| 1. |
- Andersson, Mikael, 1986, et al.
(författare)
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Impact of Control Rod Position and Homogenization on Sodium Void Effect in CFV-type SFR
- 2016
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Ingår i: PHYSOR 2016. - 9781510825734 ; 4, s. 2658-2667
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Konferensbidrag (refereegranskat)abstract
- In complex innovative fast reactor concepts, fairly detailed core modeling is essential for reliable safety analysis during severe accident scenarios. The CFV core with its axially heterogeneous design, has a negative sodium void reactivity effect, a favorable feature wich increases the inherent system safety in case of sodium boiling. In this work, we studied the impact that the control rod homogenization model used, and the control rod position, have on the sodium void-reactivityeffect and the control rod worth, in the case of a voided CFV core. Three different control rodhomogenization models were studied, the traditional 2D equivalence procedure, and two models based on a 3D equivalence procedure, taking into account the axial heterogeneity of the CFV core.It was found that the impact of control rod homogenization has a negligible effect on the sodium void reactivity effect. However, between different control rod positions, a difference of up to 1$ in the sodium void reactivity effect was found, hence the control rod position has to be carefully considered when calculating the sodium void reactivity effect. For the control rod worth in a voidedCFV core, the traditional 2D procedure, could lead to discrepancies of up to 11% for control rod positions at the top of the core. These discrepancies could be much reduced by control rod homogenization with the 3D equivalence procedure. For the total control rod worth, all models andprocedures produced results within the desired error margin of 5%.
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| 2. |
- Chambon, Amalia, 1986, et al.
(författare)
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VALIDATION OF HORUS3D/N AGAINST TRIPOLI-4®D FOR CORE DEPLETION CALCULATION OF THE JULES HOROWITZ REACTOR
- 2016
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Ingår i: Proceedings of PHYSOR 2016: Unifying Theory and Experiments in the 21st Century, Sun Valley, Idaho, USA, May 1-5, 2016; Paper No. 15947. - 9781510825734 ; 1, s. 140-151
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Konferensbidrag (refereegranskat)abstract
- The international Jules Horowitz material testing Reactor (JHR) is under construction at CEA Cadarache research center, in southern France. Its first criticality is foreseen by the end of the decade. In order to perform JHR design and safety studies, a specific neutronics calculation tool, HORUS3D/N, based on the deterministic codes APOLLO2 and CRONOS2 and on the European nuclear data library JEFF3.1.1, was developed to calculate JHR neutronics parameters taking into account fuel depletion: reactivity, power distribution, control rod reactivity worth, etc. Up to now, the biases and uncertainties on the different neutronics parameters computed with HORUS3D/N were assessed, in particular, by comparing HORUS3D/N deterministic calculations with reference route calculations based on APOLLO2-MOC and TRIPOLI-4®. The use for JHR of the recent Monte-Carlo TRIPOLI-4® in its new Depletion mode (TRIPOLI-4®D) will also allow providing biases for the main neutronics parameters under fuel depletion conditions. These biases will give a quantitative estimation of the impact of the approximations of the flux calculation in the deterministic route. This paper presents a contribution to the validation of HORUS3D/N based on the first comparisons between the calculations performed with APOLLO2-MOC and CRONOS2, and the ones from TRIPOLI-4®D. The study is performed on 2-D calculations for two different clusters in an infinite lattice configuration. It focuses on the main parameters of interest: isotopic concentrations, plate power distributions, reactivity, as functions of burnup. The results obtained show reasonable discrepancies with APOLLO2 calculation and allow to be confident on the APOLLO2.8/REL2005/CEA2005 package recommendations developed by CEA for light water reactor studies used in HORUS-3D/N. In particular, the main fuel isotopes are well predicted with TRIPOLI-4®D with discrepancies values lower than -1.5%.
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| 3. |
- Demaziere, Christophe, 1973, et al.
(författare)
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Students' "resonance broadening" to teaching or how to improve students' learning using flipped classrooms
- 2016
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Ingår i: Proceedings of PHYSOR 2016: Unifying Theory and Experiments in the 21st Century, Sun Valley, Idaho, USA, May 1-5, 2016. - 9781510825734 ; 3, s. 1471-1482
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Konferensbidrag (refereegranskat)abstract
- In this paper, the effect of flipping the classroom on two courses in nuclear engineering is analyzed. These courses were previously given in a traditional campus-based format, before being converted to a flipped classroom format. One of the courses is in addition using a pure web-based set-up, in which the students and the teachers never meet face-to-face. In both courses, the students watch pre-recorded lectures, answer on-line quizzes, and provide feedback to the teachers on a voluntary basis, before attending wrap-up sessions and tutorials. Compared to the previous teaching format, the conversion to flipped courses resulted in in-creased student-teacher asynchronous and synchronous interactions, as well as enhanced understanding of the course concepts. These results are demonstrated both in a qualitative and a quantitative way. The qualitative analysis relies on the categorization of the questions received by the teachers using Bloom’s revised taxonomy for the cognitive domain and on the teachers’ perceptions of students’ understanding during the synchronous sessions. The quan-titative analysis relies on data provided by the learning management platform, by the asyn-chronous viewing system for the pre-recorded lectures, and by the synchronous viewing system (in the case of the web-based course). By flipping the classroom and using on-line quizzes, the students come much better prepared to the synchronous sessions, which, in itself, also results in increased interactions between the students and the teachers during such ses-sions. Another main advantage of this teaching format is the enhanced learning that results when students monitor their thinking and are actively involved in their own learning.
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| 4. |
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| 5. |
- Dykin, Victor, 1985, et al.
(författare)
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Void reactivity (Cmn) coefficients as indicators of boiling water reactor stability
- 2016
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Ingår i: Proceedings of PHYSOR 2016: Unifying Theory and Experiments in the 21st Century, Sun Valley, Idaho, USA, May 1-5, 2016. - 9781510825734 ; 6, s. 3571-3578
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Konferensbidrag (refereegranskat)abstract
- This paper presents the results of some investigations performed in the area of the stability of Boiling Water Reactors (BWRs). These systems are known to become unstable under certain conditions, and thus the development of different methods for the quantification of their stability properties is of prime importance. Preliminary studies with Reduced Order Models showed that the stability behavior of the system can be described in terms of so-called Cmn-coefficients. These coefficients represent the effect of a change in the void fraction on the eigenmodes of a nuclear core. It turned out that when these coefficients are positive, the system is clearly unstable because of the corresponding positive void feedback. On the other hand, in the case of negative Cmn-coefficients, it has been found, both using ROMs and dynamic core simulators like SIMULATE-3K, that the system becomes less stable for the Cmn coefficients becoming more negative. A thorough examination of the dependence of Decay Ratio on the Cmn coefficients using ROMs also demonstrated that there is a strong correlation between the DR and the Cmn coefficients what regards the stability properties of a BWR system. As a result, the estimation of the Cmn coefficients opens up the possibility of using such coefficients as a qualitative measure of core stability in a predictive manner. This could be used for instance as means to compare the relative stability of several core loadings without the need of running lengthy time-dependent three-dimensional core calculations, and could be of great help to nuclear engineers when designing nuclear cores. Therefore the main purpose of the paper is to investigate the possibility of using Cmn-coefficients as an alternative stability indicator for Boiling Water Reactors, as well as to determine their advantages and disadvantages as compared to the traditional Decay Ratio.
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| 6. |
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| 7. |
- Montalvo, C., et al.
(författare)
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First evidence of the pivotal motion ("tilting mode") of the core Barrel in the RINGHALS-4 PWR
- 2016
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Ingår i: Physics of Reactors 2016, PHYSOR 2016: Unifying Theory and Experiments in the 21st Century. - 9781510825734 ; 4, s. 2571-2579
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Konferensbidrag (refereegranskat)abstract
- The Division of Subatomic Physics and Plasma Physics (formerly Division of Nuclear Engineering) in Chalmers, Göteborg, and the Ringhals Nuclear Plant have investigated the core barrel vibrations in the Ringhals PWRs over the last 20 years. Based on the different symmetry properties of the vibration modes, a mode separation technique was developed to enhance the contributions from the different modes. Recent observations of wear at both the lower and upper core-barrel-support structures in the Ringhals PWRs indicated that vibration modes of the core barrel other than pendular (beam mode) and shell mode are likely to occur. A beam mode type movement alone is not able to explain such a wear, and therefore, it is fair to assume that the vibration mode in question is a small amplitude periodic tilting movement of the core barrel around a horizontal, diagonal pivot at the half height of the core. In this work, ex-core data taken in the Ringhals-4 PWR were analyzed in order to find evidence of such a tilting movement. First, cross spectra between various ex-core detectors were calculated and analyzed to locate the frequency range of the new vibrational mode. Then, a model based on symmetry considerations was derived in order to extract the sought mode from the spectra. The measurements were evaluated by the new mode enhancement technique. The results show that it is possible to enhance such a mode and find it in the spectra by properly combining the signals in the time domain.
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| 8. |
- Tesinsky, M., et al.
(författare)
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Validation of the hem and moody critical flow models in polca-T
- 2016
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Ingår i: Physics of Reactors 2016, PHYSOR 2016. - : American Nuclear Society. - 9781510825734 ; , s. 2724-2732
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Konferensbidrag (refereegranskat)abstract
- The Homogeneous Equilibrium Model (HEM) and Moody critical flow models implemented in POLCA-T are validated against the Marviken experiments, which is necessary for qualification of the code for simulations of the hypothetical loss-of-coolant accident. Seven Marviken cases covering a range of initial conditions are simulated and the POLCA-T results are compared to the experimental data and to other similar codes including GOBLIN, RELAP5 and TRACE. Sensitivity studies are performed with respect to nodalisation and initial conditions. The HEM model predicts the break flow accurately with an uncertainty mostly below 20 %. The largest uncertainties are found for small exhaust pipe diameter and initial conditions far from saturation. The results could be improved by finer nodalisation and an extrapolation of the initial temperature profile inside the exhaust pipe. The Moody model is conservative in the 2-phase region, where it overpredicts the break flow as it should. The overprediction is smaller compared GOBLIN, so the conservatism is reduced.
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