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Journal Articles

Leaching behavior of radionuclides from samples prepared from spent fuel rod comparable to core debris in the 1F NPS

Onishi, Takashi; Maeda, Koji; Katsuyama, Kozo

Journal of Nuclear Science and Technology, 58(4), p.383 - 398, 2021/04

 Times Cited Count:1 Percentile:39.17(Nuclear Science & Technology)

Journal Articles

Fracture-mechanics-based evaluation of failure limit on pre-cracked and hydrided Zircaloy-4 cladding tube under biaxial stress states

Li, F.; Mihara, Takeshi; Udagawa, Yutaka; Amaya, Masaki

Journal of Nuclear Science and Technology, 57(6), p.633 - 645, 2020/06

 Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)

Journal Articles

Effects of ballooning and rupture on the fracture resistance of Zircaloy-4 fuel cladding tube after LOCA-simulated experiments

Yumura, Takanori; Amaya, Masaki

Annals of Nuclear Energy, 120, p.798 - 804, 2018/10

 Times Cited Count:3 Percentile:45.99(Nuclear Science & Technology)

Journal Articles

Application of Bayesian optimal experimental design to reduce parameter uncertainty in the fracture boundary of a fuel cladding tube under LOCA conditions

Narukawa, Takafumi; Yamaguchi, Akira*; Jang, S.*; Amaya, Masaki

Proceedings of 14th International Conference on Probabilistic Safety Assessment and Management (PSAM-14) (USB Flash Drive), 10 Pages, 2018/09

Journal Articles

Uncertainty quantification of fracture boundary of pre-hydrided Zircaloy-4 cladding tube under LOCA conditions

Narukawa, Takafumi; Yamaguchi, Akira*; Jang, S.*; Amaya, Masaki

Nuclear Engineering and Design, 331, p.147 - 152, 2018/05

 Times Cited Count:1 Percentile:17.98(Nuclear Science & Technology)

Journal Articles

The Effect of azimuthal temperature distribution on the ballooning and rupture behavior of Zircaloy-4 cladding tube under transient-heating conditions

Narukawa, Takafumi; Amaya, Masaki

Journal of Nuclear Science and Technology, 53(11), p.1758 - 1765, 2016/11

 Times Cited Count:7 Percentile:66.89(Nuclear Science & Technology)

JAEA Reports

Effect of solid boric acid on the high temperature oxidation behavior of Zircaloy-4

Komiyama, Daisuke; Amaya, Masaki

JAEA-Research 2016-013, 20 Pages, 2016/08

JAEA-Research-2016-013.pdf:6.05MB

The boric acid in the coolant may precipitate on the fuel cladding surface in the case that the blockage of coolant flow path etc. occurs and/or the cooling of fuel becomes insufficient during a LOCA (Loss-Of-Coolant Accident) in PWRs. While there is much knowledge about the compatibility between Zircaloy-4 and boric acid under normal operation conditions, such knowledge under high temperature condition, e.g. LOCA, has not been sufficient. In this study, isothermal heating tests were carried out by using Zircaloy-4 plates with solid boric acid in various atmospheres at up to 900$$^{circ}$$C; and the stability of boric acid, the reaction between Zircaloy-4 and boric acid and the effect of solid boric acid on the high temperature oxidation behavior of Zircaloy-4 were investigated. From the results obtained, it was suggested that, if boric acid anhydride remained on the surface of Zircaloy-4, the boric acid anhydride prevented the surface of Zircaloy-4 from contacting oxidizing atmosphere and mitigated the high-temperature oxidation of Zircaloy-4. In the case that solid boric acid adhered to the surface of pre-oxidized Zircaloy-4 and they have been heated up to high temperature, it was indicated that the solid boric acid penetrated into the gaps in the pre-oxide layer and the penetrated solid boric acid mitigated the oxidation of Zircaloy-4 thereafter.

Journal Articles

Experimental identification of electric field excitation mechanisms in a structural transition of tokamak plasmas

Kobayashi, Tatsuya*; Ito, Kimitaka*; Ido, Takeshi*; Kamiya, Kensaku; Ito, Sanae*; Miura, Yukitoshi; Nagashima, Yoshihiko*; Fujisawa, Akihide*; Inagaki, Shigeru*; Ida, Katsumi*; et al.

Scientific Reports (Internet), 6, p.30720_1 - 30720_7, 2016/08

 Times Cited Count:11 Percentile:67.67(Multidisciplinary Sciences)

In this Letter, we report model verifications for a key physics for the L-H transition. Radial electric field excitation, using discharges having a two-step transition. Examining time derivative of Poissons equation, it is found that the sum of the loss cone loss current and neoclassical bulk viscosity current agrees the experimentally observed current in the order of magnitude at the first transition. Following second transition and an ambipolar condition in the L-mode cannot be explained by the models.

Journal Articles

The Effect of oxidation and crystal phase condition on the ballooning and rupture behavior of Zircaloy-4 cladding tube-under transient-heating conditions

Narukawa, Takafumi; Amaya, Masaki

Journal of Nuclear Science and Technology, 53(1), p.112 - 122, 2016/01

 Times Cited Count:4 Percentile:45.9(Nuclear Science & Technology)

Journal Articles

JAEA-ISCN development programs of advanced NDA technologies of nuclear material

Seya, Michio; Kobayashi, Naoki; Naoi, Yosuke; Hajima, Ryoichi; Soyama, Kazuhiko; Kureta, Masatoshi; Nakamura, Hironobu; Harada, Hideo

Book of Abstracts, Presentations and Papers of Symposium on International Safeguards; Linking Strategy, Implementation and People (Internet), 8 Pages, 2015/03

JAEA-ISCN has been implementing basic development programs of the advanced NDA technologies for nuclear material (NM) since 2011JFY (Japanese Fiscal Year), which are (1) NRF (Nuclear resonance fluorescence) NDA technology using laser Compton scattered (LCS) $$gamma$$-rays (intense mono-energetic $$gamma$$-rays), (2) Alternative to $$^{3}$$He neutron detection technology using ZnS/B$$_{2}$$O$$_{3}$$ ceramic scintillator, and (3) NRD (Neutron resonance densitometry) using NRTA (Neutron resonance transmission analysis) and NRCA (Neutron resonance capture analysis). These programs are going to be finished in 2014JFY and have demonstration tests in February - March 2015.

Journal Articles

Effect of oxide film formed during $$gamma$$-ray irradiation on pitting corrosion of fuel cladding in water containing sea salt

Motooka, Takafumi; Tsukada, Takashi

Proceedings of 2014 Nuclear Plant Chemistry Conference (NPC 2014) (USB Flash Drive), 9 Pages, 2014/10

In Fukushima Daiichi Nuclear Power Station (1F), seawater was injected into spent fuel pools in March 2011. Zircaloy-2 is adopted for the fuel cladding at 1F. Zirconium alloys including Zircaloy-2 are susceptible to pitting corrosion in oxidizing chloride solutions. In this study, we investigated the effect of oxide film formed during $$gamma$$-ray irradiation on pitting corrosion of fuel cladding in water containing sea salt. The pitting potentials of Zircaloy-2 were measured using the water containing artificial sea salt. Changes in the composition of water containing sea salt were analyzed before and after $$gamma$$-ray irradiation. The characteristics of the oxide films formed on Zircaloy-2 were evaluated by X-ray photoelectron spectroscopy. Solution analyses for water containing sea salt showed that hydrogen peroxide was generated by the irradiation. The pitting potential of Ziracloy-2 with oxide film formed under $$gamma$$-ray irradiation was higher than that with oxide film formed without irradiation. X-ray photoelectron spectroscopy indicated that the oxide film was composed of zirconium oxide and the growth of oxide film was enhanced during the irradiation. It could thus be explained that the enhanced growth of oxide film under $$gamma$$-ray irradiation caused the higher pitting potential.

Journal Articles

RCA/IAEA third external dosimetry intercomparisons in East Asia region

Yamamoto, Hideaki; Yoshizawa, Michio; Murakami, Hiroyuki; Momose, Takumaro*; Tsujimura, Norio*; Kanai, Katsuta*; Cruz-Suarez, R.*

Radiation Protection Dosimetry, 125(1-4), p.88 - 92, 2007/07

 Times Cited Count:0 Percentile:0.01(Environmental Sciences)

The purpose of this paper is to discuss the results of the third intercomparison exercise of external radiation dosimetry organized under the Regional Cooperative Agreement (RCA) in the East Asia region of the International Atomic Energy Agency (IAEA). Twenty five laboratories from 16 member states participated in the exercise. Japan Atomic Energy Research Institute (JAERI) and Japan Nuclear Cycle Development Institute (JNC) arranged the standard irradiation of the participants' dosimeters. The results of the measurements of the irradiated dosimeters for the determination of external doses were satisfactory for all participants, demonstrating good performance in their external dosimetry.

Journal Articles

Results from studies on high burn-up fuel behavior under LOCA conditions

Nagase, Fumihisa; Fuketa, Toyoshi

NUREG/CP-0192, p.197 - 230, 2005/10

The Japanese regulatory criterion for a loss-of-coolant-accident (LOCA) is based on a threshold of fuel rod fracture during quenching, which was experimentally determined under simulated LOCA conditions. In order to evaluate the fracture threshold of high burn-up fuel rods, JAERI performs integral thermal shock tests simulating LOCA conditions. The tests have been performed with pre-hydrided, unirradiated claddings and high burn-up fuel claddings irradiated to 39 and 44 GWd/t at a PWR. It was shown that fracture/no-fracture threshold primarily depends on the oxidation amount and that the threshold decreases with increases in hydrogen concentration and axial restraint during the quench. It was also shown that fracture conditions of the tested high burn-up fuel claddings are consistent with the fracture threshold derived from unirradiated claddings with similar hydrogen concentrations.

Journal Articles

Embrittlement and fracture behavior of pre-hydrided cladding under LOCA conditions

Nagase, Fumihisa; Fuketa, Toyoshi

Proceedings of 2005 Water Reactor Fuel Performance Meeting (CD-ROM), p.668 - 677, 2005/10

A systematic research program on high burnup fuel behavior under LOCA conditions is being conducted at JAERI. As a part of the program, integral thermal shock tests simulating the whole LOCA sequence were conducted with Zircaloy-4 fuel claddings, irradiated to 39 and 44 GWd/t at a PWR, to investigate behavior and condition of cladding fracture during quenching for safety evaluation. Differences were not clearly observed between irradiated and unirradiated claddings at similar hydrogen concentrations in terms of threshold of fracture during quenching, though the threshold is reduced as initial hydrogen concentration increases. Ductility of pre-hydrided, oxidized and quenched claddings was also evaluated by using ring-tensile and ring-compression tests. Embrittlement criteria (zero-ductility limits) from both the tests were lower than the fracture conditions in the integral thermal shock tests. This indicates that loading conditions should be well simulated to evaluate cladding performance under LOCA conditions.

JAEA Reports

Effects of temperature history during cooling process on cladding ductility reduction under lost of coolant accident conditions

Udagawa, Yutaka; Nagase, Fumihisa; Fuketa, Toyoshi

JAERI-Research 2005-020, 40 Pages, 2005/09

JAERI-Research-2005-020.pdf:4.63MB

In order to investigate effects of quenching temperature and cooling rate before quench on cladding ductility reduction under LOCA conditions, samples cut from non-irradiated 17$$times$$17-type Zircaloy-4 cladding tubes for PWRs were oxidized in steam at 1373 and 1473 K, cooled at 2 to 7 K/s, and quenched at 1073 to 1373 K. The quenched samples were subjected to ring compression test, microstructure observation, and Vickers hardness test. Quenching temperature decrease obviously increased area fraction of $$alpha$$ phase in the radial cross section of the cladding, and reduced cladding ductility. Slow-cooling rate decrease increased unit size and hardness of precipitated $$alpha$$ phase, while $$alpha$$ phase area fraction and cladding ductility were not significantly changed. $$alpha$$ phase is harder than the surrounding region in the metallic layer and has higher oxygen content, indicating its low ductility. Consequently, increase in the area fraction in the cladding is a main cause of the reduction in cladding ductility with decrease in the quenching temperature.

Journal Articles

Charge-order pattern of the low-temperature phase from a monoclinic single domain of NaV$$_{2}$$O$$_{5}$$ uniquely determined by resonant X-ray scattering

Owada, Kenji; Fujii, Yasuhiko; Katsuki, Yuya*; Muraoka, Jiro*; Nakao, Hironori*; Murakami, Yoichi; Sawa, Hiroshi*; Ninomiya, Emi*; Isobe, Masahiko*; Ueda, Yutaka*

Physical Review Letters, 94(10), p.106401_1 - 106401_4, 2005/03

 Times Cited Count:24 Percentile:73.44(Physics, Multidisciplinary)

The present resonant X-ray scattering has been performed on a monoclinically-split single domain of NaV$$_{2}$$O$$_{5}$$. The observation of a critically enhanced contrast between V$$^{4+}$$ and V$$^{5+}$$ ions has led us to the unequivocal conclusion of the charge-order pattern of low-temperature phase of NaV$$_{2}$$O$$_{5}$$ below $$T_{rm c}$$ = 35 K. In spite of the possible four types of configuration of the zig-zag-type charge-order patterns in the $$ab$$-plane (A, A', B and B'), the stacking sequence along the $$c$$-axis is determined as the AAA'A' type by comparison with model calculations. By assigning the A and A' configurations to Ising spins, one can reasonably explain the previously discovered "devil's staircase"-type behavior with respect to the modulation of layer-stacking sequences at high pressures and low temperatures, which clearly resembles the global phase diagram theoretically predicted by the ANNNI model.

Journal Articles

Nondestructive observation of nuclear fuels and materials by using neutron radiography

Yasuda, Ryo; Matsubayashi, Masahito; Nakata, Masahito; Matsue, Hideaki; Nakanishi, Tomoko

Dai-5-Kai Hoshasen Ni Yoru Hihakai Hyoka Shimpojiumu Koen Rombunshu, p.31 - 34, 2005/02

Neutron radiography is an effectively nondestructive tool for inspection of irradiated nuclear fuels and materials. Neutron CT an neutron imaging plate methods, which are advanced techniques in the neutron radiography, enabled to obtain cross-section images and to evaluate an amount of the element compositions. This paper describes results of those methods using unirradiated fuels and materials and discussed the practicability of those methods to irradiated fuels and materials.

Journal Articles

Behavior of pre-hydrided Zircaloy-4 cladding under simulated LOCA conditions

Nagase, Fumihisa; Fuketa, Toyoshi

Journal of Nuclear Science and Technology, 42(2), p.209 - 218, 2005/02

 Times Cited Count:41 Percentile:93.27(Nuclear Science & Technology)

Regarding high burn-up fuel behavior under LOCA conditions, LOCA-simulated experiments were performed with unirradiated Zircaloy-4 claddings. Claddings containig 100 to 1450 ppm were isothermally oxidized at at 1220 to 1500 K in steam flow, and quenched by flooding water. Axial shrinkage of the rods during the quench was restrained controlling the maximum restraint load at four different levels. Primarily depending on fraction of the cladding thickness oxidized, the claddings fractured into two pieces during the quench, with circumferential cracking. The fracture/non-fracture threshold as for the oxidized fraction decreases as both initial hydrogen concentration and axial restraint load increase. Consequently, it was shown that the threshold is higher than 20% cladding oxidation, e.g. sufficiently higher than the limit in the Japanese ECCS acceptance criteria, irrespective of hydrogen concentration, when the restraint load is below 535 N.

Journal Articles

Investigation of hydride rim effect on failure of Zircaloy-4 cladding with tube burst test

Nagase, Fumihisa; Fuketa, Toyoshi

Journal of Nuclear Science and Technology, 42(1), p.58 - 65, 2005/01

 Times Cited Count:37 Percentile:92.04(Nuclear Science & Technology)

Tube burst tests have been performed with artificially hydrided Zircaloy-4 specimens at room temperature and at 620 K. Pressurization rate was increased to a maximum of 3.4 GPa/s in order to simulate rapid PCMI that occurs in high burnup fuel rods during a pulse-irradiation in the NSRR. Hydrogen content in the specimens ranged from 150 to 1050 ppm. Hydrides were accumulated in the cladding periphery and formed "hydride rim" as observed in high burnup PWR fuel claddings. The hydrided cladding tubes failed with an axial crack at the room temperature tests. Brittle fracture appeared in the hydride rim, and failure morphology was similar to that observed in the NSRR experiments. The hydrides rim obviously reduced burst pressure and residual hoop strain at the tests. The residual hoop strain was very small even at 620 K when thickness of the hydride rim exceeded 18% of cladding thickness. The present result accordingly indicates an important role of the hydrides layer in high burnup fuel rod failure under RIA conditions.

Journal Articles

Influence of hydride re-orientation on BWR cladding rupture under accidental conditions

Nagase, Fumihisa; Fuketa, Toyoshi

Journal of Nuclear Science and Technology, 41(12), p.1211 - 1217, 2004/12

 Times Cited Count:13 Percentile:66.18(Nuclear Science & Technology)

Hydride precipitation along the radial-axial plane increases in high burn-up BWR fuel claddings. The radial hydrides may have an important role during fuel behavior in a RIA and may reduce ductility of the cladding under PCMI conditions. In order to promote a better understanding of the influence of the radial hydrides on cladding failure behavior under the PCMI conditions, tube burst tests were conducted for unirradiated BWR claddings charged with 200 to 650 ppm of hydrogen. About 20 to 30% of hydrides were re-oriented and precipitated along the radial-axial plane. The claddings exhibited large burst openings with an axial crack at room temperature and 373 K. However, the influence of the radial hydrides on both burst pressure and residual hoop strain was very small. It is accordingly expected that ductility of high burn-up BWR cladding is significantly reduced not only by precipitation of radial hydrides as far as hydrogen concentration and radial hydride fraction range in the present study.

138 (Records 1-20 displayed on this page)