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Journal Articles

Rapid clogging of high-efficiency particulate air filters during in-cell solvent fires at reprocessing facilities

Ono, Takuya; Tashiro, Shinsuke; Amano, Yuki; Yoshida, Ryoichiro; Abe, Hitoshi

Nuclear Technology, 206(1), p.40 - 47, 2020/01

 Times Cited Count:0 Percentile:100(Nuclear Science & Technology)

Recent Japanese nuclear regulations have focused on the hazards of in-cell solvent fires at reprocessing facilities. In this work, a mixture of tributyl phosphate and dodecane-based solvents was burned to generate an aerosol composed of soot and unburned solvent that was then loaded onto a high-efficiency particulate air filter simulating the ventilation system of reprocessing facilities. A radical increase of differential pressure occurred in the filters during these tests after the dodecane burned out from the solvent in a phenomenon we named as rapid clogging, likely caused by the burnout of dodecane. This relationship provides valuable insight into the establishment of new regulations for reprocessing facilities. This work indicates that clogging of ventilation filters during solvent fires may occur more rapidly than previously estimated.

Journal Articles

Experimental evaluation of release and transport behavior of gaseous ruthenium under boiling accident in reprocessing plant

Yoshida, Naoki; Tashiro, Shinsuke; Amano, Yuki; Yoshida, Kazuo; Yamane, Yuichi; Abe, Hitoshi

NEA/CSNI/R(2017)12/ADD1 (Internet), p.293 - 305, 2018/01

The "Evaporation to Dryness due to the Loss of Cooling Functions" (EDLCF) of highly-active liquid waste (HALW) was newly defined as one of the severe accidents in Japan's nuclear safety standard for the reprocessing plant. Studies on accident scenarios and their source terms have led to an increased need for the development of accident management measures and the assessment of their effectiveness. Previous studies have shown that ruthenium was released at a greater rate than other elements because it formed volatile species such as ruthenium tetroxide (RuO4). In addition, ruthenium isotopes, 106Ru and 103Ru, have radiotoxicity. Accordingly, the accident management measures require the experimental information on the release and transport behavior of the gaseous ruthenium (Ru(g)). This paper summarizes our experimental results on the characteristics of Ru(g) in the EDLCF. This work includes the results of the experiments carried out under the agreement among JAEA, Japan Nuclear Fuel Ltd. and Japan Nuclear Energy Safety Organization.

Journal Articles

HEPA filter clogging and volatile material release under solvent fire accident in fuel reprocessing facility

Ono, Takuya; Watanabe, Koji; Tashiro, Shinsuke; Amano, Yuki; Abe, Hitoshi

Proceedings of 25th International Conference on Nuclear Engineering (ICONE-25) (CD-ROM), 7 Pages, 2017/07

After the Fukushima-Daiichi accident, countermeasures against the severe accident are newly required as regulatory items for nuclear facilities. Organic solvent fire in cell was defined as one of the accidents in the fuel reprocessing plant. When the solvent burns, aerosols including soot are released. The substances clog HEPA filters in the ventilation system and their breakthrough may happen because of differential pressure rising. Moreover, the fire can also release volatile radioactive gaseous species, which can pass through HEPA filters. These phenomena are important for evaluation of confinement capability of the facility and public exposure. We have investigated, in relating to the clogging behavior, release behavior of aerosols as well as of volatile materials from burnt solvent. In the presentation, we will report experimental data and evaluation results obtained from recent research.

JAEA Reports

Solvent extraction and release behavior of ruthenium and europium in fire accident conditions in reprocessing plants (Contract research)

Amano, Yuki; Watanabe, Koji; Masaki, Tomoo; Tashiro, Shinsuke; Abe, Hitoshi

JAEA-Technology 2016-012, 21 Pages, 2016/06

JAEA-Technology-2016-012.pdf:1.81MB

To contribute to safety evaluation of fire accident in fuel reprocessing plants, solvent extraction behavior of ruthenium, which could form volatile species, was investigated. Distribution ratios of ruthenium at fire accident conditions were obtained by extraction experiments with several solvent composition at different temperature as parameters. In order to investigate release behavior of ruthenium and europium at fire accident, release ratios of ruthenium and europium were also obtained by solvent combustion experiments.

Journal Articles

Release of radioactive materials from high active liquid waste in small-scale hot test for boiling accident in reprocessing plant

Yamane, Yuichi; Amano, Yuki; Tashiro, Shinsuke; Abe, Hitoshi; Uchiyama, Gunzo; Yoshida, Kazuo; Ishikawa, Jun

Journal of Nuclear Science and Technology, 53(6), p.783 - 789, 2016/06

 Times Cited Count:3 Percentile:57.46(Nuclear Science & Technology)

The release behavior of radioactive materials from high active liquid waste (HALW) has been experimentally investigated under boiling accident conditions. In the experiments using HALW obtained through laboratory scale reprocessing, release ratio was measured for the FP nuclides such as Ru, $$^{99}$$Tc, Cs, Sr, Nd, Y, Mo, Rh and actinides such as $$^{242}$$Cm, $$^{241}$$Am. As a result, the release ratio was 0.20 for Ru and 1$$times$$$$10^{-4}$$ for the FP and Ac nuclides. Ru was released into the gas phase in the form of both mist and gas. For its released amount, weak dependency was found to the initial concentration in the test solution. The release ratio decreased with the initial concentration. For other FP nuclides and actinides as non-volatile, released into the gas phase in the form of mist, the released amount increased with the initial concentration. The release ratio of Ru and NOx concentration increased with temperature of the test solutions. They were released almost at the same temperature between 200 and 300$$^{circ}$$C. Size distribution of the mist and other particle was measured.

Journal Articles

Release Characteristics of Ruthenium from Highly Active Liquid Waste in Drying Step

Tashiro, Shinsuke; Amano, Yuki; Yoshida, Kazuo; Yamane, Yuichi; Uchiyama, Gunzo; Abe, Hitoshi

Nippon Genshiryoku Gakkai Wabun Rombunshi, 14(4), p.227 - 234, 2015/12

The release characteristics of Ru from highly active liquid waste (HALW) have been investigated under the condition of accidental evaporation to dryness by boiling of HALW. Using a laboratory-scale apparatus, non-radioactive simulated HALW (s-HALW) was heated with an external heater to dryness to observe the release characteristics of Ru and gaseous nitrogen oxides. As a result, Ru was significantly released between 120 and 300 $$^{circ}$$C of the s-HALW. The cumulative release ratio of Ru was 0.088. It was also found that the partially released amount of Ru against the temperature of the s-HALW had two peaks with one maximal at about 140 $$^{circ}$$C and maximum at about 240 $$^{circ}$$C. Referring to the results of the release rate of gaseous nitrogen oxides and the volume of condensate, which was a collection of the mixed vapors of steam and nitric acid released from the s-HALW, we discussed the causes of Ru release around these peaks.

Journal Articles

Experimental study on boiling accident of high active liquid waste in reprocessing

Uchiyama, Gunzo; Tashiro, Shinsuke; Amano, Yuki; Abe, Hitoshi; Yamane, Yuichi; Yoshida, Kazuo; Ishikawa, Jun

Proceedings of 21st International Conference & Exhibition; Nuclear Fuel Cycle for a Low-Carbon Future (GLOBAL 2015) (USB Flash Drive), p.1056 - 1063, 2015/09

The experimental study for source term data of radioactive materials has been conducted at a boiling accident of high active liquid waste (HALW) in reprocessing plants. In the study, three kinds of tests have been conducted including a cold small scale test, a cold engineering scale test and a hot small scale test. The following results were obtained: Ruthenium and Technetium were released into the gas phase in the form of both mist and gas under the boiling accident conditions of a simulated HALW. Non-volatile fission products (FPs) such as Nd and Cs were released into the gas phase in the form of mist. The release ratios of non-volatile FPs from a vessel of the simulated HALW were about 10$$^{-4}$$. The release ratios of actinide nuclides such as Am were almost the same as those of non-volatile FPs.

Journal Articles

Distribution and anisotropy of dislocations in cold-drawn pearlitic steel wires analyzed using micro-beam X-ray diffraction

Sato, Shigeo*; Shobu, Takahisa; Sato, Kozue*; Ogawa, Hiromi*; Wagatsuma, Kazuaki*; Kumagai, Masayoshi*; Imafuku, Muneyuki*; Tashiro, Hitoshi*; Suzuki, Shigeru*

ISIJ International, 55(7), p.1432 - 1438, 2015/07

 Times Cited Count:5 Percentile:60.41(Metallurgy & Metallurgical Engineering)

To characterize the distribution and anisotropy of dislocations in cold-drawn pearlitic steel wires, X-ray diffraction line-profile analysis was performed using synchrotron radiation micro-beams. The plastic shear strain was generally more severe near the surface than the center of the wire, whereas the dislocation density distribution was almost constant from the center to the surface. On the other hand, the dislocation rearrangement, which evolves the dislocation cell structure, progressed closer to the surface. It was also revealed that a difference between the hardness in axial and transverse wire directions could be explained by anisotropic dislocation density. Line-profile analysis based on diffraction data at elevated temperatures was performed. Whereas the cementite recovery progressed at a constant rate, the ferrite phase recovery rate was temperature-dependent, suggesting that the ferrite phase recovery was less related to that of the cementite phase.

Journal Articles

Trends of nitrogen oxide release during thermal decomposition of nitrates in highly active liquid waste

Amano, Yuki; Watanabe, Koji; Tashiro, Shinsuke; Yamane, Yuichi; Ishikawa, Jun; Yoshida, Kazuo; Uchiyama, Gunzo; Abe, Hitoshi

Nippon Genshiryoku Gakkai Wabun Rombunshi, 14(2), p.86 - 94, 2015/06

Radioactive materials could be released into air due to the accidental boiling of high active liquid waste (HALW) in reprocessing plants. Volatile radioactive nuclides, such as ruthenium, are released from the tanks into the atmosphere. Nitrogen oxides (NOx) are also released due to the thermal decomposition of metal nitrates in HALW. The released NOx transport volatile ruthenium and cause redox reactions associated with the composition or decomposition of volatile ruthenium. In this study, NOx release data were obtained by heating simulated HALW up to 600$$^{circ}$$C. As a result, the release of NOx from the simulated HALW was observed from 200$$^{circ}$$C to 600$$^{circ}$$C, and the main release of NOx was observed at about 340$$^{circ}$$C. All the lanthanide nitrates were found to decompose in the simulated HALW, and the thermal decomposition temperature of the lanthanide nitrates decreased after the addition of ruthenium dioxide to the mixed lanthanide nitrates solution.

Journal Articles

Release of radioactive materials from simulated high level liquid waste at boiling accident in reprocessing plant

Tashiro, Shinsuke; Uchiyama, Gunzo; Amano, Yuki; Abe, Hitoshi; Yamane, Yuichi; Yoshida, Kazuo

Nuclear Technology, 190(2), p.207 - 213, 2015/05

 Times Cited Count:4 Percentile:54.36(Nuclear Science & Technology)

The release behavior of radioactive materials from high active liquid waste (HALW) has been investigated under boiling accident conditions. Results of the experiment using a nonradioactive simulated HALW found Ru to be a volatile element under the accident conditions and to be released into the gas phase in the form of both mist and gas. The Ru release rate and the apparent Ru volatilization rate constant were obtained under the boiling conditions of simulated HALW. The other fission product elements such as Cs were found to be nonvolatile and to be released into the gasphase in the form of mist. The mist size distribution near the surface of the simulated HALW in the reactor vessel was found to range from 0.05 to 20 $$mu$$m with a peak diameter of $$sim$$ 2 $$mu$$m.

Journal Articles

Development of Ru transfer rate correlation to vapor phase in accident of evaporation to dryness by boiling of reprocessed high-level liquid waste

Yoshida, Kazuo; Tashiro, Shinsuke; Amano, Yuki; Yamane, Yuichi; Uchiyama, Gunzo; Abe, Hitoshi

Nippon Genshiryoku Gakkai Wabun Rombunshi, 13(4), p.155 - 166, 2014/12

An accident of evaporation to dryness by boiling of high level liquid waste (HLLW) is postulated as one of the severe accidents to occur caused by the loss of cooling function at a fuel reprocessing plant. In this case, a large amount of ruthenium (Ru) will be volatilized and transfer to the vapor phase in the tank, and could be released to the environment. Therefore, the quantitative estimation of released Ru is one of the key issues in the assessment of the accident consequence. To resolve this issue, an empirical correlation for Ru transfer rate to vapor phase with the temperature, nitric acid mol fraction and activity of HLLW has been developed based on the data obtained from the accelerated experiments using simulated HLLW. A simulation study with the developed correlation demonstrated that amount of Ru transfer to vapor phase was in a good agreement with the long term experiment using actual HLLW.

Journal Articles

Accurate structure analyses of polymer crystals on the basis of wide-angle X-ray and neutron diffractions

Tashiro, Koji*; Hanesaka, Makoto*; Yamamoto, Hiroko*; Wasanasuk, K.*; Jayaratri, P.*; Yoshizawa, Yoshinori*; Tanaka, Ichiro*; Niimura, Nobuo*; Kusaka, Katsuhiro*; Hosoya, Takaaki*; et al.

Kobunshi Rombunshu, 71(11), p.508 - 526, 2014/11

 Times Cited Count:5 Percentile:74.44(Polymer Science)

The crystal structure analysis of various polymer substances has been reviewed on the basis of wide-angle high-energy X-ray and neutron diffraction data. The progress in structural analytical techniques of polymer crystals have been reviewed at first. The structural models proposed so far were reinvestigated and new models have been proposed for various kinds of polymer crystals including polyethylene, poly(vinyl alcohol), poly(lactic acid) and its stereocomplex etc. The hydrogen atomic positions were also clarified by the quantitative analysis of wide-angle neutron diffraction data, from which the physical properties of polymer crystals have been evaluated theoretically. The bonded electron density distribution has been estimated for a polydiacetylene single crystal on the basis of the so-called X-N method or by the combination of structural information derived from X-ray and neutron diffraction data analysis. Some comments have been added about future developments in the field of structure-property relationship determination.

Journal Articles

Characterization and storage of radioactive zeolite waste

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

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

 Times Cited Count:7 Percentile:39.47(Nuclear Science & Technology)

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

Journal Articles

Release behavior of radioactive materials at a boiling accident of high active liquid waste in reprocessing plants

Uchiyama, Gunzo; Tashiro, Shinsuke; Amano, Yuki; Abe, Hitoshi; Yamane, Yuichi; Yoshida, Kazuo; Ishikawa, Jun

Proceedings of International Waste Management Symposia 2014 (WM 2014) (Internet), 9 Pages, 2014/05

The experimental study for source term data of radioactive materials has been conducted at a boiling accident of high active liquid waste (HALW) in a reprocessing plant. In the small scale cold test using a non-radioactive simulated HALW, the release behavior of FP elements from the simulated HALW were investigated under various boiling accident conditions. In the engineering scale cold test, the release behavior of FP elements at boiling accident conditions was investigated mainly as a spatial function. In the small scale hot test using a radioactive simulated HALW, the release behavior of radioactive materials (FP, alpha nuclides) were obtained under typical boiling accident conditions. In the small scale hot test, the release fractions of Ru and non-volatile FPs obtained were almost the same as those of the small scale cold test.

Journal Articles

Study on release and transport of aerial radioactive materials in reprocessing plant

Amano, Yuki; Tashiro, Shinsuke; Uchiyama, Gunzo; Abe, Hitoshi; Yamane, Yuichi; Yoshida, Kazuo

Proceedings of International Nuclear Fuel Cycle Conference; Nuclear Energy at a Crossroads (GLOBAL 2013) (CD-ROM), p.1411 - 1417, 2013/09

JAEA Reports

Corrosion countermeasure for demonstration scale steam reforming system

Nakanishi, Yoshiki; Aoyama, Yoshio; Nonaka, Kazuharu; Sone, Tomoyuki; Nakazawa, Osamu; Tashiro, Kiyoshi

JAEA-Testing 2011-008, 31 Pages, 2012/03

JAEA-Testing-2011-008.pdf:2.8MB

Steam reforming technology has been developed to reduce the volume of liquid uranium waste such as a Tri-n-butyl phosphate adding n-dodecane solvent (TBP/nDD), which is difficult to incinerate. The localized corrosion like pitting corrosion occurred on the inner surface of the gasification chamber of the demonstration scale steam reforming system during the treatment of TBP/nDD. Therefore we conducted the corrosion tests to identify the form of corrosion. It is found that the form of corrosion is crevice corrosion which caused by the residues generated by treatment of TBP/nDD. The cathodic protection system using a galvanic anode was selected as the corrosion protection method of the gasification chamber. The continuous treatment test of TBP/nDD was conducted using the steam reforming system with the cathodic protection system. As a result, the crevice corrosion did not occur during 600 hours continuous treatment of TBP/nDD, and the effectiveness of the protection method was verified.

Journal Articles

Stochastic dynamics toward the steady state of self-gravitating systems

Tashiro, Toru*; Tatekawa, Takayuki

Numerical Simulations of Physical and Engineering Processes, p.301 - 318, 2011/09

The behavior of a self-gravitating system (SGS) is described using the equilibrium statistical mechanics. Although the behavior of the system is analytically solved for the spherically symmetric system, it is known that mass density in the central region and/or total mass of the system sometimes diverges. King model which is derived by modification of the statistical mechanics can explain the distribution without these difficulties. We construct a theory which can explain the dynamics toward the special steady state described by the King model. SGSs require quite long time for relaxation. Furthermore, we must compute interaction of all particle pairs. By these reasons, we require huge computation power for numerical simulation of the evolution of SGS. So we have applied special-purpose processor for computation of the interaction. From the numerical simulations of SGS, we have confirmed that our theory is appropriate for description of realistic density distribution.

Journal Articles

Performance of steam reforming technology in a long term treatment of waste TBP/dodecane

Nakagawa, Akinori; Sone, Tomoyuki; Sasaki, Toshiki; Nakazawa, Osamu; Tashiro, Kiyoshi

Proceedings of International Waste Management Symposia 2011 (WM 2011) (CD-ROM), 7 Pages, 2011/03

JAEA Reports

Treatment technology development of uranium contaminated spent TBP/n-dodecane solvent by steam reforming

Nakagawa, Akinori; Sone, Tomoyuki; Sasaki, Toshiki; Nakazawa, Osamu; Tashiro, Kiyoshi

JAEA-Technology 2010-014, 46 Pages, 2010/06

JAEA-Technology-2010-014.pdf:1.76MB

Steam reforming treatment system was developed for volume reduction of Tri-n-butyl phosphate contaminated with uranium, which is difficult to treat with incineration, due to generation of corrosive compounds, a large amount of secondary waste, etc. This system consists of a steam reforming process in which organic waste is decomposed/gasified in steam atmosphere and a submerged combustion process in which vaporized waste is burned in water and has good features such as high volume reduction rate of waste, low secondary waste generation rate, etc. Results obtained this study were as follows: Volume reduction rate of waste was 99.6%. Uranium entrainment to off-gas was suppressed and the concentration of uranium in waste water was under 0.037mg/L. The concentration of CO and NOx in the off-gas were less than 100ppm and 250ppm respectively. Plugging and corrosion control technologies were developed and it was confirmed that the waste treatment system can run for long periods.

Journal Articles

Brownian dynamics around the core of self-gravitating systems

Tashiro, Toru*; Tatekawa, Takayuki

Journal of the Physical Society of Japan, 79(6), p.063001_1 - 063001_4, 2010/06

 Times Cited Count:7 Percentile:49.86(Physics, Multidisciplinary)

We derive the non-Maxwellian distribution of self-gravitating $$N$$-body systems around the core by a model based on the random process with the additive and the multiplicative noise. The number density can be obtained through the steady state solution of the Fokker-Planck equation corresponding to the random process. We exhibit that the number density becomes equal to that of the King model around the core by adjusting the friction coefficient and the intensity of the multiplicative noise. We also show that our model can be applied in the system which has a heavier particle. Moreover, we confirm the validity of our model by comparing with our numerical simulation.

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