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- Demaziere, Christophe, 1973, et al.
(författare)
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Calculation of the eigenfunctions and corresponding eigenvalues of the two-group diffusion equation in heterogeneous systems
- 2007
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Ingår i: Proc. Joint Int. Topl. Mtg. Mathematics & Computation and Supercomputing in Nuclear Applications (M & C + SNA 2007). - 0894480596
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Konferensbidrag (refereegranskat)abstract
- This paper deals with the extension of an existing code developed at the Department of Nuclear Engineering, Chalmers University of Technology, to the calculation of the higher order eigenfunctions and corresponding eigenvalues of the two-group diffusion equations. More specifically, this code, originally meant for calculating the two-group static neutron flux and its adjoint for any two-dimensional heterogeneous system, is modified in order to calculate any higher mode of both the neutron flux and its adjoint. A one-dimensional two-region system is first considered for benchmark purposes, where the reference solution can be determined semi-analytically. The numerical solution is computed using a modified power iteration method. The agreement between the numerical solution and the reference solution is found to be excellent, both regarding the eigenfunctions and the eigenvalues, and both for the forward and adjoint problems. The modified power iteration method is then applied to the calculation of the different modes of the neutron flux and its adjoint in a two-dimensional heterogeneous representation of the Swedish Forsmark-1 BWR core corresponding to the 1996/1997 channel instability event.
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| 5. |
- Pazsit, Imre, 1948, et al.
(författare)
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Final Report on the Research Project Ringhals Diagnostics and Monitoring, Stage 12
- 2008
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This report gives an account of the work performed by the Department of Nuclear Engineering (formerly Reactor Physics), Chalmers, in the frame of a research contract with Ringhals, Vattenfall AB, contract No. 578254-003. The contract constitutes Stage 12 of a long-term co-operative research work concerning diagnostics and monitoring of the BWR and PWR units. The work in Stage 12 has been performed between March 1st, 2007 and May 31st, 2008. In Stage 12 we have worked with four items as follows:Development of the beam mode core barrel vibration diagnostics;Investigation of the axial in-core neutron noise by measurements;Calculation of the conversion factor between core barrel displacement and the relative change in the ex-core detector signal;Evaluation of detector impacting.This work was performed at the Department of Nuclear Engineering, Chalmers University of Technology by Imre Pázsit (project leader), Christophe Demazière, Carl Sunde, Petty Bernitt and Augusto Hernández-Solís. Contact persons at Ringhals were Tell Andersson (project leader) and Henrik Nylén.
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| 6. |
- Sunde, Carl, 1976, et al.
(författare)
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Calculation of the neutron noise induced by shell-mode core-barrel vibrations in a 1-D 2-group 2-region slab reactor
- 2003
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The subject of this work is the calculation of the in-core neutron noise, induced by the shell-mode vibration of the core-barrel. The original motivation was to investigate whether an out-of-phase behaviour can exist between the in-core and ex-core detectors lying on the same azimuthal position. To this order a two-region two-group diffusion model was used in one dimension. The noise was calculated in the adiabatic approximation. It was found that an out-of-phase behaviour can exist between in-core detectors, close to the core boundary, and the ex-vessel detectors, for large systems. In addition, due to the use of two-group theory, the strong local noise component at the boundary of the vibrating core was also found. The paper gives details of the calculations and the results.
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| 7. |
- Sunde, Carl, 1976, et al.
(författare)
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Calculation of the Neutron Noise Induced by Shell-Mode Core-Barrel Vibrations in a 1-D, Two-Group, Two-Region Slab Reactor Model
- 2006
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Ingår i: Nuclear Technology. ; 154:2, s. 129-141
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Tidskriftsartikel (refereegranskat)abstract
- The subject of this paper is the calculation of the in-core neutron noise induced by the shell-mode vibrations of the core barrel. The original motivation was to investigate whether an out-of-phase behavior can exist between the in-core and ex-core (ex-vessel) detectors lying at the same azimuthal position. To this end, a two-region two-group diffusion model was used in one dimension. The noise was calculated by representing the vibrations of the core barrel by a model developed earlier to describe control rod vibrations. It was found that such an out-of-phase behavior indeed exists, although only for in-core detector positions close to the core boundary. This behavior is due to the local component of the noise, which is accounted for in a two-group treatment. The finding is in accordance with the experiment whose result prompted the present work. In addition to its effect on the phase, the local component also manifests itself by a large amplitude of the noise around the vibrating core boundary, i.e., in both the core and the reflector. The appearance and the properties of the local component of the neutron noise for core-barrel vibrations is the main finding of this paper. The results suggest that the efficiency of core-barrel vibrations can be enhanced if in addition to the ex-core detectors, the in-core detectors in the outermost fuel assemblies are used.
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| 9. |
- Sunde, Carl, 1976, et al.
(författare)
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Classification of Two-Phase Flow Regimes via Image Analysis by a Neuro-Wavelet Approach
- 2004
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Ingår i: Applied Computational Intelligence, Proceedings of the 6th International FLINS Conference. - 9812388737 ; , s. 236-239
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Konferensbidrag (refereegranskat)abstract
- A non-intrusive method of two-phase flow identification is investigated in this paper. It is based on image processing of data obtained from dynamic neutron radiography recordings. Classification of the flow regime types is performed by an artificial neural network (ANN) algorithm. The input data to the ANN are some statistical functions(mean and variance) of the wavelet transform coefficients of the pixel intensity data. The investigations show that bubbly and annular flows can be identified with a highconfidence, but slug and churn-turbulent flows are more often mixed up in between themselves.
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