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Journal Articles

Resonant inelastic X-ray scattering study of charge excitations in superconducting and nonsuperconducting PrFeAsO$$_{1-y}$$

Jarrige, I.*; Nomura, Takuji; Ishii, Kenji; Gretarsson, H.*; Kim, Y.-J.*; Kim, J.*; Upton, M.*; Casa, D.*; Gog, T.*; Ishikado, Motoyuki*; et al.

Physical Review B, 86(11), p.115104_1 - 115104_4, 2012/09

 Times Cited Count:8 Percentile:59.12(Materials Science, Multidisciplinary)

We report the first observation by momentum-resolved resonant inelastic X-ray scattering of charge excitations in an iron-based superconductor and its parent compound, PrFeAsO$$_{0.7}$$ and PrFeAsO respectively, with two main results. First, using calculations based on a 16 band $$dp$$ model, we show that the energy of the lowest-lying excitations, identified as $$dd$$ interband transitions of dominant $$xz$$, $$yz$$ orbital character, exhibits a dramatic dependence on electron correlation. This enables us to estimate the Coulomb repulsion $$U$$ and Hund's coupling $$J$$, and to highlight the role played by $$J$$ in these peculiar orbital-dependent electron correlation effects. Second, we show that short-range antiferromagnetic correlations, which are a prerequisite to the occurrence of these excitations at the $$Gamma$$ point, are still present in the superconducting state.

Journal Articles

PIE technique of fuel cladding fracture toughness test

Endo, Shinya; Usami, Koji; Nakata, Masahito; Fukuda, Takuji*; Onozawa, Atsushi; Harada, Akio; Kizaki, Minoru; Kikuchi, Hiroyuki

HPR-366, Vol.1 (CD-ROM), 10 Pages, 2007/03

no abstracts in English

Journal Articles

Measurement of the spin and magnetic moment of $$^{23}$$Al

Ozawa, Akira*; Matsuta, Kensaku*; Nagatomo, Takashi*; Mihara, Mototsugu*; Yamada, Kazunari*; Yamaguchi, Takayuki*; Otsubo, Takashi*; Momota, Sadao*; Izumikawa, Takuji*; Sumikama, Toshiyuki*; et al.

Physical Review C, 74(2), p.021301_1 - 021301_4, 2006/08

 Times Cited Count:38 Percentile:10.63(Physics, Nuclear)

no abstracts in English

Journal Articles

PIE technique of LWR fuel cladding fracture toughness test

Endo, Shinya; Usami, Koji; Nakata, Masahito; Fukuda, Takuji*; Numata, Masami; Kizaki, Minoru; Nishino, Yasuharu

Proceedings of 2005 JAEA-KAERI Joint Seminar on Advanced Irradiation and PIE Technologies, p.S2_7_1 - S2_7_11, 2005/11

no abstracts in English

Oral presentation

Development of testing technique on failure behavior of fuel cladding

Fukuda, Takuji

no journal, , 

no abstracts in English

Oral presentation

Mechanical test on artificially pre-cracked cladding tube

Fukuda, Takuji

no journal, , 

It is guessed that it becomes penetration damage by the crack generation from hydride rim area in the outer part in the damage of the high burn-up fuel cladding in the RIA. This study reports on the result of evaluating the experiment that uses the EDC examination method as a method of simulating such a damage form. It reports on the result of experimenting on two kinds of pre cracking sample. One is the machining, the other is rolling.

Oral presentation

High burn-up BWR 9$$times$$9 fuel behavior under RIA conditions

Fukuda, Takuji; Sugiyama, Tomoyuki; Usami, Koji; Murao, Hiroyuki; Nagase, Fumihisa

no journal, , 

The pulse irradiation was carried out to simulate reactivity initiated accident (RIA) by using nuclear safety research reactor (NSRR). To get the fuel enthalpy when high burn-up BWR 9$$times$$9 fuel failure. Post irradiation examination was also carried out to get the information about fuel failure factor.

Oral presentation

Behavior of high burnup PWR and BWR fuel rods in reactivity-initiated accident tests at high temperature

Sugiyama, Tomoyuki; Udagawa, Yutaka; Fukuda, Takuji; Nagase, Fumihisa; Murao, Hiroyuki; Toyokawa, Takuya

no journal, , 

no abstracts in English

Oral presentation

Failure behavior of LWR fuel cladding under accident conditions; Key observations from fuel safety research program at JAEA

Nagase, Fumihisa; Sugiyama, Tomoyuki; Amaya, Masaki; Udagawa, Yutaka; Fukuda, Takuji; Mihara, Takeshi

no journal, , 

The Japan Atomic Energy Agency (JAEA) performs the comprehensive research program to better understand behavior of high burnup fuels under accident conditions. The high burnup fuel cladding fails by mechanical interaction with fuel pellets under RIA conditions. The failure threshold reduces with increasing burnup. The information has been accumulated on failure mechanism from mechanical property tests and computer code analysis as well as on the failure threshold from the NSRR experiments. Regarding fuel behavior in a LOCA, JAEA has obtained data on oxidation kinetics and fracture threshold and evaluated the high burnup effects. JAEA continues researches for clarifying fuel failure mechanism and improving safety evaluation methodologies.

Oral presentation

Evaluation on failure behavior of hydrided RAG cladding using EDC experiments

Mihara, Takeshi; Fukuda, Takuji; Udagawa, Yutaka; Sugiyama, Tomoyuki; Nagase, Fumihisa

no journal, , 

High burnup PWR fuel rods includes hydride rims that hydride accumulate the periphery of the rods. NSRR experiments of the fuels indicate that hydride rims plays a role of an initial crack of RIA failure behavior. In order to clarify the influence of interior hydrides other than the rims about RIA failure behavior, hydrided RAG (Roll after Grooving) fabricated fuel rods were performed with EDC (Expansion Due to Compression) experiments. Stress intensity factor analyses indicate that in case the radially-oriented hydrides are precipitated at the tip of the pre-crack, the stress state of the matrix at the tip of the hydrides is the same.

Oral presentation

Development of pre-cracking method for evaluating the RIA failure behavior of high burn-up fuels

Fukuda, Takuji; Sugiyama, Tomoyuki; Mihara, Takeshi; Nagase, Fumihisa

no journal, , 

The hydride Precipitation occurs due to absorption of hydrogen and its oxidation in the high burn-up fuel cladding. The hydride precipitated densely near the outer surface of the cladding could be considered the origin of the crack growth its own brittle property. RAG (Roll After Grooving) has been developed to simulate the outer surface of hydride precipitation on the origin of the crack. The fracture behavior was evaluated to define the effect of origin of the crack compared with milled cladding by EDC (Expansion Due to Compression) test. The crack extension occurred in smaller circumferential strain on RAG cladding than milled cladding. It was shown that RAG can simulate the crack growth of outer surface hydride cracking.

Oral presentation

The Effect of sea water component on the cladding oxidation at high temperature

Yamato, Masaaki; Fukuda, Takuji; Amaya, Masaki; Nagase, Fumihisa

no journal, , 

After the Great East Japan Earthquake, the reactor and spent fuel pool in Fukushima Daiichi Nuclear Plant was cooled by sea water. In order to evaluate the effect of sea component on the cladding oxidation at high temperature, isothermal oxidation tests in steam or Ar+O$$_{2}$$ were performed with zircaloy-2 cladding specimens whose surface was attached sea component. As a result, influence of sea component is not significant for the oxidation thickness, but oxidation atmosphere was influenced the adherence of the oxidation and metallic layer.

Oral presentation

Research on high burnup fuel behavior under accident conditions

Sugiyama, Tomoyuki; Fukuda, Takuji; Nagase, Fumihisa

no journal, , 

To confirm the reactor safety design, safety reviews are performed under accident conditions as well as under normal operation conditions. One of such design basis accidents is the reactivity-initiated accident (RIA); a reactor excursion typically caused by rapid ejection of the control rod. In case of high burnup fuel, mechanical failure of corroded cladding can occur due to the rapid thermal expansion of fuel pellet. Cladding mechanical test is effective to evaluate the failure limit, but the conventional tests using axial tension or hydraulic pressure cannot represent the biaxial stress state during RIA, which is generated in the cladding chemically bonded with the fuel pellet. Therefore, the biaxial stress testing apparatus was developed, which simulates the stress condition in RIA by the simultaneous axial load and hydraulic pressurization. Mechanical properties of zircaloy-4 cladding are being acquired with the apparatus to improve the accuracy of fuel failure limit evaluation.

Oral presentation

Development and test results of multi-axial stress testing machine for cladding

Fukuda, Takuji; Sugiyama, Tomoyuki; Mihara, Takeshi; Amaya, Masaki; Nagase, Fumihisa

no journal, , 

The stress condition of the cladding tube of high burnup fuel is complicated under RIA (Reactivity Initiated Accident) condition because fuel pellet and cladding bond significantly in high burnup fuel. The stress condition becomes biaxial under such condition due to the isotropy of pellet thermal expansion. We have developed a biaxial stress testing machine which can control the axial and circumferential stresses independently and evaluate the mechanical and fracture behaviors of cladding tube under biaxial stress condition. This report describes the outline of the experiment using this equipment and the test results obtained under several biaxial stress conditions at room temperature.

Oral presentation

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