Experimental Study on Buoyancy-Driven Exchange Flows through Breaches of a Tokamak Vacuum Vessel in a Fusion Reactor under the Loss-of-Vacuum-Event Condition

Takase, Kazuyuki; Kunugi, Tomoaki; Ogawa, Masurou; Seki, Yasushi

doi:10.13182/nse97-a24269

Cited by 13 publications

(4 citation statements)

References 2 publications

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“…The third concern is that these dusts are potentially combustible. Several experimental studies [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] demonstrated that the exchange flows depend on number, position, length and shape of breaches, pressure and temperature conditions and type of fluid. Therefore, it is very important to investigate the dust re-suspension characteristics during a LOVA event.…”

Section: Introductionmentioning

confidence: 99%

Dust tracking techniques applied to the STARDUST facility: First results

Malizia

Camplani

Gelfusa

et al. 2014

Fusion Engineering and Design

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HIGHLIGHTS• Use of an experimental facility, STARDUST, to analyze the dust resuspension problem inside the tokamak in case of loss of vacuum accident.• PIV technique implementation to track the dust during a LOVA reproduction inside STARDUST.• Data imaging techniques to analyze dust velocity field: first results and data discussion. ABSTRACTAn important issue related to future nuclear fusion reactors fueled with deuterium and tritium is the creation of large amounts of dust due to several mechanisms (disruptions, ELMs and VDEs). The dust size expected in nuclear fusion experiments (such as ITER) is in the order of microns (between 0.1 and 1000 (im). Almost the total amount of this dust remains in the vacuum vessel (W). This radiological dust can re-suspend in case of LOVA (loss of vacuum accident) and these phenomena can cause explosions and serious damages to the health of the operators and to the integrity of the device. The authors have developed a facility, STARDUST, in order to reproduce the thermo fluid-dynamic conditions comparable to those expected inside the W of the next generation of experiments such as ITER in case of LOVA. The dust used inside the STARDUST facility presents particle sizes and physical characteristics comparable with those that created inside the VV of nuclear fusion experiments. In this facility an experimental campaign has been conducted with the purpose of tracking the dust re-suspended at low pressurization rates (comparable to those expected in case of LOVA in ITER and suggested by the General Safety and Security Report ITER-GSSR) using a fast camera with a frame rate from 1000 to 10,000 images per second. The velocity fields of the mobilized dust are derived from the imaging of a two-dimensional slice of the flow illuminated by optically adapted laser beam. The aim of this work is to demonstrate the possibility of dust tracking by means of image processing with the objective of determining the velocity field values of dust re-suspended during a LOVA.

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Section: Introductionmentioning

confidence: 99%

Dust tracking techniques applied to the STARDUST facility: First results

Malizia

Camplani

Gelfusa

et al. 2014

Fusion Engineering and Design

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“…The preliminary LOVA apparatus [8] consists mainly of a toroidal shaped test section and weight measuring system.…”

Section: Experimental Apparatusmentioning

confidence: 99%

Thermal hydraulic characteristics during ingress of coolant and loss of vacuum events in fusion reactors

Takase¹,

Kunugi

Seki³

et al. 2000

Nucl. Fusion

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The thermal hydraulic characteristics in the vacuum vessel (VV) of a fusion reactor under an ingress of coolant event (ICE) and a loss of vacuum event (LOVA) were investigated quantitatively using preliminary experimental apparatuses. In the ICE experiments, pressure rise characteristics in the VV were clarified for experimental parameters of the wall temperature and water temperature and for cases with and without a blowdown tank. In addition, the functional performance of a blowdown tank with and without a water cooling system was examined and it was confirmed that the blowdown tank with a water cooling system is effective for suppressing the pressure rise during the ICE. In the LOVA experiments, the saturation time in the VV from vacuum to atmosphere was investigated for various breach sizes and it was found that the saturation time is in inverse proportion to the breach size. In addition, the characteristics of exchange flow through breaches were clarified for the different breach positions on the VV. It was proven from the experimental results that the exchange flow became a counter-current flow when the breach was positioned on the top of the VV and a stratified flow when it was formed on the side wall of the VV, and that the exchange flow under the stratified flow condition was smoother than that of counter-current flow. On the basis of these results, the severest breach condition in ITER was changed from the top-break case to the side-break case. To predict with high accuracy the thermal hydraulic characteristics during ICEs and LOVAs under ITER conditions, a large scale test facility will be necessary. The current conceptual design of the combined ICE-LOVA test facility with a scaling factor of 1/1000 in comparison with the ITER volume is presented.

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“…Resuspension/mobilization phenomena in case of accidents can cause explosions compromising the integrity of the plant and producing a considerable hazard for the ambient and for the health of the operators if dust is transported out of a breach since particles are radioactive and of breathable size [11][12][13][14][15]. The dust size expected is between 0.1 and 1000 µm [1,5,[15][16][17].…”

Section: Introductionmentioning

confidence: 99%

STARDUST-U experiments on fluid-dynamic conditions affecting dust mobilization during LOVAs

et al. 2016

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Since 2006 the Quantum Electronics and Plasma Physics (QEP) Research Group together with ENEA FusTech of Frascati have been working on dust re-suspension inside tokamaks and its potential capability to jeopardize the integrity of future fusion nuclear plants (i.e. ITER or DEMO) and to be a risk for the health of the operators. Actually, this team is working with the improved version of the "STARDUST" facility, i.e. "STARDUST-Upgrade". STARDUST-U facility has four new air inlet ports that allow the experimental replication of Loss of Vacuum Accidents (LOVAs). The experimental campaign to detect the different pressurization rates, local air velocity, temperature, have been carried out from all the ports in different accident conditions and the principal results will be analyzed and compared with the numerical simulations obtained through a CFD (Computational Fluid Dynamic) code. This preliminary thermo fluid-dynamic analysis of the accident is crucial for numerical model development and validation, and for the incoming experimental campaign of dust resuspension inside STARDUST-U due to well-defined accidents presented in this paper. K: Data acquisition concepts; Nuclear instruments and methods for hot plasma diagnostics 1Corresponding author.

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Experimental Study on Buoyancy-Driven Exchange Flows through Breaches of a Tokamak Vacuum Vessel in a Fusion Reactor under the Loss-of-Vacuum-Event Condition

Cited by 13 publications

References 2 publications

Dust tracking techniques applied to the STARDUST facility: First results

Dust tracking techniques applied to the STARDUST facility: First results

Thermal hydraulic characteristics during ingress of coolant and loss of vacuum events in fusion reactors

STARDUST-U experiments on fluid-dynamic conditions affecting dust mobilization during LOVAs

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