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Journal Articles

Ion and neutron beam analyses of hydrogen isotopes

Kubota, Naoyoshi; Ochiai, Kentaro; Kutsukake, Chuzo; Kondo, Keitaro*; Shu, Wataru; Nishi, Masataka; Nishitani, Takeo

Fusion Engineering and Design, 81(1-7), p.227 - 231, 2006/02

 Times Cited Count:5 Percentile:38.34(Nuclear Science & Technology)

Hydrogen isotopes play important roles in the fuel recycling, the plasma condition etc. at the surface region of plasma facing components. The Fusion Neutronics Source (FNS) of Japan Atomic Energy Research Institute has started microanalysis studies for fusion components since 2002 by applying the beam analyses. In this study, we have measured tritium depth profiles of TFTR tiles exposed to the deuterium-tritium plasma to reveal the hydrogen isotope behavior at the surface region using some microscopic techniques for material analyses at FNS. As the result of the deuteron nuclear reaction analysis, four kinds of elements; deuterium, tritium, lithium-6 and lithium-7, were identified from the energy spectra. Using the spectra, depth profiles of each element were also calculated. The tritium profile had a peak at 0.5 micron, whereas the deuterium and lithium profiles were uniform from the surface to 1.0 micron depth. In addition, the surface region of the TFTR tile has retained the tritium more than one order of magnitude in the bulk.

Journal Articles

Evaluation of $$gamma$$-ray dose components in criticality accident situations

Sono, Hiroki; Yanagisawa, Hiroshi*; Ono, Akio*; Kojima, Takuji; Soramasu, Noboru*

Journal of Nuclear Science and Technology, 42(8), p.678 - 687, 2005/08

 Times Cited Count:4 Percentile:32.08(Nuclear Science & Technology)

Component analysis of $$gamma$$-ray doses in criticality accident situations is indispensable for further understanding on emission behavior of $$gamma$$-rays and accurate evaluation of external exposure to human bodies. Such dose components were evaluated, categorizing $$gamma$$-rays into four components: prompt, delayed, pseudo components in the period of criticality, and a residual component in the period after the termination of criticality. This evaluation was performed by the combination of dosimetry experiments at the TRACY facility using a thermoluminescent dosimeter (TLD) made of lithium tetra borate and computational analyses using a Monte Carlo code. The evaluation confirmed that the dose proportions of the above components varied with the distance from the TRACY core tank. This variation was due to the difference in attenuation of the individual components with the distance from the core tank. The evaluated dose proportions quantitatively clarified the contribution of the pseudo and the residual components to be excluded for accurate evaluation of $$gamma$$-ray exposure.

JAEA Reports

Structural analysis of support structure for ITER vacuum vessel

Takeda, Nobukazu; Omori, Junji*; Nakahira, Masataka

JAERI-Tech 2004-068, 27 Pages, 2004/12

JAERI-Tech-2004-068.pdf:7.68MB

ITER vacuum vessel (VV) is a safety component confining radioactive materials such as tritium and activated dust. An independent VV support structure with multiple flexible plates located at the bottom of VV lower port is proposed. This independent concept has two advantages: (1) thermal load due to the temperature deference between VV and the lower temperature components such as TF coil becomes lower and (2) the other components such as TF coil is categorized as a non-safety component because of its independence from VV. Stress analyses have been performed to assess the integrity of the VV support structure using a precisely modeled VV structure. As a result, (1) the maximum displacement of the VV corresponding to the relative displacement between VV and TF coil is found to be 15 mm, much less than the current design value of 100 mm, and (2) the stresses of the whole VV system including VV support are estimated to be less than the allowable ones defined by ASME. Based on these assessments, the feasibility of the proposed independent VV support has been verified as a VV support.

Journal Articles

Design and structural analysis of support structure for ITER vacuum vessel

Takeda, Nobukazu; Omori, Junji*; Nakahira, Masataka; Shibanuma, Kiyoshi

Journal of Nuclear Science and Technology, 41(12), p.1280 - 1286, 2004/12

 Times Cited Count:3 Percentile:24.74(Nuclear Science & Technology)

ITER vacuum vessel (VV) is a safety component confining radioactive materials. An independent VV support structure located at the bottom of VV lower port is proposed as an alternative concept, which is deferent from the current reference, i.e., the VV support is directly connected to the toroidal coil (TF coil). This independent concept has two advantages comparing to the reference one: (1) thermal load becomes lower and (2) the TF coil is categorized as a non-safety component. Stress Analyses have been performed to assess the integrity of the VV support structure. As a result, (1) the maximum displacement of the VV corresponding to the relative displacement between VV and TF coil is found to be 15 mm, much less than the current design value of 100 mm, and (2) the stresses of the whole VV system including VV support are estimated to be less than the allowable ones defined by ASME, respectively. Based on these assessments, the feasibility of the proposed independent VV support has been verified as an alternative VV support.

JAEA Reports

Revised version of tokamak transient simulation code SAFALY, 2

Senda, Ikuo*; Fujieda, Hirobumi; Neyatani, Yuzuru; Tada, Eisuke; Shoji, Teruaki

JAERI-Data/Code 2003-012, 73 Pages, 2003/07

JAERI-Data-Code-2003-012.pdf:3.45MB

The tokamak transient simulation code, named SAFALY, was revised recently and the sensitivity analyses on the parameters in the code were carried out. This report is composed of two volumes. The formulation and the parameters in modeling the plasma and in-vessel components are described in the first volume. In this second volume, the results of the sensitivity studies are reported. The sensitivity studies were performed in two steps. In the first step, the responses of plasmas in the occurrence of plasma disturbances were analyzed for various initial conditions. For each disturbance, the initial condition of the plasma, which gave the largest increase of the fusion power, was identified. In the second step, by using initial conditions derived in the first step, the sensitivities of plasma reactions with respect to variation of the parameters in SAFALY code were analyzed. In the analyses, the increase of the fueling, the increase of the plasma confinement improvement factor and the increase of the auxiliary heating power were considered as plasma disturbances.

JAEA Reports

Revised version of tokamak transient simulation code SAFALY, 1

Senda, Ikuo*; Fujieda, Hirobumi; Neyatani, Yuzuru; Tada, Eisuke; Shoji, Teruaki

JAERI-Data/Code 2003-008, 37 Pages, 2003/06

JAERI-Data-Code-2003-008.pdf:1.58MB

Tokamak transient simulation code, named SAFALY, was revised. SAFALY code has been developed to simulate transient events in Tokamaks. Modeling of the plasma and algorithms of the simulation were revised. The code was also modified to deal with the variation of the plasma current. The code was improved to allow flexible modeling of in-vessel components. The data transfer between SAFALY and related codes was arranged to prepare data required in analyses with SAFALY, such as the distributions of heat/neutron loads and the radiation form factor between in-vessel components. The report is composed of two volumes. The formulation and the parameters in modeling plasma and in-vessel components are described in this first volume. Examples of simulation results, using the design of ITER-FDR in 2001, are presented and general properties of plasmas' responses with respect to perturbations are discussed. The results of the sensitivity studies with respect to simulation parameters and initial conditions will be reported in the second volume.

JAEA Reports

User's manual of SECOM2: A Computer code for seismic system reliability analysis

Uchiyama, Tomoaki; Oikawa, Tetsukuni; Kondo, Masaaki; Watanabe, Yuichi*; Tamura, Kazuo*

JAERI-Data/Code 2002-011, 205 Pages, 2002/03

JAERI-Data-Code-2002-011.pdf:8.52MB

This report is a user's manual of seismic system reliability analysis code SECOM2 developed at the JAERI for system reliability analysis, which is one of the tasks of seismic probabilistic safety assessment (PSA) of nuclear power plants (NPPs). The SECOM2 code has many functions such as calculation of component and system failure probabilities for given seismic motion levels at the site of an NPP based on the response factor method, calculation of accident sequence frequencies and the core damage frequency (CDF), importance analysis using various indicators, uncertainty analysis, and calculation of the CDF taking into account the effect of the correlations of responses and capacities of components. These analyses require the fault tree (FT) representing the occurrence condition of the system failures and core damage, information about responses and capacities of the components which compose the FT, and seismic hazard curve for the NPP site as input. This report presents calculation method used in the SECOM2 code and how to use those functions in the SECOM2 code.

Journal Articles

Evaluation of aseismic integrity in the HTTR core-bottom structure,IV; Structural integrity of connecting elements between graphite components

Ishihara, Masahiro; Iyoku, Tatsuo; Futakawa, Masatoshi

Nucl. Eng. Des., 154, p.83 - 95, 1995/00

 Times Cited Count:6 Percentile:55.97(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Wavelet analysis of two-phase flow in a forizontal duct

; Anoda, Yoshinari; Kukita, Yutaka

Proc. of 2nd Int. Conf. on Multiphase Flow (ICMF)95-KYOTO,Vol. 2, 0, p.P1_97 - P1_102, 1995/00

no abstracts in English

Journal Articles

Experimental and analytical studies on thermal erosion of carbon-based materials with high thermal conductivity

Akiba, Masato; Araki, Masanori; ; Ise, Hideo*; Nakamura, Kazuyuki; ; Dairaku, Masayuki; Tanaka, Shigeru

Journal of Nuclear Materials, 191-194, p.373 - 376, 1992/00

no abstracts in English

Journal Articles

Thermal transient analysis for structural integrity of high temperature components in HTTR

Hada, Kazuhiko; Fujimoto, Nozomu; Sudo, Yukio; Wada, Hozumi*

Proc. of the 1st JSME/ASME Joint Int. Conf. on Nuclear Engineering,Vol. 2, p.291 - 298, 1991/00

no abstracts in English

Oral presentation

Development of standard procedure for consequence analysis of criticality accident in fuel cycle facilities

Yamane, Yuichi; Abe, Hitoshi

no journal, , 

After the experience of the accident at the Fukushima Dai-ichi Nuclear Power Plants of Tokyo Electric Power Company (TEPCO),Japan's nuclear safety standard for reprocessing plant has been renewed and the standard now requires accident management measures and the assessment of their effectiveness to the severe accident such as criticality accident. This paper summarizes the issues for the best estimation in criticality accident consequence analysis and proposes a new method to estimate source term in criticality accident. Unique characters of criticality accident in nuclear fuel facilities, such as the production of short life nuclides, are described in association with the best estimation of public and worker's dose. In the light of those characters, this paper proposes a procedure to estimate source term in criticality accident by utilizing five-component equation described in DOE handbook.

Oral presentation

Phase-Space Pattern Extraction from 5D gyrokinetic simulation data

Asahi, Yuichi; Fujii, Keisuke*; Maeyama, Shinya*; Idomura, Yasuhiro

no journal, , 

We propose to use a dimensionality reduction technique, namely principal component analysis (PCA) to extract patterns from the series of 5D gyrokinetic plasma simulation data. It is shown that 83% of the variance of the original 6D (5D phase space + 1D time) data can be expressed with 64 principal components. Through the detailed analysis of the contribution of each principal component to the energy flux, we demonstrate that the avalanche like energy transport is driven by coherent mode structures in the phase space, indicating the key role of resonant particles.

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