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Journal Articles

Evaluation of uncertainty associated with parameters for long-term safety assessments of geological disposal

Yamaguchi, Tetsuji; Minase, Naofumi; Iida, Yoshihisa; Tanaka, Tadao; Nakayama, Shinichi

JAERI-Conf 2005-007, p.150 - 155, 2005/08

no abstracts in English

Journal Articles

Long-term alteration of bentonite; For safety evaluation of deep geological disposal

Tanaka, Tadao; Sakamoto, Yoshifumi; Yamaguchi, Tetsuji; Takazawa, Mayumi; Akai, Masanobu; Negishi, Kumi; Iida, Yoshihisa; Nakayama, Shinichi

JAERI-Conf 2005-007, p.105 - 110, 2005/08

Highly alkaline environments induced by cementitious materials in radioactive waste repositories are likely to dissolve and to alter montmorillonite, the main constituent of bentonite buffer materials. For the prediction of the long-term variations in permeability of compacted sand-bentonite mixtures, long-term alteration of bentonite should be quantified based on information accumulated by using the compacted or powdered bentonite materials, with batch experiments or column experiments. In this study, we summarize distinctive information obtained from various experimental systems, and propose functional and effective integration of experimental approaches to prediction of bentonite alteration.

Journal Articles

Measurement of neutron and $$gamma$$-ray absorbed doses inside human body in criticality accident situations using phantom and tissue-equivalent dosimeters

Sono, Hiroki; Kojima, Takuji; Soramasu, Noboru*; Takahashi, Fumiaki

JAERI-Conf 2005-007, p.315 - 320, 2005/08

Personal dosimeters provide a fundamental evaluation of external exposures to human bodies in radiation accidents. The dose distribution inside the body, which is needed to estimate the exposures from a result of personal dosimetry, has been evaluated mostly by computational simulations, while experimental data to verify the simulations are not sufficiently supplied, in particular, in criticality accident situations. For the purpose of obtaining the experimental data on external exposures inside the body, a preliminary experiment on criticality accident dosimetry was carried out at the Transient Experiment Critical Facility (TRACY) using a human phantom and tissue-equivalent dosimeters. The neutron and $$gamma$$-ray absorbed doses inside the phantom could be satisfactorily measured by the combined use of an alanine dosimeter and a thermoluminescent dosimeter made of enriched lithium tetra borate. The doses measured in and on the phantom were regarded as reasonable in dose level and distribution by comparison with the doses measured in the free air.

Journal Articles

Data acquisition on migration of radionuclides under deep geological environments

Iida, Yoshihisa; Taki, Hiroshi; Yamaguchi, Tetsuji; Tanaka, Tadao; Negishi, Kumi; Nakayama, Shinichi

JAERI-Conf 2005-007, p.230 - 235, 2005/08

A variation in data should be quantitatively incorporated in a probabilistic safety assessment of radioactive waste disposal. We focus our experimental efforts on parameters that induce major uncertainties in the radionuclide migration analysis and that have not been quantitatively assessed. Possible sources of uncertainty includes increase in ionic strength of groundwater caused by intrusion of seawater and/or dissolution of sodium nitrate in TRU waste, highly alkaline conditions originating from cementitious materials, and a variation of porewater composition accompanied with corrosion of. This study is a summary of current status of our investigations for solubility and diffusion.

Journal Articles

Sampling and treatment of rock cores and groundwater under reducing environments of deep underground

Ebashi, Katsuhiro; Yamaguchi, Tetsuji; Tanaka, Tadao; Araki, Kunio*; Saito, Masao*

JAERI-Conf 2005-007, p.242 - 247, 2005/08

no abstracts in English

Journal Articles

Experimental and modeling study to predict long-term alteration of bentonite buffer materials with alkaline groundwater

Takazawa, Mayumi; Negishi, Kumi; Sakamoto, Yoshifumi; Akai, Masanobu; Yamaguchi, Tetsuji; Iida, Yoshihisa; Tanaka, Tadao; Nakayama, Shinichi

JAERI-Conf 2005-007, p.236 - 241, 2005/08

no abstracts in English

Journal Articles

Study on dissolution behavior of molten solidified waste

Mizuno, Tsuyoshi*; Maeda, Toshikatsu; Bamba, Tsunetaka*

JAERI-Conf 2005-007, p.225 - 229, 2005/08

no abstracts in English

Journal Articles

Study on safety evaluation for nuclear fuel cycle facility under accident conditions

Abe, Hitoshi; Tashiro, Shinsuke; Morita, Yasuji

JAERI-Conf 2005-007, p.199 - 204, 2005/08

Source term data for estimating release behavior of radioactive nuclides is necessary to evaluate synthetic safety of nuclear fuel cycle facility under accident conditions, such as fire and criticality. In JAERI, the data has been obtained by performing some demonstration tests. In this paper, the data for the criticality accident in fuel solution obtained from the TRACY experiment, will be mainly reviewed. At 4.5 h after the transient criticality, the release ratio of the iodine were about 0.2% for re-insertion of transient rod at just after transient criticality and about 0.9% for not re-insertion. Similarly the release coefficient and release ratio for Xe were estimated. It was proved that the release ratio of Xe-141 from the solution was over 90% in case that the inverse period was over about 100 (1/s). Furthermore, outline of the study on the fire accident as future plan will be also mentioned.

Journal Articles

Simulation codes of chemical separation process of spent fuel reprocessing; Tool for process development and safety research

Asakura, Toshihide; Sato, Makoto; Matsumura, Masakazu; Morita, Yasuji

JAERI-Conf 2005-007, p.345 - 347, 2005/08

This paper reviews the succeeding development and utilization of Extraction System Simulation Code for Advanced Reprocessing (ESSCAR). From the viewpoint of development, more tests with spent fuel and calculations should be performed with better understanding of the physico-chemical phenomena in a separation process. From the viewpoint of process safety research on fuel cycle facilities, it is important to know the process behavior of a key substance; being highly reactive but existing only trace amount.

Journal Articles

Electrochemical studies of plutonium(IV) complexes in aqueous nitrate solutions

Kim, S.-Y.; Asakura, Toshihide; Morita, Yasuji

JAERI-Conf 2005-007, p.341 - 344, 2005/08

Electrochemistry has been used to investigate the behavior of plutonium(IV) in 1-7 M HNO$$_{3}$$ solutions. These Pu(IV) complexes were found to be reduced quasi-reversibly to Pu(III) species. The formal redox potentials (E$$^{o}$$) for Pu(IV)/Pu(III) couples were determined to be +0.721, +0.712, +0.706, +0.705, +0.704, 0.694, and +0.696 V (vs. Ag/AgCl(SSE)) for Pu(IV) complexes in 1, 2, 3, 4, 5, 6, 7 M HNO$$_{3}$$ solutions, respectively. These results indicate that the reduction product of Pu(IV) is Pu(III), which is considerably stable in HNO$$_{3}$$ solution.

Journal Articles

Study on safety evaluation for nuclear fuel cycle facility under fire accident conditions

Tashiro, Shinsuke; Abe, Hitoshi; Morita, Yasuji

JAERI-Conf 2005-007, p.348 - 350, 2005/08

Hot test at Rokkasho Reprocessing plant has been started since last year. In addition, construction of the MOX fuel fabrication facility at Rokkasho site is planning. So, the importance of safety evaluation of the nuclear fuel cycle facility is increasing. Under the fire accident, one of the serious postulated accidents in the nuclear fuel cycle facility, the equipments (glove-box, ventilation system, ventilation filters etc.) for the confinement of the radioactive materials within the facility could be damaged by a large amount of heat and smoke released from the combustion source. Therefore, the fundamental data and models calculating for the amount of heat and smoke released from the combustion source under such accident are important for the safety evaluation of the facility. In JAERI, the study focused on the evaluation of amount of heat and smoke released from the combustion source is planning. In this paper, the outline of experimental apparatus, measurement items and evaluation terms are described.

Journal Articles

Accomplishment of 10-year research in NUCEF and future development; Process safety and development research

Morita, Yasuji; Asakura, Toshihide; Mineo, Hideaki; Hotoku, Shinobu; Uchiyama, Gunzo

JAERI-Conf 2005-007, p.25 - 30, 2005/08

Researches on process safety of reprocessing, development of an advanced reprocessing and partitioning of high-level liquid waste(HLLW) have been conducted in NUCEF - BECKY (Back-end Fuel Cycle Key Elements Research Facility), which has alpha-gamma concrete cells and many glove-boxes. This paper presents 10 year accomplishment of the above researches and future activities to be conducted in the field of separation process development.

Journal Articles

Neutron Dose Assessment Using an Ebonite in Criticality Accident

Mikami, Satoshi; Yoshida, Tadayoshi; Takada, Chie; Tsujimura, Norio

JAERI-Conf 2005-007, p.326 - 331, 2005/08

Feasibility study of a hard rubber named ebonite as an activation detector for fast neutron has been carried out. It contains about 30 wt% of sulphur and $$^{32}$$S(n,p)$$^{32}$$P reaction can be utilized for fast neutron dose assessment. Characteristics of ebonite, a feasibility of it as a neutron dosemeter are investigated. According to our examination results, the neutron dose assessment method using an ebonite can be applied to dose reconstruction in the fields such as fuel fabrication plant and reprocessing plant etc., and to personal working there too. For easy dose assessment, the conversion factors to neutron tissue kerma from spectra were tabulated as a function of thickness of shielding of steel and concrete. The disc-shaped ebonite is one of the most useful tools to evaluate the dose induced by fast neutrons in case of criticality accident. It has the advantage of simple handling, measurements and rapid dose assessment.

Journal Articles

Study on evaluation method of radionuclides discharged in criticality accident using stack gas monitor

Sanada, Yukihisa; Mikami, Satoshi; Kobayashi, Hirohide; Kurimata, Tomoyuki*; Fukazawa, Satoshi*

JAERI-Conf 2005-007, p.321 - 325, 2005/08

It researched concerning the method of evaluating the radionuclide discharged by using the gas monitor at a criticality accident. The measurement condition was set from the evaluation result of the $$gamma$$-ray spectrum at a criticality accident of the use of the calculation code. The measurement system was developed in consideration of those conditions. The evaluation after three hours is possible at a criticality accident according to this system. The evaluation before three hours was examined about the method of doing the detector pulse by high-speed processing by digital oscilloscope.

Journal Articles

Application of log interpretation methods to evaluate heterogeneity in diatomaceous mudstone at Horonobe area

Hara, Akio; Tsuji, Takashi*; Nishimura, Mizue*; Hoshi, Kazuyoshi*; Yagi, Masahiko*; Kawada, Koji*; Hou, J.-Y.*

JAERI-Conf 2005-007, p.270 - 275, 2005/08

Borehole log interpretation methods, which are usually used by petroleum exploration companies, are applied for evaluating heterogeneity of deep underground diatomaceous mudstones in the Horonobe area. Natural $$gamma$$ ray log and electrical micro image (EMI) log data were used for the log interpretation. Five sedimentary facies, A to E, were established from the EMI log interpretation. Significant correlations between the sedimentary facies, the chemical contents, the natural $$gamma$$ ray level, and the electric conductivity in the diatomaceous mudstone were seen. Spatial distribution of the diatomaceous mudstone, in lithology and thickness, was recognized through borehole correlation, which seems to reflect the sedimentary environment change.

Journal Articles

The Effect of Silica Sand Content on Diffusion of CO$$_{3}$$$$^{2-}$$, Cl$$^{-}$$ and I$$^{-}$$ ions in Compacted Bentonite

Ishidera, Takamitsu; Miyamoto, Shinya*; Sato, Haruo

JAERI-Conf 2005-007, p.264 - 269, 2005/05

For safety assessment of TRU waste disposal, the effective diffusion coefficients (De) for CO$$_{3}$$$$^{2-}$$, Cl$$^{-}$$ and I$$^{-}$$ ions in compacted bentonite (Kunigel V1) were determined as a function of silica sand contents under hyper alkaline condition. The obtained De values for three diffusants were on the order of 10$$^{-13}$$ - 10$$^{-11}$$ m$$^{2}$$/s and increased with increasing silica sand content. The effective porosity for diffusion of Cl$$^{-}$$ and I$$^{-}$$ ions, estimated from the rock capacity factor values, were also increased with increasing silica sand content. This close relationship indicated that the increases in the De values were due to the increase in effective porosity with increasing silica sand content. In the case of CO$$_{3}$$$$^{2-}$$ ion, the rock capacity factor values were higher than those for Cl$$^{-}$$ and I$$^{-}$$ ions. The Da values for CO$$_{3}$$$$^{2-}$$ ion were approximately one order of magnitude lower than those for Cl$$^{-}$$ and I$$^{-}$$ ions. The differences in these behaviors suggested a possibility of isotopic exchange of $$^{14}$$C with the carbon of calcite contained in Kunigel V1.

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