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Journal Articles

Study on mechanism and threshold conditions for fuel fragmentation during loss-of-coolant accident conditions

Narukawa, Takafumi; Udagawa, Yutaka

Proceedings of TopFuel 2021 (Internet), 10 Pages, 2021/10

Journal Articles

Transient response of LWR fuels (RIA)

Udagawa, Yutaka; Fuketa, Toyoshi*

Comprehensive Nuclear Materials, 2nd Edition, Vol.2, p.322 - 338, 2020/08

Journal Articles

Simulation of fuel-coolant interaction SERENA2 test based on JASMINE version 3

Hotta, Akitoshi*; Morita, Akinobu*; Kajimoto, Mitsuhiro*; Maruyama, Yu

Nihon Genshiryoku Gakkai Wabun Rombunshi, 16(3), p.139 - 152, 2017/09

Journal Articles

An Empirical correlation to predict the distance for fragmentation of simulated Molten-Core materials discharged into a sodium pool

Matsuba, Kenichi; Isozaki, Mikio; Kamiyama, Kenji; Suzuki, Toru; Tobita, Yoshiharu

Proceedings of 11th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, Operation and Safety (NUTHOS-11) (USB Flash Drive), 8 Pages, 2016/10

In order to evaluate the distance for fragmentation of molten core material discharged into the lower sodium plenum during core disruptive accidents in sodium-cooled fast reactors, experiments with simulated molten materials and coolants (water, sodium) was carried out, where an empirical correlation of the distance for fragmentation was developed. The empirical correlation developed by this study showed a good agreement with the measurement results obtained by the present experiments. It was found that in order to well-predict the distance for fragmentation in sodium, thermal phenomena, such as sodium boiling and resultant vapor expansion, needed to be considered.

Journal Articles

Distance for fragmentation of a simulated molten-core material discharged into a sodium pool

Matsuba, Kenichi; Isozaki, Mikio; Kamiyama, Kenji; Tobita, Yoshiharu

Journal of Nuclear Science and Technology, 53(5), p.707 - 712, 2016/05

 Times Cited Count:9 Percentile:75.69(Nuclear Science & Technology)

In order to develop an evaluation method of the distance for fragmentation of molten core material discharged into the sodium plenum, a sodium experiment with visual observation was conducted using an X-ray imaging system. In the current experiments, 0.9 kg of molten aluminum (initial temperature: around 1473 K) was discharged into a sodium pool (initial temperature: 673 K) through a nozzle (inner diameter: 20 mm). Based on the experimental results, the distance for fragmentation of the liquid column was estimated to be 100 mm in the experiments. Through the sodium experiment, useful knowledge was obtained for the future development of an evaluation method of the distance for fragmentation of molten core material. As a next step, sodium experiments using higher-density molten materials will be conducted to enrich the experimental knowledge. Besides, a new semi-empirical correlation will be developed to evaluate more appropriately the distance for fragmentation under CDA conditions.

Journal Articles

Experimental discussion on fragmentation mechanism of molten oxide discharged into a sodium pool

Matsuba, Kenichi; Kamiyama, Kenji; Toyoka, Junichi; Tobita, Yoshiharu; Zuev, V. A.*; Kolodeshnikov, A. A.*; Vasilyev, Y. S.*

Proceedings of 23rd International Conference on Nuclear Engineering (ICONE-23) (DVD-ROM), 6 Pages, 2015/05

To develop a method for evaluating the distance for fragmentation of molten core material discharged into sodium, the particle size distribution of alumina debris obtained in the FR tests was analyzed. The mass median diameters of solidified alumina particles were around 0.4 mm, which are comparable to particle sizes predicted by hydrodynamic instability theories such as Kelvin-Helmholtz instability. However, even though hydrodynamic instability theories predict that particle size decreases with an increase of Weber number, such the dependence of particle size on We was not observed in the FR tests. It can be interpreted that the tendency of measured mass median diameters (i.e., non-dependence on Weber number) suggests that before hydrodynamic instabilities sufficiently grow to induce fragmentation, thermal phenomena such as local coolant vaporization and resultant vapor expansion accelerate fragmentation.

Journal Articles

Distance for fragmentation of a simulated molten-core material discharged into a sodium pool

Matsuba, Kenichi; Isozaki, Mikio; Kamiyama, Kenji; Suzuki, Toru; Tobita, Yoshiharu

Proceedings of 10th International Topical Meeting on Nuclear Thermal Hydraulics, Operation and Safety (NUTHOS-10) (USB Flash Drive), 7 Pages, 2014/12

In order to develop an evaluation method of the distance for fragmentation of molten core material discharged into the sodium plenum, a sodium experiment with visual observation was conducted using an X-ray imaging system. In the current experiments, 0.9 kg of molten aluminum (initial temperature: around 1473 K) was discharged into a sodium pool (initial temperature: 673 K) through a nozzle (inner diameter: 20 mm). Based on the experimental results, the distance for fragmentation of the liquid column was estimated to be 100 mm in the experiments. Through the sodium experiment, useful knowledge was obtained for the future development of an evaluation method of the distance for fragmentation of molten core material. As a next step, sodium experiments using higher-density molten materials will be conducted to enrich the experimental knowledge. Besides, a new semi-empirical correlation will be developed to evaluate more appropriately the distance for fragmentation under CDA conditions.

Journal Articles

An Observation of a nascent fractal pattern in MD simulation for a fragmentation of an fcc lattice

Chikazumi, Shimpei*; Iwamoto, Akira

Chaos, Solitons and Fractals, 23(1), p.73 - 78, 2005/01

To seek for a possible origin of fractal pattern in nature, we perform a molecular dynamics simulation for a fragmentation of an infinite fcc lattice. The fragmentation is induced by the initial condition of the model that the lattice particles have the Hubble-type radial expansion velocities. As time proceeds, the average density decreases and density fluctuation develops. By using the box counting method, it is found that the frequency-size plot of the density follows instantaneously a universal power-law for each Hubble constant up to the size of a cross-over. This cross-over size corresponds to the maximum size of fluctuation and is found to obey a dynamical scaling law as a function of time. This instantaneous generation of a nascent fractal is purely of dynamical origin and it shows us a new formation mechanism of a fractal patters different from the traditional criticality concept.

Journal Articles

Phenomenon identification and ranking tables (PIRTs) for rod ejection accidents in pressurized water reactors containing high burnup fuel

Boyack, B. E.*; Motta, A. T.*; Peddicord, K. L.*; Alexander, C. A.*; Deveney, R. C.*; Dunn, B. M.*; Fuketa, Toyoshi; Higar, K. E.*; Hochreiter, L. E.*; Langenbuch, S.*; et al.

NUREG/CR-6742, 263 Pages, 2001/09

no abstracts in English

Journal Articles

Behavior during on RIA

Fuketa, Toyoshi

Saishin Kaku Nenryo Kogaku; Kodoka No Genjo To Tembo, p.141 - 147, 2001/06

no abstracts in English

Journal Articles

Nuclear fragmentation by tunneling

Maruyama, Toshiki; Bonasera, A.*; Chiba, Satoshi

Physical Review C, 63(5), p.057601_1 - 057601_4, 2001/05

 Times Cited Count:4 Percentile:34.56(Physics, Nuclear)

Fragmentation of nuclear system by tunneling is discussed by molecular dynamics simulation coupled with imaginary time method. In this way we obtain informations on the fragmenting systems at low densities and low temperatures. These conditions cannot be reached normally (i.e. above the barrier) in nucleus-nucleus or nucleon-nucleus collisions. The price to pay is the small probability of fragmentation by tunneling but we obtain some observables which can be a clear signature of such phenomena.

Journal Articles

Mechanical energy generation during high burnup fuel failure under reactivity initiated accident conditions

Sugiyama, Tomoyuki; Fuketa, Toyoshi

Journal of Nuclear Science and Technology, 37(10), p.877 - 886, 2000/10

no abstracts in English

JAEA Reports

Study about the dissolution behavior of the irradiated fast reactor fuels in CPF

; Koyama, Tomozo; Funasaka, Hideyuki

JNC TN8400 2000-014, 78 Pages, 2000/03

JNC-TN8400-2000-014.pdf:2.13MB

We investigated the factors which affected the dissolution of U and Pu to the nitric acid solution with the fragmentation model, which was based on the results of dissolution experiments for the irradiated fast reactor fuels in the Chemical Processing Facility(CPF). The equation that gave the fuel dissolution rate was estimated with the condition of fabrication (Pu ratio (Pu/(U+Pu))), irradiation (burn-up) and dissolution (nitric acid concentration, solution temperature and U+Pu concentration) by evaluating these effects quantitatively. We also investigated the effects of fuel volume ratio to the solution in the dissolver, burn-up and flouring ratio of the fuel on the f-value (the parameter which shows the diffusion and osmosis of nitric acid to the fuel) in the fragmentation model. It was confirmed that the fuel dissolution rate calculated with this equation had better agreement with the results of dissolution experiments for the irradiated fast reactor fuels in the CPF than that estimated with the surface area model. In addition, the efficiency of this equation was recognized for the dissolution of unirradiated U pellet and high Pu enriched MOX fuel. It was shown that the dissolution rate of the fuel slowed down at the condition of the high U-Pu concentration dissolution by the calculation of the dissolution behavior with this equation. The dissolution of the fuel can be improved by increasing the nitric acid concentration and temperature, but from the viewpoint of lowering the corrosion of the dissolver materials, it is desirable that the f-value is increased by optimizing the condition of shearing and stirring for the improvement of dissolution.

Journal Articles

High brunup BWR fuel response to reactivity transients and a comparison with PWR fuel response

Fuketa, Toyoshi; Nakamura, Takehiko; Kusagaya, Kazuyuki*; Sasajima, Hideo; Uetsuka, Hiroshi

NUREG/CP-0172, p.191 - 203, 2000/00

no abstracts in English

Journal Articles

Study on premixing phase of steam explosion at JAERI

; Moriyama, Kiyofumi; Maruyama, Yu; H.Park*; Y.Yang*; Sugimoto, Jun

Nucl. Eng. Des., 189(1-3), p.205 - 221, 1999/00

 Times Cited Count:3 Percentile:29.56(Nuclear Science & Technology)

no abstracts in English

JAEA Reports

The Premixing and propagation phases of fuel-coolant interactions; A Review of recent experimental studies and code developments

A.R.Antariksawan*; Moriyama, Kiyofumi; H.Park*; Maruyama, Yu; Y.Yang*; Sugimoto, Jun

JAERI-Review 98-012, 66 Pages, 1998/09

JAERI-Review-98-012.pdf:3.36MB

no abstracts in English

Journal Articles

Site-specific fragmentation in Na$$_{2}$$S$$_{2}$$O$$_{3}$$ by sulfur K-edge photoexcitation

Baba, Yuji; Teraoka, Yuden; Sasaki, Teikichi

Photon Factory Activity Report 1998, Part B, P. 92, 1997/11

no abstracts in English

Journal Articles

Fuel failure and fission gas release in high burnup PWR fuels under RIA conditions

Fuketa, Toyoshi; Sasajima, Hideo; *; Ishijima, Kiyomi

Journal of Nuclear Materials, 248, p.249 - 256, 1997/00

 Times Cited Count:41 Percentile:93.17(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

NSRR/RIA experiments with high burnup PWR fuels

Fuketa, Toyoshi; Sasajima, Hideo; *; *; Nakamura, Takehiko; Ishijima, Kiyomi

Proc. of 1997 Int. Topical Meeting on LWR Fuel Performance, 0, p.669 - 676, 1997/00

no abstracts in English

33 (Records 1-20 displayed on this page)