Experimental Study of Three-Dimensional Void Fraction Distribution in Heated Tight-Lattice Rod Bundles Using Three-Dimensional Neutron Tomography

Kureta, Masatoshi

doi:10.1299/jpes.1.225

Cited by 27 publications

(5 citation statements)

References 13 publications

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“…Cold neutrons provide an excellent contrast even inside of metallic casings for the smallest amount of water (like thin liquid films) opposed to, e.g., X-rays. They have been used to study two-phase flows in pipes and nuclear fuel bundle models [10,11] and liquid-metal two-phase flows and steam explosions [12]. Cold neutron tomography has also been extensively used and validated by one of the co-authors to study thin (few 100 of microns) liquid films in annular flows in nuclear fuel bundles [13].…”

Section: Cold Neutron Imagingmentioning

confidence: 99%

Infrared film thickness measurement: comparison with cold neutron imaging

Dupont

Mignot²,

Zboray³

et al. 2016

Journal of Nuclear Science and Technology

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Near InfraRed FILM thickness PROfile (NIR-FILMPRO) is an optical technique for non-intrusive measurement of water film thickness. The technique is based on absorption of NIR light. A passband filter centered at 1612 nm was selected to measure isothermal gravity-driven films flowing on a vertical wall with sand blasted surface. Non-intrusive 2D mapping of the film thickness was acquired at 200 fps, with an image size of 320 × 256 pixels and a spatial resolution of 0.677 mm. Theoretical developments were brought to consider multiple reflections of light in the liquid film providing a more accurate model to compute the film thickness. Further improvements were made regarding the calibration procedure and the image processing. The measurements were compared against cold neutron imaging, an established technique which provides images of the time averaged thickness. An excellent correspondence between the two methods was found. The root mean square of the deviation between the two techniques taken over a region covered by a wavy film was found to be 2.3% of the measurement with film thicknesses fluctuating between approximately 100 and 500 μm. The spatial comparison with cold neutron imaging complements the previous comparisons and validates the application of the technique.

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Section: Cold Neutron Imagingmentioning

confidence: 99%

Infrared film thickness measurement: comparison with cold neutron imaging

Dupont

Mignot²,

Zboray³

et al. 2016

Journal of Nuclear Science and Technology

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“…However, the usage of NT on thermal-hydraulic flows has to this date only been applied at NT laboratories, where neutron beam lines are available from research reactors or spallation sources, 13,14 Since such sources are stationary, they cannot be used at dedicated large-scale thermal-hydraulic test loops. Therefore, this paper explores the feasibility of NT on stationary thermal-hydraulic test loops using portable neutron generators, where we focus on Deuterium-Tritium neutron generators emitting neutrons at an energy of 14 MeV.…”

Section: B Fast Neutrons For Transmission Tomography Of Void Distribmentioning

confidence: 99%

Neutron tomography of axially symmetric objects using 14 MeV neutrons from a portable neutron generator

Andersson

Andersson-Sundén

Sjöstrand

et al. 2014

Review of Scientific Instruments

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In nuclear boiling water reactor cores, the distribution of water and steam (void) is essential for both safety and efficiency reasons. In order to enhance predictive capabilities, void distribution assessment is performed in two-phase test-loops under reactor-relevant conditions. This article proposes the novel technique of fast-neutron tomography using a portable deuterium-tritium neutron generator to determine the time-averaged void distribution in these loops. Fast neutrons have the advantage of high transmission through the metallic structures and pipes typically concealing a thermal-hydraulic test loop, while still being fairly sensitive to the water/void content. However, commercially available fast-neutron generators also have the disadvantage of a relatively low yield and fast-neutron detection also suffers from relatively low detection efficiency. Fortunately, some loops are axially symmetric, a property which can be exploited to reduce the amount of data needed for tomographic measurement, thus limiting the interrogation time needed. In this article, three axially symmetric test objects depicting a thermal-hydraulic test loop have been examined; steel pipes with outer diameter 24 mm, thickness 1.5 mm, and with three different distributions of the plastic material POM inside the pipes. Data recorded with the FANTOM fast-neutron tomography instrument have been used to perform tomographic reconstructions to assess their radial material distribution. Here, a dedicated tomographic algorithm that exploits the symmetry of these objects has been applied, which is described in the paper. Results are demonstrated in 20 rixel (radial pixel) reconstructions of the interior constitution and 2D visualization of the pipe interior is demonstrated. The local POM attenuation coefficients in the rixels were measured with errors (RMS) of 0.025, 0.020, and 0.022 cm(-1), solid POM attenuation coefficient. The accuracy and precision is high enough to provide a useful indication on the flow mode, and a visualization of the radial material distribution can be obtained. A benefit of this system is its potential to be mounted at any axial height of a two-phase test section without requirements for pre-fabricated entrances or windows. This could mean a significant increase in flexibility of the void distribution assessment capability at many existing two-phase test loops.

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“…As shown in figure 2b, the detection efficiency initially increases linearly with the converter thickness, and then saturates (at a value of around 0.07%) when the converter thickness approach the range of the most energetic recoil protons. For forward scattered recoil protons of 2.45 MeV in polyethylene (with mass density of ρ = 0.93 g/cm 3 ), the range is around 100 µm. For comparison, the conversion efficiency (namely the total fraction of neutrons interacting in the converter foil) is also shown in figure 2b.…”

Section: Thickness Of the Polyethylene Foilsmentioning

confidence: 99%

“…In the past, X-and gamma-ray radiography and tomography have been the first choice among the non-invasive imaging techniques, both for general two-phase flow research and for nuclear fuel bundle investigation [2]. More recently, imaging techniques such as thermal-neutron radiography [3] and three-dimensional neutron tomography [4] were also used for investigation of liquid-metal two phase flows in the context of generation IV reactors [4,5] and corium-water thermal interactions (e.g., steam explosions) [6,7].…”

Section: Introductionmentioning

confidence: 99%

Concept of a novel fast neutron imaging detector based on THGEM for fan-beam tomography applications

et al. 2012

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The conceptual design and operational principle of a novel high-efficiency, fast neutron imaging detector based on THGEM, intended for future fan-beam transmission tomography applications, is described. We report on a feasibility study based on theoretical modeling and computer simulations of a possible detector configuration prototype. In particular we discuss results regarding the optimization of detector geometry, estimation of its general performance, and expected imaging quality: it has been estimated that detection efficiency of around 5-8% can be achieved for 2.5MeV neutrons; spatial resolution is around one millimeter with no substantial degradation due to scattering effects. The foreseen applications of the imaging system are neutron tomography in non-destructive testing for the nuclear energy industry, including examination of spent nuclear fuel bundles, detection of explosives or drugs, as well as investigation of thermal hydraulics phenomena (e.g., two-phase flow, heat transfer, phase change, coolant dynamics, and liquid metal flow).

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Experimental Study of Three-Dimensional Void Fraction Distribution in Heated Tight-Lattice Rod Bundles Using Three-Dimensional Neutron Tomography

Cited by 27 publications

References 13 publications

Infrared film thickness measurement: comparison with cold neutron imaging

Infrared film thickness measurement: comparison with cold neutron imaging

Neutron tomography of axially symmetric objects using 14 MeV neutrons from a portable neutron generator

Concept of a novel fast neutron imaging detector based on THGEM for fan-beam tomography applications

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