JAEA Abstracts

-Research results below have been sorted by order of journals name.

-Sorry, some research results below have no English abstract.

January 2011

39000017
Fluorine-vacancy defects in fluorine-implanted silicon studied by electron paramagnetic resonance
Umeda, Takahide*; Isoya, Junichi*; Oshima, Takeshi; Onoda, Shinobu; Morishita, Norio; Okonogi, Kensuke*; Shiratake, Shigeru*
Applied Physics Letters 97(4), p.041911_1-041911_3(2010) ; (JAEA-J 08248)

In this study, fluorine-vacancy defects (F_nV_m) in Silicon (Si) were investigated by electron paramagnetic resonance, EPR. The F_nV_m vacancies in Si were created using fluorine ion implantation at room temperature and subsequent annealing up to 700 °C. As a result, the most primitive center was FV₂ (the F0 center) in the case of initial stage of F implantation. With increasing the implanted F ions or annealing to the sample, other F_nV_m defects with more accumulation of F atoms appeared. Then, the F₁ center (F_nV₅) was observed as the most stable center. The next one was the F₂ center (F_nV₂). F_nV₃ defects were not found in this study. F_nV₄ defects were probably detected as the F₃ center.

39000018
Activities on public awareness of a prototype fast breeder reactor, Monju, and casebook of potential troubles
Yanagisawa, Tsutomu; Tabata, Hiroaki; Mori, Masaomi
E-Journal of Advanced Maintenance (Internet) 2(1), 7p.(2010) ; (JAEA-J 08249)

Monju, the Japanese prototype of fast breeder reactor, has engaged in various activities to restore the public trust since the sodium leak accident occurred in 1995. Among the activities is the publication of a risk communication booklet "Response to the possible accident and trouble in Monju" which is compiled according to the operational progress of "Monju". This booklet is intended for promoting the public understanding toward the restart. The supplement of the booklet illustrates the outline and characteristics of "Monju", the recent troubles at not only "Monju", but also home and abroad, and the assumed troubles during the core confirmation test which is implemented when the system start-up test is commenced. These efforts for the restart are also explained.

39000019
A Review of fusion and tokamak research towards steady-state operation; A JAEA contribution
Kikuchi, Mitsuru
Energies (Internet) 3(11), p.1741-1789(2010) ; (JAEA-J 08250)

As a memory of 50 years of fusion research, a review of fusion fundamentals, concept and research towards steady state tokamak reactor is reviewed. Since the development of SSTR concept in 1990, tokamak research made significant progresses as advanced tokamak research. Current formation and MHD stability in tokamak is reviewed.

39000020
Proton resonance elastic scattering in inverse kinematics on the medium heavy nucleus ⁶⁸Zn
Imai, Nobuaki*; Hirayama, Yoshikazu*; Ishiyama, Hironobu*; Jeong, S.-C.*; Miyatake, Hiroari*; Watanabe, Yutaka*; Makii, Hiroyuki; Mitsuoka, Shinichi; Nagae, Daisuke*; Nishinaka, Ichiro; Nishio, Katsuhisa; Yamaguchi, Kanako*
European Physical Journal A 46(2), p.157-160(2010) ; (JAEA-J 08251)

An isobaric analog resonance of ⁶⁹Zn was studied by the resonance elastic scattering of p(⁶⁸Zn,p) with a 5.5-MeV/nucleon ⁶⁸Zn beam and a thick polyethylene target. The excitation function of the differential cross section of proton elastic scattering was measured around 0 degrees in the laboratory frame by the thick target inverse kinematics method. The angular momentum, and proton and total widths of the resonance assigned using an R-matrix calculation are in good agreement with earlier measurements performed using normal kinematics, demonstrating that the thick target inverse kinematics method is a useful tool for studying the single particle structures of neutron-rich nuclei.

39000021
Tritium permeation behavior in SiC/SiC composites
Isobe, Kanetsugu; Yamanishi, Toshihiko; Konishi, Satoshi*
Fusion Engineering and Design 85(7-9), p.1012-1015(2010) ; (JAEA-J 08252)

The measurement of tritium permeation behavior of NITE-SiC/SiC composites in both low tritium partial pressure and tritium diluted with hydrogen was carried out. Steady-state tritium permeation fluxes of NITE-SiC/SiC that has low permeability of hydrogen could be measured successfully by using tritium, even though low partial pressure (0.6 Pa). Steady-state tritium permeation fluxes were estimated to be 9.5×10^-12[mol/m²sec]. In the experiment of tritium diluted with hydrogen, it was found that steady-states permeation fluxes was decreased with the increase of distillation rate, although the partial pressure of tritium in all condition was same (0.6 Pa).

39000022
Measurement of TPR distribution in natural Li₂TiO₃/Be assembly with DT neutrons
Kondo, Keitaro; Tatebe, Yosuke; Ochiai, Kentaro; Sato, Satoshi; Takakura, Kosuke; Onishi, Seiki; Konno, Chikara
Fusion Engineering and Design 85(7-9), p.1229-1233(2010) ; (JAEA-J 08253)

In the previous blanket neutronics experiments conducted at the FNS facility of Japan Atomic Energy Agency, the following disagreements between experiments and analyses have been pointed out: (1) In the experiment with a ⁶Li-enriched Li₂TiO₃ layer and a beryllium layer, approximately 10% overestimation was found for the tritium production rate (TPR) when a neutron reflector composed of SS316 was attached. (2) In the experiment with natural Li₂O pebbles sandwiched by beryllium layers, TPR was overestimated near the rear beryllium layer by up to 10%. In order to confirm the above problems clearly, a new blanket neutronics experiment using a natural Li₂TiO₃ layer and beryllium layers with DT neutrons was conducted at FNS. TPR distributions inside the Li₂TiO₃ layer were measured with Li₂CO₃ pellets with and without the source reflector. The measured TPR well agreed with the calculation within an estimated experimental error of 6% in the both experiments. The influence of the reflector was not remarkable in the present experiment. Contrary to our expectation, no remarkable difference was observed in the TPR distribution around the rear beryllium layer.

39000023
Search for reality of solid breeder blanket for DEMO
Tobita, Kenji; Uto, Hiroyasu; Liu, C.; Tanigawa, Hisashi; Tsuru, Daigo; Enoeda, Mikio; Yoshida, Toru; Asakura, Nobuyuki
Fusion Engineering and Design 85(7-9), p.1342-1347(2010) ; (JAEA-J 08254)

For a tokamak fusion DEMO reactor with the fusion output of 2.95 GW, neutronics and thermal design was carried out to find a blanket concept with reality. For the continuity with the Japanese ITER-TBM options, this study considered water-cooled blanket with solid breeding materials of Li ceramics and Be multipliers. A neutronics-heat coupled analysis determined an optimal arrangement of blanket interior under the constraints of the operating temperature of breeding materials and multipliers. When the cooling water is used under 23 MPa and 290-360 °C, the overall tritium sufficiency is marginally satisfied although blankets with high neutron wall load (P_n = 5 MW/m²) around the mid-plane do not meet the required local TBR. Based on the results, possible directions for further research are presented.

39000024
Recent R&D results on polymeric materials for a SPE-type high-level tritiated water electrolyzer system
Iwai, Yasunori; Sato, Katsumi; Hiroki, Akihiro; Tamada, Masao; Hayashi, Takumi; Yamanishi, Toshihiko
Fusion Engineering and Design 85(7-9), p.1421-1425(2010) ; (JAEA-J 08255)

The deteriorations of polymeric materials for a SPE-type high-level tritiated water electrolyzer composed of the Water Detritiation System (WDS) against sulfonic acid environment and radiation environment were discussed. A long-term durability of VITON, AFLAS, denaturated polyphenylene ether, and Kapton polyimide immersed in a sulfonic acid was demonstrated. Negligible degradation in percent elongation at break of these polymeric materials was observed up to the immersing period of 2 years. The detectable radiation deterioration in ionic conductivity of Nafion N117CS ion exchange membrane irradiated with electron beams up to the integrated dose of 1500 kGy was measured. The ionic conductivity of Nafion N117CS ion exchange membrane irradiated at more than 1000 kGy was slightly deteriorated. As for the elastomers for its use as a seal, the radiation degradation in hardness of VITON, AFLAS was investigated. Negligible degradation in hardness of these rubbers was observed up to the integrated dose of 1500 kGy. The water uptake of rubbers was generally increased as the integrated dose was increased. However, irradiated VITON rubbers had constant water uptake up to the integrated dose of 1500 kGy.

39000025
Failure and its mechanism of LWR and research reactor fuels
Yanagisawa, Kazuaki
International Journal of Nuclear Safety and Simulation 1(3), p.246-257(2010) ; (JAEA-J 08256)

A LWR fuel consisted of UO₂ pellet with zircaloy cladding and a research reactor fuel consisted of aluminide or silicide fuel cores with Al alloy. (1) LWR fuels were irradiated at the HBWR up to burn-up of 20 MWd/kgU and power ramped to have the PCI failure. The failure threshold of LWR was lower than that of HBWR. The in-core data was useful for obtaining the input data for the computer code FEMAXI. (2) Fresh or pre-irradiated LWR fuels were pulse-irradiated at the NSRR. For the fresh fuel, a failure occurred at 260 cal/g with cladding melt-brittle mechanism. For the pre-irradiated PWR fuel, a cladding split along one generatrix occurred at 118 cal/g. The failure mechanism may be the strong PCMI combined with the transient FGR. (3) Research reactor fuels failed by the through-plate cracking (les than 640 °C) or cladding melt (above 640 °C). A failure mechanism for the former was a tensile stress caused by a local uneven temperature profile during a quench.

39000026
Composition dependence of magnetic and magnetotransport properties in C₆₀-Co granular thin films
Sugai, Isamu*; Sakai, Seiji; Matsumoto, Yoshihiro; Naramoto, Hiroshi*; Mitani, Seiji*; Takanashi, Koki; Maeda, Yoshihito
Journal of Applied Physics 108(6), p.063920_1-063920_7(2010) ; (JAEA-J 08257)

Composition dependence of magnetic and magnetotransport properties in C₆₀Co_x thin films exhibiting large magnetoresistance TMR effect was investigated in the Co composition range of x=8-20, where x denotes the number of Co atoms per C₆₀ molecule. The composition dependence of magnetic property revealed a structural transition from well-defined granular structures in the range of x=8-17 to magnetically and electronically coupled states of Co nanoparticles over x=17. As a result of the structural change, the MR behavior became different between the two composition regions separated at x=17. It is found that the zero-bias MR ratio and also the strength of the voltage dependence are in proportion to the charging energy to Co nanoparticles in the samples with well-defined granular structures. The present results indicate that the charging effect of Co nanoparticles plays an important role in the anomalously large MR effect of C₆₀-Co granular films.

39000027
Iron distributions in the water column of the Japan Basin and Yamato Basin (Japan Sea)
Fujita, Satoshi*; Kuma, Kenshi*; Ishikawa, Satoko*; Nishimura, Shotaro*; Nakayama, Yuta*; Ushizaka, Satomi*; Isoda, Yutaka*; Otosaka, Shigeyoshi; Aramaki, Takafumi*
Journal of Geophysical Research 115(C12), p.C12001_1-C12001_12(2010) ; (JAEA-J 08259)

Vertical distributions of dissolved iron (D-Fe, less than 0.22 micrometer fraction), total iron (T-Fe, unfiltered), and chemical and biological components (e.g., nutrients) in seawater were determined at seven stations in the Japan Sea to understand the mechanisms that control iron behavior. Distributions of the D-Fe were characterized by surface depletion, mid-depth maxima, then slight decrease with depth in deep water and uniform concentration in bottom water because of biological uptake in the surface water and release from microbial decomposition of sinking organic matter in mid-depth water. The T-Fe concentrations in the deep-water column were variable with different T-Fe levels among stations and depths. We found a significant relationship of the exponential increase in the T-Fe concentrations with decreasing water transmittance, resulting from the iron supply into the deep and bottom waters due to the lateral transport of resuspended sediment from the continental slope.

39000028
Measurement of neutron capture cross section ratios of ²⁴⁴Cm resonances using NNRI
Goko, Shinji*; Kimura, Atsushi; Harada, Hideo; Oshima, Masumi; Ota, Masayuki*; Furutaka, Kazuyoshi; Kin, Tadahiro; Kitatani, Fumito; Koizumi, Mitsuo; Nakamura, Shoji; Toh, Yosuke; Igashira, Masayuki*; Katabuchi, Tatsuya*; Mizumoto, Motoharu*; Kiyanagi, Yoshiaki*; Kino, Koichi*; Furusaka, Michihiro*; Hiraga, Fujio*; Kamiyama, Takashi*; Hori, Junichi*; Fujii, Toshiyuki*; Fukutani, Satoshi*; Takamiya, Koichi*
Journal of Nuclear Science and Technology 47(12), p.1097-1100(2010) ; (JAEA-J 08262)

To obtain the accurate nuclear data of minor actinides required for a nuclear transmutation system or an innovative nuclear fuel cycle system, measurement of neutron-capture cross section of ²⁴⁴Cm was performed using NNRI installed at beam line No.4 (BL04) of MLF in J-PARC. Using "4π Ge spectrometer" that is a component of NNRI, neutron time of flight spectra and prompt γ ray spectra were measured. Then neutron-capture cross section ratios of ²⁴⁴Cm resonances were derived and compared with the evaluated values of JENDL-3.3. The previous experimental data was measured using a nuclear explosion as a pulsed neutron source, and the present result is the first time in the world that such measurements have been carried out at an accelerator facility. By developing techniques for more detailed analysis and improvement of the experimental conditions, the absolute values of capture cross section are expected to be obtained.

39000029
Reliability of core exit thermocouple for accident management action during SBLOCA and abnormal transient tests at ROSA/LSTF
Suzuki, Mitsuhiro; Nakamura, Hideo
Journal of Nuclear Science and Technology 47(12), p.1193-1205(2010) ; (JAEA-J 08263)

Presented in the paper are experimental results on general performance of core exit thermocouple (CET) to detect core overheat for accident management (AM) action. Thirteen tests simulating small break loss-of-coolant accident (SBLOCA) and abnormal transient are studied by using the Large Scale Test Facility (LSTF) which is a full-height, full-pressure and 1/48 volumetric-scaled PWR model. Clarified are as follows, (1) general CET performance with certain delay in time and temperature rise from core overheating in most cases, (2) one common reason of the delay due to cooling effects of metal structures in core and core exit, (3) an indication of superheat instead of its temperature necessary for significantly high or low pressure transients, (4) no CET heat-up in case of large water fall-back from hot legs and in addition, discussion on applicability to PWR is presented.

39000030
Reply to comment on "A Statistical-mechanical method to evaluate hydrogen solubility in metal"
Ogawa, Hiroaki
Journal of Physical Chemistry C 114(36), p.15544-15545(2010) ; (JAEA-J 08264)

39000031
The Configuration and electronic state of SO₃ adsorbed on Au surface
Suzuki, Chikashi; Nakagiri, Toshio
Journal of Physics and Chemistry of Solids 72(1), p.10-16(2011) ; (JAEA-J 08265)

We evaluated the adsorption of SO₃ molecule on the Au (111) surface using the first-principles calculations by a slab model with a periodic boundary condition. We find that there are six stable adsorption configurations on the Au surface, where SO₃ molecules are adsorbed above the three-fold fcc and hcp hallow sites and atop site. In two of these configurations, S and two O atoms are bound to the Pt atoms, and in two other of them, all the three O atoms are bound to Pt surface atoms, and then, S atom is bound to Au surface atom on the atop site and O atoms are situated on the hallow sites. In addition, it is found that molecular orbitals of SO₃ and those of Au surface are hybridized in the active metal d-bands region, that the localized molecular orbitals in SO₃ are stabilized, and that the charge is transferred from Au to S 3p by SO₃ adsorption on Au surface though the other interaction of S and O (bound to Au) component with Au is little. In addition, the bond between S and O bound to Au become weak by SO₃ adsorption on Au surface because the charge polarization to O-Au bond weakens the bond between S and O bound to Au. This interaction is assumed to encourage the breakage of S-O bond.

39000032
First-principles description for coherent phonon generation in diamond
Shinohara, Yasushi*; Kawashita, Yosuke*; Iwata, Junichi*; Yabana, Kazuhiro*; Otobe, Tomohito; Bertsch, G. F.*
Journal of Physics; Condensed Matter 22(38), p.384212_1-384212_4(2010) ; (JAEA-J 08266)

We report a first-principle description for coherent phonon generation in diamond based on the time-dependent density functional theory. The time-dependent Kohn-Sham equation is solved in real-time to calculate the electron dynamics in periodic solid under an ultrashort laser pulse. We find the calculated forces acting on ions are consistent with measurements in selection rule and in dependence on laser intensity.

39000033
Orientation dependence of Pd growth on Au electrode surfaces
Takahashi, Masamitsu; Tamura, Kazuhisa; Mizuki, Junichiro; Kondo, Toshihiro*; Uosaki, Kohei*
Journal of Physics; Condensed Matter 22(47), p.474002_1-474002_9(2010) ; (JAEA-J 08267)

Thin Pd films which were electrochemically grown on Au(111) and Au(001) electrodes have been investigated by surface X-ray scattering. Comparison of Pd/Au(111) and Pd/Au(001) growth modes shows similarity in the first layer deposition. On Au(111) and Au(001) substrates, Pd follows the crystal structure of the substrates and forms a pseudomorphic monolayer. Beyond 2 ML, however, Pd films grown on Au(111) are relaxed, although there are still pseudomorphic layers at the interface. In contrast, Pd films on Au(001) continue to grow pseudomorphically over 10 ML. The difference in the growth mode between (111) and (001) surfaces is not ascribable only to anisotropy in the elasticity of the film. The relationship between a growing surface and an allowed gliding plane in misfit dislocations is presented as a crucial factor determining the critical thickness of the film.

39000034
Magnetic properties and ferromagnetic microstructures in Al-doped La_1-xSr_xMnO₃
Mori, Shigeo*; Yoshidome, Kazuhiro*; Nagamine, Yuki*; Togawa, Yoshihiko*; Yoshii, Kenji; Takenaka, Koshi*
Journal of Physics; Conference Series 200, p.012129_1-012129_4(2010) ; (JAEA-J 08268)

Doping effect on ferromagnetic (FM) properties in perovskite manganites La_1-xSr_xMnO₃ (x=0.175) were investigated by low-temperature Lorentz transmission electron microscopy (TEM), in combination with the conventional magnetic measurements. It is found that La_0.825Sr_0.175Mn_0.95Al_0.05O₃ exhibits a structural phase transition from the rhombohedral to orthorhombic structures at Ts∼116 K. During the rhombohedral-to-orthorhombic transition, the FM domain structures changed from the macroscopic FM domains to the FM ones with the wavy stripe pattern. The ac magnetic measurements also revealed that La_0.825Sr_0.175Mn_0.95Al_0.05O₃ shows unconventional magnetic behaviour at low temperature below 65 K. Partial substitution of non-magnetic Al³⁺ for Mn³⁺ has some influence on magnetic ordering and double-exchange interaction, which should induce insulator behaviour in the orthorhombic phase.

39000035
Electrodynamics and intrinsic Josephson effects in multi-gap superconductors
Koyama, Tomio*; Ota, Yukihiro; Machida, Masahiko
Journal of Physics; Conference Series 248, p.012036_1-012036_6(2010) ; (JAEA-J 08269)

We develop a theory for the Josephson effects in 2-gap intrinsic Josephson junctions stacks (IJJs). The coupled dynamical equations for the phase differences are derived from the low-energy effective Lagrangian. The equations describe the longitudinal Josephson plasma and the Josephson-Leggett (JL) mode propagating in the direction perpendicular to the junctions. Numerical results for the I-V characteristics are presented. The I-V characteristics shows multiple-branch structures similar to that in Bi-2212 IJJ's. When the Josephson frequency is approached to the JL mode frequency in non-uniform voltage branches, the JL mode is resonantly exited. At the resonant voltage a step-like structure appears in the I-V curves in low-voltage branches.

39000036
Theory of Josephson effects in iron-based multi-gap superconductor junctions
Ota, Yukihiro; Machida, Masahiko; Koyama, Tomio*
Journal of Physics; Conference Series 248, p.012090_1-012090_8(2010) ; (JAEA-J 08270)

Since the discovery of iron-based superconductors, Josephson junctions including such new materials have been intensively studied in order to explore their pairing symmetry and application potential. One of interesting features of this type of materials is the presence of multiple (more than two) bands on Fermi surface and their contributions to superconductivity. As a result, iron-based superconductor junctions are possible to have multiple tunneling channels between the superconducting electrodes. In this paper, we show a theory of Josephson junctions with multigap superconductors. We discuss how the relative fluctuations between multiple gaps and the pairing symmetry modify the Shapiro steps.

39000037
X-ray photoemission spectroscopy analysis of N-containing carbon-based cathode catalysts for polymer electrolyte fuel cells
Niwa, Hideharu*; Kobayashi, Masaki*; Horiba, Koji*; Harada, Yoshihisa*; Oshima, Masaharu*; Terakura, Kiyoyuki*; Ikeda, Takashi; Koshigoe, Yuka*; Ozaki, Junichi*; Miyata, Seizo*; Ueda, Shigenori*; Yamashita, Yoshiyuki*; Yoshikawa, Hideki*; Kobayashi, Keisuke*
Journal of Power Sources 196(3), p.1006-1011(2011) ; (JAEA-J 08271)

We report on the electronic structure of three different types of N-containing carbon-based cathode catalysts for polymer electrolyte fuel cells observed by hard X-ray photoemission spectroscopy. C 1s spectra show the importance of sp² carbon network formation for the oxygen reduction reaction (ORR) activity. Samples having high oxygen reduction reaction activity in terms of oxygen reduction potential contain high concentration of graphite-like nitrogen. Based on a quantitative analysis of our results, the oxygen reduction reaction activity of the carbon-based cathode catalysts will be improved by increasing concentration of graphite-like nitrogen in a developed sp² carbon network.

39000038
Magnetic and dielectric study of R_0.5Sr_0.5MnO₃ (R = Gd, Tb and Dy)
Yoshii, Kenji; Hiramitsu, Yusuke*; Okajima, Yuka*; Yoneda, Yasuhiro; Nishihata, Yasuo; Mizuki, Junichiro; Nakamura, Akio; Shimojo, Yutaka; Ishii, Yoshinobu*; Morii, Yukio; Ikeda, Naoshi*
Materials Research Bulletin 45(11), p.1574-1580(2010) ; (JAEA-J 08272)

Magnetic and dielectric properties of perovskite manganites R_0.5Sr_0.5MnO₃ (R = Gd, Tb and Dy) have been investigated. DC and AC magnetic measurements showed short-range glassy magnetic ordering at Tg about 40 K. Such ordering was observed by neutron diffraction and is ascribable to the size mismatch of R³⁺ and Sr³⁺ settled randomly at the same crystallographic site. Dielectric constants for each material were about 1000-10000 between about 50 K and 300 K and showed broad maximums above Tg. Dielectric dispersion showed poor coherency of the motion of polar regions, plausibly because of the size-mismatch effect; both the magnetic and dielectric properties of this system are governed by the randomness at the R/Sr site. The tanδ and EXAFS data suggest that the dielectric response is rooted in a transfer of the Mn-3d electrons.

39000039
New surprises "down below"; Recent successes in the synthesis of actinide materials
Sarrao, J. L.*; Haga, Yoshinori; Ward, R. C. C.*
MRS Bulletin 35(11), p.877-882(2010) ; (JAEA-J 08273)

Recent discoveries of novel electronic states, including relatively high-temperature superconductivity, in the actinides point to exciting prospects for future discoveries at the bottom of the periodic table. A key ingredient in all of the successes discussed here is the role of high-quality synthesis in enabling advances. Results on PuCoGa₅, NpPd₅Al₂, and single crystal uranium are discussed.

39000040
Empirical scaling of sawtooth period for onset of neoclassical tearing modes
Chapman, I. T.*; Buttery, R. J.*; Coda, S.*; Gerhardt, S.*; Graves, J. P.*; Howell, D. F.*; Isayama, Akihiko; La Haye, R. J.*; Liu, Y.*; Maget, P.*; Maraschek, M.*; Sabbagh, S.*; Sauter, O.*; ASDEX Upgrade*; DIII-D*; HL-2A*; JT-60U*; MAST*; NSTX*; TCV*; Tore Supra Teams*; JET-EFDA Contributors*
Nuclear Fusion 50(10), p.102001_1-102001_7(2010) ; (JAEA-J 08275)

39000041
Fuelling characteristics of supersonic molecular beam injection in JT-60U
Takenaga, Hidenobu; Miyo, Yasuhiko; Bucalossi, J.*; Marty, V.*; Urano, Hajime; Asakura, Nobuyuki; Nishiyama, Tomokazu; Sasajima, Tadayuki; Masaki, Kei; Kaminaga, Atsushi
Nuclear Fusion 50(11), p.115003_1-115003_10(2010) ; (JAEA-J 08276)

The supersonic molecular beam injection (SMBI) was successfully operated in JT-60U. Frequent density jumps were clearly observed in the main plasma against the SMBI pulses with the background gas pressure (P_BK) of 2-6 bar. Fuelling efficiency exhibited weak dependence on P_BK and the injection direction (high- and low-field-side injections). The amount of the fuelling necessary for achieving the same density level is much smaller for the SMBI than for the gas-puffing. It is comparable for the SMBI and the pellet injection even with shallower penetration of the SMBI as discussed below. The SMBI ionization area was estimated based on emission measured using the fast TV camera with a time resolution of 0.167 ms. The estimations indicated similar penetration position for P_BK = 6 and 2 bar, although the ionization area was larger for 6 bar. This result supports the weak P_BK dependence of the fuelling efficiency. The front of the ionization area moved between first and second frames of the fast TV camera and it reached just inside the separatrix in the second frame. The ionization area was significantly expanded from the expected SMB size and the expansion was also enhanced between two frames. These relatively slow changes between two frames suggest that interaction between SMB and plasma significantly influences the fuelling characteristics.

39000042
Low temperature structure of FeSr₂YCu₂O_6+δ magnetic superconductor
Mochiku, Takashi*; Hata, Yoshiaki*; Wuernisha, T.*; Igawa, Naoki; Hoshikawa, Akinori*; Ishigaki, Toru*; Yasuoka, Hiroshi*; Hirata, Kazuto*
Physica C 470(Suppl.1), p.S158-S159(2010) ; (JAEA-J 08277)

We have performed neutron powder diffraction of the superconducting FeSr₂YCu₂O₆₊_δ and the nonsuperconducting FeSr₂Y(Cu_0.95Zn_0.05)₂O₆₊_δ samples at low temperature and room temperature to investigate the relation between the crystal structure ant the physical properties. Neutron diffraction study indicates that the magnetic order in this compound is not long-range order because we observed no extra reflection due to the magnetic superstructure. We have observed structural anomaly related to Cu in the superconducting sample around 30 K although we could not observe it in the nonsuperconducting sample. There is possibility of the change of the charge distribution around 30 K in the superconducting sample.

39000043
Spin excitations in iron oxypnictide superconductor system
Shamoto, Shinichi; Ishikado, Motoyuki; Wakimoto, Shuichi; Kodama, Katsuaki; Kajimoto, Ryoichi; Arai, Masatoshi; Fukuda, Tatsuo; Nakamura, Hiroki; Machida, Masahiko; Eisaki, Hiroshi*
Physica C 470(Suppl.1), p.S284-S287(2010) ; (JAEA-J 08278)

The spin excitations in the LaFeAsO_1-xF_x system have been studied by inelastic neutron scattering measurements with powder samples. In the parent compound, the spin excitation was observed as a magnetic rod at (π, π, ℓ) in the downfolded tetragonal Brillouin zone. It persisted even in the tetragonal phase at T = 280 K. In the superconducting compounds with x = 0.057 and 0.082, the spin excitations developed below the superconducting transition temperatures up to the same order of magnitude as that in the parent compound, and they were peaked at about 11 meV. The spin excitation, however, almost disappeared in an overdoped compound with x = 0.158, which exhibited only filamentary superconductivity below 7 K. These results indicate that the present superconductivity intimately correlates with the spin fluctuation possibly in relation to the nesting condition between the Fermi surfaces at Γ and M points.

39000044
Magnetic ordering in blocking layer and highly anisotropic electronic structure of high-T_c iron-based superconductor Sr₂VFeAsO₃: LDA+U study
Nakamura, Hiroki; Machida, Masahiko
Physical Review B 82(9), p.094503_1-094503_5(2010) ; (JAEA-J 08279)

We calculate electronic structures of a high-T_c iron-based superconductor Sr₂VFeAsO₃ by LDA+U method. We assume a checker-board antiferromagnetic order on its blocking layers including vanadium and strong correlation in d-orbits of vanadium through the Hubbard U. While the standard LDA brings about metallic blocking layers and complicated Fermi surface as in the previous literatures, our calculation changes the blocking layer into insulating one and the Fermi surface becomes quite similar to those of other iron-based superconductors. Moreover, the appearance of the insulating blocking-layers suggests high anisotropy on quasi-particle transports as experimental results and predicts new types of intrinsic Josephson effects.

39000045
La substitution effect and hyperfine-enhanced ¹⁴¹Pr nuclear spin dynamics in PrPb₃; ¹³⁹La NMR study in Pr_0.97La_0.03Pb₃
Tokunaga, Yo; Sakai, Hironori; Chudo, Hiroyuki; Kambe, Shinsaku; Yasuoka, Hiroshi; Suzuki, Hiroyuki*; Walstedt, R. E.*; Homma, Yoshiya*; Aoki, Dai*; Shiokawa, Yoshinobu*
Physical Review B 82(10), p.104401_1-104401_6(2010) ; (JAEA-J 08280)

¹³⁹La NMR studies have been performed on PrPb₃ substituted with 3% La. The temperature dependence of the local magnetic susceptibility around La ions has been extracted from the ¹³⁹La Knight shift. These data show that the non-magnetic Γ₃ crystalline-electric-field (CEF) ground state (GS) is preserved even at the nearest neighboring Pr ions, although their CEF level scheme is slightly modified due to the La substitution. On the other hand, the temperature dependence of the nuclear spin-lattice relaxation rate 1/T₁ is found to be well reproduced by assuming the same CEF level scheme over a wide temperature range. However, 1/T₁ shows a strong upturn below 10 K, which is not expected from the non-magnetic CEF GS. We show that the low temperature anomaly can be quantitatively understood in terms of a cross-relaxation process between ¹⁴¹Pr and ¹³⁹La nuclear spins.

39000046
Shapiro steps as a direct probe of ±s-wave symmetry in multigap superconducting Josephson junctions
Ota, Yukihiro; Machida, Masahiko; Koyama, Tomio*
Physical Review B 82(14), p.140509_1-140509_4(2010) ; (JAEA-J 08281)

We theoretically study the Shapiro steps in a hetero-Josephson junction made of a single-gap superconductor and a two-gap one. We find that an anomalous dc Josephson current is induced by tuning the frequency of an applied microwave to the Josephson-Leggett mode frequency, which creates an extra step structure in the I-V characteristics besides the conventional Shapiro steps. The step heights at the resonance voltages exhibit an alternate structure of a large and small value reflecting the gap symmetry of the two-gap superconductor. In the ±s-wave case in which the two gaps have opposite signs in the two-gap superconductor the steps with odd index are enhanced, whereas in the s-wave case the ones with even index have larger values. The existence of the fractional Shapiro steps is also predicted.

39000047
Quantum critical behavior in heavy-fermion superconductor CeIrIn₅
Kambe, Shinsaku; Sakai, Hironori; Tokunaga, Yo; Walstedt, R. E.*
Physical Review B 82(14), p.144503_1-144503_7(2010) ; (JAEA-J 08282)

Based on analysis of nuclear (¹¹⁵In) spin-lattice relaxation time measurements on the heavy fermion superconductor CeIrIn₅, q, w, and temperature-dependences of the dynamical susceptibility Im χ(q,ω_n) near the antiferromagnetic wave vector Q at low energy ω_n ∼ 10^-4 meV have been estimated. The T-dependences found, Im χ(Q,ω_n) ∼ T^-3/2 and antiferromagnetic correlation length ξ∼ T^-3/4, are consistent with quantum critical behavior for a three dimensional antiferromagnet (d=3, z=2) having a spin density wave instability.

39000048
Coherent phonon generation in time-dependent density functional theory
Shinohara, Yasushi*; Yabana, Kazuhiro*; Kawashita, Yosuke*; Iwata, Junichi*; Otobe, Tomohito; Bertsch, G. F.*
Physical Review B 82(15), p.155110_1-155110_10(2010) ; (JAEA-J 08283)

We apply the adiabatic time-dependent density functional theory (TDDFT) to the generation of coherent optical phonons in Si crystals by intense laser pulses. The theory reproduces the main phenomena observed experimentally: dependence on polarization, strong growth at the direct band gap, and the change in phase from below to above the band gap. Both show that two mechanisms invoked in phenomenological theory, namely, impulsively stimulated Raman scattering and displacive excitation, are present in the TDDFT. The calculated phase of the coherent phonon is in qualitative agreement with experiment and with phenomenological modeling in the vicinity of the direct band gap. At higher laser frequencies, the TDDFT predicts additional structure not present in the modeling.

39000049
Effects of spin-orbit coupling and strong correlation on the paramagnetic insulating state in plutonium dioxides
Nakamura, Hiroki; Machida, Masahiko; Kato, Masato
Physical Review B 82(15), p.155131_1-155131_6(2010) ; (JAEA-J 08284)

We perform first-principles calculations taking account of both relativistic and strong correlation effects on plutonium dioxides in order to numerically obtain its observed ground state, i.e., the paramagnetic insulating state and properly calculate the material properties. Generally, it is known for plutonium dioxides that the standard LDA calculations give metallic states and even LDA + U considering the strong correlation on Pu f-orbitals fails to attain the paramagnetic insulating state. In this paper, we clarify that inclusion of the spin-orbit coupling in addition to the strong correlation is responsible for the paramagnetic insulating state. Using the obtained paramagnetic insulating state, we calculate various material properties and claim that the proper state preparation is essential for quantitative evaluation of the material properties.

39000050
Inelastic neutron scattering study of the resonance mode in the optimally doped pnictide superconductor LaFeAsO_0.92F_0.08
Shamoto, Shinichi; Ishikado, Motoyuki; Christianson, A. D.*; Lumsden, M. D.*; Wakimoto, Shuichi; Kodama, Katsuaki; Iyo, Akira*; Arai, Masatoshi
Physical Review B 82(17), p.172508_1-172508_4(2010) ; (JAEA-J 08285)

An optimally doped iron-based superconductor LaFeAsO_0.92F_0.08 with T_c=29 K has been studied by inelastic powder neutron scattering. The magnetic excitation at Q = 1.15 Å^-1 is enhanced below T_c, leading to a peak at E_res=13 meV as the resonance mode.

39000051
Direct observation of low-temperature superstructure in spin- and charge-frustrated ferrite YFe₂O_4-δ
Horibe, Yoichi*; Ikeda, Naoshi*; Yoshii, Kenji; Mori, Shigeo*
Physical Review B 82(18), p.184119_1-184119_5(2010) ; (JAEA-J 08286)

The low-temperature superstructure of YFe₂O_4-δ was carefully investigated by transmission electron microscopy. We found that the unique superstructure at about 100 K is characterized by 1/14 2/7 1/14-type superlattice reflection spots, suggesting the presence of charge reordering process. The low-temperature high-resolution images clearly show superlattice modulations in Y-O layers as well as Fe-O layers. The modification of intra-bilayer charge interactions due to lattice distortions in Y-O layers is discussed to play a crucial role in the stabilization of long-periodic superstructures at low temperatures.

39000052
Signature of hidden order and evidence for periodicity modification in URu₂Si₂
Yoshida, Rikiya*; Nakamura, Yoshiaki*; Fukui, Masaki*; Haga, Yoshinori; Yamamoto, Etsuji; Onuki, Yoshichika; Okawa, Mario*; Shin, S.*; Hirai, Masaaki*; Muraoka, Yuji*; Yokoya, Takayoshi*
Physical Review B 82(20), p.205108_1-205108_6(2010) ; (JAEA-J 08287)

The detail of electronic structures near the Fermi level in URu₂Si₂ has been investigated employing state-of-art laser angle-resolved photoemission spectroscopy. The observation of a narrow dispersive band near the Fermi level in the ordered state as well as its absence in RH-substituted sample strongly suggest that the emergence of the narrow band is a clear signature of the hidden-order transition.

39000053
Schwinger limit attainability with extreme power lasers
Bulanov, S. S.*; Esirkepov, T. Z.; Thomas, A. G. R.*; Koga, J. K.; Bulanov, S. V.
Physical Review Letters 105(22), p.220407_1-220407_4(2010) ; (JAEA-J 08288)

High intensity colliding laser pulses can create abundant electron-positron pair plasma, which can scatter the incoming electromagnetic waves. This process can prevent reaching the critical field of Quantum Electrodynamics at which vacuum breakdown and polarization occur. Considering the pairs are seeded by the Schwinger mechanism, it is shown that the effects of radiation friction and the electron-positron avalanche development in vacuum depend on the electromagnetic wave polarization. For circularly polarized colliding pulses, which force the electrons to move in circles, these effects dominate not only the particle motion but also the evolution of the pulses. While for linearly polarized pulses, where the electrons (positrons) oscillate along the electric field, these effects are not as strong. There is an apparent analogy of these cases with circular and linear electron accelerators with the corresponding constraining and reduced roles of synchrotron radiation losses.

39000054
Effect of magnetic island associated with neoclassical tearing modes on plasma rotation in JT-60U
Isayama, Akihiko; Matsunaga, Go; Ishii, Yasutomo; Sakamoto, Yoshiteru; Moriyama, Shinichi; Kamada, Yutaka; Ozeki, Takahisa; JT-60 Team
Plasma and Fusion Research (Internet) 5, p.037_1-037_6(2010) ; (JAEA-J 08290)

39000055
Anhydrobiosis-associated nuclear DNA damage and repair in the Sleeping Chironomid; Linkage with radioresistance
Gusev, O.*; Nakahara, Yuichi*; Vanyagina, V.*; Malutina, L.*; Cornette, R.*; Sakashita, Tetsuya; Hamada, Nobuyuki*; Kikawada, Takahiro*; Kobayashi, Yasuhiko; Okuda, Takashi*
PLoS ONE (Internet) 5(11), p.e14008_1-e14008_9(2010) ; (JAEA-J 08291)

Anhydrobiotic chironomid larvae can withstand prolonged complete desiccation as well as other external stresses including ionizing radiation. To understand the cross-tolerance mechanism, we have analyzed the damage and repair in the nuclear DNA using DNA comet assays and gene expression in relation to anhydrobiosis and radiation. We found that dehydration causes alterations in chromatin structure and a severe fragmentation of nuclear DNA in the cells of the larvae despite successful anhydrobiosis. Furthermore, while the larvae have restored physiological activity within an hour following rehydration, nuclear DNA restoration typically took 72 to 96 h.

39000056
Simulations of the MATROSHKA experiment at the international space station using PHITS
Sihver, L.*; Sato, Tatsuhiko; Puchalska, M.*; Reitz, G.*
Radiation and Environmental Biophysics 49(3), p.351-357(2010) ; (JAEA-J 08292)

In this paper we will present simulations using the three-dimensional Monte Carlo Particle and Heavy Ion Transport code System (PHITS) of long term dose measurements performed with the European Space Agency (ESA) supported experiment MATROSHKA (MTR), which is an anthropomorphic phantom containing over 6000 radiation detectors, mimicking a human head and torso.

39000057
Neutron, photon and proton energy spectra at high altitude measured using a phoswich-type neutron detector
Takada, Masashi*; Yajima, Kazuaki*; Yasuda, Hiroshi*; Sato, Tatsuhiko; Nakamura, Takashi*
Radiation Measurements 45(10), p.1297-1300(2010) ; (JAEA-J 08293)

In this study, we carried the phoswich-typed neutron detector on the business jet, and measured neutron energy spectrum above Japan.

39000058
Design of a graphite-moderated ²⁴¹Am-Li neutron field to simulate reactor spectra
Tsujimura, Norio; Yoshida, Tadayoshi
Radiation Measurements 45(10), p.1359-1362(2010) ; (JAEA-J 08294)

The neutron calibration field using ²⁴¹Am-Li sources and a moderator was designed to simulate neutron fields found outside the reactor. The moderating assembly selected for the design calculation consists of a cube of graphite blocks with dimensions of 50 cm by 50 cm by 50 cm, in which ²⁴¹Am-Li sources are placed. The depths of the source position were optimized to be 15 cm through Monte Carlo calculations. This moderated neutron source will provide a test field that has a large number of intermediate energy neutrons with a small portion of MeV component.

39000059
Degradation mechanisms of cable insulation materials during radiation-thermal ageing in radiation environment
Seguchi, Tadao*; Tamura, Kiyotoshi; Oshima, Takeshi; Shimada, Akihiko; Kudo, Hisaaki*
Radiation Physics and Chemistry 80(2), p.268-273(2011) ; (JAEA-J 08295)

The cables applied in radiation facility such as a nuclear power plant degrade by radiation and thermal combined ageing. The degradation of polymers for cable insulation is induced by oxidation, and the oxidation is accelerated by synergism of radiation and thermal oxidation. The degradation mechanisms were studied at accelerated degradation for various cable insulation materials. The distribution of degradation in film samples was investigated with various techniques. It was found that the antioxidant agent for stabilizer of insulation materials is closely related to the synergism. With progress of ageing, the concentration of effective antioxidant decreases by radiation decomposition and also by evaporation in thermal ageing. When the concentration of antioxidant is reduced to a limited value, the thermal oxidation is progressing.

39000060
Sorption and diffusion of Eu in sedimentary rock in the presence of humic substance
Seida, Yoshimi; Terashima, Motoki; Tachi, Yukio; Iijima, Kazuki; Nakazawa, Toshiyuki*; Yamada, Norikazu*; Yui, Mikazu
Radiochimica Acta 98(9-11), p.703-709(2010) ; (JAEA-J 08296)

Diffusion and sorption behaviors of Eu in sedimentary rock were investigated in the presence of humic substance in the present study. Sedimentary rock obtained from Horonobe URL test site in Hokkaido, Japan, (accessible pore diameter is around several to several ten nanometer) was used. The Diffusion behaviors of Eu were examined based on reservoir depletion method coupled with analysis of inner distribution of the radioactive elements in the rock. Time sequence of concentration of each radioactive element as well as the humic substance in the reservoir was obtained as a function of concentration and molecular size of humic substance. Coexistence of humic substance reduced the depletion of Eu in the reservoir, indicating complexation between the radioactive elements and the humic substance. On the contrary, obvious decrease of humic substance in the reservoir was not observed in the system. This observation suggests that the radioactive elements became hard to diffuse into the sedimentary rock due to an increase of their size through complexation with the humic substance. The sorption of Eu was reduced with increase of the humic substance although the sorption of the humic substance was not influenced by the existence of Th or Eu. The diffusion and sorption of Eu were found to be reduced in the presence of humic substance.

39000061
Diffusion and sorption of neptunium(V) in compacted montmorillonite; Effects of carbonate and salinity
Tachi, Yukio; Nakazawa, Toshiyuki*; Ochs, M.*; Yotsuji, Kenji; Suyama, Tadahiro; Seida, Yoshimi; Yamada, Norikazu*; Yui, Mikazu
Radiochimica Acta 98(9-11), p.711-718(2010) ; (JAEA-J 08297)

Diffusion and sorption of radionuclides in compacted bentonite are the key processes in the safe geological disposal. The effects of carbonate and salinity on Np(V) diffusion and sorption in compacted montmorillonite were investigated by experimental and modeling approaches. Effective diffusion coefficients (D_e) and distribution coefficients (K_d) of Np in montmorillonite compacted to dry density of 800 kg/m³ were measured under four conditions with different salinities (0.05/0.5 M NaCl) and carbonate concentrations (0/0.01 M NaHCO₃). The D_e for carbonate-free conditions decreased as salinity increased, and those for carbonate conditions showed the opposite dependency. The K_d decreased by one order of magnitude under high carbonate condition. Diffusion and sorption behaviors were interpreted by coupling the thermodynamic aqueous speciation, the thermodynamic sorption model based on ion exchange and surface complexation, and the diffusion model based on electrical double layer theory in narrow pores. The mechanistic model could be useful in predicting the sorption and diffusion behavior of complex species in compacted systems.

39000062
Isotope ratio analysis of individual sub-micrometer plutonium particles with inductively coupled plasma mass spectrometry
Esaka, Fumitaka; Magara, Masaaki; Suzuki, Daisuke; Miyamoto, Yutaka; Lee, C. G.; Kimura, Takaumi
Talanta 83(2), p.569-573(2010) ; (JAEA-J 08298)

In the present work, an analytical technique by a combination of chemical separation and inductively coupled plasma mass spectrometry (ICP-MS) is developed and applied to isotope ratio analysis of individual sub-micrometer plutonium particles. The ICP-MS results for individual plutonium particles prepared from a standard reference material (NIST SRM-947) indicate that the use of a desolvation system for sample introduction improves the precision of isotope ratios. In addition, the accuracy of the ²⁴¹Pu/²⁸⁹Pu isotope ratio is much improved, owing to the chemical separation of plutonium and americium. In conclusion, the performance of the proposed ICP-MS technique is sufficient for the analysis of individual plutonium particles.

39000063
High sensitive and reliable FFDL technique for SFR using laser resonance ionization mass spectrometry
Ito, Chikara; Iwata, Yoshihiro; Harano, Hideki*; Iguchi, Tetsuo*; Aoyama, Takafumi
Transactions of the American Nuclear Society 102(1), p.416-417(2010) ; (JAEA-J 08299)

39000064
Candidate iodides for LLFP transmutation in FR core
Tachi, Yoshiaki; Wakabayashi, Toshio*
Transactions of the American Nuclear Society 103(1), p.268-269(2010) ; (JAEA-J 08300)

It is very attractive technique to transmute long-lived fission products such as iodine-129 included in spent fuel by using Fast Reactors (FRs) to minimize environmental burden and toxic risk due to high level waste disposal. Iodine has low melting point (386K) and low boiling points (457K) compared with FR core temperature. Furthermore, it is corrosive against iron based materials. Then, it is the most important issue to search suitable chemical forms for FR core conditions, having high stability at elevated temperature and good compatibility with cladding material. From the viewpoint of melting point, nuclides generation by neutron irradiation, reactivity with stainless steel, easy fabrication method and recyclability, 5 kinds of iodides of CuI, MgI₂, YI₃, RbI and YI₃ were selected as the candidate chemical form of iodine for transmutation in FR. In order to evaluate stability of the candidate iodides at elevated temperature, TG-DTA of CuI, RbI, BaI₂ and YI₃ were performed. According to TG-DTA results, no significant mass change showed in BaI₂ beyond those temperatures. Mass of CuI, RbI and YI₃ started to be lost severely at the lower temperature than their melting points. Compatibility test between iodides and cladding materials were conducted. Cladding materials in contact with iodides were heated in a capsule filled with pure Ar gas at 873K for 5000h maximum. Results of cross-section observation showed that MgI₂ and YI₃ made pit corrosion on SUS316 and ODS. It appeared that the upper part of the inner surface test capsules with RbI, YI₃ were degraded severely. Based on the experimental results, the most applicable iodide for transmutation by FR is BaI₂ from the viewpoints of stability at elevated temperature and compatibility with cladding material.

39000065
Radiolytic iodine volatilization with organic impurities and low oxygen concentrations
Moriyama, Kiyofumi; Nakamura, Hideo; Nakamura, Koichi*
Transactions of the American Nuclear Society 103(1), p.463-464(2010) ; (JAEA-J 08301)

A computer code, Kiche, was developed at JAEA for the evaluation of the influence of radiolytic volatilization of iodine in the containment of light water reactors during an accident. It solves a chemical kinetics model including water radiolysis, reactions among iodine species, water radiolysis products, and organic compounds. The reactions and rate constants were collected from the literature. The organic iodine production model of Kiche, which was initially based on LIRIC model, was not applicable to low oxygen concentration conditions like inserted containments of BWRs. We modified the model by considering different reaction paths according to the availability of oxygen. The modified model showed improved agreement with our experimental data with various concentrations of organic impurity and oxygen.

39000066
Thirty years experience at the experimental fast reactor Joyo; High quality core management and irradiation field characterization technique
Maeda, Shigetaka; Ito, Chikara; Aoyama, Takafumi; Maeda, Yukimoto; Chatani, Keiji
Transactions of the American Nuclear Society 103(1), p.581-582(2010) ; (JAEA-J 08302)

The experimental fast reactor Joyo of the Japan Atomic Energy Agency is the first liquid sodium fast reactor in Japan. Thirty years of successful operation of Joyo has shown excellent safety and reliability, and has contributed much to the LMFBR development program. Many kinds of irradiation experience have been accumulated to develop the fuels and materials for the prototype reactor Monju and future fast reactors. Accumulated data have been registered with OECD/NEA database with expectation that these data will be widely used. Joyo is presently temporary shutdown because of periodical inspection including in-vessel inspection and repair. After restart, Joyo will play a key role for a wide variety of science and technology fields as fast neutron irradiation bed.

39000067
Monju reactor physics experiments in the restart core
Kitano, Akihiro; Okawachi, Yasushi; Kishimoto, Yasufumi*; Hazama, Taira
Transactions of the American Nuclear Society 103(1), p.785-786(2010) ; (JAEA-J 08303)

The Japanese prototype fast breeder reactor Monju has restarted its operation in May, 2010 after 14-year interruption. This paper summarizes reactor physics experiments in the restart core, for criticality, control rod worth, and isothermal temperature coefficient. The largest change from the previous core, a core before the interruption, is in the contents of ²⁴¹Pu and ²⁴¹Am. The content of ²⁴¹Pu has halved and that of ²⁴¹Am doubled through the ²⁴¹Pu decay during the interruption. The calculation accuracy on the transition from the previous core to the restart core is investigated. The transition is best simulated with JENDL-4 among three nuclear data; JENDL-3.3, JENDL-4, and ENDF/B-VII. The difference mainly appears in ²⁴¹Pu fission and ²⁴¹Am capture cross sections. It is confirmed that the reactor physics data measured in the Monju restart core is valuable to verify nuclear data of the two nuclides.

39000068
Determination of trace amounts of uranium by stripping voltammetry using a boron-doped diamond electrode (in Japanese)
Taguchi, Shigeo; Surugaya, Naoki; Kurosawa, Akira; Hiyama, Toshiaki; Tanaka, Tatsuhiko*
Bunseki Kagaku 59(11), p.1035-1041(2010) ; (JAEA-J 08305)

39000069
Experimental determination of effective attenuation length for SiO₂ thin film with synchrotron radiation phottoemission spectroscopy (in Japanese)
Inoue, Keisuke; Teraoka, Yuden
Denki Gakkai Rombunshi, C 130(10), p.1817-1818(2010) ; (JAEA-J 08306)

The effective attenuation length (EAL) is a necessary parameter to estimate the thickness of SiO₂ overlayer by X-ray photoemission spectroscopy (XPS). Inelastic mean free path (IMFP) is often used instead of EAL because EAL is scarcely known. EAL values were determined experimentally in the photon energy region from 480 eV to 800 eV using synchrotron radiation photoemission spectroscopy. Although EALs estimated are different from calculated IMFPs, EALs, estimated without suboxides, are mostly close to theoretically-calculated IMFPs.

39000070
Research and development using quantum beam at Takasaki Advanced Radiation Research Institute, JAEA (in Japanese)
Tsuji, Hirokazu
Hoshasen To Sangyo (128), p.2-3(2010) ; (JAEA-J 08307)

39000071
Development of new beam technologies at TIARA (in Japanese)
Tanaka, Shigeru; Yokota, Wataru; Kamiya, Tomihiro
Hoshasen To Sangyo (128), p.16-22(2010) ; (JAEA-J 08308)

Beam technologies newly developed at TIARA after the establishment of JAEA in October, 2005 are reviewed. In chapter 2, the technology for micro beam formation of heavy ions at energies of a few hundreds of MeV from AVF cyclotron ,using flat-top acceleration technique and the technology of fast automatic aiming single ion hitting system by heavy ions at energies of a few hundreds of MeV ,are described. In chapter 3, the technologies for micro-nano beam formation of ions at energies of a several MeV from electro-static accelerators and their application to micro fabrication of materials are firstly described, the development of in-air micro PIXE technique and its application are secondly explained, and then research and development of cluster ion beams and their application are described in detail.

39000072
Operation and utilization of irradiation facilities at TARRI (in Japanese)
Kojima, Takuji
Hoshasen To Sangyo (128), p.23-28(2010) ; (JAEA-J 08309)

39000073
Development of the multi-level displacement sensor using Fiber Bragg Gratings (FBG) (in Japanese)
Sanada, Hiroyuki; Sugita, Yutaka; Daimaru, Shuji; Matsui, Hiroya; Kashiwai, Yoshio*
Journal of MMIJ 126(10,11), p.569-576(2010) ; (JAEA-J 08310)

When the structures such as rock slopes, underground caverns for the geological disposal of high level radioactive waste and underground power plants are constructed, the potential for displacement and damage in the surrounding rock mass is increased due to stress concentration and creep phenomenon. Therefore, the long-term monitoring of rock stability for construction of rock cavern and slopes is important to maintain stability of rock structures. Recently, development of sensors that use optical fiber have expanded mainly in the field of civil engineering and, in rock and soil mechanics, since several parameters such as temperature, strain, pressure, pH etc. can be obtained by using backscattered light in optical fibers. Additionally, some important advantages using optical fiber are its high resistance to the electric insulation failure, long-term endurance and ability to transmit data over long distances. This paper describes development of a multiple-type displacement sensor using FBG, which has potential for the long-term durability and high accuracy. Laboratory tests were carried out to investigate the relational expression computed from the relationship of the variation in the Bragg wavelength, temperature and displacement. Accuracy of the prototype developed in this research is better than 0.5% or 1/100 mm. The in situ tests involving long-term monitoring using boreholes were conducted to confirm the workability and applicability of the prototype. From the results of the in situ tests, workability is equivalent to the extensometers usually used for long-term monitoring, and the displacement computed from the variation of Bragg wavelength is almost equal to the artificially induced deformation.

39000074
Experimental reactor physics "Past, present and future"; Towards establishment of safety basis in next generation, 5; Status and outlook of thermal reactor physics experiments in JAEA (in Japanese)
Tonoike, Kotaro
Nippon Genshiryoku Gakkai-Shi 52(12), p.819-823(2010) ; (JAEA-J 08311)

Almost 50 years have passed since the former Japan Atomic Energy Research Institute (JAERI) started the operation of the first critical assembly (CA). Since then, CAs of various types have been served for the experimental research of the reactor physics in the former JAERI, the former Power Reactor and Nuclear Fuel Development Corporation, and current Japan Atomic Energy Agency (JAEA), where the nuclear development history of Japan can be seen. From the view point of the power reactor development, the light water reactor (LWR) was not an obvious option in the early days while all nuclear power plants (NPPs) in Japan are LWRs. Concepts of the graphite reactor and the heavy water reactor were also studied with CAs, where possibility of the breeding with the thermal reactors was investigated as well. Only for the LWR development, various research activities have been conducted for the core and fuel design advancement of NPPs, the reactor of a nuclear propulsion ship, the high conversion reactor, etc. The criticality safety (CS) is an important research field, too, which is prevention of the criticality while the power reactor development is the research how to achieve and maintain the criticality and how to burn fuel well. The CS and the critical experiments are inseparable because the basic way of CS is the critical mass measurement of nuclear material and the enough mass reduction for the nuclear material handling in the safe subcritical condition. History from the past to the present is introduced focusing on critical experiments of the thermal reactor system conducted in JAEA. Its future perspective is also mentioned.

39000075
Novel system for recovering scandium from hot spring water with fibrous graft adsorbent
Seko, Noriaki; Hoshina, Hiroyuki; Kasai, Noboru; Ueki, Yuji; Tamada, Masao; Kiryu, Toshiyuki*; Tanaka, Kazuya*; Takahashi, Makikatsu*
Nippon Ion Kokan Gakkai-Shi 21(3), p.117-122(2010) ; (JAEA-J 08312)

The concentration of scandium dissolved in the hot spring water of Yukawa River, which is located in Kusatsu Town, Gunma, Japan is 17 mg-Sc/ton; this resource corresponds to 1.2 tons in daily flow. We have developed experimental equipment that uses fibrous adsorbents and is capable of selectively collecting scandium from hot spring water. Scandium recovery was carried out by pumping into hot spring water an adsorbent that was packed into a column of 155 mm in inner diameter and 500 mm in height. Such equipment was placed in the Yukawa River at Kusatsu Town. This equipment could be scaled up from lab scale to pilot scale. We found that this system is capable of collecting 200 g/yr of scandium per column when hot spring water flows with 1,000 L/day.

39000076
Aminated adsorbent synthesized by radiation-induced graft polymerization of 4-chloromethylstyrene onto nonwoven polylactic acid fabric and its adsorption capacity for metal ions
Liyanage Don, C. N.*; Ueki, Yuji; Seko, Noriaki; Hoshina, Hiroyuki; Tamada, Masao
Nippon Ion Kokan Gakkai-Shi 21(3), p.123-126(2010) ; (JAEA-J 08313)

Graft adsorbent attracts much attention as a superior metal adsorbent since its adsorption rate is over 10 times higher than that of a commercial granular resin. However, most of metal adsorbents are synthesized from non-biodegradable petroleum materials. The disposal of non-degradable adsorbent disturbs and damages the global environment. Polylactic acid (PLA) is a well-known biodegradable and plant-derived polymer. In this study, nonwoven PLA fabric was used as a trunk polymer of grafting to conserve the global environment and to reduce the consumption of petroleum resources. PLA-based metal adsorbent was synthesized by radiation-induced graft polymerization of 4-chloromethylstyrene onto a nonwoven PLA fabric followed by amination with ethylenediamine. The degree of grafting reached 80% under the optimized grafting conditions. The aminated adsorbent could effectively capture metal ions from weak acid and neutral solutions, and the adsorption capacities at pH 6 were 2.37, 0.32, 0.21 and 0.19 mmol/g for Cu²⁺, Cd²⁺, Pb²⁺ and Zn²⁺, respectively.

39000077
Recovery of scandium with phosphoric chelating adsorbent prepared by direct radiation graft polymerization
Basuki, F.*; Seko, Noriaki; Tamada, Masao
Nippon Ion Kokan Gakkai-Shi 21(3), p.127-130(2010) ; (JAEA-J 08314)

Scandium (Sc) was recovered from aqueous solution by using fibrous phosphoric adsorbent which was prepared directly by radiation-induced grafting of 2-hydroxyethyl methacrylate phosphoric acid onto polyethylene nonwoven fabrics. In batch adsorption evaluation, the grafted fibrous phosphoric adsorbent (FPA) has a high absorption rate for Sc uptake of 100 μg/L, which was 99% adsorbed in contact time of 40 min. In column mode adsorption, the breakthrough point of Sc was independent of flow rate up to 1740 h^-1 in terms of space velocity. In the range of pH 1-3, no significant change in the breakthrough point was observed, which was 700 bed volume (BV) and 250 BV for feeding solutions of 1 and 5 mg/L, respectively. The adsorbed Sc on FPA could be completely eluted by triammonium citrate and the FPA maintained its adsorption capability without any significant loss until 12 cycles of use.

39000078
Weld residual stress evaluation of reactor pressure vessel considering material property changes of heat-affected zone due to weld-overlay cladding (in Japanese)
Nishikawa, Hiroyuki; Katsuyama, Jinya; Udagawa, Makoto; Nakamura, Mitsuyuki; Onizawa, Kunio
Nippon Kikai Gakkai Rombunshu, A 76(770), p.56-64(2010) ; (JAEA-J 08315)

In order to evaluate residual stress distributions in the vessel wall of a reactor pressure vessel (RPV) due to weld-overlay cladding and post-weld heat-treatment (PWHT), thermal-elastic-plastic-creep analysis considering the changes of material properties in heat-affected zone (HAZ) has been performed. Analytical results of stress distributions considered the material property changes in HAZ agreed well with the ones measured experimentally from weld-overlay cladded plates. Applying the analysis method to a RPV model, through-wall residual stress distributions caused by weld-overlay cladding, PWHT, hydrostatic test, operational load and transient loads during pressurized thermal shock (PTS) events have been computed. Effects of the weld-overlay cladding on the stress distributions in the vessel wall of a RPV have been evaluated. Using the stress distributions, stress intensity factors for a postulated crack during PTS events have been studied.

39000079
Introduction; Plasma profile control is the key to a fusion reactor (in Japanese)
Kurihara, Kenichi
Purazuma, Kaku Yugo Gakkai-Shi 86(9), p.517-518(2010) ; (JAEA-J 08318)

While construction of the ITER aiming at full D-T burning has just started in Southern France, activities in DEMO reactor design and fusion nuclear research are now eagerly progressing. The design/manufacturing of the satellite tokamak JT-60SA has been also conducted under the Japan-EU Broader Approach collaboration on fusion research. To attain a steady state, high performance plasma, profile control of plasma current, density, temperature, and toroidal rotation is considered a key issue for a burning high-beta plasma. In Section 1, contents of the following sections are briefly presented as an introduction to this special issue together with difficulties and interest in this research area.

39000080
Purposes and subjects of the plasma control (in Japanese)
Kamada, Yutaka
Purazuma, Kaku Yugo Gakkai-Shi 86(9), p.519-523(2010) ; (JAEA-J 08319)

39000081
Profile control and its response properties (in Japanese)
Sakamoto, Yoshiteru
Purazuma, Kaku Yugo Gakkai-Shi 86(9), p.524-529(2010) ; (JAEA-J 08320)

39000082
Progress of real-time control experiments and open issues (in Japanese)
Suzuki, Takahiro
Purazuma, Kaku Yugo Gakkai-Shi 86(9), p.530-535(2010) ; (JAEA-J 08321)

39000083
Introduction to surface and interface structural analysis by neutron reflectometry (in Japanese)
Takeda, Masayasu
Radioisotopes 59(11), p.675-692(2010) ; (JAEA-J 08324)

The traveling waves reflect and refract at the well-defined interface between two different media. This phenomenon is known as optics in the case of visible light. Neutron has the wave character besides the particle nature; therefore, neutron also shows optical phenomena under the special condition, and it is called neutron optics. Neutron reflectometry as well as X-ray reflectometry is the most powerful and nondestructive tool to analyze the structure of buried interfaces in the films which have the internal layered structure. Structural information on such interfaces is a clue to develop the nanoscale science and technology.

39000084
Sprouting and rooting inhibition of garlic with Co-60 γ-rays (in Japanese)
Kobayashi, Yasuhiko; Kikuchi, Masahiro; Todoriki, Setsuko*; Saito, Kimie*; Katsura, Yoko*; Kameya, Hiromi*; Ichikawa, Mariko*; Iizuka, Tomoko*; Chiba, Etsuko*; Ukai, Mitsuko*
Shokuhin Shosha 45(1, 2), p.26-33(2010) ; (JAEA-J 08325)

Effect of γ-irradiation on sprouting and rooting of garlic was investigated. Sprouting and rooting of garlic were inhibited by irradiation of bulbs at 2 months after harvest with doses more than 30 Gy. Four weeks-later irradiation requires higher doses to complete sprouting/rooting inhibition.

39000085
Relaxation phenomena of radicals induced in irradiated fresh papayas (in Japanese)
Kikuchi, Masahiro; Kakita, Daisuke*; Shimoyama, Yuhei; Ukai, Mitsuko*; Kobayashi, Yasuhiko
Shokuhin Shosha 45(1, 2), p.34-38(2010) ; (JAEA-J 08326)

Electron spin resonance spectrometry of the γ-irradiated fresh papayas followed by freeze-drying and powderization was performed. We found a strong single peak in the flesh was observed at g = 2.004 and attributed to organic free radicals. Using the method of Lund et al., relaxation times of the peak from 0 to 14 days-stored samples after γ-irradiation were calculated. T₂ showed a dose response, while T₁ kept almost constant by the increment of doses. The γ-radiation-induced radicals showing progressive saturation behaviors can be caused through a different pathway from indirect effects by the low LET radiations.

39000086
Understanding of behaviors in organisms based on systems engineering; Studies with C. elegans, rats and zebra fishes (in Japanese)
Tsuji, Toshio*; Suzuki, Michiyo; So, Zu*; Terawaki, Mitsuru*; Takiguchi, Noboru*; Otake, Hisao*
Sofutowea Baioroji 9, p.3-12(2010) ; (JAEA-J 08327)

39000087
Corrosion behavior of carbon steel in compacted bentonite saturated with simulated groudwater under anaerobic condition (in Japanese)
Taniguchi, Naoki; Kawasaki, Manabu; Naito, Morimasa
Zairyo To Kankyo 59(11), p.418-429(2010) ; (JAEA-J 08328)

Immersion tests of carbon steel were performed in compacted bentonite for 10 years duration under anaerobic condition. The ferrous carbonates were identified as the corrosion product by XRD and XPS analysis in almost test cases. The amount of corrosion in high carbonate concentration was smaller than those of other test conditions throughout the test periods. Although the corrosion rate at 50°C was initially smaller than that at 80°C, it resulted in larger value after several years. Such the effects of carbonate content and temperature on the long-term corrosion rate seemed to be correlated to the behavior of dissolution/precipitation of iron carbonate. Additionally, the correlation between initial corrosion amount and the protectiveness of corrosion product film was examined. Except for high carbonate condition, as the corrosion amount at early stage of immersion was larger, the corrosion product film tended to become more protective. The long-term corrosion depth was estimated by the extrapolation of the laboratory test results. The range of the estimated value was well agreed with that of archaeological analogue data.

39000088
Lifetime measurements for the first 2⁺ states in ^162,164Gd populated by the β decay of ^162,164Eu
Nagae, Daisuke*; Ishii, Tetsuro; Takahashi, Ryuta*; Asai, Masato; Makii, Hiroyuki; Osa, Akihiko; Sato, Tetsuya; Ichikawa, Shinichi; Shimizu, Yoshifumi*; Shoji, Takuya*
AIP Conference Proceedings 1224 , p.156-160(2010) ; (JAEA-J 08329)

Lifetimes of the first 2⁺ states in ^162,164Gd have been measured by means of β - γ delayed coincidence technique for mass-separated ¹⁶²Eu and ¹⁶⁴Eu isotopes. Using the obtained lifetimes τ(¹⁶²Gd) = 3.98(8) ns and τ(¹⁶⁴Gd) = 4.0(2) ns, B(E2;0⁺→ 2⁺) values were deduced as B(E2;0⁺→ 2⁺)(¹⁶²Gd) = 5.45(11) e²b² and B(E2;0⁺→ 2⁺)(¹⁶⁴Gd) = 5.2(3) e²b².

39000089
E1 and E2 cross sections of the ¹²C(α,γ)¹⁶O reaction at E_eff ∼ 1.2 MeV using pulsed α beams
Makii, Hiroyuki; Ueda, Hitoshi*; Temma, Yasuyuki*; Nagai, Yasuki*; Shima, Tatsushi*; Fujimoto, Shinya*; Segawa, Mariko; Mishima, Kenji*; Nishiyama, Jun*; Igashira, Masayuki*
AIP Conference Proceedings 1269 , p.283-288(2010) ; (JAEA-J 08330)

The ¹²C(α,γ)¹⁶O reaction cross section plays an important role in stellar evolution at the stage of helium-burning. However, the cross section at low energy still has a large uncertainty mainly due to the poor determination of the ratio of E2 cross section to E1 one. Hence, we have installed new system to make a precise measurement of the cross section. In this experiment, we used the high efficiency anti-Compton NaI(Tl) spectrometers with a large S/N ratio, an intense pulsed α beams, and the monitoring system of target thickness. With use of the system we succeeded in removing a background due to neutron and could clearly detect the γ-ray from the ¹²C(α,γ)¹⁶O reaction with high statistics. We determined the E1 and E2 cross section down to E_eff ∼ 1.2 MeV, and thus obtained results are compared to recent theoretical calculations.

39000090
Analytic approaches to the structure formation in the accelerating universe
Tatekawa, Takayuki; Mizuno, Shuntaro*
Dark Energy; Theories, Developments, and Implications , p.241-294(2010) ; (JAEA-J 08331)

The existence of dark energy is a serious problem in modern cosmology. For the origin of the dark energy, many models including a cosmological constant have been proposed. Although these models can explain the present acceleration of the Universe, some of the models would not be able to explain the observed large-scale structure of the universe. Therefore, in order to constrain the models of the dark energy, we should consider the structure formation in the universe. From primordial density fluctuation, the large-scale structure is formed via its own self-gravitational instability. In this review, we summarise various analytic approaches to the evolution of the density fluctuation in Newtonian cosmology and show they can be helpful to distinguish models when applied to the quasi-nonlinear region. We also mention several applications of the analytic approaches including the initial condition problems for cosmological N-body simulations, higher-order Lagrangian perturbation theory.

39000091
Modeling of subgrain growth kinetics; 3D Monte-Carlo simulation
Suzudo, Tomoaki; Kaburaki, Hideo; Itakura, Mitsuhiro
Materials Research Society Symposium Proceedings, Vol.1225E (Internet) , 7p.(2010) ; (JAEA-J 08332)

We used a three-dimensional Monte Carlo method to investigate subgrain growth with different initial values for average grain-boundary misorientation, and found that abnormal grain growth emerges for relatively large average misorientation, with remaining cases revealing an exponential kinetics of subgrain growth. We also found that the growth exponent was ∼4.4, and that it was virtually independent of the average misorientation. Self-similarity of the misorientation distribution was observed during growth.

39000092
A Basic radiation-education method using a handy-type cloud chamber and natural radiation sources
Kushita, Kohei
Proceedings of 17th Pacific Basin Nuclear Conference (PBNC-17) (CD-ROM) , 9p.(2010) ; (JAEA-J 08333)

At NuHRDeC/JAEA, many kinds of nuclear and radiation education have been conducted through its half-century history. High level education is required for the specialists of nuclear technology including nuclear power plants operators and engineers, while basic knowledge on nuclear energy and, especially, on radiations and radioisotopes should be given to school students and public. One of the useful basic experiments is the cloud chamber experiment. Using a new-type cloud chamber developed at NuHRDeC, we have further developed a new method so that the participants can more deeply understand the phenomena and the nature of radiation and radioisotopes. In this method, using a radiation source of natural uranium ore and gaseous radiation source containing Rn-220, trainees can not only observe the radiation tracks but also measure the length and count the number of the tracks. Then they can calculate the energy of the radiation (alpha ray) and can estimate the half-life of the radioisotope (Rn-220). This method can be applied for high-school and general university students as well as for the public as a useful and effective method in the radiation education.

39000093
Study the effects of proton irradiation on GaAs/Ge solar cells
Elfiky, D.*; Yamaguchi, Masafumi*; Sasaki, Takuo*; Takamoto, Tatsuya*; Morioka, Chiharu*; Imaizumi, Mitsuru*; Oshima, Takeshi; Sato, Shinichiro; Elnawawy, M.*; Eldesuky, T.*; Ghitas, A.*
Proceedings of 35th IEEE Photovoltaic Specialists Conference (PVSC-35) (CD-ROM) , p.002528-002532(2010) ; (JAEA-J 08334)

Proton energy dependence of radiation damage to GaAs/Ge solar cells irradiated with protons with various energies (50 keV, 200 keV, 1 MeV and 9.5 MeV) were analyzed by using PC1D simulation together with SRIM simulations to investigate their electrical properties. The degradation of the open-circuit voltage is highest for 50 keV irradiation and lowest for 9.5 MeV irradiation. According to SRIM simulations the above changes in electrical properties are mainly related to damage in different regions of the solar sells.

39000094
Photo- and dark conductivity variations of solar cell quality a-Si:H thin films irradiated with protons
Sato, Shinichiro; Sai, Hitoshi*; Oshima, Takeshi; Imaizumi, Mitsuru*; Shimazaki, Kazunori*; Kondo, Michio*
Proceedings of 35th IEEE Photovoltaic Specialists Conference (PVSC-35) (CD-ROM) , p.002620-002624(2010) ; (JAEA-J 08335)

We investigated conductivity variations of hydrogenated amorphous silicon thin films during and following 10 MeV proton irradiations at the fluences of 2.0×10¹³ or 4.0×10¹⁴/cm². In addition, we compared behaviors of the light-induced degradations before and after 10 MeV proton irradiations. The results showed that the conductivity during the irradiation initially increased and after that decreased. These conductivity behaviors were in good agreement with the photoconductivity variations. The conductivity value never fell below the value before the irradiation even in the case of 4.0×10¹⁴/cm² irradiation.

39000095
Function as a natural barrier of various geological units in Japan from the perspective of uranium mineralization
Sasao, Eiji
Proceedings of 3rd East Asia Forum on Radwaste Management Conference (2010 EAFORM) , p.270-281(2010) ; (JAEA-J 08336)

Long-term stability of the geological environment is one of the important issues for HLW disposal in the geologically active Japanese Islands. Uranium mineralization in Japan has been subjected to many geological processes. Mode of occurrence of the uranium mineralization in Japan would be expected to provide useful information for assessing the function of various geological units as a natural barrier in a HLW disposal strategy. Uranium is sorbed onto various minerals and materials. Occurrence of secondary minerals indicates formation of uranium-bearing minerals in the oxidization zone. These modes of the uranium mineralization occurrences indicate that formation of uranium-bearing mineral as well as sorption are expected in both sedimentary and crystalline rocks. The functioning of the natural barrier to retard uranium would be expected in various geological environments in the Japanese Islands, because of the uranium occurrences in the various rock types.

39000096
Impact of capture cross-section of carbon on nuclear design for HTGRs
Shimakawa, Satoshi; Goto, Minoru; Nakagawa, Shigeaki; Tachibana, Yukio
Proceedings of 5th International Topical Meeting on High Temperature Reactor Technology (HTR 2010) (CD-ROM) , 6p.(2010) ; (JAEA-J 08337)

Capture cross section of carbon in thermal energy range has been regarded as unimportant in neutronics calculations on general reactor design, because of its infinitesimal value of only 3 mb at 2200 m/s. However, it is not negligible for design works for graphite-rich reactors, such as the High Temperature Gas-cooled Reactors (HTGRs). For the High Temperature Engineering Test Reactor (HTTR) of JAEA, five percent differences in capture cross section of carbon makes 0.24% change in thermal utilization factor of the four factor formula. This impact is for the HTTR with a core configuration of full-loaded core, named the packed core. In this case, change of multiplier factor will be equivalent to a change of thermal utilization factor. The impact of the cross section is dependent on an atomic number ratio of graphite/235-uranimu in reactor core.For more graphite-rich core such as the HTTR with ring core configuration, the five percent change of the cross section value makes a 0.47%Δk on multiplier factor. From our studies in the HTTR analysis, a value of capture cross section at 2200 m/s has been revised to 3.86 mb in evaluated nuclear data library of JENDL-4. Comparing with the value of JENDL4, the values in other libraries are about 10-15% smaller as 3.36 mb in ENDF/B-VII, 3.36 mb in JEFF-3.1 and 3.53 mb in JENDL-3.3. It was observed that discrepancy of a multiplier factor between former calculation and experiment of the HTTR showed disagreement in the evaluation of the critical approach tests. Monte Carlo calculation results using JENDL3.3 are overestimated about 0.4%Δk with packed core configuration and 1.0%Δk with ring core, respectively. In this report, the improvement of excess reactivity calculation for the HTTR with newly JENDL-4 is described.

39000097
Numerical analysis of windowless target in accelerator driven system by use of TPFIT
Yoshida, Hiroyuki; Suzuki, Takayuki*; Takase, Kazuyuki
Proceedings of 7th Korea-Japan Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-7) (CD-ROM) , 7p.(2010) ; (JAEA-J 08338)

A windowless target is currently developed within EUROTRANS. The target couples an Accelerator Driven Systems (ADS) to a subcritical reactor core. In the windowless target, heavy liquid metal is flowing downwards through a concentric feeder surrounding the beam tube and forms a conical free surface. Then, to design the windowless target, a numerical simulation method for this free surface is required. In this paper, as a first step of development of the numerical simulation method for free surface in the windowless target, the detailed two-phase flow simulation code TPFIT developed in JAEA is applied to steam-water experiments that modeled the windowless target. In the results, TPFIT could simulate complicated two-phase flow structure in the windowless target. In addition, recirculation at the center of the free surface was reproduced very well by the present numerical simulation.

39000098
Current research activities on thermal hydraulics in Japan Sodium-cooled Fast Reactor (JSFR)
Kamide, Hideki; Hayafune, Hiroki
Proceedings of 7th Korea-Japan Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-7) (CD-ROM) , 7p.(2010) ; (JAEA-J 08339)

Design study and related researches are carried out for Japan Sodium-cooled Fast Reactor (JSFR). Several innovative technologies, e.g., compact reactor vessel, two-loop system, fully natural circulation decay heat removal, and recriticality free core, have been investigated in order to reduce construction cost and to achieve higher level of reactor safety. Preliminary evaluations of innovative technologies to be applied to JSFR are undergoing. Here progress of design study is introduced. Then, research and development activities on the thermal hydraulics related to the innovative technologies are briefly reviewed.

39000099
Numerical simulation of air-water two-phase flow in 38 mm diameter pipe by advanced two-fluid model including effects of turbulent diffusion on bubbles
Hosoi, Hideaki*; Yoshida, Hiroyuki
Proceedings of 7th Korea-Japan Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-7) (CD-ROM) , 8p.(2010) ; (JAEA-J 08340)

In the Japan Atomic Energy Agency, an advanced two-fluid model has been developed for analytical procedure for nuclear reactor systems. In the model, an interface tracking method is combined with the two-fluid model to predict large interface structure behavior accurately. The turbulent dispersion force term is one of the most important constitutive equations for the advanced two-fluid model. Then, in this study, we proposed a new turbulent dispersion force term model based on the analogy of Brownian motion. The turbulent kinetic energy and bubble-induced kinetic energy are considered to evaluate the driving force in the turbulent diffusion of small bubbles. The advanced two-fluid model and the model for turbulent diffusion term were incorporated to the 3-dimensional two-fluid model code ACE-3D, and verification analyses were performed with the air-water two-phase flow experimental data in vertical pipes with diameters of 200 mm and 38 mm. >From these results, the qualitative phenomena could be expressed and the model constants including suggested model were selected.

39000100
Influences of fluid viscosity on the occurrences of cavitation due to sub-surface vortex
Ezure, Toshiki; Kimura, Nobuyuki; Tobita, Akira; Kamide, Hideki
Proceedings of 7th Korea-Japan Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-7) (CD-ROM) , 8p.(2010) ; (JAEA-J 08341)

A fundamental water experiment was performed in a cylindrical tank geometry to investigate the influences of fluid viscosity on the cavitation due to sub-surface vortex (vortex cavitation). In order to clarify the influence of fluid viscosity, the fluid temperature was varied from 10 °C to 80 °C to change the kinetic viscosity (ν) of fluid from 1.3×10^-6 to 3.7×10^-7m²/s. The occurrences of vortex cavitation were detected by image analysis on digital images of vortex cavitation captured by a digital CMOS camera. Then, the occurrences of vortex cavitation were evaluated from the relation between the yield fraction curves of vortex cavitation and the cavitation factor under several different ν conditions. The experimental results showed that the influence of ν was obvious under the large ν conditions. However, the influence became smaller according to the decrease of ν.

39000101
Study on flow-induced vibration evaluation of large-diameter pipings in a sodium-cooled fast reactor; Study on unsteady flow structure and characteristics of pressure fluctuation
Ono, Ayako; Kimura, Nobuyuki; Kamide, Hideki; Tobita, Akira
Proceedings of 7th Korea-Japan Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-7) (CD-ROM) , 9p.(2010) ; (JAEA-J 08342)

In the design of Japan Sodium-cooled Fast Reactor (JSFR), the flow-induced vibration (FIV) arising from the piping geometry and operating condition may occur in the short-elbow pipe. In this study, water experiments using two types of 1/8 scaled elbows with different curvature ratio, r/D = 1.0 and 1.5, were conducted in order to investigate the mechanism of flow fluctuation due to the elbow curvature. The measurements of the velocity fields and pressure fluctuation revealed that the periodic pressure fluctuation of St = 0.56 occurred near the separation region which was formed constantly on the wall of inside.

39000102
Growing mechanism of dendritic oxide during sodium combustion
Nishimura, Masahiro; Kamide, Hideki; Sugiyama, Kenichiro*; Otake, Shiro*
Proceedings of 8th International Topical Meeting on Nuclear Thermal-Hydraulics, Operation and Safety (NUTHOS-8) (CD-ROM) , 11p.(2010) ; (JAEA-J 08343)

The purpose of this study is to understand oxidation behavior of sodium precisely for FR safety against sodium combustion. It was recognized that dendritic oxide took an important role for the combustion reaction such as supplying the sodium to the reaction interface. In this study, we proposed a mechanistic model of supplying liquid sodium through the dendritic oxide based on the observation result of the growing behavior of dendritic oxide during combustion. In this model we made an attention to the kinds of chemical compounds. The formation of sodium peroxides can provide the sodium supplying route in the dendritic oxide. On the other hand the formation of sodium monoxide will block sodium supplying. The kinds of chemical compounds were decided by the Gibbs's free energy of thermodynamics in the reaction field such as temperature and oxygen concentration. This mechanistic model can explain the oxidation behavior consistently with the observation results.

39000103
Effects of wire spacer contact and pellet-cladding eccentricity on fuel cladding temperature under natural circulation decay heat removal conditions in sodium-cooled fast reactor
Doda, Norihiro; Ohshima, Hiroyuki; Kamide, Hideki; Watanabe, Osamu*; Okubo, Yoshiyuki*
Proceedings of 8th International Topical Meeting on Nuclear Thermal-Hydraulics, Operation and Safety (NUTHOS-8) (CD-ROM) , 11p.(2010) ; (JAEA-J 08344)

Toward the commercialization of fast reactors, design study of JSFR is being performed. Adoption of fully natural circulation system is being examined as the decay heat removal system. In order to confirm feasibility of the system, we are developing a new evaluation method of core hot spot in transition from rated operation to natural circulation decay heat removal conditions, which requires uncertainty factor assessment for the natural circulation conditions as well as for the rated operation conditions. In this paper, we focus on effects of wire-spacer contact and pellet- cladding eccentricity on the peak cladding temperature as typical uncertainty factors and evaluated these two effects under natural circulation conditions quantitatively.

39000104
COMPASS code development; Validation of multi-physics analysis using particle method for core disruptive accidents in sodium-cooled fast reactors
Koshizuka, Seiichi*; Morita, Koji*; Arima, Tatsumi*; Tobita, Yoshiharu; Yamano, Hidemasa; Ito, Takahiro*; Naito, Masanori*; Shirakawa, Noriyuki*; Okada, Hidetoshi*; Uehara, Yasushi*; Inoue, Fusao*; Nagamine, Yasuo*; Yugo, Hiroaki*; Yamamoto, Yuichi*; Himi, Masashi*; Hirano, Etsujo*; Shimizu, Sensuke*; Oue, Masaya*
Proceedings of 8th International Topical Meeting on Nuclear Thermal-Hydraulics, Operation and Safety (NUTHOS-8) (CD-ROM) , 11p.(2010) ; (JAEA-J 08345)

In this paper, FY2009 results of the COMPASS code development are reported. Validation calculations for melt freezing and blockage formation, eutectic reaction of metal fuel, duct wall failure (thermal-hydraulic analysis), fuel pin failure and disruption and duct wall failure (structural analysis) are shown. Phase diagram calculations, classical and first-principles molecular dynamics were used to investigate physical properties of eutectic reactions: metallic fuel/steel and control rod material/steel. Basic studies for the particle method and SIMMER code calculations supported the COMPASS code development. COMPASS is expected to clarify the basis of experimentally-obtained correlations used in SIMMER. Combination of SIMMER and COMPASS will be useful for safety assessment of CDAs as well as optimization of the core design.

39000105
Development of level 2 PSA methodology for sodium-cooled fast reactors, 5; Development of technical basis for the protected loss of heat sink
Tobita, Yoshiharu; Yamano, Hidemasa
Proceedings of 8th International Topical Meeting on Nuclear Thermal-Hydraulics, Operation and Safety (NUTHOS-8) (CD-ROM) , 11p.(2010) ; (JAEA-J 08346)

As part of level-2 PSA methodology development for sodium cooled fast reactors, the phenomenological event tree for the Protected Loss of Heat Sink (PLOHS) is constructed for JSFR (Japan Sodium-cooled Fast Reactor). The early stage of PLOHS accident, where the heating of coolant, coolant boiling and uncovering of core occur, is analyzed by the ARGO code. The event progression in the subsequent core degradation phase, where the meltdown of core and the power transient by re-criticality occurs, is analyzed by the APPLOHS and SIMMER-III codes. The dominant factors, which affect the event progression in PLOHS, are recognized through these analyses and by considering the phenomenological event progression. The event tree of PLOHS is developed assigning these dominant factors as the headings. For each of the headings, available information for judgment of branching probability are reviewed and integrated as database for level-2 PSA.

39000106
Development of level 2 PSA methodology for sodium-cooled fast reactors, 6; Development of technical basis in ex-vessel accident sequences
Ono, Shuji; Seino, Hiroshi; Miyahara, Shinya
Proceedings of 8th International Topical Meeting on Nuclear Thermal-Hydraulics, Operation and Safety (NUTHOS-8) (CD-ROM) , 12p.(2010) ; (JAEA-J 08347)

This research has compiled technical basis which is necessary to carry out a probabilistic safety assessment (Level 2 PSA) for a sodium-cooled fast reactor. The accumulated technical information consists of experimental and analytical information which help ones to understand the loading to a containment vessel, as well as the existing information on dominant factors of important ex-vessel phenomena.

39000107
Development of Level 2 PSA methodology for sodium-cooled fast reactors, 2; Development of technical basis in the initiating phase of unprotected events
Sato, Ikken; Tobita, Yoshiharu; Yamano, Hidemasa
Proceedings of 8th International Topical Meeting on Nuclear Thermal-Hydraulics, Operation and Safety (NUTHOS-8) (CD-ROM) , 12p.(2010) ; (JAEA-J 08348)

As part of Level-2 PSA methodology development for sodium cooled fast reactors (SFR), event trees for the initiating phase (IP) of Anticipated Transient Without Scram (ATWS) are constructed. ULOF (Unprotected Loss of Flow), UTOP (Unprotected Transient Overpower) and ULOHS (Unprotected Loss of Heat Sink) are selected as typical and important accident categories. Based on the state-of-the-art knowledge, the headings of these event trees are selected so that dominant factors in accident consequences can be represented appropriately. For each of the headings, available information for judgment are reviewed and integrated as database for Level-2 PSA. It is clarified that the headings of ULOF, for which experimental database and evaluation models have been reasonably established, can be commonly applied to certain part of the different accident categories. While, some points specific for UTOP and ULOHS are identified. ULOHS, in which significant heat up of the primary system is expected before start of the core disruption, necessitates an additional event tree before the core disruption providing various boundary conditions for the core disruption process.

39000108
Change in current induced from silicon carbide metal-oxide-semiconductor capacitors by oxygen ions
Oshima, Takeshi; Iwamoto, Naoya; Onoda, Shinobu; Makino, Takahiro; Deki, Manato; Nozaki, Shinji*
Proceedings of 9th International Workshop on Radiation Effects on Semiconductor Devices for Space Applications (RASEDA-9) , p.85-88(2010) ; (JAEA-J 08349)

In order to investigate radiation response of Silicon Carbide (SiC) Metal-Oxide-Semiconductor (MOS) devices, current induced from SiC MOS capacitors by oxygen (O) ion was investigated. MOS capacitors were fabricated on an n-type 6H-SiC epitaxial layer, and charge induced in the MOS capacitors by 15 MeV oxygen ion microbeams was measured using Transient Ion Beam Induced Current (TIBIC). As a result, the peak amplitude of TIBIC signals decreases and the fall time increases with increasing number of incident ions. The decrease in peak amplitude of the TIBIC signal eventually saturated after an incidence of 1000 ions. The TIBIC signal peak value can be refreshed to its original value by applying a positive bias of 1V to the oxide electrode. Charge collection, also, shows similar behavior to that of the TIBIC peak. These results can be interpreted in terms of charge trapping or de-trapping by deep hole traps near the interface of SiC and SiO₂.

39000109
Reduction in majority-carrier concentration in N-doped or Al-doped 4H-SiC epilayer by electron irradiation
Matsuura, Hideharu*; Yanagisawa, Hideki*; Nishino, Kozo*; Nojiri, Takunori*; Onoda, Shinobu; Oshima, Takeshi
Proceedings of 9th International Workshop on Radiation Effects on Semiconductor Devices for Space Applications (RASEDA-9) , p.89-91(2010) ; (JAEA-J 08350)

Change of temperature dependence of hole concentration (p(T)) in lightly Aluminium (Al)-doped 4H-SiC (Silicon Carbide) epilayers by 100 or 150 keV electron irradiation was investigated. Moreover, the decrease in the electron concentration (n(T)) in lightly Nitrogen(N)-doped n-type 4H-SiC epilayers by 200 keV electron irradiation was investigated. In the lightly Al-doped 4H-SiC, p(T) was unchanged by 100 keV electron irradiation at fluences up to 7×10¹⁶ cm^-2. However, 150 keV electron irradiation, the reduction of p(T) was observed. This suggests that the 150 keV electron irradiation can displace substitutional carbon (C) atoms in SiC. In the lightly N-doped 4H-SiC, n(T) over the temperature range of the measurement was reduced by 200 keV electrons. This result is quite different from that in the lightly Al-doped 4H-SiC, because p(T) in Al-doped 4H-SiC was reduced only at low temperatures by 200 keV electrons.

39000110
Electric conductivity of device grade hydrogenated amorphous silicon thin films irradiated with protons
Sato, Shinichiro; Sai, Hitoshi*; Oshima, Takeshi; Imaizumi, Mitsuru*; Shimazaki, Kazunori*; Kondo, Michio*
Proceedings of 9th International Workshop on Radiation Effects on Semiconductor Devices for Space Applications (RASEDA-9) , p.183-186(2010) ; (JAEA-J 08351)

In this paper, we present in-situ measurement results of the conductivity variations of hydrogenated amorphous silicon thin films during and after 10 MeV proton irradiations. The results showed that the conductivities drastically increased at first and turned into decrease with further irradiation. On the other hand, the photosensitivity had a minimum value at around a maximum value of the conductivity. This fact indicates that the conductive carriers generated by light illumination are not dominant to the electric conduction in this regime, and thus the extremely high conductivity cannot be explained by a general interpretation of radiation induced conductivity.

39000111
Laser modification aiming at the enhancement of local electrical conductivities in SiC
Deki, Manato; Ito, Takuto*; Tomita, Takuro*; Matsuo, Shigeki*; Hashimoto, Shuichi*; Kitada, Takahiro*; Isu, Toshiro*; Onoda, Shinobu; Oshima, Takeshi
Proceedings of 9th International Workshop on Radiation Effects on Semiconductor Devices for Space Applications (RASEDA-9) , p.218-221(2010) ; (JAEA-J 08352)

Femtosecond laser exhibits extremely high peak intensity and short pulse duration, and can process inside transparent materials without damaging the surface of sample. In this study, the local electrical conductivity in Silicon Carbide (SiC) is evaluated. As a result of femtosecond laser irradiation with various irradiation fluences, the drastic change of electrical conductivity is observed in resistivity ranges from 10⁹ to 10⁷ Ω. It is found that the local conductivity strongly depends on the fluence. We suggest that the local conductivity is attributed to the phase transition. From the surface observations by Secondary Electron Microscopy (SEM), we conclude that the formation of the classical laser-induced periodic structures causes the sudden increase in the electrical conductivities.

39000112
Time-dependent collected charges of 6H-SiC p⁺n diodes measured using alpha particles
Iwamoto, Naoya; Onoda, Shinobu; Makino, Takahiro; Oshima, Takeshi; Kojima, Kazutoshi*; Koizumi, Atsushi*; Uchida, Kazuo*; Nozaki, Shinji*
Proceedings of 9th International Workshop on Radiation Effects on Semiconductor Devices for Space Applications (RASEDA-9) , p.222-225(2010) ; (JAEA-J 08353)

Time-dependent collected charges of 6H-SiC (Silicon Carbide) p⁺n diodes have been studied by using alpha particles. To investigate the impact of electron irradiation-induced defects on the time-dependent collected charges, temperatures of the samples were varied from 180 K to 310 K during the measurements. For electron-irradiated diode, the collected charges increase promptly and continue to increase slightly for tens of microseconds. The slight increases of charges are results of carrier detrapping by the electron irradiation-induced defects. It is also found that amount of detrapped charges depends on the temperatures. Two clear peaks at 205 K and 280 K are found for the electron-irradiated diode. These peaks are considered to be attributed to the defects which located at two different energy levels in the band gap.

39000113
Raman and FT-IR spectroscopy of electron irradiated LiNbO₃
Miyazaki, Hisashi*; Morimoto, Jun*; Toda, Koji*; Onoda, Shinobu; Oshima, Takeshi
Proceedings of 9th International Workshop on Radiation Effects on Semiconductor Devices for Space Applications (RASEDA-9) , p.226-229(2010) ; (JAEA-J 08354)

LiNO₃ has several advantages for opto-electronic and acousto-optic applications including waveguides, modulators, second harmonic generators and surface acoustic wave (SAW) devices. In this study, we characterized the defects in electron irradiated LiNbO₃ single crystal substrates using Raman. The Raman peak of symmetrical O-Nb-O bending mode drastically decreased with increasing electron irradiation. It is thought that the electron irradiation gives the biggest influence on the Nb-O bond.

39000114
Enhanced charge collection in drain contact of 6H-SiC MOSFETs induced by heavy ion microbeam
Onoda, Shinobu; Vizkelethy, G.*; Makino, Takahiro; Iwamoto, Naoya; Kojima, Kazutoshi*; Nozaki, Shinji*; Oshima, Takeshi
Proceedings of 9th International Workshop on Radiation Effects on Semiconductor Devices for Space Applications (RASEDA-9) , p.230-233(2010) ; (JAEA-J 08355)

Metal Oxide Semiconductor Field Effect Transistor (MOSFET) fabricated on Silicon Carbide (SiC) is regarded as a promising candidate for high-power and high-frequency electronic devices because of its excellent electrical and thermal properties. Transient currents were measured for 6H-SiC MOSFETs fabricated with three different gate oxides by using 18 MeV Oxygen and 50 MeV Cu microbeams at JAEA and Sandia National Laboratories. The 2-Dimensional Technology Computer Aided Design (TCAD) simulations were performed to clarify the mechanisms behind the transient events. According to both experiments and simulations, the typical parasitic bipolar amplification is observed when an ion strikes the drain contact. As a result of bipolar amplification, the drain current is larger than the ideal value.

39000115
Verification of LSD spikes prepared in Japan from a MOX source material
Sumi, Mika; Abe, Katsuo; Kageyama, Tomio; Nakazawa, Hiroaki; Kurosawa, Akira; Yamamoto, Masahiko; Mason, P.*; Neuhoff, J.*; Doubek, N.*; Balsley, S.*; Verbruggen, A.*; Richter, S.*; Jakopič, R.*; Zuleger, E.*; van-Belle, P.*
Proceedings of INMM 51st Annual Meeting (CD-ROM) , 9p.(2010) ; (JAEA-J 08356)

Large Size Dried (LSD) spikes are currently used in many facilities in Japan (and around the world) for U and Pu accountancy analysis by Isotope Dilution Mass Spectrometry (IDMS). Because of the large quantity of plutonium standard materials are needed to support Japanese facilities for nuclear fuel cycle and expected difficulties in the long term supply and transport of Pu reference materials, JAEA decided to evaluate the possibility of using MOX stored at Plutonium Fuel Development Center (PFDC) as a source of Pu standard material for LSD spike preparation. At PFDC, Pu nitrate solution was prepared from MOX and two types of the LSD spikes were prepared. The samples of each spike were distributed for verification measurements to international and domestic laboratories. Details of the Pu make-up value evaluation, the LSD spike preparation and the evaluation of the verification results will be presented.

39000116
Numerical visualization on melting and solidification of micron-sized metallic particles by laser irradiation
Takase, Kazuyuki; Muramatsu, Toshiharu; Shobu, Takahisa
Proceedings of International Symposium on Visualization in Joining & Welding Science through Advanced Measurements and Simulation (Visual-JW 2010) , p.54-55(2010) ; (JAEA-J 08357)

As aiming at the enhancement of safety of currently operated nuclear reactors, development of a repair technology using laser welding has been performed. An experimental study on welding of micron-sized metallic particles on a stainless steel plate by laser irradiation has already been carried out. Moreover, an analytical study was also begun to predict numerically the experimental results. The micron-sized metallic particle that is made of iron is heated by the laser irradiation and then melts exceeding the melting temperature and finally the solid metallic particle changes perfectly the liquid metal. After a long time, the liquid metal rechanges the solid metal with decreasing the temperature. This paper describes visualized numerical simulation results of the melting and solidification behavior of the micron-sized metallic particles that changes from the solid to liquid and the liquid to solid.

39000117
First-principles study of the grain-boundary embrittlement of metals
Yamaguchi, Masatake; Ebihara, Kenichi; Itakura, Mitsuhiro; Suzudo, Tomoaki; Kaburaki, Hideo
Proceedings of Joint International Conference of 7th Supercomputing in Nuclear Application and the 3rd Monte Carlo (SNA + MC 2010) (USB Flash Drive) , 4p.(2010) ; (JAEA-J 08358)

It is not known in detail how much solute atoms segregate in grain boundaries of metals and how much the cohesive energy (work of fracture) of grain boundary is decreased by the segregation. From first-principles, we calculated the segregation energy of some solute elements like boron (B), carbon (C), phosphorous (P), and sulfur (S) in bcc Fe Sigma 3 (111) symmetrical tilt grain boundary with varying the segregation density. We find that these elements can segregate up to a high concentration in the grain boundary. We also find that the segregation energy on the fracture surface is significantly larger than that in the grain boundary for the embrittling elements like P and S. On the contrary, the cohesive energy is increased by B and C segregation. The increase-decrease rate in the calculated cohesive energy by solute segregation is found to be well correlated with experimentally observed shift in ductile-to-brittle transition temperature by solute segregation.

39000118
Two-phase flow simulation of gas entrainment phenomena in large-scale fast reactor
Ito, Kei; Kunugi, Tomoaki*; Ohshima, Hiroyuki; Kawamura, Takumi*
Proceedings of Joint International Conference of 7th Supercomputing in Nuclear Application and the 3rd Monte Carlo (SNA + MC 2010) (USB Flash Drive) , 6p.(2010) ; (JAEA-J 08359)

The authors have been developed a high-precision numerical simulation algorithm for gas-liquid two-phase flows to simulate the gas entrainment (GE) phenomena in a large-sized sodium-cooled fast reactor in Japan (JSFR). In this paper, the developed simulation algorithm is applied to the GE phenomena in a large-scale water experiment which models the complicated geometrical configurations of the system components in JSFR. For the numerical simulation, an unstructured mesh with about one million cells are generated and optimized to simulate the interfacial deformations near inlet and outlet pipes which cause vortical flows behind them to induce the GE phenomena. As a result of the unsteady simulation, a typical interfacial dynamic behavior, i.e. the development of a gas core (interfacial dent), is well simulated. Therefore, it is confirmed that the developed simulation algorithm is suitable to evaluate numerically the GE phenomena in JSFR.

39000119
Evaluation of local stress and local hydrogen concentration at grain boundary using three-dimensional polycrystalline model
Ebihara, Kenichi; Itakura, Mitsuhiro; Yamaguchi, Masatake; Kaburaki, Hideo; Suzudo, Tomoaki
Proceedings of Joint International Conference of 7th Supercomputing in Nuclear Application and the 3rd Monte Carlo (SNA + MC 2010) (USB Flash Drive) , 6p.(2010) ; (JAEA-J 08360)

The decohesion model in which hydrogen segregating at grain boundaries reduces their strength is considered to explain hydrogen embrittlement of steels. Therefore in order to understand hydrogen embrittlement from this model, stress and hydrogen concentration at grain boundaries need be evaluated under the fracture condition for tensile test specimens. From this consideration, we evaluated the stress and the hydrogen concentration at grain boundaries in the three-dimensional polycrystalline model which was generated by Voronoi tessellation. The different crystallographic orientation was given to each grain. Extracted data from the calculation in the notched round-bar specimen model under the tensile test condition was given to the polycrystalline model as the boundary condition. As a result, it was found that the valuated stress does not reach the fracture stress which was estimated under the condition of the evaluated hydrogen concentration by first principles calculation.

39000120
Numerical simulation of boiling two-phase flow in a simulated subchannel of fuel assemblies excited by earthquake oscillation
Misawa, Takeharu; Yoshida, Hiroyuki; Takase, Kazuyuki
Proceedings of Joint International Conference of 7th Supercomputing in Nuclear Application and the 3rd Monte Carlo (SNA + MC 2010) (USB Flash Drive) , 6p.(2010) ; (JAEA-J 08361)

As a part of development of a thermal-structure coupling analysis method, we have performed evaluation of boiling two-phase flow in a nuclear reactor core under an earthquake condition by using three-dimensional two-fluid model code ACE-3D. The ACE-3D code was improved so that the boiling two-phase flow in a fuel assembly excited by earthquake acceleration can be calculated. The boiling two-phase flow behavior in 2×2 subchannels of the fuel assembly with the earthquake acceleration was analyzed numerically. The flow condition in the present analysis simulates the operating condition of current BWRs. The earthquake acceleration is simulated by the sine wave which oscillates in the horizontal and axial directions. As a result, it was confirmed that the time-averaged void fraction distribution in the horizontal direction under the earthquake condition is different from that under no oscillation case, and the region in 2×2 subchannels where the void fraction fluctuation is large moves from near wall to subchannel center. Finally, we could make sure that the improved ACE-3D code is able to predict the boiling two-phase flow characteristics in fuel assemblies excited by the earthquake acceleration.

39000121
Ratcheting deformation effect on fatigue and creep-fatigue life in Mod.9Cr-1Mo steel (in Japanese)
Ando, Masanori; Isobe, Nobuhiro*; Date, Shingo*; Kikuchi, Koichi*; Enuma, Yasuhiro*
Dai-48-Kai Koon Kyodo Shimpojiumu Maezurishu , p.110-114(2010) ; (JAEA-J 08362)

39000122
Research on swelling behavior of ion irradiation for fuel cladding in fast reactor (in Japanese)
Sasase, Masato*
Heisei-21-Nendo Zaidan Hojin Wakasawan Enerugi Kenkyu Senta Kenkyu Seika Nempo, 12 , p.52(2010) ; (JAEA-J 08363)

39000123
Behavior data acquisition and research of the cutting dust by the mechanical and thermal cutting method for decommissioning of Fugen Decommissioning Engineering Center (in Japanese)
Shigeta, Tatsuo*; Amada, Kenichi*; Sasase, Masato*; Endo, Nobuyuki*; Nagatomo, Jinro*
Heisei-21-Nendo Zaidan Hojin Wakasawan Enerugi Kenkyu Senta Kenkyu Seika Nempo, 12 , p.78(2010) ; (JAEA-J 08364)

39000124
Research on hydrogen purification system containing basic test, 6 (in Japanese)
Amada, Kenichi*; Nagatomo, Jinro*; Kobayashi, Shigetada*
Heisei-21-Nendo Zaidan Hojin Wakasawan Enerugi Kenkyu Senta Kenkyu Seika Nempo, 12 , p.61-62(2010) ; (JAEA-J 08365)

For the purpose of improving hydrogen purification method, feasibility of impurity concentration by temperature/pressure swinging and automated continued operation experiments were conducted, based on a series of fundamental tests conducted till FY2008. The assumed hydrogen generation method is the hybrid thermo-chemical method and the assumed main impurity gas is hydrogen sulfide. A set of design and installation technical information items for a pilot-scale hybrid thermo-chemical hydrogen generation plant have been studied and compiled.

39000125
Estimation of groundwater recharge rate by water balance method in Horonobe area, Hokkaido, Japan; Dec. 2004 ∼ Nov. 2009 (in Japanese)
Yokota, Hideharu; Yamamoto, Yoichi; Yamazaki, Masanori; Maekawa, Keisuke
Nippon Chikasui Gakkai 2010-Nen Shuki Koenkai Koen Yoshi , p.160-165(2010) ; (JAEA-J 08366)

39000126
Spatial estimation of hydrological quantities at Horonobe basin in Hokkaido (in Japanese)
Yamamoto, Yoichi; Maekawa, Keisuke; Yabuuchi, Satoshi; Yokota, Hideharu
Nippon Chikasui Gakkai 2010-Nen Shuki Koenkai Koen Yoshi , p.166-171(2010) ; (JAEA-J 08367)

39000127
Recharge evaluation using distributed tank model (in Japanese)
Ikeda, Makoto; Munakata, Masahiro; Sakai, Ryutaro; Fuchiwaki, Hirotaka; Kimura, Hideo; Matsuba, Hisashi*
Nippon Chikasui Gakkai 2010-Nen Shuki Koenkai Koen Yoshi , p.282-287(2010) ; (JAEA-J 08368)

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