| 1. |
- Bécares-Palacios, V., et al.
(författare)
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Reactivity monitoring with imposed beam trips and pulsed mode detectors in the subcritical experiment YALINA-Booster
- 2009
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Ingår i: Proceedings of International Topical Meeting on Nuclear Research Applications and Utilization of Accelerators. - : International Atomic Energy Agency. - 9789201504104
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Konferensbidrag (refereegranskat)abstract
- Reactivity monitoring is one of the urgent problems that require a solution in order to achieve a license for a future full-scale ADS. As a part of the EUROTRANS experiments at the YALINA-Booster facility, presented in this conference, a set of measurements with imposed beam-trips has been performed. Traditionally, the source jerk method has been used in subcritical systems to obtain the reactivity by comparing the total neutron flux before the neutron source removal to the semi-stable delayed neutron flux after the source removal. The deuterium-tritium neutron source of the YALINA-Booster facility can, in addition to pulsed mode operation, operate with continuous beam with short imposed millisecond-scale interruptions, thus providing the possibility to monitor the reactivity at each beam trip in the source jerk manner. In order to test the validity of the beam-trip reactivity values determined by using detectors operating in current-mode (also presented in this conference), the reactivity values of the YALINA-Booster assembly obtained through the beam-trip technique using pulsed-mode detectors is presented in this work. In these experiments, a beam-trip frequency of 1 Hz and an interruption time of ∼20 ms have been chosen and two different core loadings with effective multiplication factor around 0.95 have been investigated. These two different loadings with close to equal reactivity but different source multiplication characteristics make it possible to explore the effect of the different source multiplications. In addition, the response of the imposed beam-trip reactivity monitoring technique to reactivity insertions and removals has been studied through control rod movements. Experimental data from fission chambers have been acquired from all three zones of the core: the fast booster zone, the thermal zone and the reflector.
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| 2. |
- Becares, V., et al.
(författare)
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Evaluation of the criticality constant from Pulsed Neutron Source measurements in the Yalina-Booster subcritical assembly
- 2013
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Ingår i: Annals of Nuclear Energy. - : Elsevier BV. - 0306-4549 .- 1873-2100. ; 53, s. 40-49
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Tidskriftsartikel (refereegranskat)abstract
- The prompt decay constant method and the area-ratio (Sjostrand) method constitute the reference techniques for measuring the reactivity of a subcritical system using Pulsed Neutron Source experiments (PNS). However, different experiments have shown that in many cases it is necessary to apply corrections to the experimental results in order to take into account spectral and spatial effects. In these cases, the approach usually followed is to develop different specific correction procedures for each method. In this work we discuss the validity of prompt decay constant method and the area-ratio method in the Yalina-Booster subcritical assembly and propose a general correction procedure based on Monte Carlo simulations.
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| 3. |
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| 4. |
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| 5. |
- Becares, V., et al.
(författare)
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Validation of ADS reactivity monitoring techniques in the Yalina-Booster subcritical assembly
- 2013
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Ingår i: Annals of Nuclear Energy. - : Elsevier BV. - 0306-4549 .- 1873-2100. ; 53, s. 331-341
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Tidskriftsartikel (refereegranskat)abstract
- The development of a reactivity monitoring system for subcritical reactors is a major task prior to industrial scale accelerator driven system (ADS) construction. Within the 6th European Framework Program, the IP-EUROTRANS project has performed a series of experiments at the Yalina-Booster subcritical assembly located at the Joint Institute for Power and Nuclear Research (JIPNR) of the National Academy of Sciences of Belarus, using a continuous (D, T) (fusion) neutron source in pulsed and continuous mode with short interruptions (beam trips). In this paper, the implementation and results of three different monitoring techniques intended to operate with continuous neutron sources will be presented, namely the source-jerk technique, the prompt decay constant technique and the current-to-flux technique. The results will be compared with the values of the reactivity obtained using the pulsed source in PNS experiments, discussed in detail in another paper.
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| 6. |
- Berglöf, Carl, et al.
(författare)
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Auto-correlation and variance-to-mean measurements in a subcritical core obeying multiple alpha-modes
- 2011
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Ingår i: Annals of Nuclear Energy. - : Elsevier BV. - 0306-4549 .- 1873-2100. ; 38:2-3, s. 194-202
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Tidskriftsartikel (refereegranskat)abstract
- Neutron noise measurements based on the Rossi-alpha and Feynman-alpha methodologies have been performed in a heterogeneous subcritical system. It is shown that the traditional single alpha-mode formulations of the Rossi-alpha and Feynman-alpha methods are not applicable due to the presence of higher alpha-modes. Formalisms taking into account multiple alpha-modes are applied resulting in satisfactory results. Three alpha-modes could be identified using the Rossi-alpha method, whereas only two could be obtained using the Feynman-alpha method. In the Feynman-alpha case, the possibility to obtain the fastest decaying alpha-mode was diminished due to detector dead time effects. It was found that the slowest decaying alpha-mode does not exactly correspond to the prompt decay found in pulsed neutron source measurements, which confirms the results of previous studies. Strengths and weaknesses of the multiple alpha-mode Rossi-alpha and Feynman-alpha methods observed in this study are pointed out.
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| 7. |
- Berglöf, Carl, et al.
(författare)
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Neutron noise measurements in the YALINA-Booster experiments
- 2009
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Ingår i: Proceedings of International Topical Meeting on Nuclear Research Applications and Utilization of Accelerators. - : International Atomic Energy Agency. - 9789201504104
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Konferensbidrag (refereegranskat)abstract
- In addition to the pulsed neutron source measurements and the continuous source beam-trip and current-to-flux measurements performed in the YALINA-Booster facility, also presented in this conference, a set of neutron noise measurements has been performed to achieve a complete characterization of the core. The neutron noise measurements have been performed in three different configurations covering a subcriticality range from 0.85 to 0.977. The Rossi-α neutron noise technique has been applied to detector counts from two channels in the thermal part of the core. The Rossi-α results are compared to the experimental prompt neutron decay constants obtained from the pulsed neutron source measurements. A first approach fitting procedure reveals a need of three exponentials to describe the Rossi-α histograms. It has been found that at deep subcriticality, the fundamental mode decay may coincide with or be close to a higher eigenmode, thus making it difficult to determine the prompt neutron decay constant correctly.
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| 8. |
- Berglöf, Carl, 1980-
(författare)
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On measurement and monitoring of reactivity in subcritical reactor systems
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Accelerator-driven systems have been proposed for incineration of transuranic elements from spent nuclear fuel. For safe operation of such facilities, a robust method for reactivity monitoring is required. Experience has shown that the performance of reactivity measurement methods in terms of accuracy and applicability is highly system dependent. Further investigations are needed to increase the knowledge data bank before applying the methods to an industrial facility and to achieve license to operate such a facility. In this thesis, two systems have been subject to investigation of various reactivity measurement methods. Conditions for successful utilization of the methods are presented, based on the experimental experience. In contrast to previous studies in this field, the reactivity has not only been determined, but also monitored based on the so called beam trip methodology which is applicable also to non-zero power systems. The results of this work constitute a part of the knowledge base for the definition of a validated online reactivity monitoring methodology for facilities currently being under development in Europe (XT-ADS and EFIT).
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| 9. |
- Berglöf, Carl, et al.
(författare)
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Pulsed neutron source reference measurements in the subcritical experiment YALINA-Booster
- 2009
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Ingår i: Proceedings of International Topical Meeting on Nuclear Research Applications and Utilization of Accelerators. - : International Atomic Energy Agency. - 9789201504104
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Konferensbidrag (refereegranskat)abstract
- In support of an online reactivity monitoring experiment, also presented in this conference, this work presents the reactivity calibration measurements performed with a pulsed neutron source in the coupled fast-thermal subcritical facility YALINA-Booster. These experiments reveal the complexity of experimentally obtaining a global reactivity from a highly heterogeneous core. Moreover, the effect of varying the source multiplication at constant reactivity on the area ratio technique is explored. It is found that the reactivity obtained with the area ratio technique carry strong spatial dependence, but it can be handled by calculated correction factors. On the other hand the method is showed not to be sensitive to changes in the source multiplication. It is also shown that the prompt neutron decay constant does not vary strongly over the core except at deep subcritical states.
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| 10. |
- Berglöf, Carl, et al.
(författare)
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Spatial and Source Multiplication Effects on the Area Ratio Reactivity Determination Method in a Strongly Heterogeneous Subcritical System
- 2010
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Ingår i: Nuclear science and engineering. - 0029-5639 .- 1943-748X. ; 166:2, s. 134-144
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Tidskriftsartikel (refereegranskat)abstract
- The area ratio method of Sjostrand is generally considered one of the most reliable reactivity determination methods and thus is a major candidate for off-line calibration purposes in future accelerator-driven systems for high-level waste incineration. In this work, the Sjostrand area ratio method has been evaluated experimentally under thorough conditions in the strongly heterogeneous subcritical facility YALINA-Booster. Both strengths and weaknesses of the method have been identified. Most surprisingly, it has been found that the area ratio reactivity estimates may differ a factor of 2 depending on detector position. It is also shown that this strong spatial dependence can be explained based on a simple two-region point-kinetics model and corrected by means of correction factors obtained through Monte Carlo simulations. A new Monte Carlo correction method is proposed that includes, at the same time, the spatial disturbance and the effective delayed neutron fraction. In that way, the value of the effective multiplication factor is obtained from the measured dollar reactivity without the need of calculating the effective delayed neutron fraction explicitly, and thereby, the delayed neutron transport is performed only once. Further, it has been found that the Sjostrand area ratio method is not sensitive to perturbations of the source multiplication factor.
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| 11. |
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| 12. |
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| 13. |
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| 14. |
- Fernandez-Ordonez, M., et al.
(författare)
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Reactivity determination techniques in ads systems for the incineration of radioactive wastes
- 2010
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Ingår i: International Conference on the Physics of Reactors 2010, PHYSOR 2010. - 9781617820014 ; , s. 2933-2945
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Konferensbidrag (refereegranskat)abstract
- The Subcritical Accelerator Driven Systems (ADS) have been proposed as one of the strategies for reducing the inventory and radiotoxicity of the spent nuclear fuel. The reactivity monitoring of ADS has been found to play a key role in the development of this technology. Although the current-to-power technique has been proposed as the main reactivity monitoring technique, it is necessary to periodically calibrate it using additional techniques. In this work, the standard reactivity monitoring techniques using Pulsed Neutron Source experiments have been evaluated in the coupled fast-thermal subcritical assembly YALINA-Booster. In addition, a new method to measure the absolute value of the system reactivity is proposed by using micro-interruptions of the continuous external neutron source (beam-trips). This technique, used for the first time in a subcritical core, provided results compatible with the standard PNS methods and can be used in future power ADS. Even more, to allow instantaneous reactivity checks, we have developed and tested the necessary electronic chains and data acquisition system to determine the system reactivity during a single beam trip, thus allowing the determination of the reactivity within a second.
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| 15. |
- Fernandez-Ordonez, M., et al.
(författare)
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Reactivity monitoring of a subcritical assembly using beam-trips and current-mode fission chambers : The YALINA-Booster program
- 2009
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Ingår i: Proceedings of International Topical Meeting on Nuclear Research Applications and Utilization of Accelerators. - : International Atomic Energy Agency. - 9789201504104
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Konferensbidrag (refereegranskat)abstract
- Transmutation of spent nuclear fuel in Accelerator-Driven Systems (ADS) is considered as a key technology for achieving sustainable nuclear energy. In the design of future ADS facilities, the reactivity monitoring system is of highest importance. An extensive experimental program devoted to reactivity monitoring of ADS has been carried out at the subcritical facility YALINA-Booster in the framework of IP-EUROTRANS. The main objective, besides the qualification of the reactivity monitoring techniques, has been to develop electronic chains that can be used in a full power ADS. For this purpose, YALINA-Booster couples a D-T neutron generator to a flexible zero-power subcritical assembly with a coupled fast-thermal neutron spectrum. The high intensity of the accelerator and the possibility to work in continuous or pulsed mode allowed the study of the current-to-flux relationship, beam-trip experiments and dedicated experiments for loading and start-up procedures. In addition, the experimental facility provided the opportunity to test electronic chains in current mode, which correspond to the most probable condition in a full power ADS. The experimental program has mainly been focused on the current-to-flux and beam-trip methodologies using detectors operating either in current or pulsed mode. However, in order to achieve the reference reactivity values of the different loading configurations, an extensive set of measurements based on pulsed neutron source techniques has been carried out. In addition, neutron noise measurements have also been performed. These studies are presented in separated papers within this conference. At present, the experimental campaign has been finished and, for the first time, the reactivity of a subcritical system has been measured within a single instantaneous beam trip (∼20 ms) using fission chambers operating in current mode. The necessary electronic chains to operate the fission chambers in this mode have been developed at CIEMAT. The preliminary results of our analysis show that the reactivity values obtained applying the Sjöstrand method and the slope-fit method using data from current-mode detectors are compatible with those obtained when using standard pulsed-mode detectors (presented also in this conference). The validity of the reactivity determination methods using fission chambers operating in current mode has been stated.
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| 16. |
- Muñoz-Cobo, José-Luis, et al.
(författare)
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Feynman-alpha and Rossi-alpha formulas with spatial and modal effects
- 2011
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Ingår i: Annals of Nuclear Energy. - : Elsevier BV. - 0306-4549 .- 1873-2100. ; 38:2-3, s. 590-600
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Tidskriftsartikel (refereegranskat)abstract
- Feynman-alpha and Rossi-alpha formulas including multiple alpha-modes are derived for stochastic and continuous neutron sources. The presented formalism is further developed to achieve spatial correction factors for the single alpha-mode point kinetics representations of the Feynman-alpha and Rossi-alpha formulas. As a natural extension of the multiple alpha-mode formalism, delayed neutrons are included in the Feynman-alpha formula. The obtained formulas are validated experimentally in a strongly heterogeneous system obeying multiple alpha-modes, resulting in good agreement with the presented theoretical framework.
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| 17. |
- Tesinsky, Milan, et al.
(författare)
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Comparison of calculated and measured reaction rates obtained through foil activation in the subcritical dual spectrum facility YALINA-Booster
- 2011
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Ingår i: Annals of Nuclear Energy. - : Elsevier BV. - 0306-4549 .- 1873-2100. ; 38:6, s. 1412-1417
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Tidskriftsartikel (refereegranskat)abstract
- Reaction rates were measured by the foil activation technique to obtain neutron spectrum information in a subcritical core driven by an external neutron source. The experimental results are compared with Monte Carlo calculations in order to examine the capability of the Monte Carlo code MCNP together with ENDFB-6.8. JEFF-3.1.1 and CENDL-3.1 neutron cross section libraries to predict the neutron spectrum dependent reaction rates correctly in a subcritical core. The focus lies on fast neutrons. A discrepancy is found in the calculated-to-experimental values of the reaction rates and an inaccurate cross section is identified in CENDL-3.1.
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| 18. |
- Villamarín, D., et al.
(författare)
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Current-to-flux experimental results in the YALINA-Booster subcritical assembly
- 2009
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Ingår i: Proceedings of International Topical Meeting on Nuclear Research Applications and Utilization of Accelerators. - : International Atomic Energy Agency. - 9789201504104
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Konferensbidrag (refereegranskat)abstract
- As a part of the IP-EUROTRANS experimental program at YALINA-Booster, presented in this conference, a set of measurements concerning the current-to-flux techniques has been performed. In a subcritical assembly coupled to an accelerator operating in continuous mode, the power of the reactor is related to the accelerator beam current and the external neutron source strength. It is generally assumed that by monitoring the ratio between the accelerator beam current and the neutron source intensity as well as the ratio between the neutron source intensity and the core power, any change in the system can be detected. With this methodology, changes in the system caused by reactivity transients can be isolated. However, it has been observed that this is only true for transients in the time scale of seconds. At CIEMAT, an acquisition system capable of monitoring the core power, the accelerator beam current and the neutron source intensity in the millisecond scale has been developed. It has been observed that, in these short time ranges, the proportionality relationship between these three quantities is not always fulfilled.
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