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| 2. |
- De Izarra, G., et al.
(författare)
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Design of a high order Campbelling mode measurement system using open source hardware
- 2016
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Ingår i: Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. - : Elsevier BV. - 0168-9002. ; 839, s. 12-22
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Tidskriftsartikel (refereegranskat)abstract
- This paper reviews a new real-time measurement instrument dedicated for online neutron monitoring with fission chambers in nuclear reactors. The instrument implements the higher order Campbelling methods and self-monitoring capabilities on an open source development board. The board includes an CPU/FPGA System on a Chip. The feasibility of the measurement instrument was tested both in laboratory with a signal generator and in the Minerve reactor. It is shown that the instrument provides reliable and robust count rate estimation over a wide reactor power range based on the third order statistics of the fission chamber signal. In addition, the system is able to identify whether the measured count rate change is due to the malfunction of the detector or due to the change in the neutron flux. The applied self-monitoring method is based on the spectral properties of the fission chamber signal. During the experimental verification, the considered malfunction was the change of the polarization voltage.
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| 3. |
- Elter, Zsolt, 1987, et al.
(författare)
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Energy Correlation of Prompt Fission Neutrons
- 2016
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Ingår i: EPJ Web of Conferences. - : EDP Sciences. - 2101-6275 .- 2100-014X. - 9782759819706 ; 111, s. Art no 05003-
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Konferensbidrag (refereegranskat)abstract
- In all cases where neutron fluctuations in a branching process (such as in multiplicity measurements) are treated in an energy dependent description, the energy correlations of the branching itself (energy correlations of the fission neutrons) need to be known. To date, these are not known from experiments. Such correlations can be theoretically and numerically derived by modelling the details of the fission process. It was suggested earlier that the fact that the prompt neutrons are emitted from the moving fission targets, will influence their energy and angular distributions in the lab system, which possibly induces correlations. In this paper the influence of the neutron emission process from the moving targets on the energy correlations is investigated analytically and via numerical simulations. It is shown that the correlations are generated by the random energy and direction distributions of the fission fragments. Analytical formulas are derived for the two-point energy distributions, and quantitative results are obtained by Monte-Carlo simulations. The results lend insight into the character of the two-point distributions, and give quantitative estimates of the energy correlations, which are generally small.
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| 4. |
- Elter, Zsolt, 1987
(författare)
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Neutron monitoring based on the higher order statistics of fission chamber signals
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The work in this thesis corresponds to the safety aspect of Generation IV nuclear systems. One of the safety aspects concerns the enhancement of the performance of the in-vessel on-line core monitoring with neutron flux measurements. It was concluded earlier that fission chambers are the best candidate to provide in-vessel measurements in sodium cooled fast reactors. This thesis focuses on the performance of signal processing methods in order to unfold the count rate of fission chambers. The main goal is to investigate the possible application of processing methods based on the higher order statistics of the signal in order to provide accurate count rate estimation over a wide range both for stationary and transient signals. The work also consists of the study of self-monitoring capabilities in order to detect fission chamber malfunctions at an early stage. The investigation is based on analytic assessments, on simulation of fission chamber responses and signals, and on experimental application of processing methods.The thesis covers five main studies. The first part presents the theoretical description of fission chamber signals. The second part investigates the performance of the traditionally applied methods (pulse and Campbelling mode) through simulations. It is shown that these methods are not capable to cover the whole count rate range of the chamber. Therefore, the third part studies the possible application of methods based on higher order statistics of the signal through simulations and experiments. It is shown that these methods can provide accurate estimations over a wide count rate range. The fourth part covers the theoretical background of self-monitoring capabilities based on the spectral properties of the signal. Finally, the fifth part presents the implementation of the methods in a real-time neutron monitoring system based on a System on a Chip, which embeds a field-programmable gate array.By the methods elaborated in this thesis, a faster, more effective and more accurate monitoring of the reactor power is possible than with the methods used so far, even when the normal operating state is changing.
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| 5. |
- Elter, Zsolt, 1987, et al.
(författare)
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Performance investigation of the pulse and Campbelling modes of a fission chamber using a Poisson pulse train simulation code
- 2015
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Ingår i: Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. - : Elsevier BV. - 0168-9002. ; 774, s. 60-67
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Tidskriftsartikel (refereegranskat)abstract
- The detectors of the neutron flux monitoring system of the foreseen French GEN-IV sodium-cooled fast reactor (SFR) will be high temperature fission chambers placed in the reactor vessel in the vicinity of the core. The operation of a fission chamber over a wide-range neutron flux will be feasible provided that the overlap of the applicability of its pulse and Campbelling operational modes is ensured. This paper addresses the question of the linearity of these two modes and it also presents our recent efforts to develop a specific code for the simulation of fission chamber pulse trains. Our developed simulation code is described and its overall verification is shown. An extensive quantitative investigation was performed to explore the applicability limits of these two standard modes. It was found that for short pulses the overlap between the pulse and Campbelling modes can be guaranteed if the standard deviation of the background noise is not higher than 5% of the pulse amplitude. It was also shown that the Campbelling mode is sensitive to parasitic noise, while the performance of the pulse mode is affected by the stochastic amplitude distributions.
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| 6. |
- Elter, Zsolt, 1987, et al.
(författare)
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Performance of Higher Order Campbell methods, Part I: review and numerical convergence study
- 2016
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Ingår i: Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. - : Elsevier BV. - 0168-9002. ; 821, s. 66-72
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Tidskriftsartikel (refereegranskat)abstract
- This paper investigates, through numerical simulations, the performance of a signal analysis method by which a high temperature fission chamber can be used over a wide range of count rates. Results reported in a previous paper (Elter et al., 2015 [I]) indicated that the traditional Campbell method and the pulse mode cannot provide a sufficient overlap at medium count rates. Hence the use of the so-called Higher Order Campbell (HOC) methods is proposed and their performance is investigated. It is shown that the HOC methods can guarantee the linearity (i.e. correctness) of the neutron flux estimation over a wide count rate, even during transient conditions. The capabilities of these methods for suppressing parasitic noise (originating from various sources) are verified.
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| 7. |
- Elter, Zsolt, 1987, et al.
(författare)
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Performance of Higher Order Campbell methods, Part II: calibration and experimental application
- 2016
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Ingår i: Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. - : Elsevier BV. - 0168-9002. ; 835, s. 86-93
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Tidskriftsartikel (refereegranskat)abstract
- Applying Higher Order Campbelling methods in neutron flux monitoring with fission chambers is advantageous due to their capabilities to suppress the impact of unwanted noises and signal contributions (such as gamma radiation). This work aims to verify through experimental results that the basic assumptions behind the Higher Order Campelling methods are valid in critical reactors. The experiments, reported in this work, were performed at the MINERVE reactor in Cadarache. It is shown that the calibration of a fission chamber and the associated electronic system is possible in higher order mode. With the use of unbiased cumulant estimators and with digital processing, it is shown that over a wide count rate range, accurate count rate estimation can be achieved based on signal samples of a few ms, which is a significant progress compared to similar experimental results in the literature. The difference between the count rate estimated by pulse counting and by the Higher Order Campelling is less than 4%. The work also investigates the possibility of monitoring transient events. For this purpose, a control rod drop event was followed in Higher Order Campbelling mode.
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| 8. |
- Elter, Zsolt, 1987
(författare)
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pyFC: a TRIM-based fission chamber pulse shape simulator
- 2015
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This report presents the code system pyFC (python-based simulation of Fission Chambers) which simulates the pulse creation in fission chambers. The current pulses in a fission chamber are generated due to the ionization of the filling gas by the heavy ion emitted from the neutron induced fission in the fissile deposit. In pyFC the path of the heavy ion and the spatial distribution of the charges emerging from the ionization process are simulated with the TRIM code, and the parameters of the charge collection between the electrodes are computed with the BOLSIG software. The coupling of the codes is done in Python.The report presents the physical and geometrical considerations implemented in pyFC and the verification of the code through comparison with the results of Chester, a CEA code for simulation of fission chambers.
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| 9. |
- Elter, Zsolt, 1987, et al.
(författare)
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Remark on the applicability of Campbelling techniques for transient signals
- 2016
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Ingår i: Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. - : Elsevier BV. - 0168-9002. ; 813, s. 10-12
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Tidskriftsartikel (refereegranskat)abstract
- The signals of fission chambers are traditionally evaluated with Campbelling methods at medium count rates. Lately there has been a growing interest in the extension of Campbelling methods to cover a wider range of count rates. These methods are applied to measure the neutron flux in the stationary state of the reactor. However, there has not been any attempt to generalize these techniques for transient reactor states. This short note is devoted to a discussion of this question. It is shown through analytic and numerical calculations that for practical reasons the traditional, stationary Campbelling methods can be applied for transient scenarios as well. (C) 2016 Elsevier B.V. All rights reserved.
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