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Journal Articles

Fracture limit of high-burnup advanced fuel cladding tubes under loss-of-coolant accident conditions

Narukawa, Takafumi; Amaya, Masaki

Journal of Nuclear Science and Technology, 57(1), p.68 - 78, 2020/01

 Times Cited Count:2 Percentile:12.54(Nuclear Science & Technology)

Journal Articles

Control and instrumentation for the ITER magnet system

Yoshida, Kiyoshi; Takahashi, Yoshikazu; Iida, Hiromasa

IEEE Transactions on Applied Superconductivity, 16(2), p.775 - 778, 2006/06

 Times Cited Count:1 Percentile:12.03(Engineering, Electrical & Electronic)

The ITER superconducting coil system consists of 18 TF coils, 6 PF coils, 6 CS modules, 18 Correction Coils and their feeders. An extensive measurement and control system is required to monitor and to control these coils and feeders for safety and optimal operational availability. For each coil, both current and helium are supplied from external systems and are controlled from a central control system that manages flow distribution at each cooling pass to smooth the cryoplant loads by a virtual model of the coil thermo-hydraulic system. Quench detection is provided as stand alone system. Monitoring of the electric insulation system inside the coils is performed to detect incipient problems before serious damage. The ITER will procure directly all sensors, wires, electrical insulation breaks and cryogenic components for all the coils and feeders to a common specification. This will avoid duplication of qualification work and guarantee a common interface. This paper introduces the requirements and specifications of the control and instrumentation for the ITER magnet system.

Journal Articles

Simulation of quench tests of the central solenoid insert coil in the ITER central solenoid model coil

Takahashi, Yoshikazu; Yoshida, Kiyoshi; Nabara, Yoshihiro; Edaya, Masahiro*; Mitchell, N.*

IEEE Transactions on Applied Superconductivity, 16(2), p.783 - 786, 2006/06

 Times Cited Count:9 Percentile:46.93(Engineering, Electrical & Electronic)

To investigate the conductor behavior during a quench, quench tests of Center Solenoid (CS) insert coils were carried out with various initial conditions in DC and pulse modes. The conductor has very similar configuration and parameters. The inductive heater, attached at the center of the length, initiated an artificial quench in DC mode. A quench has also occurred during the pulse operation with the ramping rate of 0.4-2 T/s. Simulations of electric, thermal and hydraulic behaviors of the conductor during the quench tests in both modes were carried out by using the thermohydraulic simulation code. The experimental results were compared with the simulation and good agreement was obtained. These results are described and the implication for quench detection in ITER is discussed in this paper. The voltage tap method will be used for the quench detection for the CS, and the sensitivity of the detection and the maximum temperature of the conductor during a quench are described. It is shown that the detection system could be designed with high enough detection sensitivity.

Journal Articles

Analysis of the direction of plasma vertical movement during major disruptions in ITER

Lukash, V.*; Sugihara, Masayoshi; Gribov, Y.*; Fujieda, Hirobumi*

Plasma Physics and Controlled Fusion, 47(12), p.2077 - 2086, 2005/12

 Times Cited Count:9 Percentile:31.68(Physics, Fluids & Plasmas)

Vertical directions of plasma movement after the thermal quench (TQ) of major disruptions in ITER are investigated using the predictive mode of the DINA code. Three dominant parameters in determining the direction of plasma movement are identified; (1) the rate of plasma current quench, (2) change of the internal plasma inductance li associated with the TQ and (3) the initial vertical position of plasma column before the TQ. It is shown that the reference ITER plasma moves upward after the TQ, if the current quench rate is higher than 200kA/ms and the drop of li does not exceed 0.2 for the present reference initial vertical position (55.5 cm above the center of machine).

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


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

Quench detection using pick-up coils for the ITER Central Solenoid

Takahashi, Yoshikazu; Yoshida, Kiyoshi; Mitchell, N.*

IEEE Transactions on Applied Superconductivity, 15(2), p.1395 - 1398, 2005/06

 Times Cited Count:8 Percentile:43.96(Engineering, Electrical & Electronic)

The quench detection is important and necessary for the coil protection. The voltage tape method and the flow meter method are both considered for the ITER Central Solenoid (CS). The voltage tap method is primary due to its quick response. The CS consists of six pancake wound modules, which are operated with individual operating current patterns in ac mode. The induced voltage in the windings must be compensated to detect the voltage due to any normal transition during pulse operation. We have investigated the optimum configuration for pick-up coils (PC) for compensation. The results of simulations show that the compensated voltages are very low (70 mV) compared with the inductive voltage and adequate normal voltage sensitivity is obtained. The hot spot temperature in the CS during the operation was estimated from the simulation and the experimental data of the CSMC quench. The hot spot temperature estimated is about 144 K, lower than the ITER design criterion (150 K). It is shown that the detection system using the PCs could be designed with a high enough detection sensitivity.

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:45 Percentile:93.06(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

Luminescence study of lanthanide(III) ions in non-aqueous solutions containing azide ions

Lis, S.*; Kimura, Takaumi; Yoshida, Zenko; But, S.*

Journal of Alloys and Compounds, 380(1-2), p.173 - 176, 2004/10

 Times Cited Count:6 Percentile:41.57(Chemistry, Physical)

no abstracts in English

Journal Articles

Edge safety factor at the onset of plasma disruption during VDEs in JT-60U

Sugihara, Masayoshi; Lukash, V.*; Khayrutdinov, R.*; Neyatani, Yuzuru

Plasma Physics and Controlled Fusion, 46(10), p.1581 - 1589, 2004/10

 Times Cited Count:11 Percentile:35.19(Physics, Fluids & Plasmas)

Detailed examinations of the value of the edge safety factor q at the onset of thermal quench during intentional VDE experiments in JT-60U are performed using two different reconstruction methods, FBI/FBEQU and DINA. Results by both methods are very similar and show that the thermal quench occurs when the q value is in the range between 1.5-2. This result suggests that the predictive simulations for VDEs should be performed within this range of q to examine the subsequent differences in the halo currents, plasma movement and other plasma behavior during the current quench.

Journal Articles

Results from simulated LOCA experiments with high burnup PWR fuel claddings

Nagase, Fumihisa; Fuketa, Toyoshi

Proceedings of 2004 International Meeting on LWR Fuel Performance, p.500 - 506, 2004/09

A systematic research program is being conducted at the Japan Atomic Energy Research Institute (JAERI), which aims at a wide range database for evaluating the influence of further burnup extension on fuel behavior under LOCA conditions. As a part of the program, integral thermal shock tests simulating the whole LOCA sequence have been conducted with Zircaloy-4 fuel claddings, irradiated to 39 and 44GWd/t at a PWR. One cladding, oxidized to about 30% ECR, fractured during the quench. The fracture condition agrees with the fracture criteria for non-irradiated claddings that have similar hydrogen concentrations (about 25% ECR). Two claddings, oxidized to about 16 and 18% ECR, survived the quench, indicating that fracture/non-fracture boundary is not reduced so significantly by irradiation for the examined burnup range. The present paper describes information obtained from the tests including oxidation kinetics and rupture behavior.

Journal Articles

Effect of pre-hydriding on thermal shock resistance of Zircaloy-4 cladding under simulated loss-of-coolant accident conditions

Nagase, Fumihisa; Fuketa, Toyoshi

Journal of Nuclear Science and Technology, 41(7), p.723 - 730, 2004/07

 Times Cited Count:45 Percentile:92.93(Nuclear Science & Technology)

Experiments simulating loss-of-coolant accident (LOCA) conditions were performed to evaluate effect of pre-hydriding on thermal-shock resistance of oxidized Zircaloy-4 cladding. Artificially hydrided (400 to 600 ppm) and non-hydrided claddings were subjected to the tests. Since cladding fracture on quenching primarily depends on the oxidation amount, fracture threshold was evaluated in terms of "Equivalent Cladding Reacted (ECR)". Under axially non-restrained condition, the fracture threshold is 56% ECR and the influence of pre-hydriding is not seen. The fracture threshold is decreased by restraining the test rods on quenching, and it is more remarkable in pre-hydrided claddings than in non-hydrided claddings. Consequently, the fracture threshold was 20% ECR and 10% ECR for non-hydrided and pre-hydrided claddings, respectively, under the fully restrained condition. These results indicate possible decrease of fracture threshold of high burnup fuel claddings under LOCA conditions.

Journal Articles

Quench analysis of an ITER 13T-40kA Nb$$_{3}$$Sn coil (CS insert)

Inaguchi, Takashi*; Hasegawa, Mitsuru*; Koizumi, Norikiyo; Isono, Takaaki; Hamada, Kazuya; Sugimoto, Makoto; Takahashi, Yoshikazu

Cryogenics, 44(2), p.121 - 130, 2004/02

 Times Cited Count:6 Percentile:28.04(Thermodynamics)

In order to analyze the quench characteristic of a cable-in-conduit (CIC) conductor that has a sub-cooling channel at the center of conductor cross section, an axisymmetrical two-dimensional calculation model was developed. The test and calculation results of the CS insert were compared regarding the pressure drop and the behavior of the total voltage, temperature and normal zone propagation in the quench. They show good agreement. Therefore, the effectiveness of the calculation model is verified. It was also found that there is coolant convection between the central channel and bundle region even in a steady state. This makes the pressure drop in the central channel larger than that in a cylindrical pipe which has a smooth surface. In addition, it was found that the higher temperature of the coolant flowing through the central channel heats the coolant and the cable in the bundle region. It can be said that the hot coolant flowing through the central channel accelerates normal zone propagation.

Journal Articles

Wave form of current quench during disruptions in Tokamaks

Sugihara, Masayoshi; Lukash, V.*; Kawano, Yasunori; Yoshino, Ryuji; Gribov, Y.*; Khayrutdinov, R.*; Miki, Nobuharu*; Omori, Junji*; Shimada, Michiya

Purazuma, Kaku Yugo Gakkai-Shi, 79(7), p.706 - 712, 2003/07

The time dependence of the current decay during the current quench phase of disruptions, which can significantly influence the electro-magnetic force on the in-vessel components due to the induced eddy currents, is investigated using data obtained in JT-60U experiments in order to derive a relevant physics guideline for the predictive simulations of disruptions in ITER. It is shown that an exponential decay can fit the time dependence of current quench for discharges with large quench rate (fast current quench). On the other hand, for discharges with smaller quench rate (slow current quench), a linear decay can fit the time dependence of current quench better than exponential.

Journal Articles

Quench characteristics and AC loss measurement in the ITER TF insert

Isono, Takaaki; Koizumi, Norikiyo; Matsui, Kunihiro; Sugimoto, Makoto; Hamada, Kazuya; Nunoya, Yoshihiko; Rodin, I.*; CS Model Coil Test Group

Teion Kogaku, 37(10), p.539 - 544, 2002/10

The Toroidal Field (TF) insert has been developed by Russia to demonstrate the TF conductor performance and tested in the bore of the Central Solenoid (CS) model coil, which applies a 13-T magnetic field. In this paper, quench property and AC loss measurement is described. Major difference between TF and CS conductor is the jacket shape and existence of mandrel and they effect on quench property and AC loss measurement. Quench test was performed at 46kA, 12T, 6.5K and the currents of the TF insert and the CS model coil were kept for 9 seconds after normal zone appearance. An inductive heater of 200mm length made a quench. Normal zone length was 16m, and the maximum velocity was 2m/s. Maximum temperature is estimated to be 160 K with some errors. Hysteresis loss was measured by calorimetric method and the values are almost same as the expected values from strand data. It was pointed out that coupling loss measurement using calorimetric method is difficult because loss at the mandrel is more than 10 times higher than coupling loss.

Journal Articles

Axisymmetric disruption dynamics including current profile changes in the ASDEX-Upgrade tokamak

Nakamura, Yukiharu; Pautasso, G.*; Gruber, O.*; Jardin, S. C.*

Plasma Physics and Controlled Fusion, 44(8), p.1471 - 1481, 2002/08

 Times Cited Count:12 Percentile:38.56(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Study of high burnup fuel behavior under LOCA conditions at JAERI; Hydrogen effects on the failure-bearing capability of cladding tubes

Nagase, Fumihisa; Uetsuka, Hiroshi

NUREG/CP-0176, p.335 - 342, 2002/05

no abstracts in English

Journal Articles

Neutral point validation studies on JT-60U, alcator C-Mod and ASDEX-upgrade tokamaks

Nakamura, Yukiharu; Yoshino, Ryuji; Granetz, R. S.*; Pautasso, G.*; Gruber, O.*; Jardin, S. C.*

Purazuma, Kaku Yugo Gakkai-Shi, 78(4), p.347 - 355, 2002/04

no abstracts in English

Journal Articles

Phenomenon identification and ranking tables (PIRTs) for loss-of-coolant accidents in pressurized and boiling water reactors containing high burnup fuel

Boyack, B. E.*; Motta, A. T.*; Peddicord, K. L.*; Alexander, C. A.*; Andersen, J. G. M.*; Blaisdell, J. A.*; Dunn, B. M.*; Ebeling-Koning, D.*; Fuketa, Toyoshi; Hache, G.*; et al.

NUREG/CR-6744, 455 Pages, 2001/12

no abstracts in English

107 (Records 1-20 displayed on this page)