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JAEA Reports

Development of a new fuel handling machine suitable for an upper inner structure with a slit; The Performance test of a large-sized bearing in Argon gas atmosphere

Chikazawa, Yoshitaka; Usui, Shinichi; Hayafune, Hiroki; Konomura, Mamoru

JAEA-Research 2007-001, 91 Pages, 2007/02

JAEA-Research-2007-001.pdf:9.42MB

In Feasibility Study on Commercialized Fast Breeder Reactor Cycle Systems, Large and Middle scale sodium cooled reactors which have an upper inner structure (UIS) with a slit have been studied for the size reduction of reactor structure. A new fuel handling machine (FHM) which is suitable for the UIS with a slit has been developed in this study. The FHM is required not to contact to UIS under the earthquake condition when its arm is extended into the slit. In the previous study, it is confirmed that the reduction of clearance in bearing of FHM is effective to reduce the deflection of FHM unit. But the general lubricant such as grease can not be used for the bearing because that of FHM will be set in argon gas atmosphere of the reactor vessel. In FY2005, the performance test of large-sized bearing with the selected lubrication specification has been performed in the high temperature argon gas atmosphere.

JAEA Reports

Research on the state-of-the-art of probabilistic safety assessment for non-reactor nuclear facilities (II)

Yoshida, Kazuo; Abe, Hitoshi; Yamane, Yuichi; Tashiro, Shinsuke; Muramatsu, Ken

JAEA-Research 2007-002, 127 Pages, 2007/03

JAEA-Research-2007-002.pdf:6.64MB

Japan Atomic Energy Agency (JAEA) entrusted with a research on the state-of-the-art of probabilistic safety assessment (PSA) of non-reactor nuclear facilities (NRNF) such as fuel reprocessing and fuel fabrication facilities to the Atomic Energy Society of Japan (AESJ). The objectives of this research is to obtain the basic useful information related for establishing the quantitative performance requirement and for risk-informed regulation through qualifying issues needed to be resolved for applying PSA to NRNF. A special committee of "Research on the analysis methods for accident consequence in NFRF" was organized by the AESJ. The research activities of the committee were mainly focused on the analysis method for upper bounding consequences of accidents such as events of criticality, explosion, fire and solvent boiling postulated in NRNF resulting in release of radio active material to the environment. This report summarizes the results of research conducted by the committee in FY 2005.

JAEA Reports

A Study for improvement of the credibility of evaluation method for the long-term dynamical behavior of near-field rock mass

Hiramoto, Masayuki; Kobayashi, Yasushi; Aoyagi, Shigeo*; Miyanomae, Shunichi*; Morita, Atsushi*

JAEA-Research 2007-003, 54 Pages, 2007/03

JAEA-Research-2007-003.pdf:3.67MB

For the study on the long-term stability of near-field rock mass, the following studies were carried out in this report. (1) Inspection of applicability of a valuable-compliance-type constitutive equation that used the measurement data of the existing tunnel. (2) Suggestion of the informatization construction that used a valuable-compliance-type constitutive equation (1) FEM model was developed to estimate the time dependet behavior of rock mass surrounding tunnel. The calculated results such as tunnel convergence and the axial force exerted on tunnel support were compared with the measured results in-situ. It was found that the calculated results reasonably well coincided with the measured results. (2) The informatization construction that used a valuable-compliance-type constitutive equation was suggested. This method will be used for disposal ground construction. It will be led to improving reliability of long-term evaluation after closedown.

JAEA Reports

Development of mechanical coupled analysis technique for the long term behavior of the near field

Nishimura, Mayuka; Tanai, Kenji; Takaji, Kazuhiko*; Shigeno, Yoshimasa*; Shimogochi, Takafumi*

JAEA-Research 2007-004, 87 Pages, 2007/03

JAEA-Research-2007-004.pdf:14.61MB

The 3-D mechanical coupled analysis technique for the near field is developed, upgrading a 2-D non-coupled technique for the buffer material. The analysis object is extended to the disposal gallery and the near field rock, in addition to the EBS. And following problems are approached; (1) modeling the near field rock with the valuable- compliance-type constitutive equation, (2) modeling a degraded behavior of the concrete support, (3) changing the expanding deform method of the overpack corrosion, (4) examining the effect of drainage conditions on water pressure behavior of the near field rock, (5) setting parameters of the backfill material modeled with Sekiguchi-Ohta model. The prototype model is developed adopting the result for the above approaches, excluding a degradation model of concrete support. The result of long term analysis with the prototype model shows a reasonable behavior of the near field that reflects the models of the near field rock and the backfill material.

JAEA Reports

Molecular dynamics simulation study on behavior of metallic ion in molten salt mixture bath

Okamoto, Yoshihiro; Tsuruoka, Takuya*; Yaita, Tsuyoshi; Madden, P. A.*

JAEA-Research 2007-005, 25 Pages, 2007/03

JAEA-Research-2007-005.pdf:1.8MB

Behavior of very small amount of metallic ion in molten alkali chloride mixture melt is very important information in pyrochemical reprocessing of spent nuclear fuels. In the present work, mixing behavior of molten LaCl$$_3$$ in LiCl-KCl eutectic melt was simulated by molecular dynamics simulations. It has been reported that molten pure LaCl$$_3$$ has an 8-fold (LaCl$$_8$$)$$^{5-}$$ structure. The coordination number decreases by mixing with LiCl-KCl eutectic mixture melt and indicates a value close to 6 less than 31%LaCl$$_3$$ composition. It suggests that molten LaCl$$_3$$ has an octahedral coordination structure in the mixture, as shown in molten YCl$$_3$$ systems. In the MD simulation, the mixing effect was different between LiCl and KCl. It is due to high number density of Cl$$^-$$ ion in molten LiCl comparable to molten LaCl$$^3$$ and strong Coulomb force introduced by a small Li$$^+$$ ion.

JAEA Reports

Development of measurement system of aperture and tracer concentration distribution in a single fracture by optical visualization method

Sato, Hisashi; Xiao, J.; Sawada, Atsushi

JAEA-Research 2007-006, 53 Pages, 2007/03

JAEA-Research-2007-006.pdf:6.15MB

It is important to investigate fracture aperture distribution in order to study the influences of heterogeneous aperture distribution onto the fracture hydraulic and mass transport properties. There are several aperture measurement methods, but an optical method has an advantage that measurement resolution is high and tracer movement can be observed. We have developed aperture measurement and tracer movement measuring system by optical method, and have made transparent replica, and measured aperture distribution and tracer concentration distribution. As a result, the optical method was able to confirm the effectiveness of aperture measurement. In addition, the optical method could acquire the tracer concentration distribution which was not disturbed by the influence of heterogeneous aperture distribution.

JAEA Reports

Investigation of the applicability of the model based on the ion exchange reaction for the cesium sorption onto Horonobe sedimentary rocks

Doi, Reisuke; Xia, X.*; Shibata, Masahiro; Kitamura, Akira; Yoshikawa, Hideki

JAEA-Research 2007-007, 21 Pages, 2007/03

JAEA-Research-2007-007.pdf:1.57MB

Assessment for radionuclides sorption onto a rock in deep underground is important for the safety assessment of HLW geological disposal. Distribution coefficient, K$$_{d}$$ is an available parameter to assess the sorption in the current safety assessment. We applied a model that the sorption of Cs is dominated by the ion exchange reaction on illite to experimental results of Cs sorption onto Horonobe sedimentary rocks. The equilibrium concentration of Cs was calculated under the conditions same as those adopted in the experiment to estimate the K$$_{d}$$ value. Comparing the calculated results with the experimental data, the model could explain well the dependence of K$$_{d}$$ values on Cs equilibrium concentration. By using the model, it is possible to assess Cs sorption onto a sedimentary rock. However, some differences were also obtained between the experimental data and the calculated one.

JAEA Reports

Multi-scale analysis of deformation behavior at SCC crack tip, 2 (Contract research)

Kaji, Yoshiyuki; Miwa, Yukio; Tsukada, Takashi; Hayakawa, Masao*; Nagashima, Nobuo*

JAEA-Research 2007-008, 69 Pages, 2007/03

JAEA-Research-2007-008.pdf:25.87MB

The research was carried out to evaluate the validity of the SCC growth data acquired in the IGSCC project based on a mechanistic understanding of SCC. The hardness measured in nano, meso and macro scales was employed as a common index of the strength, and the essential data necessary to understand the SCC propagation behavior were acquired and analyzed that are mainly a size of plastic deformation region and a microstructural information in the region, e.g. data of crystallografy, microscopic deformation and dislocations at the inside of grains and grain boundaries. In this year, we analyzed the state of plastic deformation region at the crack tip of IGSCC under various conditions and investigated relationship between crack growth behavior and stress intensity factor. Especially, we investigated in detail about two different hardened specimens used in the SCC growth tests in the IGSCC project.

JAEA Reports

Investigation concerning influence of cosmic rays on criticality accident alarm system; Relationship between "Single Detection" and cosmic rays

Izaki, Kenji; Suzuki, Hideki; Tsubaki, Hirohiko; Ozeki, Kiyoshi

JAEA-Research 2007-009, 40 Pages, 2007/03

JAEA-Research-2007-009.pdf:4.17MB

Criticality Accident Alarm System (CAAS) has been used in Nuclear Fuel Cycle Engineering Laboratories for about 20 years, and there is occurrence of the abnormal signal called "Single Detection", as an operational problem of CAAS. Radiation Protection Division has investigated the causes affecting "Single Detection", as well as reducing the influence of noises such as electromagnetic waves and power source variations. This report shows the result of the long-term observation with detectors of CAAS and describes that cosmic rays have high possibility to cause "Single Detection".

JAEA Reports

Study on investigation of microbial effects for geological disposal, 1 (Joint research)

Tochigi, Yoshikatsu; Yoshikawa, Hideki; Aoki, Kazuhiro; Yui, Mikazu; Honjo, Hideko*; Haginuma, Masashi*; Kawakami, Yasushi*; Suzuki, Kazunori*

JAEA-Research 2007-010, 51 Pages, 2007/03

JAEA-Research-2007-010.pdf:4.82MB

Results of joint research on Fiscal 2005 between Japan Atomic Energy Agency (JAEA) and Institute of Research and Innovative (IRI) titled as "Study for investigation of microbial effects on geological disposal" are described in this report. The objective of this study is constructing advanced method for examining microbial effect for barrier performance of geological disposal site. In fiscal 2005, groundwater and rock core sample have been collected from drilled well on observation field near Horonobe Underground Research Center of JAEA and chemical analysis for collected ground water have been carried out and sensitivity analysis for existing observed data of groundwater with numerical analysis program code "MINT" considering microbial effect have been carried out.

JAEA Reports

Evaluation of energy deposition to the urinary bladder wall considering radiosensitive basal cells by beta-ray emitters

Watanabe, Yoko; Kinase, Sakae; Saito, Kimiaki

JAEA-Research 2007-011, 19 Pages, 2007/03

JAEA-Research-2007-011.pdf:1.21MB

The present report describes the dose evaluation of the urinary bladder since its absorbed dose from radiopharmaceuticals tends to be higher than other organs. For an accurate dose evaluation, a simple bladder model considering radiosensitive basal cells was used to calculate SAF (specific absorbed fractions) for the basal cells and the whole bladder wall from mono energetic photon and electron sources using Monte Carlo simulation. Furthermore, S values (the mean absorbed doses for the target organ per unit cumulated activity in the source organ) were evaluated for 36 beta-ray emitters. Consequently, considering basal cells and beta particle spectra in the evaluation of absorbed dose for the urinary bladder are very important for an accurate evaluation.

JAEA Reports

Photocatalytic activity of Sulfur-doped TiO$$_{2}$$ fiber under visible light illumination (Joint research)

Takeyama, Akinori; Yamamoto, Shunya; Yoshikawa, Masahito; Hasegawa, Yoshio*; Awatsu, Satoshi*

JAEA-Research 2007-012, 29 Pages, 2007/03

JAEA-Research-2007-012.pdf:3.77MB

The Sol-Gel derived precursor fiber was annealed under hydrogen disulfeid (H$$_{2}$$S) following oxygen atmosphere, Sulfer-doped titanium dioxide (TiO$$_{2}$$) fiber was obtained. Crystal structure of the fiber was identified as anatase phase of TiO$$_{2}$$. The energy band gap of the fiber was narrower by about 0.06 eV than that of anatase, which showed that it could absorb visible light. The fiber contains about 0.58 atomic % of Sulfer, and they located at the oxygen lattice site of TiO$$_{2}$$. Under visible light illumination, the fiber degraded Trichroloethylen (TCE) and produced carbon dioxide (CO$$_{2}$$). This shows Sulfer-doped TiO$$_{2}$$ fiber has the photocatalytic activity under visible light illumination.

JAEA Reports

Behavior on O/M ratio for Am containing MOX fuel

Sato, Isamu; Seki, Takayuki*; Ishi, Yohei; Mondo, Kenji; Yoshimochi, Hiroshi; Tanaka, Kenya

JAEA-Research 2007-013, 63 Pages, 2007/03

JAEA-Research-2007-013.pdf:4.89MB

In air atmosphere, the weight of Am-MOX fuel relatively rapidly increased, which change rate strongly depended on the initial O/M ratio. The lower initial O/M ratio is, the higher the rate is. However, for the other MOX fuel containing little Am, the equivalent behavior have been observed, which indicated that not only Am but also the property of law material powder affected the behavior. The X-ray diffraction pattern change as time goes by was observed, which was a evidence that the O/M ratio change might arise from crystallographic one. The rate of O/M ratio change is a function of water vapor pressure in the atmosphere. If the water vapor pressure would is set to be quite low (ex. $$<$$ 1ppm), the O/M ratio change could effectively been avoided. On a model basis of Am(III) and U(V) existence, we could explain the O/M ratio dependence of the lattice parameter of Am-MOX fuel near O/M ratio, 2.00 better.

JAEA Reports

Performance test of the Japanese ENGIN-X type linear scintillation neutron detector

Nakamura, Tatsuya; Sakasai, Kaoru; Katagiri, Masaki; Birumachi, Atsushi; Hosoya, Takaaki; Soyama, Kazuhiko; Sato, Setsuo*; Shooneveld, E.*; Rhodes, N.*

JAEA-Research 2007-014, 14 Pages, 2007/03

JAEA-Research-2007-014.pdf:1.9MB

The ENGIN-X type linear scintillation neutron detector was manufactured in Japan and the detector performances were evaluated. The ENGIN-X type linear scintillation neutron detector was originally developed by the detector group in Rutherford Appleton Laboratory and the Japanese prototype detector was identical to that which is one of the detector modules installed in the ENGIN-X diffractometer at ISIS pulsed neutron source. The prototype detector can install 240 elements of neutron-sensitive scintillator, where each element has 3 mm in width and 196 mm in length. The prototype detector exhibited a spatial resolution of 3 mm, detection efficiency of 64% for neutrons with wave-lengths of 1.8${AA}$, count uniformity of 6$$sim$$7%, $$^{60}$$Co $$gamma$$ sensitivity of $$sim$$5$$times$$10$$^{-7}$$. Technological transfer to the Japanese manufacturer was done successfully and the mass production of these detectors for the J-PARC project is feasible.

JAEA Reports

Study on a method to evaluate heterogeneity of sedimentary rocks using a forward model, 3 (Contract research)

Hara, Akio*; Hoshi, Kazuyoshi*; Kato, Arata*; Maekawa, Keisuke

JAEA-Research 2007-015, 104 Pages, 2007/03

JAEA-Research-2007-015.pdf:25.1MB

It is very important for performance assessment of high-level radioactive waste disposal to develop a method to estimate heterogeneity of sedimentary rocks. We studied siliceous shale from boreholes in the Horonobe area, and developed a sedimentary process modeling software in order to establish a method to estimate heterogeneity of sedimentary rocks. In this study, we aimed for addition of functions in sedimentary process modeling software and improvement of operability. For the former aim, we added functions which were enable to consider the second sedimentation style and influences by subsidence and upheaval of basement of sedimentary basin at the time of a shoreline movement calculation. And, on the occasion of the output of calculation results, we changed the file format in order to enable to adapt to the current visualization software. For the latter aim, we developed the Graphic User Interface (GUI) to support a work for data input. Using this sedimentary process modeling software with the above-mentioned improvement, we carried out simulations for Horonobe area. For making of input data, we utilized the existing data from geological surveys which were carried out by not only Japan Atomic Energy Agency but the others. Therefore we showed two realizations of geological model of Horonobe area. Moreover, we suggested a possibility of sand deposition in a remote area from accutual boreholes. From these results, we showed an applicability of this modeling methodology.

JAEA Reports

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

Shimo, Michito*; Kumamoto, So*; Maekawa, Keisuke

JAEA-Research 2007-016, 141 Pages, 2007/03

JAEA-Research-2007-016.pdf:20.36MB

It is important for safety assessment of HLW geological disposal to evaluate groundwater flow and mass transport in deep underground accurately. 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. The objective of this study is to establish a conceptual model for flow and mass transport in fractured soft sedimentary rock. In previous study, a series of laboratory hydraulic and tracer tests and numerical analyses were carried out using sedimentary rock specimens obtained from Koetoi and Wakkanai formation. Single natural fractured cores and rock block specimen were used for the tests and analyses. The results indicated that the matrix diffusion played an important role for mass transport in the fractured soft sedimentary rocks. In this study, the following two tasks were carried out: (1) laboratory hydraulic and tracer experiments of rock cores of koetoi and Wakkanai formation obtained at HDB-9, HDB-10 and HDB-11 boreholes and a rock block specimen, Wakkanai formation, obtained at an outcrop in the Horonobe area, (2) a numerical study on the conceptual model of flow and mass transport through fractured soft sedimentary rocks. Non-sorbing tracer experiments using naturally fractured cores and rock block specimens were carried out. Potassium iodide was used as a tracer. The obtained breakthrough curves were interpreted and fitted by using a numerical simulator, and mass transport parameters, such as longitudinal dispersivity, matrix diffusion coefficient, transport aperture, were obtained. Mass transport simulations using a fracture network model, a continuum model and a double porosity model were performed to study the applicability of continuum model and double porosity model for transport in fractured sedimentary rock.

JAEA Reports

Study on simulation of salt accumulation (Joint research)

Fujita, Tomoo; Yui, Mikazu; Suzuki, Hideaki*; Fujisaki, Kiyoshi; Sazarashi, Masami*

JAEA-Research 2007-017, 47 Pages, 2007/03

JAEA-Research-2007-017.pdf:9.27MB

This report describes the results of a joint research entitled "Study on Simulation of Salt Accumulation" which was conducted under the collaboration between the Institute of Research and Innovation and the Japan Atomic Energy Agency. In the experiments for salt accumulation, accumulation of ${it Na$_{2}$SO$_{4}$}$ and ${it CaSO$_{4}$}$ was observed near the heater surface. Based on the facts from experiments, we have made hypothesis for mechanism of salt accumulation, and developed the model for it. Then, we conducted numerical simulations for salt accumulation phenomena under the saturated condition using the geochemical code "PHREEQC". It became clear that salt accumulation behavior can be evaluated qualitatively from these simulations, but quantitative evaluation requires more realistic modeling. Moreover we evaluated salt accumulation phenomena by simulations using coupled thermo - hydro - mechanical and chemical model / code assuming the unsaturated and / or saturated condition. A series of simulations were conducted focusing on accumulation of gypsum, and the result showed that tendency of salt accumulation phenomena was in agreement with that of experiments, but the profile of distribution of accumulated gypsum was not in agreement. In conclusion, it became clear that more realistic boundary condition should be considered and problems on coupled model / code were identified for further study.

JAEA Reports

Hydrothermal experiments using Fe-bentonite, 2; Identification of change of Fe-bentonite under low oxygen and 150$$^{circ}$$C conditions

Suyama, Tadahiro*; Shibata, Masahiro; Ueno, Kenichi; Sasamoto, Hiroshi

JAEA-Research 2007-018, 31 Pages, 2007/03

JAEA-Research-2007-018.pdf:4.79MB

A present study was carried out to understand the long-term behavior of Fe-smectite. The starting material (i.e., Fe-bentonite) was prepared by mixing Na-bentonite (Kunipia-F) with FeCl$$_{2}$$ solution in a controlled-atmosphere glove box (O$$_{2}$$$$<$$1ppm, N$$_{2}$$). The experiments were conducted for 1 year and 20 months at 150$$^{circ}$$C. As the results, it was suggested that a dissolution of Fe-smectite and a generation of secondary material which might precipitate on the layer surface of smectite. However the original smectite structure (i.e., 2:1 type octahedral structure) and the initial characteristic of bentonite (e.g., swelling capacity, ion exchange capacity) were maintained. The generation of non-swelling clay mineral which was observed in the similar experiment at 250$$^{circ}$$C was not identified in the present study by XRD analysis.

JAEA Reports

Study of ageing effect of long-term storage fuel in prototype fast breeder reactor Monju

Kato, Yuko; Umebayashi, Eiji; Okimoto, Yutaka; Okuda, Eiichi; Takayama, Koichi; Ozawa, Takayuki; Maeda, Seiichiro; Matsuzaki, Masaaki; Yoshida, Eiichi; Maeda, Koji; et al.

JAEA-Research 2007-019, 56 Pages, 2007/03

JAEA-Research-2007-019.pdf:6.79MB

In order to resume the System Startup Test (SST) of Monju, replacement fuel have to be loaded in exchange for some of initial fuel now loaded in the core to compensate core reactivity lost by decay of Pu-241 in them. The replacement fuel were being stored either in sodium in an ex-vessel storage tank or in air in a storage rack for about 10 years since their fabrication. The initial fuel were irradiated during the SST which was suspended in the end of 1995 and then stayed being loaded in the sodium-circulated core. As this long-term storage and loading may deteriorate mechanical integrity of the assemblies, a study has been made thoroughly on its thermal-hydraulic, structural and material effects on them that might be caused by irradiation in the core, sodium and mechanical environment. The study has shown that the mechanical integrity of them is well maintained even with this long-term storage and loading.

JAEA Reports

Effect of the concentration of NaNO$$_{3}$$ solution on hydraulic conductivity of compacted bentonite

Mihara, Morihiro; Kobayashi, Ichizo*

JAEA-Research 2007-020, 45 Pages, 2007/03

JAEA-Research-2007-020.pdf:10.2MB

In this study, the dependencies of hydraulic conductivity of the compacted bentonite of which a dry density was 1.8 Mg/m$$^{3}$$ on sodium nitrate concentration were investigated experimentally. The enhancement of hydraulic conductivity was observed using sodium nitrate solution of high concentration. The enhancement of 0$$sim$$2mol/L of the nitrate concentration was significant high. In the solution of $$>$$ 2mol/L nitrate, the hydraulic conductivities were hardly changed. The hydraulic conductivities using the sodium nitrate solution of high concentration, $$>$$ 2mol/L, were less than 10$$^{-11}$$m/s which was required value in the repository to restrict the ground water flow. It was more difficult that nitrate concentration of solution affects hydraulic conductivity of the highly compacted bentonite comparing with the lower compacted density bentonite. It was found that the effects of the viscosities of nitrate solution were small.

JAEA Reports

Requirements for expected performance of closure components in crystalline rock

Fujita, Tomoo; Suyama, Yasuhiro*; Toida, Masaru*

JAEA-Research 2007-021, 41 Pages, 2007/03

JAEA-Research-2007-021.pdf:4.51MB

Based on the results and experiences obtained from the tunnel sealing experiments in the Canadian underground research laboratory in crystalline rock under the collaboration with JNC (now JAEA), this report summarizes the requirements for closure components such as backfilling material and hydraulic plug from the viewpoint of expected barrier performance, taking account of key issues on sealing technologies which have been left open after H12 project. The results of the tunnel sealing experiments indicate that the constructability of closure components and low permeability of the hydraulic plug is well performed. Requirements for the closure components and key issues for further study are identified from the viewpoint of barrier performance considering a range of events related to the sealing and taking account of where these are occurred as well as appropriate countermeasure for them. It is also discussed how to apply these preferable closure components to the scale of repository layout, and further technical issues are then identified.

JAEA Reports

Effect of sulfide on the corrosion behavior of pure copper under anaerobic condition and possibility of super long lifetime for copper overpacks

Taniguchi, Naoki; Kawasaki, Manabu*; Naito, Morimasa

JAEA-Research 2007-022, 64 Pages, 2007/03

JAEA-Research-2007-022.pdf:11.4MB

In general, copper is thermodynamically stable under anaerobic condition, so that corrosion due to water reduction can not be occurred on copper. In the presence of sulfide, however, this property of immunity to corrosion is lost and corrosion as copper sulfide is occured. Therefore, it is necessary to understand the effect of sulfide on the corrosion behavior of copper for using the copper as a material for overpacks. In this study, immersion tests and stress corrosion cracking tests were carried out using synthetic seawater containing sodium sulfide. Based on the experimental results, the possibility of super long lifetime for copper overpacks was discussed. The results were summarized as follows; (1) As the results of the immersion tests of copper in buffer material for 2 years, the corrosion rates became large with increase in the concentration of sodium sulfide. The corrosion rates of copper in sodium sulfide of 0.001M, 0.005M and 0.1M were estimated to be 0.55micro-m/y, 2.2micro-m/y, 15micro-m/y respectively. (2) Corrosion product film with black or dark-gray was formed on the surface of copper specimens, and it was identified as Cu$$_{2}$$S(Chalcocite) by the X-ray diffraction. (3) As the results of stress corrosion cracking experiments by means of slow strain rate technique, copper has little susceptibility to crack initiation in the condition of 0.001M-Na$$_{2}$$S. Obvious cracks were observed in the condition of Na$$_{2}$$S concentration over 0.005M. (4) According to the results of immersion tests and stress corrosion cracking tests, copper overpacks have a potential to accomplish super long lifetime far over 1000years if the sulfide concentration in repository condition is promised to be less than 0.001M because of very low corrosion rate and no stress corrosion cracking.

JAEA Reports

Discussion on sealing performance required in disposal system; Preliminary study on hydraulic analysis of disposal panel

Sugita, Yutaka*; Takahashi, Yoshiaki*; Uragami, Manabu*; Kitayama, Kazumi*; Fujita, Tomoo; Yui, Mikazu

JAEA-Research 2007-023, 70 Pages, 2007/03

JAEA-Research-2007-023.pdf:26.16MB

The sealing performance of a repository is very important for the safety assessment of the geological disposal system for high-level radioactive waste. NUMO and JAEA set up a technical commission to investigate sealing technology in a repository in 2004 following a cooperation agreement between these two organisations. The objectives of this commission were to present a concept of sealing performance required in the disposal system and to direct future R&D for design requirements of closure components (backfilling material, clay plug, etc.). Hydraulic analyses on tunnel intersections were carried out during the first year in 2004. This was expanded into a hydraulic analysis of a complete disposal panel with all tunnels during the second year in 2005. Since the model structure in 2005 was more complicated than the one used in 2004, the concept of equivalent permeability was adopted in and around each tunnel in the hydraulic analyses. Parameters used in the hydraulic analyses were installation positions of clay plugs, permeability of the backfilling material, permeability of disposal tunnel and directions of hydraulic gradient to estimate influences to the analytical results preliminary. Analytical results showed that flow rate in a disposal tunnel was influenced by directions of hydraulic gradient, installation of the clay plug at the both ends of each disposal tunnel and permeability of the main tunnel.

JAEA Reports

Study on diffusion depth of matrix in granitic rock

Tochigi, Yoshikatsu; Kogawa, Noritaka*; Mukai, Satoru*; Jintoku, Takashi*; Sasamoto, Hiroshi; Shibata, Masahiro; Yui, Mikazu

JAEA-Research 2007-024, 27 Pages, 2007/03

JAEA-Research-2007-024.pdf:1.83MB

In the safety assessment of high-level radioactive waste (HLW) geological disposal, it is important to understand diffusion behavior of radionuclides for evaluation of retardation capacity in the host rock. In this study, non steady state diffusion experiments with non-sorbing ion ware carried out using several granitic rock samples of different length and the matrix diffusion depth was evaluated. As the results of experiment, it is confirmed that the non-sorbing ion can diffuse into the unaltered zone of granitic rock at least about 200 mm in depth and almost same diffusion coefficient is estimated for all rock samples independent of length. Based on these results, it is expected that matrix diffusion of nuclides is acting on a scale of several dozens of centimeters in the granitic rock.

JAEA Reports

Neutronics design for power flattening of accelerator-driven system

Iwanaga, Kohei; Nishihara, Kenji; Tsujimoto, Kazufumi; Kurata, Yuji; Oigawa, Hiroyuki

JAEA-Research 2007-025, 42 Pages, 2007/03

JAEA-Research-2007-025.pdf:3.37MB

Japan Atomic Energy Agency (JAEA) promotes research and development of Accelerator-Driven system (ADS) to reduce the burden for conditioning and disposal of the high level radioactive waste by transmuting minor actinide (MA). In the present neutronics design, we investigated several methods to reduce the power peak, and showed the reduction of the temperature of cladding tubes and influence to the beam current. These methods are adjustment of inert matrix content in fuel in each burn-up cycle, multi-region design in terms of plutonium enrichment, pin radius and inert matrix content, modification of the level of the beam window position and height of the central fuel assemblies. As the result, the maximum temperature at the surface of fuel cladding tubes can be reduced by 110 $$^{circ}$$C by combining the adjustment of inert matrix content in each burn-up cycle and multi-regin design in terms of pin radius or inert matrix content.

JAEA Reports

Post-irradiation examinations of inert matrix nitride fuel irradiated in JMTR (01F-51A capsule)

Iwai, Takashi; Nakajima, Kunihisa; Kikuchi, Hironobu; Honda, Junichi; Hatakeyama, Yuichi; Ono, Katsuto; Matsui, Hiroki; Arai, Yasuo

JAEA-Research 2007-026, 75 Pages, 2007/03

JAEA-Research-2007-026.pdf:13.6MB

A plutonium nitiride fuel pin containing inert matrix such as ZrN and TiN was encapsuled in 01F-51A and irradiated in JMTR. Minor actinides are surrogated by plutonium. Average linear powers and burnups were 408W/cm, 30000MWd/t(Zr+Pu)(132000MWd/t-Pu) for (Zr,Pu)N and 355W/cm, 38000MWd/t(Ti+Pu)(153000MWd/t-Pu) for (TiN,PuN). The irradiated capsule was transported to Reactor Fuel Examination Facility and subjected to non-destructive and destructive post irradiation examinations. Any failure was not observed in theirradiated fuel pin. Very low fission gas release rate of about 1.6% was measured. The inner surface of cladding tube did not show any signs of chemical interaction with fuel pellets.

JAEA Reports

Preparation of gadolinium chloride without using corrosive gases

Shibata, Hiroki; Hayashi, Hirokazu; Minato, Kazuo

JAEA-Research 2007-027, 17 Pages, 2007/03

JAEA-Research-2007-027.pdf:1.4MB

For application to the preparation of MA chlorides with high-purity, a preparation method, in which corrosive gas like chlorine or hydrogen chloride and so on was not used, of the chloride from the oxide was developed. The preparation conditions of this method were optimized by carrying out preliminary examinations in which gadolinium was used as surrogate for MA. An anhydrous complex chloride ((NH$$_4$$)$$_2$$GdCl$$_5$$) was obtained by heating an HCl solution dissolving gadolinium sesquioxide (Gd$$_2$$O$$_3$$) and ammonium chloride (NH$$_4$$Cl) under a nitrogen gas flow. An anhydrous GdCl$$_3$$ with high-purity was obtained by heating (NH$$_4$$)$$_2$$GdCl$$_5$$ at 350 degrees under a dynamic vacuum.

JAEA Reports

Study on geological environment model using geostatistics method (Joint research)

Honda, Makoto*; Suzuki, Makoto*; Sakurai, Hideyuki*; Iwasa, Kengo*; Matsui, Hiroya

JAEA-Research 2007-028, 91 Pages, 2007/04

JAEA-Research-2007-028.pdf:17.93MB

The purpose of this study is to develop the geostatistical procedure for modeling geological environments and to evaluate the quantitative relationship between the amount of information and the reliability of the model using the data sets obtained in Phase 1 of the Horonobe Underground Research Laboratory Project. In FY 2006 research, the data obtained from the deep boreholes which were executed in FY 2005 were newly used in addition to the data sets used in the previous study. And the hydrogeological models were built by using the same geostatistical procedure developed in the previous study. The relationship between the amount of information and the reliability of the model was demonstrated as well through a comparison of the models at each step which corresponds to the investigation stage in each FY. Furthermore, in the case of hydro-chemical model, the modeling procedure was applied to each dissolved principal component and their characteristics of distribution were clarified.

JAEA Reports

Hydraulic and migration study of the shallow accessible groundwater in biosphere modeling for HLW disposal

Inagaki, Manabu; Kato, Tomoko; Yoshida, Hideji*; Oyamada, Kiyoshi*; Fukaya, Yukiko*; Suzuki, Yuji*; Oi, Takao

JAEA-Research 2007-029, 81 Pages, 2007/03

JAEA-Research-2007-029.pdf:10.88MB

The project of high-level radioactive waste disposal is in activity for the site selection of HLW disposal facility and the performance assessment should be more site-specific rather than site-generic, where the applicability of the achievement of site-generic study such as second progress report (H12) to the site specific is to be clarified. In the same way, it is necessary for biosphere assessment to incorporate the site specific condition to the model. The exposure pathway or concentration of the radio nuclides should be determined according to the site specific geological condition, for example. In this paper, following topics have been selected to start the study to reflect specific geological condition to the biosphere modeling. (1) The literature survey of international and national approaches and issues relating to the treatment of GBIs within biosphere assessments, (2) To develop methodology to estimate the release point of the deep groundwater to the shallow accessible groundwater. (3) To prepare information to estimate water balance this is, in turn, necessary to assess the dilution and/or dispersion of the radionuclides in the shallow accessible groundwater body.

JAEA Reports

Study of sub-surface disposal concepts for uranium waste, 3

Tsujimura, Seiichi; Funabashi, Hideyuki; Ishibashi, Makoto*; Takase, Toshio*; Kurosawa, Mitsuru*

JAEA-Research 2007-030, 105 Pages, 2007/03

JAEA-Research-2007-030.pdf:7.72MB

Uranium waste has characteristics that it is rarely expected to decay its radioactivity and it is not almost recessary to consider external exposure to radiation from waste package. We studied resonable sub-surface disposal concepts for uranium waste considering the characteristics. It showed feasibility of this system. In 2006, the study was done to evaluate the correlation between dose to the public and the parameter in consideration of the uncertainty of the parameter by comprehensive sensitivity analysis calculating repeatedly dose with the data sets by random sampling in parameter ranges given adequately, because last year's study was an evaluation intended for a limited site. The result was that two parameters, "flow velocity of underground water of repository neighborhood" and "distribution coefficient of uranium in natural barrier", had correlation with dose to the public.

JAEA Reports

Effect of neptunium ions on corrosion of stainless steel in nitric acid solution

Motooka, Takafumi; Ishikawa, Akiyoshi; Numata, Masami; Endo, Shinya; Itonaga, Fumio; Kiuchi, Kiyoshi; Kizaki, Minoru

JAEA-Research 2007-031, 20 Pages, 2007/03

JAEA-Research-2007-031.pdf:2.0MB

An effect of neptunium ions on corrosion of stainless steel in nitric acid solution was investigated by corrosion tests. Type SUS304L stainless steel was used for the tests. The corrosion tests were conducted in 9kmol/m$$^{3}$$ nitric acid solutions containing neptunium ions, where test specimens were immersed or heat-transferred. As a result, we found that neptunium ions promote corrosion of stainless steels in nitric acid solution. This finding would contribute to modifications of the materials for spent fuel reprocessing process.

JAEA Reports

Fundamental study on flow characteristics of disrupted core pool at a low energy level (Joint research)

Morita, Koji*; Liu, P.*; Matsumoto, Tatsuya*; Fukuda, Kenji*; Tobita, Yoshiharu; Sato, Ikken

JAEA-Research 2007-032, 47 Pages, 2007/03

JAEA-Research-2007-032.pdf:4.04MB

Dynamic behaviors of solid particle beds in a liquid pool against pressure transients were investigated to model the mobility of core materials in a low-energy disrupted core of a liquid metal fast reactor. A series of experiments was performed with a particle bed of different heights, comprising different monotype solid particles, where variable initial pressures of the originally pressurized nitrogen gas were adopted as the pressure source. Computational simulations of the experiments were performed using SIMMER-III, a fast reactor safety analysis code. Experimental analyses using the SIMMER-III code show that physical models and methods used in the code can reasonably represent the transient behaviors of multiphase flows with rich solid phase as observed in the experiments. The validation of several key models of SIMMER-III was also discussed for treating transient behaviors of the solid-particle phase in multiphase flows.

JAEA Reports

Development of ACROSS (Accurately Controlled, Routinely Operated, Signal System) to realize constant monitoring the invisible Earth's interiors by means of stationary coherent elastic and electromagnetic waves

Kumazawa, Mineo; Kunitomo, Takahiro; Nakajima, Takahiro; Tsuruga, Kayoko*; Hasada, Yoko*; Nagao, Hiromichi*; Matsumoto, Hiroshi*; Kasahara, Junzo*; Fujii, Naoyuki; Shigeta, Naotaka

JAEA-Research 2007-033, 155 Pages, 2007/03

JAEA-Research-2007-033.pdf:11.04MB

The developmental study made at Tono Geoscience Center under the Earthquake Frontier Research Project since 1996 is reported for a brand new technology system called ACROSS (Accurately Controlled, Routinely Operated, Signal System). Several examples of the field application are demonstrated by the test experiments at Tono Mine site. After the developmental works of 10 years, the ACROSS is brought to be a practical method applied to the remote monitoring of temporal variation of underground states at the Horonobe Underground Research Laboratory and also it is being applied to the expected focal region of the coming Tokai earthquake near Hamaoka in Shizuoka prefecture. Whereas ACROSS technology is not mature enough yet, it is shown to be a potential and versatile methodology applied even for the health monitoring of the construction such as building strongly coupled with the ground in addition to the underground study.

JAEA Reports

Stepwise hydrogeological modeling and groundwater flow simulation on site scale, Step 4

Onoe, Hironori; Saegusa, Hiromitsu; Oyama, Takuya; Endo, Yoshinobu*

JAEA-Research 2007-034, 106 Pages, 2007/03

JAEA-Research-2007-034.pdf:32.86MB

One of the main goals of the Mizunami Underground Research Laboratory Project is to establish comprehensive techniques for investigation, analysis, and assessment of the deep geological environment. To achieve this goal, a variety of investigations are being conducted using an iterative approach. In this study, hydrogeological modeling and groundwater flow analyses have been carried out using the data from surface-based investigation (Phase I) at the Step 4, in order to synthesize the investigation results, to evaluate the uncertainty of the groundwater flow system, and to specify items for Construction (Phase II). As a result of the study, it could be confirmed the uncertainty of groundwater flow system was decreased as stepwise investigation in Phase I. To characterize groundwater flow system, it could be understood that field investigation, hydrogeological modeling and groundwater flow simulation iteratively is most efficiently. Also, it could be learned techniques to decrease the uncertainty efficiently. The main items specified for Phase II investigation are summarized as follows: (1) Execution of monitor to understand change of groundwater flow system according to excavation of the shafts and research galleries; (2) Modification of hydrogeological model of Phase1.

JAEA Reports

Groundwater flow simulation on local scale; Setting boundary conditions of groundwater flow simulation on site scale model in the Step 4

Onoe, Hironori; Saegusa, Hiromitsu; Oyama, Takuya

JAEA-Research 2007-035, 63 Pages, 2007/03

JAEA-Research-2007-035.pdf:20.36MB

Japan Atomic Energy Agency has been conducting a wide range of geoscientific research in order to build a foundation for multidisciplinary studies of the deep geological environment as a basis of research and development for geological disposal of nuclear wastes. Ongoing geoscientific research programs include the Regional Hydrogeological Study (RHS) project and Mizunami Underground Research Laboratory (MIU) project in the Tono region, Gifu Prefecture. The main goal of these projects is to establish comprehensive techniques for investigation, analysis, and assessment of the deep geological environment at several spatial scales. The RHS project is a Local scale study for understanding the groundwater flow system from the recharge area to the discharge area. The Surface-based Investigation Phase of the MIU project is a Site scale study for understanding the deep geological environment immediately surrounding the MIU construction site using a multiphase, iterative approach. In this study, the hydrogeological modeling and roundwater flow simulation on Local scale were carried out in order to set boundary conditions of the Site scale model based on the data obtained from surface-based investigations in the Step4 in Site scale of the MIU project. As a result of the study, boundary conditions for groundwater flow simulation on the Site scale model of the Step4 could be obtained.

JAEA Reports

Groundwater flow analysis in the Horonobe Underground Research Laboratory project; Recalculation based on the investigation until fiscal year 2005

Kurikami, Hiroshi

JAEA-Research 2007-036, 39 Pages, 2007/03

JAEA-Research-2007-036.pdf:13.39MB

Horonobe Underground Research Laboratory of Japan Atomic Energy Agency has been conducting hydrogeological investigations and modeling works as a geoscientific research. Hydrogeological model has been revised and groundwater flow has been recalculated according to the progress of the investigations to decrease its uncertainty. This report shows the results of revision of hydrogeological model and recalculation of groundwater flow based on the investigations since fiscal year 2005. The depth dependency of hydraulic conductivities in Koetoi and Wakkanai formation and Omagari fault was reevaluated. Based on the database of hydraulic conductivity, firstly, sensitivity analyses were performed. Then, the optimization was tried. Although the revised model showed better agreement with measured hydraulic pressure distribution than the last model, it did not illustrate the hydraulic pressure distribution at shallower part such as HDB-4 and 7, relatively lower pressure at HDB-10 and relatively high pressure at deeper part such as HDB-1 and 11. Hereafter, more accurate model including revision of the governing equations will be performed.

JAEA Reports

A Study on timing of rapid depressurization action during PWR vessel bottom break LOCA with HPI failure and AIS-gas inflow, ROSA-V/LSTF test SB-PV-06

Suzuki, Mitsuhiro; Takeda, Takeshi; Asaka, Hideaki; Nakamura, Hideo

JAEA-Research 2007-037, 150 Pages, 2007/03

JAEA-Research-2007-037.pdf:7.55MB

A small break LOCA experiment (SB-PV-06) was conducted at the LSTF of ROSA-V program to study effects of rapid secondary depressuriza-tion action on core cooling as one of accident management (AM) measures for a PWR in case of high pressure injection system failure and non-condensable gas inflow from the accumulator injection system. The break simulated 10 instrument tubes rupture equivalent to 0.2% cold leg break. It was clarified through comparison with former experiments that (1) the depressurization initiated by detecting the vessel level below the primary loop (4545s) was degraded by the gas inflow resulting in whole core uncovery prior to the start of low pressure injection and (2) an alternative start of the depressurization by detecting level decrease at the SG outlet plenum (2330s), would limit the core uncovery suggesting more effective parameter for the AM measures. The report presents the experiment results with the effects of rapid depressurization initiation timing.

JAEA Reports

Development of sodium conversion technology; Method and basic features of sodium conversion process

Matsumoto, Toshiyuki; Yoshida, Eiichi; Suzuki, Shigeaki*; Yasu, Tomohisa*

JAEA-Research 2007-038, 32 Pages, 2007/03

JAEA-Research-2007-038.pdf:5.06MB

Decommissioning of a sodium cooled fast reactor or an experimental facility which used radioactive sodium will bring a lot of radioactive sodium. However, technology to deal with such the radioactive sodium and decommission is not well established in Japan. Then, basic experimental study has been carried out in order to find and estimate an economic and safety process of the radioactive sodium decommission. There were some examples in overseas to convert the sodium into sodium hydroxide via sodium-water reaction. This method was examined by a basic sodium conversion test apparatus. In the experiment, liquid metal sodium was injected into the sodium hydroxide. Influences of temperature and concentration of the sodium hydroxide were investigated. Nitrogen gas was injected into the sodium hydroxide as atomizing gas in order to protect the sodium injection nozzle and also to mix the sodium. Then the gas flow rate was also varied to see the desired effects. Injected sodium temperature and mass flow rate were fixed at 200$$^{circ}$$C and 10kg/h, respectively. The atomizing gas flow rate, the temperature and concentration of the sodium hydroxide were varied in ranges of 60-100 l/min, 70-100$$^{circ}$$C and 40-60wt%, respectively. The influences of these parameters on the sodium conversion reaction were evaluated. The experiments showed that increase of the atomizing gas resulted in stable injection of the sodium and also larger reaction area. The temperature of the sodium hydroxide had small influences on the reaction, however, the sodium injection nozzle tended to choke up when the temperature was less than 70$$^{circ}$$C. The lower concentration resulted in larger temperature fluctuation and also enlarged the reaction area. Unstable reaction, for example, sudden increase of reaction rate due to excess sodium, was not found under the conditions above listed ranges and stable sodium conversion was confirmed.

JAEA Reports

Boundary delineation for regional groundwater flow through Geographic Information System (Contract research)

Yamakawa, Tadashi; Munakata, Masahiro; Kimura, Hideo; Hyodo, Hiroshi*

JAEA-Research 2007-039, 26 Pages, 2007/03

JAEA-Research-2007-039.pdf:4.68MB

Radionuclide migration toward human society through geologic processes is to be assessed as part of long-term safety assessments of geologic disposal for radioactive waste. This study was conducted to develop methodologies of boundary delineation for regional groundwater flow system. Geographic Information System, GIS, was applied to Miyakoji in the Abukuma as an area of interest. The present study revealed that, taking the groundwater flows and fracture characteristics of the area into consideration, the groundwater flow system in Miyakoji drainage basin should be bounded by the Otakine mountain area and the northern part of Tokoha drainage basin, which occupies a larger area than understood before.

JAEA Reports

Subsurface temperature in non-Quaternary volcanic regions in Japan

Yamakawa, Tadashi; Takeda, Seiji; Kimura, Hideo; Hyodo, Hiroshi*

JAEA-Research 2007-040, 21 Pages, 2007/03

JAEA-Research-2007-040.pdf:2.95MB

Radionuclide migration toward human society through geologic processes is to be assessed as part of safety assessments of geologic disposal for radioactive waste. A subsurface temperature in non-Quaternary volcanic regions was focused as one of the changes in this study. The study was conducted to extract features of subsurface temperature in non-Quaternary volcanic regions throughout Japan. After delineating Quaternary volcanic regions, features in non-Quaternary volcanic regions were studied in various aspects. The present study clarified that a relationship between subsurface temperature and its depth was expressed by an equation in non-Quaternary volcanic regions far from about 24 km of Quaternary volcanic centers. This led to about 16$$^{circ}$$C/km in general geothermal gradient in non-Quaternary volcanic areas, which was lower than 20$$^{circ}$$C/km of the previous study.

JAEA Reports

Horonobe Underground Research Laboratory Project; Investigation program for the 2006 fiscal year (Translated document)

Matsui, Hiroya; Niizato, Tadafumi; Yamaguchi, Takehiro

JAEA-Research 2007-041, 40 Pages, 2007/02

JAEA-Research-2007-041.pdf:13.17MB

As part of the R&D program on geological disposal of HLW, the Horonobe Underground Research Center, a division of the JAEA, is implementing the Horonobe URL Project for sedimentary formations. This Project is planned to extend over a period of 20 years. The investigations are to be conducted in three phases. This report summarizes the investigation program for the FY2006. The investigations in FY2006 are focused on the Hokushin area in Horonobe, which was selected as the area for URL construction. The main investigation region extends over approximately 3km$$times$$3km. Construction of the underground facilities is continued and Phase 2 investigations are carried out. Concerning the surface facilities, construction of Research and Administration Facility and Test Facility, will be complete in May, 2006. Construction of Public Information House is continued and fabrications of the exhibits are initiated. The preliminary design of International Communication House is carried out.

JAEA Reports

Conceptual design study of small sodium cooled reactors; 300MWe modular reactor (Joint research)

Aizawa, Kosuke; Chikazawa, Yoshitaka; Usui, Shinichi; Konomura, Mamoru; Ando, Masato*

JAEA-Research 2007-042, 105 Pages, 2007/06

JAEA-Research-2007-042.pdf:3.64MB

Various conceptual design studies of sodium cooled small reactor have been performed in the feasibility study. In FY2005 study, a 300MWe modular reactor which adopts metal-fueled and 1 loop cooling system in order to pursues economical competitiveness was investigated. Transient analyses were performed to show core safety under the large pipe break accident that was found to be the severest accident in case of a 1 loop cooling system. From the analysis results, it was showed a possibility to maintain the core safety without the reactor scram. Transient analyses of the natural circulation decay heat removal system were also performed, and it was showed a possibility to maintain the core safety after the reactor scram. The in-vessel storage (IVS) was adopt to eliminate the ex-vessel storage and the design of the distribution flow adjustment device in IVS is studied. It was showed that the IVS could be introduced without modifying in the reactor design in FY2004. The rationalization of the fuel handling system is investigated taking advantage of co-location plant in which the reactor, the recycle plant and the fuel fabrication plant are co-located in a site. As a result of rationalization, the volume of the reactor building becomes 0.85 times as much as that of the design in FY2004.

JAEA Reports

Final report on the surface-based investigation (phase I) at the Mizunami Underground Laboratory project

Saegusa, Hiromitsu; Seno, Yasuhiro; Nakama, Shigeo; Tsuruta, Tadahiko; Iwatsuki, Teruki; Amano, Kenji; Takeuchi, Ryuji; Matsuoka, Toshiyuki; Onoe, Hironori; Mizuno, Takashi; et al.

JAEA-Research 2007-043, 337 Pages, 2007/03

JAEA-Research-2007-043.pdf:28.14MB

The Mizunami Underground Laboratory (MIU) Project is a comprehensive research project investigating the deep underground environment within crystalline rock being conducted by Japan Atomic Energy Agency at Mizunami City in Gifu Prefecture, central Japan. This report summarizes the results of the Surface-based Investigation Phase, identifies future issues and provides direction for research to be conducted during Construction Phase and Operation Phase. The results compiled in this report will be utilized for the technical knowledge base on geological disposal of HLW, and can be used to enhance the technical basis for waste disposal in general and for development of government regulations.

JAEA Reports

Horonobe Underground Research Laboratory project synthesis of phase I investigations 2001-2005 volume "Geoscientific Research"

Ota, Kunio; Abe, Hironobu; Yamaguchi, Takehiro; Kunimaru, Takanori; Ishii, Eiichi; Kurikami, Hiroshi; Tomura, Goji; Shibano, Kazunori; Hama, Katsuhiro; Matsui, Hiroya; et al.

JAEA-Research 2007-044, 434 Pages, 2007/03

JAEA-Research-2007-044.pdf:54.58MB
JAEA-Research-2007-044(errata).pdf:0.08MB

The Horonobe URL Project started in 2000. Research and development activities are planned over three phases, that will span a total duration of about 20 years: the 1st surface-based investigarion phase (6 years), the 2nd URL construction phase (8 years) and rhe 3rd operation phase (12 years). Geological, geophysical, geo-mechanical, hydrogeological, and hydro-geochemical investigations have been carried out during the surface-based investigation.

JAEA Reports

Horonobe Underground Research Laboratory project synthesis of phase I investigation 2001-2005 volume "Geological Disposal Research"

Fujita, Tomoo; Taniguchi, Naoki; Matsui, Hiroya; Tanai, Kenji; Nishimura, Mayuka; Kobayashi, Yasushi; Hiramoto, Masayuki; Maekawa, Keisuke; Sawada, Atsushi; Makino, Hitoshi; et al.

JAEA-Research 2007-045, 140 Pages, 2007/03

JAEA-Research-2007-045-1.pdf:38.33MB
JAEA-Research-2007-045-2.pdf:44.62MB

This report summarizes the progress of research and development on geological disposal during the surface-based investigation phase (2001-2005) in the Horonobe Underground Research Laboratory project (HOR), of which aims are to apply the design methods of geological disposal and mass transport analysis to actual geological environments and derive future subjects based on the results. The design methods of geological disposal were reviewed based on the recent knowledge and the advertences were identified. Then the parameters for virtual design of engineered barrier system, backfill deposition hole and tunnel were set up based on actual geological conditions obtained from the surface-based investigations in HOR as an example of actual geological environment. The conceptual structure from site investigation and evaluation to mass transport analysis was represented as a work flow at first. Then following this work flow a series of procedures for mass transport analysis were carried out based on actual geological conditions obtained from the surface-based investigations in HOR to illustrate the functioning of the work flow and the applicability of this methodology. Consequently, knowledge that will help follow-up or future execution and planning activities was obtained.

JAEA Reports

Improvement of calculation method for temperature coefficient of HTTR by neutronics calculation code based on diffusion theory; Analysis for temperature coefficient by SRAC code system

Goto, Minoru; Takamatsu, Kuniyoshi

JAEA-Research 2007-046, 28 Pages, 2007/03

JAEA-Research-2007-046.pdf:15.1MB

The HTTR temperature coefficients required for the core dynamics calculations had been calculated from the HTTR core calculation results by the diffusion code with which the corrections had been performed using the core calculation results by the Monte-Carlo code. Then, the calculation method was improved to obtain the temperature coefficients in which the corrections by the Monte-Carlo code were not required. Specifically, from the point of view of neutron spectrum calculated by lattice calculations, the lattice model was revised which had been used for the calculations of the temperature coefficients. The HTTR core calculations were performed by the diffusion code with the group constants which were generated by the lattice calculations with the revised lattice model. The HTTR core dynamics calculation was performed with the temperature coefficient obtained from the core calculation results. In consequence, the core dynamics calculation result showed good agreement with the experimental data and the valid temperature coefficient could be calculated only by the diffusion code without the corrections by Monte-Carlo code.

JAEA Reports

Research on the state-of-the-art of accident consequence analysis method for non-reactor nuclear facilities, 1

Yoshida, Kazuo; Abe, Hitoshi; Yamane, Yuichi; Tashiro, Shinsuke; Muramatsu, Ken

JAEA-Research 2007-047, 70 Pages, 2007/06

JAEA-Research-2007-047.pdf:5.63MB

Japan Atomic Energy Agency (JAEA) entrusted with a research on the state-of-the-art of consequence analysis method for Probabilistic Safety Assessment (PSA) of non-reactor nuclear facilities (NRNF) such as fuel reprocessing and fuel fabrication facilities to the Atomic Energy Society of Japan (AESJ). The objectives of this research is to obtain the basic useful information related for establishing the quantitative performance requirement and for risk-informed regulation through qualifying issues needed to be resolved for applying PSA to NRNF. A special committee of "Research on the analysis methods for accident consequence in NFRF" was organized by the AESJ. The research activities of the committee were mainly focused on the analysis method for upper bounding consequences of accidents such as events of criticality, explosion, fire and boiling of radioactive solution postulated in NRNF resulting in release of radio active material to the environment. This report summarizes the results of research conducted by the committee in FY 2006.

JAEA Reports

Horonobe Underground Research Laboratory project investigation program for the 2007 fiscal year

Matsui, Hiroya; Nakayama, Masashi; Sanada, Hiroyuki; Yamaguchi, Takehiro

JAEA-Research 2007-048, 36 Pages, 2007/07

JAEA-Research-2007-048.pdf:13.4MB

As part of the research and development program on geological disposal of HLW, the Horonobe Underground Research Center, a division of the JAEA is implementing the Horonobe URL Project with the aim of investigating sedimentary rock formations. The Horonobe URL Project is planned to extend over a period of 20 years. The investigations will be conducted in three phases. In the 2007 fiscal year, investigations in Geoscientific Research is continuously carried out. Investigations in R&D on Geological Disposal Technology is also continuously carried out. Construction of the underground facilities is ongoing at Ventilation Shaft and Access Shaft (East). Pre-boring around Ventilation Shaft is also carried out. Construction of the Public Information House and preparation of the exhibits are still continuing and will be completed in May 2007. Public Information House will be scheduled to open in summer. An execution design will be drawn up for the International Communication House.

JAEA Reports

Development of sodium disposal technology; Experiment of sodium compound solidification process

Matsumoto, Toshiyuki; Oura, Masato*; Yato, Yasuo*

JAEA-Research 2007-049, 73 Pages, 2007/07

JAEA-Research-2007-049.pdf:40.32MB

A large amount of sodium containing radioactive waste will come up at the time of final shutdown/ decommission of FBR plant. The radioactive waste is managed as solid state material in a closed can in Japan. As for the sodium, there is no established method to convert the radioactive sodium to solid waste. Further, the sodium is highly reactive. Thus, it is recommended to convert the sodium to a stable substance before the solidification process. One of the stabilizing methods is conversion of sodium into sodium hydroxide solution. These stabilization and solidification processes should be safe, economical, and efficient. In order to develop such sodium disposal technology, nonradioactive sodium was used and a basic experiment was performed. Waste-fluid Slag Solidification method was employed as the solidification process of sodium hydroxide solution. Experimental parameters were mixing ratio of the sodium hydroxide and the slag solidification material, temperature and concentration of the sodium hydroxide. The best parameters were obtained to achieve the maximum filling ratio of the sodium hydroxide under a condition of enough high compressive strength of the solidified waste. In a beaker level test, the solidified waste was kept in a long term and it was shown that there was no change of appearance, density, and also the compressive strength was kept at a target value. In a real scale test, homogeneous profiles of the density and the compressive strength were obtained. The compressive strength was higher than the target value. It was shown that the Waste-fluid Slag Solidification method can be applied to the solidification process of the sodium hydroxide solution, which was produced by the stabilization process.

JAEA Reports

Measurement plan and observational construction program on shaft excavation at the Horonobe Underground Research Laboratory Project

Morioka, Hiroshi; Yamaguchi, Takehiro; Funaki, Hironori; Orukawa, Go

JAEA-Research 2007-050, 60 Pages, 2007/06

JAEA-Research-2007-050.pdf:5.29MB

JAEA is carrying out phased investigation in Horonobe. This investigation, named as "Horonobe Underground Research Laboratory Project" (Horonobe URL Project) targeting sedimentary formations, is intended to confirm the reliability of technologies on geological disposal of High-Level Radioactive Waste (HLW) by applying them into in-situ geological environment. On the "Development of engineering techniques for use in the deep underground environment" in Phase 1 of the Horonobe URL project, based on the various type of data acquired on investigations from the surface, basic design of underground facilities in advance was carried out. This report summarizes the measurement plan during construction of the underground facility based on the design in advance and the observational construction program for feedback measurements data into design and construction on subsequent steps. This report also describes about design and construction management program for contractor of underground facilities. The measurement plan described in this document is applied to measurements in the underground facilities for validation of the geological environmental model. Then, it will be verified the validity by application into actual construction and will be systematized with modification when necessary.

JAEA Reports

Benchmark test of evaluated nuclear data files for fast reactor neutronics application

Chiba, Go; Iwai, Takehiko*; Numata, Kazuyuki*; Hazama, Taira

JAEA-Research 2007-051, 52 Pages, 2007/07

JAEA-Research-2007-051.pdf:12.98MB

A benchmark test of the latest evaluated nuclear data files, JENDL-3.3, JEFF-3.1 and ENDF/B-VII, has been carried out for fast reactor neutronics application. For this benchmark test, experimental data obtained at fast critical assemblies and fast power reactors are utilized. This benchmark test concludes that ENDF/B-VII predicts the neutronics characteristics of fast neutron systems better than other nuclear data files.

JAEA Reports

Studies on representative disruption scenarios, associated electromagnetic and heat loads and operation window in ITER

Fujieda, Hirobumi; Sugihara, Masayoshi*; Shimada, Michiya; Gribov, Y.*; Ioki, Kimihiro*; Kawano, Yasunori; Khayrutdinov, R.*; Lukash, V.*; Omori, Junji; Neyatani, Yuzuru

JAEA-Research 2007-052, 115 Pages, 2007/07

JAEA-Research-2007-052.pdf:3.58MB

Impacts of plasma disruptions on ITER have been investigated to confirm the robustness of the design of the machine to the potential consequential loads. The loads include both electro-magnetic (EM) and heat on the in-vessel components and the vacuum vessel. Several representative disruption scenarios are specified. Disruption simulations with the DINA code and EM load analyses with a 3D finite element method code are performed for these scenarios. Some margins are confirmed in the EM load. Heat load on the first wall due to the vertical movement and the thermal quench (TQ) is calculated with a 2D heat conduction code. For vertical displacement event, beryllium ($$Be$$) wall will not melt during the vertical movement, prior to the TQ. Significant melting is anticipated for the upper $$Be$$ wall and tungsten baffle due to the TQ after the vertical movement. However, its impact could be mitigated by implementing a reliable detection system of the vertical movement and a mitigation system.

JAEA Reports

Radiation effect on oxide-dispersion-strengthened ferritic/martensitic steel under influence of applied stress and improvement of shape stability under irradiation

Sakasegawa, Hideo

JAEA-Research 2007-053, 50 Pages, 2007/11

JAEA-Research-2007-053.pdf:8.31MB

9Cr-ODS (Oxide Dispersion Strengthened) steels developed by JAEA have superior creep properties. The 9Cr ODS steel displaying an excellent creep property is a dual phase steel. The ODS steel is strengthened by the delta ferrite which has a finer dispersion of oxide particles and shows a higher hardness than the martensite. Its creep behavior is very unique and cannot be interpreted by conventional theories of heat resistant steels. Alternative model of creep mechanism was studied using the results of microstructural observations. Based on the alternative creep mechanism model, a novel creep constitutive equation was formulated. In addition to that, modifications of material processing procedures for improving the creep property under irradiation and unirradiation were performed considering procedures for mass production.

JAEA Reports

Development of multi-node can wall model for SIMMER-III/IV

Yamano, Hidemasa; Kondo, Teppei*; Sugaya, Masaaki*; Kamiyama, Kenji

JAEA-Research 2007-054, 89 Pages, 2007/06

JAEA-Research-2007-054.pdf:2.57MB

The SIMMER-III code and its three-dimensional code SIMMER-IV have been developed to evaluate the consequence of core disruptive accidents in liquid-metal cooled fast reactors. The present study has extended the number of nodes in a structure model of SIMMER code from a conventional fixed two-node model to a multi-node model. The number of nodes can be specified automatically or manually. The model also treats the effect of nuclear heating and axial heat transfer models. The model was validated by basic verification calculations. The model alleviates the limitation of conventional model significantly as well as improves the reliability and accuracy of fast reactor safety analyses. This study is expected to contribute to the design study of recriticality-free concept.

JAEA Reports

Analysis of ULOF accident in Monju reflecting the knowledge from CABRI in-pile experiments and others

Sato, Ikken; Tobita, Yoshiharu; Suzuki, Toru; Kawada, Kenichi; Fukano, Yoshitaka; Fujita, Satoshi; Kamiyama, Kenji; Nonaka, Nobuyuki; Ishikawa, Makoto; Usami, Shin

JAEA-Research 2007-055, 84 Pages, 2007/05

JAEA-Research-2007-055.pdf:16.66MB

In the first licensing procedure of the prototype FBR "Monju", the event sequence of ULOF (Unprotected Loss of Flow) was analyzed and the estimated mechanical energy was about 380 MJ as an isentropic expansion potential to atmospheric pressure. The prototype FBR has been stopped for more than 10 years since the sodium leakage accident in the secondary loop in 1995. The neutronic characteristics of reactor core changed as a consequence of radioactive decay of fissile Plutonium during this shutdown period. In order to assess the effect of this neutronic characteristics change to the mechanical energy release in ULOF, the event sequence of ULOF was analyzed reflecting the current knowledge, which was obtained by safety studies after the first licensing of the prototype reactor. It was shown that the evaluated mechanical energy release became smaller than 380 MJ, even with the change of neutronic characteristics.

JAEA Reports

A Study on scheme of stream discharge of hazardous metals in rainfall events

Matsunaga, Takeshi; Yanase, Nobuyuki; Hanzawa, Yukiko; Tsuzuki, Katsunori; Naganawa, Hirochika

JAEA-Research 2007-056, 143 Pages, 2007/07

JAEA-Research-2007-056.pdf:59.02MB

Stream discharge of metallic elements from the ground was investigated in a forested catchment in the Oda River watershed in the central Japan. The investigation revealed that several hazardous metals such as Cu, Sb and Cr in dissolved form and also rare earth elements are peculiar elements whose stream discharges are always accelerated in a rainfall event. Further, two different schemes of elemental transport in this peculiar discharge were suggested. They were (1) a coincidently occurring discharge with an initial increase in a flow rate of a stream, and (2) a discharge with slower increase and prolonged decrease, which are poorly corresponding to the change in the stream flow rate. An analysis of hydrological discharge, using chemical signatures of natural organic materials (NOM) and isotopic signatures of deuterium and oxygen of water suggested that the latter discharge is associated with that of NOM of the soil layer. The latter discharge was also effective for rare earth elements.

JAEA Reports

Sensitivity analysis on gas migration in underground repository system for TRU waste

Tanai, Kenji; Yamamoto, Mikihiko*; Seki, Yoshitaka*

JAEA-Research 2007-057, 71 Pages, 2007/07

JAEA-Research-2007-057.pdf:1.77MB

In underground repositories for radioactive waste, significant quantities of gases may be generated as a result of metal corrosion. These gases may migrate through the engineered barrier system and the geological barrier. The potential impact of gas generation, accumulation and migration on the performances of the various barriers such as drainage of contaminated water from the repository and/or damaging of the engineered barriers due to a gas over-pressure should be assessed. The sensitivity analysis was carried out using the modified TOUGH2 model in order to clarify the impact of any input parameters. The following facts became clear as a result of this study. For the cementitious material (waste/cementitious filler), an impact of the absolute permeability and residual pore-water saturation was large. For the buffer material, absolute permeability of gas, capillary exclusion pressure and residual pore-water saturation was large.

JAEA Reports

Conceptual design of the HTTR-IS hydrogen production system

Sakaba, Nariaki; Sato, Hiroyuki; Hara, Teruo; Kato, Ryoma; Ohashi, Kazutaka; Nishihara, Tetsuo; Kunitomi, Kazuhiko

JAEA-Research 2007-058, 31 Pages, 2007/08

JAEA-Research-2007-058.pdf:16.44MB

Since hydrogen produced by nuclear should be competitiveness economically compared by other method in a hydrogen society, it is important to built hydrogen production system to be coupled with the reactor as a conventional chemical plant. Japan Atomic Energy Agency started the safety study to establish a new safety philosophy with safety requirements and with considering non-nuclear grade hydrogen production system for the nuclear coupling system. Also, structural concepts with integrating functions for the Bunsen reactor and sulphuric acid decomposer were proposed to reduce construction cost of the IS process hydrogen production system. In addition, HI decomposer which enabled the process condition to be eased and could adopt conventional materials and technologies was studied. Moreover, basic approval of the HTTR-IS system in which the hydrogen production rate of 1,000 Nm$$^{3}$$/h by using the supplied heat of 10 MW from the intermediate heat exchanger of the HTTR was confirmed. This paper describes the conceptual design of the HTTR-IS hydrogen production system.

JAEA Reports

Alkaline degradation of organic materials contained in TRU wastes under repository conditions

Otsuka, Yoshiki*; Bamba, Tsunetaka

JAEA-Research 2007-059, 18 Pages, 2007/09

JAEA-Research-2007-059.pdf:4.63MB

Alkaline degradation tests for 9 organic materials were conducted under the conditions of TRU waste disposal: anaerobic alkaline conditions. The tests were carried out at 90 $$^{circ}$$C for 91 days. The sample materials for the tests were selected from the standpoint of constituent organic materials of TRU wastes. It has been found that cellulose and plastic solidified products are degraded relatively easily and that rubbers are difficult to degrade. It could be presumed that the alkaline degradation of organic materials occurs starting from the functional group in the material. Therefore, the degree of degradation difficulty is expected to be dependent on the kinds of functional group contained in the organic material.

JAEA Reports

Study on systemizing the technology on the investigation and analysis of deep underground geological environment; Japanese fiscal year, 2006 (Contract research)

Kojima, Keiji*; Onishi, Yuzo*; Watanabe, Kunio*; Nishigaki, Makoto*; Tosaka, Hiroyuki*; Shimada, Jun*; Aoki, Kenji*; Tochiyama, Osamu*; Yoshida, Hidekazu*; Ogata, Nobuhisa; et al.

JAEA-Research 2007-060, 210 Pages, 2007/09

JAEA-Research-2007-060-1.pdf:43.82MB
JAEA-Research-2007-060-2.pdf:41.2MB
JAEA-Research-2007-060-3.pdf:6.42MB

The following study was done with the aim of systemizing the technology on the investigation and analysis to grasp deep underground geological environment in relation to the radioactive waste disposal. (1) The study on the research and development (R&D) subjects which turned to the practical investigation and analysis of deep underground geological environment. (2) The study on the advanced technical basis of the investigation and analysis of deep underground geological environment. It continued in the former year and got the following results. Concerning (1), the concrete investigation, measurements, numerical analyses and chemical analyses were enforced about the following item and extracted some subjects with the viewpoint of radioactive waste disposal. More over, the way to make the co-operative program among each field of the following (a), (b) and (c) was discussed. (a) The subjects extracted with the viewpoint of the repository design and engineering technology. (b) The subject extracted with the viewpoint of the safety assessment. (c) The subjects extracted with the viewpoint of the geological environment. The joint research subjects among each field of (a), (b), (c) were also discussed. Concerning (2), the evaluation of the results and a way to the practical use were discussed on the R&D activities. The Study group also discussed and gave the comment on the 2nd stage of the MIU (Mizunami Underground Research Laboratory) research program in the JAEA.

JAEA Reports

Investigation on inspection methods for ZrC-coated fuel particle; Applicability evaluation of inspection methods for SiC-coated fuel particle

Takayama, Tomoo*; Ueta, Shohei; Aihara, Jun; Yasuda, Atsushi*; Ishibashi, Hideharu*; Sawa, Kazuhiro

JAEA-Research 2007-061, 32 Pages, 2007/09

JAEA-Research-2007-061.pdf:15.93MB

As the conventional SiC coated fuel particle, the ZrC coated fuel particle is proposed as a fuel for the Very High Temperature Gas-cooled Reactor (VHTR) which is one of Generation IV nuclear reactors. Applicability of inspection methods of SiC-coated fuel particle for ZrC-coated fuel particle has been examined by comparing properties of ZrC with SiC. It was suggested that hardness, absorption X-ray coefficient, density, oxidation-resistant and chemical stability of SiC were dominant properties for conventional inspection methods such as SiC coating layer thicknesses, coating layers densities for both SiC and O-PyC layers, thorough-coatings failure fraction and SiC coating layer failure fraction. With regards to the applicability of the inspection for the SiC-coated particle, some difficulties are revealed on coating layers densities for both ZrC and O-PyC layers and of ZrC failure fraction, and it was suggested that they were major issues to be solved.

JAEA Reports

A Systematic concept of assuring structural integrity of components and parts for applying to highly ductile materials through brittle materials

Suzuki, Kazuhiko

JAEA-Research 2007-062, 95 Pages, 2007/09

JAEA-Research-2007-062.pdf:9.8MB

Concepts of assuring structural integrity of plant components have been developed under limited conditions of either highly ductile or brittle materials. There are some cases where operation in severe conditions causes a significant reduction in ductility for materials with a high ductility before service. Current concepts of structural integrity assurance under the limited conditions of material properties or on the requirement of no significant changes in material properties even after long service will fail to incorporate expected technological innovations. A systematic concept of assuring the structural integrity should be developed for applying to ductile materials through brittle materials. In this report, first, background of concepts of existing structural codes are discussed. Next, issues of existing codes for brittle material parts are identified and then resolutions to the issues are proposed. Based on these discussions and proposals, a systematic concept is proposed.

JAEA Reports

Surface hydrological investigation of Horonobe Underground Research Laboratory Project

Tomura, Goji; Kurikami, Hiroshi; Shibano, Kazunori; Kunimaru, Takanori; Hara, Minoru

JAEA-Research 2007-063, 46 Pages, 2007/11

JAEA-Research-2007-063.pdf:8.1MB

Horonobe Underground Research Center of Japan Atomic Energy Agency has been investigating surface hydrogeological features in and around the Horonobe Underground Research Laboratory (URL) area as a part of Horonobe URL project. In the surface hydrogeological investigation, for the purpose of understanding of groundwater recharge rate and groundwater flow in the shallower part, which are required for the setting of boundary and initial condition of the groundwater flow analysis, meteorological observations, observation of river flux and water quality, soil moisture observation, groundwater level observation, etc are being continued. This report shows present status and results of surface hydrogeological investigation in the Horonobe URL project.

JAEA Reports

A Preliminary study on application of risk assessment to seismic risk management of nuclear fuel facilities

Yoshida, Kazuo; Muramatsu, Ken

JAEA-Research 2007-064, 30 Pages, 2007/10

JAEA-Research-2007-064.pdf:15.45MB

Studies on risk-informed safety regulation and/or management of nuclear installations are being carried out world widely on the background of progress in development of probabilistic safety assessment (PSA) methodology and its application. A study in this area is also on going at Japan Atomic Energy Agency. A PSA methodology has been developed for MOX fuel fabrication facilities in this study. A preliminary study on application of risk assessment to examine seismic risk management of nuclear fuel facilities has been also carried out as one of those research activities. A simple approach of assessing seismic risk has been investigated with a sample case of uranium fuel fabrication facility based on the analytical policy so called "graded approach" in which detail of risk analysis can be changed corresponding with the level of potential risk of facilities.

JAEA Reports

Assessment of heterogeneous geological environment at Tono -Japanese fiscal year 2004- (Contract research)

Toida, Masaru*; Suyama, Yasuhiro*; Mori, Takayuki*; Inaba, Takeshi*; Sasakura, Takeshi*; Atsumi, Hiroyuki*; Masumoto, Kazuhiko*; Kobayashi, Ichizo*; Iwano, Keita*; Furuichi, Mitsuaki*; et al.

JAEA-Research 2007-065, 210 Pages, 2007/09

JAEA-Research-2007-065-1.pdf:28.82MB
JAEA-Research-2007-065-2.pdf:42.37MB
JAEA-Research-2007-065-3.pdf:24.46MB
JAEA-Research-2007-065-4.pdf:48.78MB

"Geoscientific research" at the Tono Area is developing site investigation, characterization and assessment techniques for understanding of geological environment. Their important goals are to establish a methodology for analyzing uncertainties in heterogeneous geological environment and to develop investigation techniques for efficiently reducing the uncertainties. The current study proposes a new approach where all the possible options in the models and data-sets, which cannot be excluded in the light of the evidences available, are identified. This approach enables uncertainties associated with the understanding at a given stage of the site characterization to be made explicitly using an uncertainty analysis technique based on Fuzzy geostatistics. This approach supports the design of the following investigation stage and reduces the uncertainties efficiently. In FY H16 the technique has been tested through geological modelling and groundwater analyses with Tono Area case based on current knowledge, to demonstrate its applicability and to compile the knowledge / information required to describe the H17 report. This report can be summarized as follows: (1) The knowledge / information required to describe the heterogeneous characteristics was compiled and connected to uncertainties associated with the characterization of a geological environment using a synthesis diagram. (2) Methodologies for assignment and screening of parameters were developed by using Evidential Support Logic (ESL). (3) Applicability of the techniques could be confirmed with Tono Area case. (4) This report proposed a new methodology that integrates the technique into JAEA ordinary technique to good advantage in the geoscientific research project.

JAEA Reports

Development of safety assessment method under uncertainty for Horonobe URL project (Contract research)

Takase, Hiroyasu*; Inagaki, Manabu*; Noguchi, Toshihide*; Shimaoka, Akiko*; Martin, A. J.*; Wakamatsu, Hisanori*; Takase, Kyoko*; Tabara, Michiko*; Matsui, Hiroya

JAEA-Research 2007-066, 215 Pages, 2007/08

JAEA-Research-2007-066-01.pdf:43.05MB
JAEA-Research-2007-066-02.pdf:58.73MB
JAEA-Research-2007-066-03.pdf:13.08MB

In this study a systematic approach to explicitly address type and size of uncertainties associated with safety assessment due mainly to incomplete knowledge on a spatially heterogeneous geological environment was developed. In this approach a wide range of model variations including the ones with relatively law plausibility are taken into account so that ambiguity remaining in the knowledge is illustrated, which is a distinctive feature of the approach compared with the conventional methodology where only a limited number of best plausible model variations are considered. The study also proposed an approach to assessing plausibility of each model variation based on multiple pieces of evidence by using evidential support logic (ESL). Furthermore the approach was applied to Horonobe area to demonstrate its applicability to the similar class of geological environment as an example.

JAEA Reports

Research and development for treatment and disposal technologies of TRU waste; JFY 2006 annual report

Kamei, Gento; Honda, Akira; Mihara, Morihiro; Oda, Chie; Murakami, Hiroshi; Masuda, Kenta; Yamaguchi, Kohei; Nakanishi, Hiroshi*; Sasaki, Ryoichi*; Ichige, Satoru*; et al.

JAEA-Research 2007-067, 130 Pages, 2007/09

JAEA-Research-2007-067.pdf:28.78MB

After the publication of the 2nd progress report of geological disposal of TRU waste in Japan, policy and general scheme of future study for the waste disposal in Japan was published by ANRE and JAEA. This annual report summarized aim and progress of individual problem, which was assigned into JAEA in the published policy and general scheme. The problems are as follows; characteristics of TRU waste and its geologic disposal, treatment and waste production, quality control and inspection methodology for waste, mechanical analysis of near-field, data acquisition and preparation on radionuclides migration, cementitious material transition, bentonite and rock alteration in alkaline solution, nitrate effect, performance assessment of the disposal system and decomposition of nitrate as an alternative technology.

JAEA Reports

Applications of TAGS data in beta decay energies and decay heat calculations

Pham, N. S.*; Katakura, Junichi

JAEA-Research 2007-068, 53 Pages, 2007/10

JAEA-Research-2007-068.pdf:2.74MB

The recent data of beta-decay intensity measured by using the total absorption $$gamma$$-ray spectrometer (TAGS), for several fission products (FP), has been applied for calculations of the average energies and spectra, and decay heat summations. The calculations were performed based on the Gross theory of beta decay, in which the beta strength functions were experimentally derived from TAGS data. The deviations of decay heat power predictions from the original decay data of JENDL Decay Data File 2000, when applying the present values of average energies, were investigated. New estimations of decay energy data for $$^{144}$$La and $$^{141}$$Cs are proposed.

JAEA Reports

Error of the standard Gibbs free energy of formation of smectite and 2:1 clay minerals estimated from alternative modeling approach

Ueno, Kenichi; Shibata, Masahiro*

JAEA-Research 2007-069, 36 Pages, 2007/09

JAEA-Research-2007-069.pdf:1.49MB

Development of the thermodynamic data of clay minerals including smectite is difficult. In order to estimate thermodynamic data of clay minerals, estimation model for thermodynamic data had been proposed. In this report, in order to select of the best estimation model for ${it $Delta$G$_{f}$$^{circ}$}$ for clay minerals and estimate for its error, five models to predict of ${it $Delta$G$_{f}$$^{circ}$}$ were reviewed. ${it $Delta$G$_{f}$$^{circ}$}$ values were calculated by using these estimation models. Estimated value and experimental values were intercompared, not only error between their values, but also standard deviation of each value on their calculation. The best estimation model of ${it $Delta$G$_{f}$$^{circ}$}$ is considered that mean of errors and $$sigma$$ are the smallest, and the best value of ${it $Delta$G$_{f}$$^{circ}$}$ is predicted by the model.

JAEA Reports

Application of tritium behavior simulation code (TBEHAVIOR) to an actual-scale tritium handling room

Iwai, Yasunori; Hayashi, Takumi; Kobayashi, Kazuhiro; Yamanishi, Toshihiko

JAEA-Research 2007-070, 18 Pages, 2007/11

JAEA-Research-2007-070.pdf:15.66MB

It is essential from the viewpoint of fusion safety to confine and remove tritium in a room since tritium handling room is placed as final barrier of fusion plant to prevent the environmental discharge of tritium. At the Tritium Process Laboratory (TPL) of Japan Atomic Energy Agency (JAEA), the application of our original three-dimensional TBEHAVIOR code to the tritium behavior in a room of 3000 m$$^{3}$$ was verified. The Renormalization Group Theory (RNG) model was selected as Low-Reynolds model for practical calculation time as well as to reasonable precision in evaluation of velocity from the engineering viewpoint. Evaluation of attenuating behavior is important since the ventilation is normally stopped for the tritium confinement in the case of tritium leakage. We demonstrated that an attenuating behavior can also be evaluated well by the TBEHAVIOR code. The presence of apparatuses in a room did not generally affect tritium behavior.

JAEA Reports

Assessment of uncertainties associated with the characterization of the geological environment in the Tono Area -Japanese fiscal year, 2005- (Contract research)

Toida, Masaru*; Suyama, Yasuhiro*; Mori, Takayuki*; Inaba, Takeshi*; Atsumi, Hiroyuki*; Tanaka, Toshiyuki*; Kobayashi, Ichizo*; Nakajima, Makoto*; Ogata, Nobuhisa

JAEA-Research 2007-071, 159 Pages, 2007/09

JAEA-Research-2007-071.pdf:48.05MB

"Geoscientific research" at the Tono Area is developing site investigation, characterization and assessment techniques for understanding of geological environment. Their important goal is to establish a methodology for analyzing uncertainties in a heterogeneous geological environment and to develop investigation techniques for efficiently reducing the uncertainties. In Fiscal Year 17, in addition to information from the MIZ-1 borehole investigation, present knowledge has been compiled. The proposed technique has been improved through conceptual geological modeling and groundwater analyses at the Tono Area. Design options for handling geological uncertainties based on the characterization of the geological environment have also been tested. The results of this study can be summarized as follows: (1) It was shown that the fracture group with NW strike has high correlation with maximum measured transmissivity. This was maybe caused by the effect of regional in situ stress. (2) Through conceptual geological modelling and groundwater analysis, a procedure for modelling of the geological environment with heterogeneous characteristics was proposed. (3) From the viewpoint of improving the design of an underground facility, the existence of uncertainties of the geological environment with heterogeneous characteristics requests multiple options. A design option should be adapted to the geological environment with heterogeneous characteristics.

JAEA Reports

Evaluation of containment failure probability due to ex-vessel steam explosions in LWR severe accidents

Moriyama, Kiyofumi; Takagi, Seiji*; Muramatsu, Ken; Nakamura, Hideo; Maruyama, Yu

JAEA-Research 2007-072, 54 Pages, 2007/11

JAEA-Research-2007-072.pdf:25.89MB

The containment failure probability due to ex-vessel steam explosions was evaluated for BWR and PWR model plants. A stratified Monte Carlo technique (Latin Hypercube Sampling (LHS)) was applied for the evaluation of steam explosion loads, in which a steam explosion simulation code JASMINE was used as a physics model. The evaluation was made for three scenarios: a steam explosion in the pedestal area or in the suppression pool of a BWR model plant with Mark-II containment, and in the reactor cavity of a PWR model plant. The scenario connecting the generation of steam explosion loads and the containment failure was assumed to be displacement of the reactor vessel and pipings, and failure at the penetration in the containment boundary. We evaluated the conditional containment failure probability (CCFP) based on the preconditions of failure of molten core retention within the reactor vessel, relocation of the core melt into the water pool without significant interference, and a strong triggering at the time of maximum premixed mass. The obtained mean and median values of the CCPF were 6.4E-2 (mean) and 3.9E-2 (median) for the BWR suppression pool case, 2.2E-3 (mean) and 2.8E-10 (median) for the BWR pedestal case, and 6.8E-2 (mean) and 1.4E-2 (median) for the PWR cavity case. The evaluation of CCFPs on the basis of core damage needs consideration of probabilities for the above-mentioned preconditions. Thus, the CCFPs per core damage should be lower than the values given above. The specific values of the probability were most dependent on the assumed range of melt flow rate and fragility curve that involved conservatism and uncertainty due to simplified scenarios and limited information. Additionally, the source term significance of the fine particles generated by steam explosions was discussed.

JAEA Reports

Development of evaluation method of residual stress for graphite component of HTGR by micro-indentation method, 1 (Contract research)

Sumita, Junya; Shibata, Taiju; Tada, Tatsuya; Sawa, Kazuhiro

JAEA-Research 2007-073, 17 Pages, 2007/11

JAEA-Research-2007-073.pdf:5.72MB

In High Temperature Gas-cooled Reactor (HTGR), graphite materials are used as core internal structural components. The neutron irradiation and thermal gradient induce residual stress of graphite components which is a crucial factor to determine the lifetime of them. It is hence important to measure and assess the stress for lifetime extension of the components. Since the residual stress gives characteristics change to the micro-indentation behavior, it is possible to evaluate the residual stress to measure indentation depth. Therefore, in order to evaluate the change of residual stress of graphite components non-destructively, we are now developing the indentation method to evaluate it. This report showed the relationship between indentation depth and residual stress based on experimental data obtained by changing the stress condition of graphite specimen parametrically.

JAEA Reports

Sorption studies of radioelements on geological materials

Berry, J. A.*; Yui, Mikazu; Kitamura, Akira

JAEA-Research 2007-074, 87 Pages, 2007/11

JAEA-Research-2007-074.pdf:3.98MB

Batch sorption experiments have been carried out to study the sorption of uranium, technetium, curium, neptunium, actinium, protactinium, polonium, americium and plutonium onto bentonite, granodiorite and tuff. Mathematical modelling using the HARPHRQ program and the HATCHES database was carried out to predict the speciation of uranium and technetium in the equilibrated seawater, and neptunium, americium and plutonium in the rock equilibrated water. Review of the literature for thermodynamic data for curium, actinium, protactinium and polonium was carried out. Where sufficient data were available, predictions of the speciation and solubility were made. This report is a summary report of the experimental work conducted by AEA Technology during April 1991 $$sim$$ March 1998, and the main results have been presented at Material Research Society Symposium Proceedings and published as proceedings of them.

JAEA Reports

Study on evaluation of containment capability of grove box under fire accident, 2

Abe, Hitoshi; Watanabe, Koji; Tashiro, Shinsuke; Uchiyama, Gunzo

JAEA-Research 2007-075, 50 Pages, 2007/11

JAEA-Research-2007-075.pdf:6.35MB

In the MOX fuel fabrication facility, MOX is required to be handled in Grove-box to sustain containment of MOX into the facility. In case of fire in the facility, the containment capability of Grove-box may be deteriorated by pyrolysis or combustion of the plastic materials as components of Grove-box caused by thermal stress from flame. The purpose of this study is to examine pyrolysis and combustion properties of the materials for applying quantitative evaluation method for the containment capability of Grove-box under fire. This report summarize experimental results about the properties under the Air condition and investigation of evaluation model for estimating time-course of deteriorating containment capability of Grove-box under fire.

JAEA Reports

Development of selective stripping method by DTPA for trivalent actinides from rare earth elements in DIDPA solvent; Evaluation of separation performance by simulation code

Fujiwara, Takeshi; Morita, Yasuji

JAEA-Research 2007-076, 29 Pages, 2007/11

JAEA-Research-2007-076.pdf:2.05MB

In the 4-Group Partitioning Process developed in Japan Atomic Energy Research Institute (presently: Japan Atomic Energy Agency), we examined selective stripping method by DTPA for Am and Cm from the rare earth elements (REs) in DIDPA solvent. In the present study, the performance of the selective stripping and the optimization of the separation process was examined by a simulation program which uses the values of distribution ratios of Am and REs obtained by batch experiments. The validity of the simulation program was confirmed by comparing the results of the simulation with the results of continuous stripping tests of REs with DTPA solution from the DIDPA solvent using mini-mixer-settlers. The distributions of the REs in mini-mixer-settlers were adequately predictable in the condition with low concentration of the REs by the simulation program. It is effective to add the scrubbing steps by organic solvent in order to decrease the amount of REs that contaminate the Am and Cm product.

JAEA Reports

Analysis of the characteristics of AE wave using boring core of sedimentary soft rock and study on the field measurement of AE for the evaluation of EDZ (Joint research)

Aoki, Kenji*; Mito, Yoshitada*; Minami, Masayuki*; Matsui, Hiroya; Niunoya, Sumio*

JAEA-Research 2007-077, 126 Pages, 2007/09

JAEA-Research-2007-077.pdf:16.68MB

To understand the size and state of EDZ is one of the problems in the technological development for geological disposal of HLW. AE which is measured directly and evaluate EDZ is paid to attention inside and outside the country, and the utility is reported for the crystalline rock. However, there are few cases to measure AE in sedimentary soft rocks because of the difficulty to acknowledge a few AE waves with small energy. The author consulted AE properties of Horonobe siliceous rocks from laboratory tests and evaluated size and state of EDZ from numerical analysis.

JAEA Reports

Sensitivity study of the ITER poloidal polarimeter

Yamaguchi, Taiki; Kawano, Yasunori; Kusama, Yoshinori

JAEA-Research 2007-078, 43 Pages, 2008/03

JAEA-Research-2007-078.pdf:8.92MB

The poloidal polarimeter will be installed in the International Thermonuclear Experimental Reactor (ITER) to measure the profile of the toroidal current (safety factor) in the plasma core region. For the optimization of the viewing chord arrangement of the ITER poloidal polarimeter, we studied the sensitivity of the viewing chord arrangement on the current profile. We proposed the new method for the sensitivity study, in which the Faraday rotation angle due to the toroidal current only is used as the sensitive index. As the result, we could find the viewing chords which are sensitive to the central current density, the finite beta effect and the ratio of the central current density and the maximum current density in case of the hollow current profile. Next, we proposed the viewing chord arrangements which are sensitive to the current profiles of ITER operation scenarios.

JAEA Reports

Development of oxidation damage evaluation method for HTGR graphite component by ultrasonic-wave propagation characteristics, 1 (Contract research)

Tada, Tatsuya; Shibata, Taiju; Sumita, Junya; Sawa, Kazuhiro

JAEA-Research 2007-079, 22 Pages, 2008/01

JAEA-Research-2007-079.pdf:13.34MB

Graphite materials used for in-core components of High Temperature Gas-cooled Reactor are gradually oxidized by quite small amount of impurities in primary coolant during long term operation. The oxidation damage is addressed one of crucial factors to determine their lifetime, and it is important to evaluate the damage for components lifetime extension. Since ultrasonic-waves are propagated through interactions with pores in porous ceramics including graphite, it is possible to evaluate the porous condition by propagation characteristics such as velocity and attenuation. We are now developing the oxidation damage evaluation method non-destructively by the wave propagation characteristics. This report shows evaluation formulas to evaluate uniform oxidation condition of graphite. They are obtained experimental data of wave propagation characteristics for parametrically oxidized IG-110 and IG-430 graphite specimens.

JAEA Reports

Excavation disturbance analysis based on MBC Model for predicting of the rock mass behavior during excavation of shafts and research galleries at the Mizunami Underground Research Laboratory

Seno, Yasuhiro; Nakama, Shigeo; Sato, Toshinori*; Mori, Takayuki*; Morikawa, Seiji*; Tabei, Kazuto*; Suyama, Yasuhiro*; Murakami, Koji*

JAEA-Research 2007-080, 112 Pages, 2008/01

JAEA-Research-2007-080.pdf:8.37MB

A 3D MBC(Micro-mechanics Based Continuum model) numerical 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).

JAEA Reports

Excavation disturbance analysis based on Crack Tensor Model and Virtual Fracture Model for predicting the rock mass behavior during excavation of shafts and research galleries at the Mizunami Underground Research Laboratory

Seno, Yasuhiro; Nakama, Shigeo; Sato, Toshinori*; Goke, Mitsuo*; Tada, Hiroyuki*; Sakurai, Hideyuki*

JAEA-Research 2007-081, 120 Pages, 2008/01

JAEA-Research-2007-081.pdf:13.48MB

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.

JAEA Reports

Study on hazardous substances contained in radioactive waste

Kuroki, Ryoichiro; Takahashi, Kuniaki

JAEA-Research 2007-082, 215 Pages, 2008/01

JAEA-Research-2007-082.pdf:7.2MB

The environmental impact of hazardous materials and possibility of criticality were investigated to construct technical specification of radioactive waste packages. The contents and results are as following. (1) Concerning hazardous materials included in TRU waste, regulations on disposal of industrial wastes and on environmental preservation were investigated. (2) The assessment methods for environmental impact of hazardous materials included in radioactive waste in U.K, U.S.A. and France were investigated. (3) The upper limits of amounts of hazardous materials in waste packages to satisfy the environmental standard were calculated with mass transport assessment for some disposal concepts. (4) It was suggested from criticality analysis for waste packages in disposal facility that the occurrence of criticality was almost impossible under the realistic conditions.

JAEA Reports

Study on groundwater flow system in a sedimentary rock area, 2; Case study for the Yoro River basin, Chiba prefecture

Sakai, Ryutaro; Munakata, Masahiro; Kimura, Hideo

JAEA-Research 2007-083, 38 Pages, 2008/01

JAEA-Research-2007-083.pdf:3.29MB

Japan Atomic Energy Agency has investigated a sedimentary rock area in the central part of Yoro river basin, in Chiba Prefecture for verification of analytical groundwater flow model. For the purpose of establishing a methodology for evaluation of regional groundwater flow system, investigations of flow rates, chemical compositions and isotope ratios for water samples collected from wells, rivers and springs were carried out. As a result, considerable amount of ground water which is NaCa-HCO$$_{3}$$ type or evolved Ca-HCO$$_{3}$$ type meteoric origin cultivated at the high permeable sand dominant layer preferentially flows toward its strike direction discharging at the downstream region of river. The evolved Ca-HCO$$_{3}$$ type or Na-HCO$$_{3}$$ type ground water with long residence time was inferred to form different flowpath toward the dipping direction of bedrock more than 100m at depth and to upwell to the downstream region of Urajiro River as a feeder of Yoro River through the low permeable mud layer.

JAEA Reports

Study on reactor core and fuel design of sodium cooled fast reactor, Mixed oxide fuel core; Results in JFY2006

Ogawa, Takashi; Kobayashi, Noboru; Oki, Shigeo; Naganuma, Masayuki; Kubo, Shigenobu*; Mizuno, Tomoyasu

JAEA-Research 2007-084, 63 Pages, 2008/01

JAEA-Research-2007-084.pdf:4.3MB

The sodium-cooled large-scale "high internal conversion (HIC) type" core with MOX fuel is the most promising core concept in FaCT Project in Japan. Design study on core and fuel in JFY2006 is reported. (1) Design study of the core with MOX fuel containing MA; Based on the large-scale HIC type core in FS Phase II, we have developed a core using TRU of high MA content recovered from ALWR spent fuel. MA content in the fuel heavy metal is temporarily assumed to be 3 wt%. We have confirmed the core design feasibility with the detailed evaluations of thermal hydraulic characteristics and fuel integrity. (2) Design study of the nonproliferation core by adding Pu to the blankets; As one of the measures to enhance the intrinsic nonproliferation property of fast reactors, we have developed the nonproliferation core concept that can keep the Pu in blankets to "Reactor Grade ($$^{240}$$Pu isotope abundance ratio $$>$$ 18%)" with premixing Pu (or TRU) of core fuel to blanket fuel.

JAEA Reports

Feasibility study of oxygen getter for FBR MOX fuel; Selection of material and examination of loading method into a cladding

Morihira, Masayuki; Segawa, Tomoomi

JAEA-Research 2007-085, 29 Pages, 2008/02

JAEA-Research-2007-085.pdf:2.88MB

The "FaCT project" is a program toward the commercialization of FBR cycle carried out in JAEA. High burn-up of 250 GWd/HMt at bundle peak is targeted in the project. To restrain the fuel cladding chemical interaction (FCCI) in a high burn-up, adoption of low O/M ratio pellets is chosen. Considering the difficulty of accurate oxygen potential control in a commercial scale electric furnace as well as the difficulty of keeping O/M ratio of sintered pellets under the high decay heat from the low decontaminated TRU MOX, it may be difficult to realize commercial mass production of low O/M ratio pellets. If so, excess oxygen released during irradiation should be absorbed by an oxygen getter not but in the matrix of low O/M ratio MOX pellets. Then MOX pellets with higher initial O/M ratio can be acceptable. In this research, a selection of oxygen getter candidates was carried out with the examination of their loading method in a cladding.

JAEA Reports

Investigation of the long term corrosion resistance of the overpack FY2006 (Contract research)

Tachikawa, Hirokazu*; Kawakubo, Fumie*; Shimizu, Akihiko*; Shibata, Toshio*; Azumi, Kazuhisa*; Inoue, Hiroyuki*; Sugimoto, Katsuhisa*; Tsuru, Toru*; Fujimoto, Shinji*

JAEA-Research 2007-086, 74 Pages, 2008/02

JAEA-Research-2007-086.pdf:5.96MB

The corrosion life time of the overpack has been investigated on the basis of experimental data and past research, assuming the ranging geological environment of Japan. However, some subject for the realization of the overpack design, such as the behavior of the overpack under high pH conditions, the behavior of the overpack with change of near-field environmental condition and the corrosion behavior of the welds have still been left. To take into account these conditions, expert committee composed of metal corrosion science experts were established in the Nuclear Safety Research Association and past research outcomes and the theory of safety assessment for long term corrosion resistance were investigated from the view points of metal corrosion science.

JAEA Reports

Annual report for research on long-term stability of geological environment in FY2005

Nohara, Tsuyoshi; Umeda, Koji; Sasao, Eiji; Asamori, Koichi; Hanamuro, Takahiro; Moriya, Toshifumi*; Nakatsuka, Noboru

JAEA-Research 2007-087, 102 Pages, 2008/02

JAEA-Research-2007-087.pdf:35.58MB

The Japanese islands are located in the tectonically active Circum-Pacific Mobile Belt. As a result, Japan has a high frequency of earthquakes and eruptions. Special consideration is given to the long-term stability of the geological environment, taking into account volcanism, faulting, uplift, denudation, climatic change and sea-level change in Japan. Development of research/prediction technologies for geotectonic events has been carried out to evaluate the long-term stability of the geological environment in Japan. Until fiscal year 2005, to confirm existence of phenomena that have a influence on geological disposal system (e.g. active fault or Quarternary volcanoes) and to confirm that there was not the trace that the phenomena occurred in the past and to predict/evaluate possibility of the phenomena, development of the research/prediction techniques for geotectonic events (e.g. Research techniques for earthquake source faults, Research techniques for detecting magmas and high-temperature fluids, Three-dimensional landform development simulator) were carried out. This report describes our efforts of these technologies based on its R&D program until fiscal year 2005.

JAEA Reports

Phenomelogical study on crystalline rock for evaluating of long-term behavior (Contract research)

Okubo, Seisuke*; Seno, Yasuhiro; Nakama, Shigeo; Sato, Toshinori*; Hirano, Toru

JAEA-Research 2007-088, 118 Pages, 2008/03

JAEA-Research-2007-088.pdf:27.7MB

This report describes the results of the works in the FY2005 and 2006. In Chapter 2, as the fundamental study on time-dependent behavior, followings were described; (1) The result of continuing creep test of Tage tuff which was started from the FY1997. (2) The results of multi-stage creep test of Inada granite at mid-range temperature. (3) The consideration of the generalized relaxation test. (4) The consideration of new testing method to determine the parameter in the constitutive equation supposed by Okubo. In Chapter 3, followings were described; (1) The results of rock mechanical tests of Toki granite. (2) The results of obtained parameters for the constitutive equation considering time-dependent behavior by mechanical tests and numerical simulations. Furthermore, in this report, following two related studies were attached in appendix; (1) Study on evaluating the effects of scatter in in-situ rock properties. (2) Study on new rock classification method considering long-term behavior of rock mass.

JAEA Reports

Study on applicability of low alkaline cement in Horonobe Underground Research Laboratory Project (Contract research)

Matsuda, Takeshi*; Noda, Masaru*; Iriya, Keishiro*; Konishi, Kazuhiro*; Nakayama, Masashi; Kobayashi, Yasushi

JAEA-Research 2007-089, 139 Pages, 2008/05

JAEA-Research-2007-089.pdf:13.57MB

In Horonobe Underground Research Center construction of underground facility began in 2005 and construction practicality test with HFSC (Highly Fly-ash contained Silica-fume Cement) is planned in a part of the gallery. Before the HFSC will be contracted in the gallery it is necessary to check that the HFSC has performance under the actual construction. The main work of this Japanese fiscal year is making a detailed test plan for the HSFC construction practicality, that is scheduled after 2007 and laboratory tests on lowering behavior of pH in the HFSC concrete were conducted. On the construction practicality test with low alkaline concrete, HFSC in-situ experiment plan was studied in case using HSFC424N as shotcrete. The aims of the in-situ test are the validation in applicability of low alkaline concrete as a support member for underground opening in the realistic geological environment and building the method to evaluate influence to the surrounding geological environment. The location of the in-situ test is in the connection tunnel of a depth of 140m and the geology is the Koetoi formation. The period of the test is approximately 10 years. The test plan was designed to be able to make a comparison with Ordinary Portland Cement. As it is necessary to confirm the strength property of the HFSC concrete with materials procured at construction site, strength of the base concrete using local procured fine aggregate and coarse aggregate based on the result of the selection of mix proportion in 2005 research was checked. On laboratory tests on lowering behavior of pH in HFSC concrete, the pH of immersion fluid was measured and components of the immersion fluid and the solid phase were analyzed using test specimens in a long-term immersion test which had been continued since 2005.

JAEA Reports

Heat calculation for gasification chamber of steam reformer

Okanuma, Hiroshi; Sasaki, Toshiki; Yamaguchi, Hiromi

JAEA-Research 2007-090, 46 Pages, 2008/02

JAEA-Research-2007-090.pdf:2.57MB

JAEA has many kinds of low level radioactive wastes and some of them are difficult to be decomposed by an incinerator. Steam reforming as treatment technology for low level radioactive wastes has been developed for decomposition and mineralization of the wastes in waste management department of JAEA, which contributes to appropriate disposal of the wastes. In this report, a heat calculation model for the gasification chamber of the steam reformer has been developed for estimation what samples can be treated or not, and effective and efficient improvement of operation. The following two cases have been calculated by the heat calculation model and it has been verified by comparing the results of calculation with the experimental data which were obtained in the latter half of fiscal year 2006. One calculation case is concerned with the operation of gasification chamber without sample feed. The other is concerned with the operation of gasification chamber with sample feed. The results of heat calculation without sample feed are in agreement with the experimental data relatively, but those of with sample are more different from the experimental data than those of without sample. This shows that the heat calculation model we have developed is feasible in terms of gas heating, but has problems in terms of physical and chemical changes of the sample in the gasification chamber. We need to modify the model in the part of physical and chemical changes of the sample in it.

JAEA Reports

Evaluation of creep strength on SUS304 under off-normal over-heating

Kato, Shoichi; Hasebe, Shinichi; Yoshida, Eiichi

JAEA-Research 2007-091, 33 Pages, 2008/02

JAEA-Research-2007-091.pdf:7.22MB

Loss of heat removal system at reactor shutdown is one of the objects of the probabilistic safety assessment of fast breeder reactors. In this research, the creep rupture data of type 304 stainless steel in high temperature has been obtained for the purpose of evaluation of mechanical strength of the structural materials at the severe accident, and applicability of the creep rupture formula adopted as the material strength standard for proto type fast breeder reactors has been investigated.

JAEA Reports

Horonobe Underground Research Laboratory Project; Investigation report for the 2006 fiscal year

Matsui, Hiroya; Nakayama, Masashi; Sanada, Hiroyuki

JAEA-Research 2007-092, 83 Pages, 2008/05

JAEA-Research-2007-092.pdf:16.75MB

The Horonobe URL project is planned to extend over a period of 20 years. The investigations will be conducted in three phases, namely Surface-based investigations, Construction Phase (investigations during construction of the underground facilities) and Operation phase (research in the underground facilities). This report summerizes the results of the investigations for 2006 fiscal year (2006/2007), the second year of the Phase 2 investigations. The investigations, which are composed of Geoscientific research and R&D on geological disposal of high-level radioactive waste (HLW), were carried out according to Horonobe Underground Research Laboratory Project Investigation Program for the 2006 Fiscal Year.

JAEA Reports

BEM-DDM modelling of rock damage and its implications on rock laboratory strength and in-situ stresses

Lanaro, F.*; Matsui, Hiroya

JAEA-Research 2007-093, 237 Pages, 2008/03

JAEA-Research-2007-093.pdf:7.06MB

This study was conducted to determine the effects of sample damage on the strength obtained from laboratory results (uniaxial compression and Brazilian test). Results of testing on samples of Toki granite taken at Shobasama and at the construction site for the Mizunami Underground Research Laboratory (MIU) were analysed. Some spatial variation of the results along the boreholes suggested the presence of a correlation between the laboratory strength and the in-situ stresses measured by means of the hydro-fracturing method. To confirm this, numerical analyses of the drilling process in brittle rock by means of a BEM-DDM program (FRACOD2D) were carried out to study the induced fracture patterns. Moreover, a numerical study of the fracture patterns induced by removal of the overburden on a large scale produces fracture patterns and stress distributions corresponding to observations in crystalline hard rock in Canada, Japan and Sweden.

JAEA Reports

A Study on extrusion behavior of buffer material into fractures using X-ray CT method

Tanai, Kenji; Matsumoto, Kazuhiro*

JAEA-Research 2007-094, 11 Pages, 2008/02

JAEA-Research-2007-094.pdf:5.34MB

The buffer that will be used as a component of the engineered barriers system for geological disposal of high-level radioactive waste is designed to swell when it becomes saturated by groundwater. As a result of the swelling, bentonite buffer material may penetrate through open fractures into the surrounding host rock. If it is sustained for extremely long periods of time, the bentonite extrusion could lead to reduction of the buffer density, which may in turn degrade the expected performance (e.g. low permeability, diffusion control, colloid filtration, load-bearing capacity, etc). In this study, extrusion test with X-ray CT measurement was carried out to clarify the mechanical behavior of bentonite extrusion through fractures in the surrounding rock. In the extrusion test, the out flow distance into fracture is affected by bentonite content ratio and ionic strength of ground water. X-ray CT measurement is available to evaluate the density distribution of bentonite into the fractures. The X-ray CT measurement will play an important role for study of extrusion behavior of buffer material, particularly for development of extrusion models for compacted bentonite.

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