnel wall

Imai, Hisashi*; Amemiya, Kiyoshi*; Matsui, Hiroya; Sato, Toshinori; Saegusa, Hiromitsu; Watanabe, Kunio*

Doboku Gakkai Rombunshu, C (Chiken Kogaku) (Internet), 69(3), p.285 - 296, 2013/07

The more accurate understanding and appropriate control of unsaturated area around tunnel excavated in deep rock-mass are required, for the geological isolation of radioactive waste project and also underground rock cavern storage project of liquefied petroleum gas. The numerical simulation of seepage flow is usually conducted to understand and evaluate the unsaturated zone around tunnel. The unsaturated parameters (such as moisture characteristic curve and relative permeability) and appropriate control of boundary condition are indispensable for the simulation. Authors developed methodology to measure unsaturated parameters utilizing the measuring method conventionally applied to soils and showed the efficiency of the method via a laboratory experiment. The idea of combining seepage face condition and flow rate fixed condition was derived, and the efficiency was shown in an model simulation. The two developments enabled the accurate estimation and understanding the evolution of unsaturated zone around tunnel.

Journal Articles

Simultaneous measurements of a single fracture surface morphology and aperture distribution by an optical method

Sato, Hisashi; Sawada, Atsushi

Dai-13-Kai Iwa No Rikigaku Kokunai Shimpojiumu Koen Rombunshu (CD-ROM), p.501 - 506, 2013/01

The authors have developed the fracture surface geometry measurement method applied by the optical measurement system of a transparent fracture replica specimen, under the same conditions as hydraulic test. Fracture surface geometry measured by the optical method shows closer shape by an alternative method, laser displacement meter. This method require to be improved, because noisy error at local points and at the edge of the specimen was found. The fracture surface geometry data is useful to correlate transmissivity estimated from aperture data based on local cubic law. The transmissivity is successfully correlated by taking account for effects of fracture slope onto transmissivity and length along flow paths.

Journal Articles

Safe storage of zeolite adsorbents used for treatment of accident-generated water at Fukushima Daiichi Power Station

Yamagishi, Isao; Nagaishi, Ryuji; Terada, Atsuhiko; Kamiji, Yu; Kato, Chiaki; Morita, Keisuke; Nishihara, Kenji; Tsubata, Yasuhiro; Ji, W.*; Fukushima, Hisashi*; et al.

IAEA-CN-211 (Internet), 5 Pages, 2013/01

Since the accident at Fukushima Daiichi Nuclear Power Station, a large amount of radioactive contaminated water has been generated to cool damaged reactor cores. Adsorption of cesium with zeolite-like media was employed for treatment of this contaminated saline water. As spent zeolite media are highly radioactive, their safe storage is a pressing issue. Japan Atomic Energy Agency has extensively conducted R&D on the management of secondary wastes produced by the operation of the treatment system. Subjects on the safe storage of spent zeolites include the analysis of their characteristics and the evaluation of effectiveness of the present safety measures in consideration of decay heat emission and hydrogen generation by water radiolysis as well as durability of vessels exposed to saline. Preliminary results obtained are described in the present paper.

JAEA Reports

An Evaluation of fracture characteristic for replica specimen casted by granite artificial tensile fracture

Sato, Hisashi; Sawada, Atsushi

JAEA-Research 2011-052, 55 Pages, 2012/02


In order to obtain the hydraulic property, mass transport property and three-dimensional fracture void geometry which need for elucidate the permeability and mass transport phenomena in a single fracture, we conducted a flow test, measurement of fracture shape, aperture measurement by optical method, tracer test by optical method for three transparent replica specimens. As a result, the flow rate of two-dimensional seepage flow analysis based on LCL became about 1.5 to 2 times of the flow test results, which results was consistent with previously reported results. To investigate the influence of fracture shape for the flow analysis results, corrected the transmissivity using the acquired data of aperture distribution and fracture shape data. As a results, the fracture permeability by applying the corrected transmissivity considering local slope of the fracture was decreased which is closer to the flow test results.

Journal Articles

Dependence of fracture geometry and spatial variation in pressure on hydraulic conductivity in rock fractures

Kishida, Kiyoshi*; Hosoda, Takashi*; Sawada, Atsushi; Sato, Hisashi; Nakashima, Shinichiro*; Yasuhara, Hideaki*

Harmonising Rock Engineering and the Environment, p.1327 - 1330, 2011/10

Although it is generally known that a natural rock fracture indicates a complex aperture distribution, the fracture is an ideal representation of the parallel plate model. The cubic law is applied to evaluate the hydraulic properties of fractured rock. From several previous research works, it is known that the cubic law can be applied when the Reynolds number is less than 1.0 and that the advection term can basically be ignored in such fracture flows. In this research work, two-dimensional seepage flow analyses, using the authors' proposed 2D model which is considered with the advection term, are carried out for single fracture hydro-conductivity experiments under conditions which allow for the application of the cubic law. From the numerical results, the validity of the 2D model is discussed along with the local Reynolds number and the application of the cubic law.

Journal Articles

Optical measurement of the salinity distribution by saltwater intrusion experiment

Oda, Yoshihiro; Takasu, Tamio*; Sato, Hisashi; Sawada, Atsushi; Watahiki, Takanori*

Doboku Gakkai Rombunshu, C (Chiken Kogaku) (Internet), 67(2), p.186 - 197, 2011/04

Because of the density difference between fresh groundwater and saline groundwater, the groundwater behaves complicated flow. It is well known that the expected barrier functions such as candidate buffer materials and others for high level radioactive waste geological isolation are inhibited by the saline water. The simulations have been required to evaluate the groundwater flow, because the available data by in-situ investigation of the saline and fresh ground water flows is very limited. In the simulation, the complex coupled process of advection-dispersion, seepage flow and density drive flow should be implemented in the simulation codes. The extensive verification studies have been done for modeling and simulation codes until now, but those results were compared only with qualitative experimental data. For the quantitative evaluations, we developed the quantitative measurement technique by optical method for saltwater intrusion, especially for the saltwater concentration distribution in transition zone, on laboratory experiment. We have obtained the quantitative data of the shape of saltwater wedge and saltwater concentration distribution at both transient and steady states.

JAEA Reports

Geometrical properties of tension-induced fractures in granite

Sato, Hisashi; Yasuhara, Hideaki*; Sawada, Atsushi

JAEA-Research 2010-069, 45 Pages, 2011/03


Considering a safe, long-term sequestration of energy byproducts such as high level radioactive wastes, it is of significant importance to well-constrain the hydraulic and transport behavior of targeted permeants within fractured rocks. Specifically, fluid flow within low-permeability crystalline rock masses (e.g., granite) is often dominated by transport in through-cutting fractures, and thus careful considerations are needed on the behavior. There are three planes along that granites fail most easily under tension, and those may be identified as the rift, grain, and hardway planes. In this research, geometrical properties of tension-induced fractures were evaluated. Results show that rift planes are less rougher than the other planes of grain and hardway, and grain planes are generically rougher than the other planes of rift and hardway.

JAEA Reports

Study on flow and mass transport through fractured sedimentary rocks (Joint research)

Shimo, Michito*; Kumamoto, So*; Ito, Akira*; Karasaki, Kenji*; Sawada, Atsushi; Oda, Yoshihiro; Sato, Hisashi

JAEA-Research 2010-040, 57 Pages, 2010/11


In safety analysis of geological disposal of the high-level nuclear waste, it is important to evaluate appropriately the mass transport characteristics of the bedrock as the natural barrier. Especially, it has been found that the porosity of the rock matrix is high and fractured zones are developing and therefore the mass transport characteristics will be the mixture of those for porous media and the fractured media. In this work, we conducted, (1) a study on the method to mine out the rock block sample of tens of-centimeter to maximum 1 m scale, (2) a study on a method of the tracer test using a rock block sample and a series of scoping analysis. We also examined the uncertainty associated the hydrogeological model using a method combining a forward and inverse analysis, based on the various type of data sets obtained at Horonobe site, such as the temperature distribution and hydraulic head and salinity distribution.

JAEA Reports

Advection dispersion and density flow simulation for salinity distribution on the transition zone of saltwater intrusion experiment

Oda, Yoshihiro; Watahiki, Takanori*; Sato, Hisashi; Sawada, Atsushi

JAEA-Research 2010-020, 23 Pages, 2010/08


For the geological disposal of high level radioactive waste, it is important to know the groundwater flow to evaluate the geological isolation system. Simulation codes are used for the evaluation of the saline groundwater flow and distribution, because various and a lot of investigations and experiments are needed. At in-situ, simulation codes have to solve advection-dispersion flow coupling with density flow which occurs by the density difference between saline and fresh groundwater. But the results of laboratory experiments are qualitative data, then the verification cannot be done in quantitatively. The quantitative data of saltwater intrusion experiment, then we try to simulate saltwater intrusion by Dtransu2D-EL code which can calculate advection-dispersion flow coupled with density flow. Between the results of the simulation and the experiments, the toe point of wedge by the simulation shows good coincidence, but the top point is not good coincidence. As for the transition zone of saltwater intrusion, the band width of the experimental result decrease from the toe to the top, but the simulation result shows countertrend.

JAEA Reports

Conceptual design of the SlimCS fusion DEMO reactor

Tobita, Kenji; Nishio, Satoshi*; Enoeda, Mikio; Nakamura, Hirofumi; Hayashi, Takumi; Asakura, Nobuyuki; Uto, Hiroyasu; Tanigawa, Hiroyasu; Nishitani, Takeo; Isono, Takaaki; et al.

JAEA-Research 2010-019, 194 Pages, 2010/08


This report describes the results of the conceptual design study of the SlimCS fusion DEMO reactor aiming at demonstrating fusion power production in a plant scale and allowing to assess the economic prospects of a fusion power plant. The design study has focused on a compact and low aspect ratio tokamak reactor concept with a reduced-sized central solenoid, which is novel compared with previous tokamak reactor concept such as SSTR (Steady State Tokamak Reactor). The reactor has the main parameters of a major radius of 5.5 m, aspect ratio of 2.6, elongation of 2.0, normalized beta of 4.3, fusion out put of 2.95 GW and average neutron wall load of 3 MW/m$$^{2}$$. This report covers various aspects of design study including systemic design, physics design, torus configuration, blanket, superconducting magnet, maintenance and building, which were carried out increase the engineering feasibility of the concept.

Journal Articles

Measurement of a single fracture with heterogeneous aperture distribution by optical method and evaluation of flow characteristics

Sato, Hisashi; Sawada, Atsushi

Doboku Gakkai Rombunshu, C, 66(3), p.487 - 497, 2010/07

The high resolution, 0.15 mm spacing, fracture aperture distribution data, tracer migration data with hydraulic test data under the same conditions were obtained by using optical measurement method of 100 mm $$times$$ 100 m transparent replica specimen, making a duplicate copy of rock fracture. This series of experimental data is useful for verifying the previous studies conducted by using mainly numerical method that showed the characteristics of in-plane heterogeneity of a single fracture and the effect of one onto hydraulic phenomena. For example, it was reported that the two-dimensional numerical simulation with assuming that the local transmissivity might be calculated from measured aperture data by a cubic law is overestimated the flow rate larger than hydraulic test result. In this study the similar result was obtained.

JAEA Reports

Study on flow and mass transport through fractured sedimentary rocks, 3

Shimo, Michito*; Kumamoto, So*; Ito, Akira*; Karasaki, Kenji*; Sawada, Atsushi; Oda, Yoshihiro; Sato, Hisashi

JAEA-Research 2009-060, 70 Pages, 2010/03


It is important for safety assessment of HLW geological disposal to evaluate groundwater flow and mass transport in deep underground appropriately. Though it is considered that the mass transport in sedimentary rock occurs in pores between grains mainly, fractures of sedimentary rock can be main paths. In this study the following three tasks were carried out: (1) laboratory hydraulic and tracer experiments using the rock cores of Wakkanai formation, (2) a study on the tracer test and sampling technique for the larger scale, (3) a study on the reduction technique of uncertainty of the hydrogeological models using data from surface-based investigation. On the block scale tracer test technique, the sampling technique using wire saw and tracer test technique using block samples were suggested. As for the reduction technique of uncertainty of the hydrogeological model, availability of the information other than pressure data, such as the temperature and salinity and all, were presented.

Journal Articles

A Study of hydraulic properties in a single fracture with in-plane heterogeneity; An Evaluation using optical measurements of a transparent replica

Sawada, Atsushi; Sato, Hisashi

Nuclear Engineering and Technology, 42(1), p.9 - 16, 2010/02

Experimental studies for evaluating fracture were conducted by using transparent replica of a single fracture, in order to obtain data for contributing to the methodology improving how we define representative parameter values used for a parallel plate fracture model. Quantitative aperture distribution and tracer concentration data were obtained by measuring the attenuation of transmitted light through the fracture, in high spatial resolution. The representative aperture values evaluated from the multiple measurement methods, such as arithmetic mean of aperture distribution, transport aperture, average aperture evaluated from fracture void volume measurement, converged to a unique value, which indicates the accuracy of this experimental study. The aperture data was employed for studying the validity of numerical simulation under the assumption of local cubic law and showed that the calculated flow rate through the fracture is 10% - 100% larger than hydraulic test results.

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