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Journal Articles

Burn-up characteristics and criticality effect of impurities in the graphite structure of a commercial-scale prismatic HTGR

Fukaya, Yuji; Goto, Minoru; Nishihara, Tetsuo

Nuclear Engineering and Design, 326, p.108 - 113, 2018/01


 Times Cited Count:3 Percentile:31.96(Nuclear Science & Technology)

Burn-up characteristics and criticality of impurity contained into graphite structure for commercial scale prismatic High Temperature Gas-cooled Reactor (HTGR) have been investigated. For HTGR, of which the core is filled graphite structure, the impurity contained into the graphite has unignorable poison effect for criticality. Then, GTHTR300, commercial scale HTGR, employed high grade graphite material named IG-110 to take into account the criticality effect for the reflector blocks next to fuel blocks. The fuel blocks, which should also employ IG-110, employ lower grade graphite material named IG-11 from the economic perspective. In this study, the necessity of high grade graphite material for commercial scale HTGR is reconsidered by evaluating the burn-up characteristics and criticality of the impurity. The poison effect of the impurity, which is used to be expressed by a boron equivalent, reduces exponentially like burn-up of $$^{10}$$B, and saturate at a level of 1 % of the initial value of boron equivalent. On the other hand, the criticality effect of the boron equivalent of 0.03 ppm, which corresponds to a level of 1 % of IG-11 shows ignorable values lower than 0.01 %$$Delta$$k/kk' for both of fuel blocks and reflector blocks. The impurity can be represented by natural boron without problem. Therefore, the poison effect of the impurity is evaluated with whole core burn-up calculations. As a result, it is concluded that the impurity is not problematic from the viewpoint of criticality for commercial scale HTGR because it is burned clearly until End of Cycle (EOC) even with the low grade graphite material of IG-11. According to this result, more economic electricity generation with HTGR is expected by abolishing the utilization of IG-110.

JAEA Reports

Determination of metal impurities in MOX powder by direct current arc atomic emission spectroscopy; Application of standard addition method for direct analysis of powder sample

Furuse, Takahiro*; Taguchi, Shigeo; Kuno, Takehiko; Surugaya, Naoki

JAEA-Technology 2016-028, 19 Pages, 2016/12


Metal impurities in MOX powder obtained from uranium and plutonium recovered from reprocessing process of spent nuclear fuel are needed to be determined for its characterization. Direct current arc atomic emission spectroscopy (DCA-AES) is one of the useful methods for direct analysis of powder sample without dissolving the analyte into aqueous solution. However, the selection of standard material, which can overcome concerns such as matrix matching, is quite important to create adequate calibration curves for DCA-AES. In this study, we apply standard addition method using the certified U$$_{3}$$O$$_{8}$$ containing known amounts of metal impurities to avoid the matrix problems. The proposed method provides good results for determination of Fe, Cr and Ni at a significant quantity level contained in MOX samples.

Journal Articles

Tungsten impurity density in fusion plasma

Nakano, Tomohide; Shumack, A.*; Maggi, C. F.*

Journal of Physics B; Atomic, Molecular and Optical Physics, 2 Pages, 2016/01

Collaboration of researchers from Japan Atomic Energy Agency and EUROfusion Consortium (Dutch Institute For Fundamental Energy Research, Max-Planck-Institut f$"{u}$r Plasmaphysik and so on) successfully led to determination of tungsten ion density in high temperature plasmas in Joint European Torus (JET) with an upgraded X-ray spectrometer. The researchers used the FAC code and successfully identified $$mbox{W}^{45+}$$, $$mbox{W}^{46+}$$ and $$mbox{Mo}^{32+}$$ spectral lines. The $$mbox{Mo}^{32+}$$ line identification was confirmed experimentally by Mo injection to the plasma. From the measured absolute intensity of these spectral lines, tungsten and molybdenum ion densities in the plasma core were determined.

JAEA Reports

Report on research and development of nuclear forensics technologies

Okubo, Ayako; Kimura, Yoshiki; Shinohara, Nobuo; Toda, Nobufumi; Funatake, Yoshio; Watahiki, Masaru; Sakurai, Satoshi; Kuno, Yusuke

JAEA-Technology 2015-001, 185 Pages, 2015/03


Nuclear forensics is the analysis of intercepted illicit nuclear or radioactive material and any associated material to provide evidence for nuclear attribution by determining origin, history, transit routes and purpose involving such material. Nuclear forensics activity includes sampling of the illicit material, analysis of the samples and evaluation of the attribution by comparing the analyzed data with database or numerical simulation. Because the nuclear forensics technologies specify the origin of the nuclear materials used illegal dealings or nuclear terrorism, it becomes possible to identify and indict offenders, hence to enhance deterrent effect against such terrorism. Worldwide network on nuclear forensics can contribute to strengthen global nuclear security regime. In this paper, the results of research and development of fundamental nuclear forensics technologies performed in Japan Atomic Energy Agency during the fiscal term of 2011-2013 were reported.

Journal Articles

Radiation and spectroscopy of high temperature plasma

Sugie, Tatsuo

Purazuma Shindan No Kiso To Oyo, p.116 - 131, 2006/03

Radiation from the plasma degrades the performance of energy confinement. In addition, the efficiency of fusion reaction will be decreased by the fuel dilution due to the impurity ions in the plasma. Therefore, the impurity control (generation, reduction of the contamination, exhaust) becomes an important research subject. Spectroscopic diagnostics is the one of the most important methods to study such subjects. On the other hand, it is also utilized for the measurements of plasma parameters such as ion temperature, plasma current distribution etc. In this section, the radiation behavior and the spectroscopic diagnostics of high temperature plasma are described.

Journal Articles

Atomic and molecular data activities for fusion research at JAERI

Kubo, Hirotaka; Sataka, Masao; Shirai, Toshizo

Journal of Plasma and Fusion Research SERIES, Vol.7, p.352 - 355, 2006/00

no abstracts in English

Journal Articles

Radiation loss by impurities measured from the large helical device

Kato, Takako*; Murakami, Izumi*; Goto, Motoshi*; Morita, Shigeru*; Ida, Katsumi*; Peterson, B. J.*; Funaba, Hisamichi*; Nakano, Tomohide

Journal of Plasma and Fusion Research SERIES, Vol.7, p.1 - 4, 2006/00

We analyzed impurity VUV spectral emission quantitatively. Electron temperature is derived from the intensity ratio of CIII line intensities. Radiation loss sources are identified using spectroscopy and bolometer in the case of radiation collapse caused by neon gas puffing. Time dependent radiation loss of impurity ions are derived from line intensities of impurities.

Journal Articles

Overview of goals and performance of ITER and strategy for plasma-wall interaction investigation

Shimada, Michiya; Costley, A. E.*; Federici, G.*; Ioki, Kimihiro*; Kukushkin, A. S.*; Mukhovatov, V.*; Polevoi, A. R.*; Sugihara, Masayoshi

Journal of Nuclear Materials, 337-339, p.808 - 815, 2005/03

 Times Cited Count:63 Percentile:96.37(Materials Science, Multidisciplinary)

ITER is an experimental fusion reactor for investigation and demonstration of burning plasmas, characterised of its heating dominated by alpha-particle heating. ITER is a major step from present devices and an indispensable step for fusion reactor development. ITER's success largely depends on the control of plasma-wall interactions(PWI), with power and particle fluxes and time scales one or two orders of magnitude larger than in present devices. The strategy for control of PWI includes the semi-closed divertor, strong fuelling and pumping, disruption and ELM control, replaceable plasma-facing materials and stepwise operation.

Journal Articles

Coolant chemistry of the High Temperature Gas-Cooled Reactor 'HTTR'

Sakaba, Nariaki; Nakagawa, Shigeaki; Furusawa, Takayuki*; Emori, Koichi; Tachibana, Yukio

Nihon Genshiryoku Gakkai Wabun Rombunshi, 3(4), p.388 - 395, 2004/12

Chemistry control is important for the helium coolant of High Temperature Gas-cooled Reactors (HTGRs) because impurities cause oxidation of the graphite used in the core and corrosion of high temperature materials used in the heat exchanger. In the High Temperature Engineering Test Reactor (HTTR) which is the first HTGR in Japan, the chemical impurity concentration is restricted and its behaviour is monitored during reactor operations. The impurity is reduced by the helium purification system and the concentration is measured by the helium sampling system installed to the primary and secondary helium system, continuously. This paper describes the impurity behaviour during the rise-to-power test which is the initial power-up of the HTTR. Also, the amount of the emitted impurity to the primary circuit from the graphite component and insulator used at the concentric hot gas duct are evaluated. During the power up, any abnormal impurity increases were not obtained and the chemical composition of the primary circuit is sufficiently in the stability area to avoid carbon deposition.

Journal Articles

Short design descriptions of other systems of the HTTR

Sakaba, Nariaki; Furusawa, Takayuki; Kawamoto, Taiki; Ishii, Yoshiki; Ota, Yukimaru

Nuclear Engineering and Design, 233(1-3), p.147 - 154, 2004/10

 Times Cited Count:10 Percentile:56.13(Nuclear Science & Technology)

The HTTR mainly consists of the core components, reactor pressure vessel, cooling systems, instrumentation and control systems, and containment structures. The design of remaining utility systems is described in this paper. They are: auxiliary helium systems which include the helium purification system, the helium sampling system, and the helium storage and supply system; fuel handling and storage system. The helium purification systems are installed in the primary and secondary helium cooling systems in order to reduce the quantity of chemical impurities. The helium sampling systems monitor the concentration of impurities. The helium storage and supply systems keep the steady pressure of the helium system during the normal operation. The fuel handling and storage system is utilised to handle the new and spent fuels safely and reliably.

Journal Articles

Progress of boundary plasma investigation toward ITER

Shimada, Michiya

Purazuma, Kaku Yugo Gakkai-Shi, 80(3), p.222 - 226, 2004/03

Discussion is made on objectives of edge plasma and plasma-wall interaction studies, divertor performance projection of ITER and key R&D issues on plasma-wall interaction including material issues, tritium retention, and transient events like ELMs and disruptions. A perspective of future development is discussed for the purpose of projection to and control of ITER plasma.

Journal Articles

Formation of a charge-exchange target for fast ions in the plasma of large-scale toroidal devices under NBI conditions

Mironov, M. I.*; Khudoleev, A. V.*; Kusama, Yoshinori

Plasma Physics Reports, 30(2), p.164 - 168, 2004/02

 Times Cited Count:0 Percentile:0.02(Physics, Fluids & Plasmas)

High-energy charge-exchange diagnostics can determine the distribution function of fast atoms produced via the neutralization of hydrogen ions by hydrogen-like impurity ions. Deriving the distribution function requires to know the composition and spatial distribution of the target ions in a plasma. A charge-exchange target forms as a result of the interaction between impurity nuclei and beam atoms. Depending on the arrangement of heating beams with respect to the diagnostics, it is necessary to calculate their trajectories. A model which takes into account elementary processes resulting in the ionization equilibrium of the ions of impurities in a specific tokamak configuration is proposed. The model is applied to the JT-60U plasma. Mechanisms for the formation of charge-exchange atomic flows are considered. The relative contributions of different heating injectors to the charge-exchange flow are estimated. Based on the calculated results, a method is proposed for local measurements of the ion distribution function with a stationary analyzer.

Journal Articles

Coolant chemistry characteristics during safety demonstration test using HTTR

Sakaba, Nariaki; Nakagawa, Shigeaki; Furusawa, Takayuki; Tachibana, Yukio

Transactions of the American Nuclear Society, 91, P. 377, 2004/00

Carbon deposition occurred occasionally in the graphite-moderated gas-cooled reactors was evaluated for the reactor pressure vessel, intermediate heat exchanger, etc. using the measured chemical impurity data for the initial condition of the safety demonstration test. By the evaluated result, it is confirmed that the high-temperature components keep their structural integrity during the any temperature transients in safety demonstration tests.

JAEA Reports

Review of JT-60U experimental results in 2001 and 2002

JT-60 Team

JAERI-Review 2003-029, 197 Pages, 2003/11


no abstracts in English

Journal Articles

Spectroscopic diagnostics for ITER

Sugie, Tatsuo; Costley, A. E.*; Malaquias, A.*; Walker, C.*

Purazuma, Kaku Yugo Gakkai-Shi, 79(10), p.1051 - 1061, 2003/10

The main regions - the core, the edge, the scrape-off layer, and the divertor - will be probed by an extensive array of spectroscopic instrumentation covering the visible to X-ray wavelength range. Plasma parameters will be determined including impurity species/density/input-flux, ion temperature, He density, fueling ratio, plasma rotation, effective ionic charge and safety factor q. The measurements will be used for plasma control and in studies to understand and improve the performance of ITER. A diagnostic neutral beam (~100 keV) will be installed for Charge Exchange Recombination Spectroscopy. Motional Stark Effect measurements (for q profile) will be made using the heating beam (1 MeV). Diagnostic components, such as mirrors, windows, and optical fibers etc, mounted close to the plasma will experience higher levels of radiation due to neutron, gamma ray and particle irradiations than in present devices. Potentially their performance characteristics can be degraded and so the materials of the components have to be carefully selected and mitigating methods adopted where possible.

Journal Articles

Spectroscopic measurement system for ITER divertor plasma; Divertor impurity monitor

Sugie, Tatsuo; Costley, A. E.*; Malaquias, A.*; Medvedev, A.*; Walker, C.*

Proceedings of 30th EPS Conference on Controlled Fusion and Plasma Physics (CD-ROM), 4 Pages, 2003/07

The main functions of the Divertor Impurity Monitor are to measure the parameters of impurities and isotopes of hydrogen in the divertor plasmas by using spectroscopic techniques in the wavelength range of 200-1000 nm. This system will have three different types of spectrometers; a) Visible survey spectrometers for impurity species monitoring. b) Filter spectrometers for two-dimensional measurements of particle influxes. c) High dispersion spectrometers for measuring the ion temperature and the particle energy distribution. The divertor region will be observed from the divertor-, the equatorial- and the upper-port. Optical components, such as mirrors, windows etc, mounted close to the plasma will experience higher levels of radiation due to neutron, gamma ray and/or particle irradiations than in present devices. Therefore, the materials of the components have to be carefully selected and mitigating methods adopted where possible. In addition, in-situ and remote calibration methods for diagnostic systems, which will be installed in the strong radiation field, are absolutely essential.

Journal Articles

Radiation enhancement and impurity behavior in JT-60U reversed shear discharges

Kubo, Hirotaka; Sakurai, Shinji; Higashijima, Satoru; Takenaga, Hidenobu; Itami, Kiyoshi; Konoshima, Shigeru; Nakano, Tomohide; Koide, Yoshihiko; Asakura, Nobuyuki; Shimizu, Katsuhiro; et al.

Journal of Nuclear Materials, 313-316(1-3), p.1197 - 1201, 2003/03

 Times Cited Count:19 Percentile:76.11(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Status of activities on the lithium target in the key element technology phase in IFMIF

Nakamura, Hiroo; Burgazzi, L.*; Cevolani, S.*; Dell'Ocro, G.*; Fazio, C.*; Giusti, D.*; Horiike, Hiroshi*; Ida, Mizuho*; Kakui, Hideo*; Loginov, N.*; et al.

Journal of Nuclear Materials, 307-311(Part.2), p.1675 - 1679, 2002/12

 Times Cited Count:4 Percentile:29.4(Materials Science, Multidisciplinary)

This paper describes the latest design of the IFMIF liquid Li target system reflecting the KEP results. Future prospects will be also summarized. To handle an averaged heat flux of 1 GW/m2 under a continuous 10 MW D beam deposition, a high-speed Li flow of 20 m/s, a double reducer nozzle and a concaved flow are applied to the target design. Hydraulic characteristics of the Li target design have been validated in a water jet experiment. To obtain a control scenario of the Li loop in an accident of the D beam trip, a transient analysis has been done. To control tritium and impurities in Li, a cold trap and two kinds of hot trap are adopted in Li purification loop. To maintain reliable continuous operation, various diagnostics are attached to the target assembly. To exchange the target assembly and back wall, a remote handling system with a multi axis arm and welding/cutting tool are designed. As an option, design of a replaceable back wall with a mechanical seal is being in progress. In a next phase of IFMIF beyond 2004, a Li test loop will be constructed for engineering validation.

Journal Articles

Extension of integrated high performance regimes with impurity and deuterium particle control in Japan Atomic Energy Research Institute Tokamak-60 Upgrade (JT-60U)

Kubo, Hirotaka; JT-60 Team

Physics of Plasmas, 9(5), p.2127 - 2133, 2002/05

 Times Cited Count:18 Percentile:51.2(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Fast thermal shutdown of tokamak discharges without runaway electron avalanching

Bakhtiari, M.; Yoshino, Ryuji; Nishida, Yasushi*

Fusion Science and Technology, 41(2), p.77 - 87, 2002/03

 Times Cited Count:6 Percentile:39.81(Nuclear Science & Technology)

no abstracts in English

92 (Records 1-20 displayed on this page)