Daejeon, South Korea
Daejeon, South Korea
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Wang S.J.,NFRI | Wi H.H.,NFRI | Kim H.J.,NFRI | Kim J.,NFRI | And 2 more authors.
Nuclear Fusion | Year: 2017

A helicon wave current drive is proposed as an efficient off-axis current drive in the high electron β plasmas that are expected in fusion reactors. A high frequency helicon wave coupling was analyzed using the surface impedance at a plasma boundary. A slow wave coupling, which may compete with the helicon wave coupling at a frequency of 500 MHz, is estimated to be lower than the fast wave coupling by an order of magnitude in the KSTAR edge plasma density and in practical Faraday shield misalignment with the magnetic pitch. A traveling wave antenna, which is a two port combline antenna, was analyzed using a simplified lumped element model. The results show that the traveling wave antenna provides load resiliency because of its insensitivity to loading resistance, provided that the loading resistance at a radiating element is limited within a practical range. The combline antenna is attractive because it does not require a matching system and exhibits a high selectivity of parallel refractive index. Based on the analysis, a seven element combline antenna was fabricated and installed at an off-mid-plane offset of 30 cm from the mid-plane in KSTAR. The low power RF characteristics measured during several plasma discharges showed no evidence of slow wave coupling. This is consistent with the expectation made through the surface impedance analysis which predicted low slow wave coupling. The wave coupling to the plasma is easily controlled by a radial outer-gap control and gas puffing. No plasma confinement degradation was observed during the radial outer-gap control of up to 3 cm in H-mode discharges. In a ELMy plasmas, only a small reflection peak was observed during a very short portion of the ELM bursting period. If the number of radiating elements is increased for high power operation, then complete load resiliency can be expected. A very large coupling can be problematic for maintaining a parallel refractive index, although this issue can be mitigated by increasing the number of elements. © 2017 IAEA, Vienna.

Kim J.,NFRI | Wang S.,NFRI | Hillairet J.,French Atomic Energy Commission | Wi H.,NFRI | And 3 more authors.
Fusion Engineering and Design | Year: 2016

The major upgrade of KSTAR LHCD system to 4MW is planned in 2021. 4-MW RF power will be provided by 8×0.5MW klystrons. Highly oversized circular waveguide transmitting TE01° mode will be adopted for the low loss transmission line longer than 50m. The design of the 4-MW mid-plane Passive Active Multijunction launcher has been performed. Considering parallel refractive index N|| for the efficient current drive and the maximum power density at the launcher mouth, the launcher is composed of 256 active waveguides whose dimension is 58mm x 7mm and 18mm of spatial period for N||0 =2.5. Multijunction with Emax < 3.5kV/cm and high power waveguide components have been designed using HFSS code. The antenna properties were evaluated using ALOHA. Prototype PAM launcher with 32 active waveguides is under development for 0.5-MW pulsed operation. © 2017.

Breschi M.,University of Bologna | Devred A.,ITER Organization | Casali M.,University of Bologna | Bessette D.,ITER Organization | And 12 more authors.
Superconductor Science and Technology | Year: 2012

The performance of the toroidal field (TF) magnet conductors for the ITER machine are qualified by a short full-size sample (4m) current sharing temperature (T cs) test in the SULTAN facility at CRPP in Villigen, Switzerland, using the operating current of 68kA and the design peak field of 11.8T. Several samples, including at least one from each of the six ITER Domestic Agencies participating in TF conductor fabrication (China, European Union, Japan, Russia, South Korea and the United States), have been qualified by the ITER Organization after achieving T cs values of 6.06.9K, after 7001000 electromagnetic cycles. These T cs values exceed the ITER specification and enabled the industrial production of these long-lead items for the ITER tokamak to begin in each Domestic Agency. Some of these samples did not pass the qualification test. In this paper, we summarize the performance of the qualified samples, analyze the effect of strand performance on conductor performance, and discuss the details of the test results. © 2012 IOP Publishing Ltd.

Rice J.E.,Massachusetts Institute of Technology | Hughes J.W.,Massachusetts Institute of Technology | Diamond P.H.,NFRI | Diamond P.H.,University of California at San Diego | And 10 more authors.
Physical Review Letters | Year: 2011

Intrinsic rotation has been observed in I-mode plasmas from the C-Mod tokamak, and is found to be similar to that in H mode, both in its edge origin and in the scaling with global pressure. Since both plasmas have similar edge T, but completely different edge n, it may be concluded that the drive of the intrinsic rotation is the edge T rather than P. Evidence suggests that the connection between gradients and rotation is the residual stress, and a scaling for the rotation from conversion of free energy to macroscopic flow is calculated. © 2011 American Physical Society.

Kwak J.-G.,NFRI | Kim H.S.,NFRI | Cheon M.S.,NFRI | Oh S.T.,NFRI | And 2 more authors.
Fusion Engineering and Design | Year: 2016

The main mission of Korea Superconducting Tokamak Advanced Research (KSTAR) program is exploring the physics and technologies of high performance steady state Tokamak operation that are essential for ITER and fusion reactor. Since the successful first operation in 2008, the plasma performance is enhanced and duration of H-mode is extended to around 50s which corresponds to a few times of current diffusion time and surpassing the current conventional Tokamak operation. In addition to long-pulse operation, the operational boundary of the H-mode discharge is further extended over MHD no-wall limit(βN ∼4) transiently and higher stored energy region is obtained by increased total heating power (∼6MW) and plasma current (I p up to 1MA for ∼10s). Heating system consists of various mixtures (NB, ECH, LHCD, ICRF) but the major horse heating resource is the neutral beam(NB) of 100keV with 4.5MW and most of experiments are conducted with NB. So there is a lot of production of fast neutrons coming from via D(d,n)3He reaction and it is found that most of neutrons are coming from deuterium beam plasma interaction. Nominal neutron yield and the area of beam port is about 1013-1014/s and 1m2 at the closest access position of the sample respectively and neutron emission could be modulated for application to the neutron radiography by varying NB power. This work reports on the results of quantitative analysis of neutron emission measurements and results are discussed in terms of beam-plasma interaction and plasma confinement. It also includes the feasibility study of neutron radiography using KSTAR. © 2016 Elsevier B.V.

Kim H.J.,NFRI | Heo G.,Kyung Hee University | Kim J.K.,Hanyang University | Kim H.C.,NFRI | And 2 more authors.
Fusion Science and Technology | Year: 2012

The Fusion DEMO Program of Korea is a mega program consisted of phased three programs: DEMO Preparatory Program from 2009 through 2011, DEMO R&D Program from 2012 through 2021 and DEMO Construction Program from 2022 through the 2036. The DEMO R&D Program is further divided into three subprograms: DEMO-Plant Design-Concept Study from 2012 through 2014, DEMO-Plant Design Study from 2015 through 2018 and DEMO Plant FEED (Front End Engineering Design) from 2019 through 2021 at the same time with initiating validation tests for the design methods. Until 2011, preparatory works for DEMO, such as developing the strategic plans, defining a pathway to DEMO and initiating some R&D works necessarily required for defining the pathway, will have been carried out. In this paper, the R&D activities planned in the 2 ndphase sub-program, with an overview of the strategic plans and preparatory works of the Fusion DEMO Program of Korea, are discussed.

Kim H.J.,NFRI | Kim H.C.,NFRI | Lee C.-S.,Daejeon University | Kwon M.,NFRI | Lee G.-S.,NFRI
Fusion Science and Technology | Year: 2011

The strategic plans for the Korean fusion DEMO program of which the total investment and duration are estimated to be 5 to 11 billion US dollars and around 27 years respectively were developed by adopting various practical skills of the business management and project management disciplines including gap study, analytic hierarchy process and work breakdown structure. The vision, mission and strategic objectives of the program were set in line with the national policies on the promotion of the fusion energy development. The key strategies and strategic initiatives of the program were derived from SWOT (Strengths, Weaknesses, Opportunities and Threats) and matched pair analysis. The implementing measures for the strategic initiatives were studied and the critical success factors for the program were also defined. To facilitate the R&D portfolio management, the Program was divided into three sub-programs in accordance with the three phases of the Program. The R&D activities and facilities of the 2 nd phase program were pulled from the final product of the program that is the fusion DEMO Plant by carrying out a gap study. The implementation plans including the estimated costs, human resource plans and timelines are also prepared and introduced.

Yoon H.K.,Dong - Eui University | Jung H.C.,NFRI | Hinoki T.,Kyoto University | Kohyama A.,Muroran Institute of Technology
Transactions of the Korean Society of Mechanical Engineers, A | Year: 2014

In this study, joining methods with SiC powder as the joining adhesives were studied in order to avoid the residual stresses coming from CTE (Coefficient of Thermal Expansion) mismatch between substrate and joining layer. The shear strength and microstructure of joined material between SiC substrates are investigated. The commercial Hexoloy-SA (Saint-Gobain Ceramics, USA) used in this work as substrate material. The fine β-SiC nano-powder which the average particle size is below 30 nm, Al2O3, Y 2O3, and SiO2 were used as joining adhesives. The specimens were joined with 20MPa and 1400-1900oC by hot pressing in argon atmosphere. The shear test was performed to investigate the bonding strength. The cross-section of the joint was characterized by using an optical microscope and scanning electron microscopy (SEM). © 2014.

Nafradi G.,EURATOM | Kovacsik A.,EURATOM | Por G.,EURATOM | Lampert M.,EURATOM | And 2 more authors.
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment | Year: 2015

A PCO Pixelfly VGA CCD camera which is part a of the Beam Emission Spectroscopy (BES) diagnostic system of the Korea Superconducting Tokamak Advanced Research (KSTAR) used for spatial calibrations, suffered from serious radiation damage, white pixel defects have been generated in it. The main goal of this work was to identify the origin of the radiation damage and to give solutions to avoid it. Monte Carlo N-Particle eXtended (MCNPX) model was built using Monte Carlo Modeling Interface Program (MCAM) and calculations were carried out to predict the neutron and gamma-ray fields in the camera position. Besides the MCNPX calculations pure gamma-ray irradiations of the CCD camera were carried out in the Training Reactor of BME. Before, during and after the irradiations numerous frames were taken with the camera with 5 s long exposure times. The evaluation of these frames showed that with the applied high gamma-ray dose (1.7 Gy) and dose rate levels (up to 2 Gy/h) the number of the white pixels did not increase. We have found that the origin of the white pixel generation was the neutron-induced thermal hopping of the electrons which means that in the future only neutron shielding is necessary around the CCD camera. Another solution could be to replace the CCD camera with a more radiation tolerant one for example with a suitable CMOS camera or apply both solutions simultaneously. © 2014 Elsevier B.V. All rights reserved.

News Article | December 17, 2016

South Korea worked to build KSTAR for over a decade, and the reactor began operating in 2008. On the NFRI website, the organization says fusion energy is an " optimal alternative " to dirty energy sources like fossil fuels, as fusion is clean, efficient, and inexhaustible.

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