Time filter

Source Type

Daejeon, South Korea

Ivanov D.P.,RAS Research Center Kurchatov Institute | Anashkin I.O.,RAS Research Center Kurchatov Institute | Khvostenko P.P.,RAS Research Center Kurchatov Institute | Kolbasov B.N.,RAS Research Center Kurchatov Institute | And 8 more authors.
IEEE Transactions on Applied Superconductivity | Year: 2012

The latest superconducting magnets (SM) for fusion are mostly force-cooled, mainly because it allows reliable electrical insulation of the coils using vacuum pressure impregnation (VPI). SM of this type have many leads, feeders and coolant tubes, located in cryostat vacuum, which must sustain high voltages, induced on them by fast current changes. However vacuum loss can spoil their insulation. A few such cases occurred during the T-15 tokamak coils testing, initially having bare leads relying upon vacuum. But its loss generated a coil quench, a protecting current dump at high voltage, followed by breakdown and arc. Even leads insulation by Teflon and fiberglass tape wrap proved to be insufficient. Nevertheless, similar tape wrap insulation of leads and feeders (ILF) was used in EAST, KSTAR, SST-1 and W-7X. So far, seven breakdowns occurred during their coil tests at operating voltage ∼<3 kV. Breakdowns never initiated in the coils, but always on their leads, feeders and sensor lines, indicating that their insulation made by tape wrap were too weak. Instead of ILF improvement some projects undertake Paschen tests. These are planned as the baseline for ITER too. But these tests are valid for the coil with open insulated surface, but are not appropriate for the final tests, when insulation should not be exposed to vacuum. Up to now ILF final tests have been done in all devices at 10-21 kV, but only in good vacuum in spite of the fact that such tests could not guarantee safe operation in case of vacuum loss. We propose to increase ILF strength to the same level, as in the coils, using vacuum-tight grounded stainless steel casings filled up by VPI over magnet leads. This will provide reliable and easily testable solid insulation. Besides, casings would exclude He leaks, providing the second vacuum tight barrier over the ILF. Thus it would increase the magnet reliability and would make it possible to avoid the needs of all single coils test. © 2011 IEEE. Source

Kim J.,NFRI | Kim J.,Daejeon University | Park C.,Korea University | Kim Y.-S.,Chung - Ang University | And 3 more authors.
Fusion Science and Technology | Year: 2013

To expedite realization of magnetic fusion energy with the tokamak concept, a parallel process of developing engineering technologies required to design, fabricate, construct, start up, and operate the fusion DEMO plant of Korea (K-DEMO Plant) at the same time with researching fusion science and technologies in KSTAR (Korean Superconductor Tokamak Advanced Research) and ITER (International Thermonuclear Experimental Reactor) was adopted in the fusion DEMO program of Korea (K-DEMO Program). As a part of these engineering studies, an exploratory study on the layout and building schematics of K-DEMO Plant have carried out in consideration of economic and safety aspects. The buildings of K-DEMO Plant are named and their volumes are estimated with an order of magnitude analysis based on the sizes of the buildings of ITER and nuclear power plants. This exploratory study on the layout and building schematics is also required to estimate the costs of K-DEMO Program and analyze its economic feasibility. Source

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. Source

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. Source

Ioki K.,ITER Organization | Choi C.H.,ITER Organization | Daly E.,ITER Organization | Dani S.,ITER Organization | And 18 more authors.
Fusion Engineering and Design | Year: 2012

After implementing a few design modifications (referred to as the "Modified Reference Design") in 2009, the Vacuum Vessel (VV) design had been stabilized. The VV design is being finalized, including interface components such as support rails and feedthroughs for the in-vessel coils. It is necessary to make adjustments to the locations of the blanket supports and manifolds to accommodate design modifications to the in-vessel coils. The VV support design is also being finalized considering a structural simplification. Design of the in-wall shielding (IWS) has progressed, considering the assembly methods and the required tolerances. The detailed layout of ferritic steel plates and borated steel plates was optimized based on the toroidal field ripple analysis. A dynamic test on the inter-modular key to support the blanket modules was performed to measure the dynamic amplification factor (DAF). An R&D program has started to select and qualify the welding and cutting processes for the port flange lip seal. The ITER VV material 316 L(N) IG was already qualified and the Modified Reference Design was approved by the Agreed Notified Body (ANB) in accordance with the Nuclear Pressure Equipment Order procedure. © 2012 Elsevier B.V. All rights reserved. Source

Discover hidden collaborations