| 1. |
- Bombarda, F., et al.
(författare)
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Runaway electron beam control
- 2019
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Ingår i: Plasma Physics and Controlled Fusion. - : IOP Publishing. - 1361-6587 .- 0741-3335. ; 61:1
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Tidskriftsartikel (refereegranskat)
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| 2. |
- Pusztai, Istvan, 1983, et al.
(författare)
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Deconvolution-based correction of alkali beam emission spectroscopy density profile measurements
- 2009
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 1089-7623 .- 0034-6748. ; 80:8, s. 083502-
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Tidskriftsartikel (refereegranskat)abstract
- A deconvolution-based correction method of the beam emission spectroscopy (BES) density profile measurement is demonstrated by its application to simulated measurements of the COMPASS and TEXTOR tokamaks. If the line of sight is far from tangential to the flux surfaces, and the beam width is comparable to the scale length on which the light profile varies, the observation may cause an undesired smoothing of the light profile, resulting in a non-negligible underestimation of the calculated density profile. This effect can be reduced significantly by the emission reconstruction method, which gives an estimate of the emissivity along the beam axis from the measured light profile, taking the finite beam width and the properties of the measurement into account in terms of the transfer function of the observation. Characteristics and magnitude of the mentioned systematic error and its reduction by the introduced method are studied by means of the comprehensive alkali BES simulation code RENATE.
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| 3. |
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- 2018
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 58:9
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Tidskriftsartikel (refereegranskat)
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| 4. |
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- 2018
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 58:1
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Forskningsöversikt (refereegranskat)
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| 5. |
- Demaziere, Christophe, 1973, et al.
(författare)
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Estimation of the Moderator Temperature Coefficient (Analysis of an MTC measurement using boron dilution method)
- 2000
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Ingår i: Proc. Int. Topl. Mtg. Nuclear Plant Instrumentation, Controls, and Human-Machine Interface Technologies (NPIC&HMIT 2000).
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Konferensbidrag (refereegranskat)abstract
- The boron dilution method is analyzed, which is widely used for Moderator Temperature Coefficient (MTC) measurement in Pressurized Water Reactors (PWRs). Data were taken from the measurement of the at-power MTC at the PWR Unit 4 of the Ringhals Nuclear Power Plant (Sweden) during fuel cycle 16 at 300 ppm. Detailed calculations were made to estimate all reactivity effects. Calculations were performed with the static code SIMULATE-3, and error limits were also estimated. The analysis showed that the contribution from the Doppler correction was almost negligible, whereas the reactivity correction due to effects other than the Doppler and the boron effects were surprisingly significant. It was found that the uncertainty associated with the boron dilution method could be larger than previously expected.
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| 6. |
- Demaziere, Christophe, 1973, et al.
(författare)
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Evaluation of the boron dilution method for Moderator Temperature Coefficient measurements
- 2002
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Ingår i: Nuclear Technology. - 0029-5450 .- 1943-7471. ; 140:1, s. 147-163
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Tidskriftsartikel (refereegranskat)abstract
- A measurement of the at-power moderator temperature coefficient (MTC) at the pressurized water reactor Unit 4 of the Ringhals Nuclear Power Plant (Sweden) during fuel cycle 16 is analyzed. The measurement was performed when the boron concentration decreased under 300 ppm in the reactor coolant system, by using the boron dilution method. Detailed calculations were made to estimate all reactivity effects taking place during such a measurement. These effects can only be accounted for through static core calculations that allow calculating contributions to the reactivity change induced by the moderator temperature change. All the calculations were performed with the Studsvik Scandpower SIMULATE-3 code. Analysis of the measurement showed that the contribution of the Doppler effect (in the fuel) was almost negligible, whereas the reactivity effects due to other than the Doppler fuel coefficient and the boron change were surprisingly significant. It was concluded that due to the experimental inaccuracies, the uncertainty associated with the boron dilution method could be much larger than previously expected. The MTC might then be close to -72 pcm/oC, whereas the main goal of the measurement is to verify that the MTC is larger (less negative) than this threshold. The usefulness of the boron dilution method for MTC measurements can therefore be questioned.
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| 7. |
- Hoppe, Mathias, 1993, et al.
(författare)
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Spatiotemporal analysis of the runaway distribution function from synchrotron images in an ASDEX Upgrade disruption
- 2021
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Ingår i: Journal of Plasma Physics. - 0022-3778 .- 1469-7807. ; 87:1
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Tidskriftsartikel (refereegranskat)abstract
- Synchrotron radiation images from runaway electrons (REs) in an ASDEX Upgrade discharge disrupted by argon injection are analysed using the synchrotron diagnostic tool Soft and coupled fluid-kinetic simulations. We show that the evolution of the runaway distribution is well described by an initial hot-tail seed population, which is accelerated to energies between 25-50 MeV during the current quench, together with an avalanche runaway tail which has an exponentially decreasing energy spectrum. We find that, although the avalanche component carries the vast majority of the current, it is the high-energy seed remnant that dominates synchrotron emission. With insights from the fluid-kinetic simulations, an analytic model for the evolution of the runaway seed component is developed and used to reconstruct the radial density profile of the RE beam. The analysis shows that the observed change of the synchrotron pattern from circular to crescent shape is caused by a rapid redistribution of the radial profile of the runaway density.
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| 8. |
- Hursin, Mathieu, et al.
(författare)
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Measurement of the gas velocity in a water-air mixture in crocus by neutron noise technique
- 2019
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Ingår i: International Conference on Mathematics and Computational Methods Applied to Nuclear Science and Engineering, M and C 2019. ; , s. 2696-2703
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Konferensbidrag (refereegranskat)abstract
- © 2019 American Nuclear Society. All rights reserved. The possibility to measure the gas phase velocity in a two-component mixture with neutron noise techniques is demonstrated in the zero-power reactor CROCUS of the Ecole Polytechnique Federale de Lausanne. It is the first step toward the experimental validation of a theoretical method aiming at the reconstruction of the void profile in a BWR channel. For this experiment, a channel is installed in the water reflector of CROCUS and two-component mixtures are generated inside the channel through injection of air at various flow rates. The signal fluctuations of two neutron detectors located at different elevations next to the channel are recorded and their Cross Power Spectral Density analyzed with various techniques to determine the transit time of the gas phase and its velocity. Experimental results are compared with predictions obtained with the TRACE thermal-hydraulic code. Results disagree in their magnitudes but the evolution of the gas velocity with the air injection rate are similar.
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| 9. |
- Hursin, Mathieu, et al.
(författare)
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Measurement of the Gas Velocity in a Water-Air Mixture in CROCUS Using Neutron Noise Techniques
- 2020
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Ingår i: Nuclear Technology. - : Informa UK Limited. - 0029-5450 .- 1943-7471. ; 206:10, s. 1566-1583
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Tidskriftsartikel (refereegranskat)abstract
- The possibility of measuring the gas-phase velocity in a two-phase mixture through the use of neutron noise techniques is demonstrated in the zero-power reactor CROCUS of the Ecole Polytechnique Federale de Lausanne. It is the first step toward the experimental validation of an existing theoretical model whose objective is the reconstruction of the void profile in a channel. The use of zero-power research reactors is advantageous due to their clean environment in terms of signal fluctuations. To this end, a channel was installed in the reflector of CROCUS. A two-component mixture is generated inside the channel through the injection of compressed air. The signal fluctuations of neutron detectors located at various axial locations next to the channel are processed to determine the transit time of the gas phase between detectors. Four methods are presented based on the detector signal time series either in the time domain (time correlations between signals) or in the frequency domain (phase of the cross-power spectral density. All four methods returned consistent transit times and similar experimental uncertainty. The largest possible gas injection rates as well as the highest possible neutron flux level improve the visibility of the traveling perturbation and reduce the experimental uncertainty on the transit time for a given acquisition time. © 2020, © 2020 American Nuclear Society.
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| 10. |
- Hursin, Mathieu, et al.
(författare)
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Validation of axial void profile measured by neutron noise techniques in crocus
- 2020
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Ingår i: International Conference on Physics of Reactors: Transition to a Scalable Nuclear Future, PHYSOR 2020. - : EDP Sciences. ; 2020-March, s. 1586-1593
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Konferensbidrag (refereegranskat)abstract
- Recently a joint project has been carried out between the Paul Scherrer Institut, the Ecole Polytechnique Federale de Lausanne and swissnuclear, an industrial partner, in order to determine the axial void distribution in a channel installed in the reflector of the zero power research reactor CROCUS, using neutron noise techniques. The main objective of the present paper is to report on the validation of the results against an alternative measurement technique using gamma-ray attenuation and simulations with the TRACE code. For the gamma-ray attenuation experiments, the channel used in CROCUS is installed out of the core in a Plexiglass water tank. The source and detector are fixed and the channel is moved axially to keep the geometry of the source/detector arrangement untouched. This is key to measure the void effect by gamma attenuation due to the low contrast of this technique. The paper compares the experimental results obtained with both techniques, with the outcomes of simulations carried out with the TRACE code. Even though the quantitative void fraction estimations are not consistent, the trends obtained with the simulation and experimental techniques are the same. The discrepancies between the various experimental techniques and the simulation outcomes are related to the heterogeneous distribution of the water-air mixture in the radial sections of the channel.
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