In this paper, we apply the so-called generalized empirical interpolation method (GEIM) to address the problem of sensor placement in nuclear reactors. This task is challenging due to the ...accumulation of a number of difficulties like the complexity of the underlying physics and the constraints in the admissible sensor locations and their number. As a result, the placement, still today, strongly relies on the know-how and experience of engineers from different areas of expertise. The present methodology contributes to making this process become more systematic and, in turn, simplify and accelerate the procedure.
•An application of GEIM to optimize sensor locations in nuclear reactors taking into account restrictions on the location of the sensors.•Rapid reconstruction of fast flux and nuclear power using a reduced basis and thermal flux measurements.•A physically coherent sensor placement with the structure of the neutronic flux in the reactor core.
New measurements of fusion cross sections at deep sub-barrier energies for the reactions 16O+{204,208}Pb show a steep but almost saturated logarithmic slope, unlike 64Ni-induced reactions. Coupled ...channels calculations cannot simultaneously reproduce these new data and above-barrier cross-sections with the same Woods-Saxon nuclear potential. It is argued that this highlights an inadequacy of the coherent coupled channels approach. It is proposed that a new approach explicitly including gradual decoherence is needed to allow a consistent description of nuclear fusion.
The goal of this paper is to identify the parameter set of a given electrical machine. The identification method is based on data assimilation coupled with the finite-element method. Data ...assimilation method is an optimization approach that limits the space of candidate parameter sets by centering it on those of the ideal machine. An application to an electrical machine is presented based on the analysis of flux sensor signals. The methodology is validated using twin experiments that consider simulated data and tested considering the measurements extracted from the real alternator.
•We present a computational scheme for the determination of reflector properties in a PWR.•The approach is based on the minimization of a functional.•We use a data assimilation method or a parametric ...complementarity principle.•The reference target is a solution obtained with the method of characteristics.•The simplified flux solution is based on diffusion theory or on the simplified Pn method.
This paper presents a computational scheme for the determination of equivalent 2D multi-group spatially dependant reflector parameters in a Pressurized Water Reactor (PWR). The proposed strategy is to define a full-core calculation consistent with a reference lattice code calculation such as the Method Of Characteristics (MOC) as implemented in APOLLO2 lattice code. The computational scheme presented here relies on the data assimilation module known as “Assimilation de données et Aide à l’Optimisation (ADAO)” of the SALOME platform developed at Électricité De France (EDF), coupled with the full-core code COCAGNE and with the lattice code APOLLO2. A first code-to-code verification of the computational scheme is made using the OPTEX reflector model developed at École Polytechnique de Montréal (EPM). As a result, we obtain 2D multi-group, spatially dependant reflector parameters, using both diffusion or SPN operators. We observe important improvements of the power discrepancies distribution over the core when using reflector parameters computed with the proposed computational scheme, and the SPN operator enables additional improvements.
Isotopic effects in the fragmentation of excited target residues following collisions of 12C on (112,124)Sn at incident energies of 300 and 600 MeV per nucleon were studied with the INDRA 4pi ...detector. The measured yield ratios for light particles and fragments with atomic number Z < or = 5 obey the exponential law of isotopic scaling. The deduced scaling parameters decrease strongly with increasing centrality to values smaller than 50% of those obtained for the peripheral event groups. Symmetry-term coefficients, deduced from these data within the statistical description of isotopic scaling, are near gamma = 25 MeV for peripheral and gamma < 15 MeV for central collisions.
A new dynamical cascade code for decaying hot nuclei is proposed and specially adapted to the synthesis of super-heavy nuclei. For such a case, the interesting channel is of the tiny fraction that ...will decay through particles emission, thus the code avoids classical Monte-Carlo methods and proposes a new numerical scheme. The time dependence is explicitely taken into account in order to cope with the fact that fission decay rate might not be constant. The code allows to evaluate both statistical and dynamical observables. Results are successfully compared to experimental data.
Multifragmentation of a "fused system" was observed for central collisions between 32 MeV/nucleon 129Xe and (nat)Sn. Most of the resulting charged products were well identified due to the high ...performances of the INDRA 4pi array. Experimental higher-order charge correlations for fragments show a weak but nonambiguous enhancement of events with nearly equal-sized fragments. Supported by dynamical calculations in which spinodal decomposition is simulated, this observed enhancement is interpreted as a "fossil" signal of spinodal instabilities in finite nuclear systems.
Kinetic energy spectra and fragment velocity correlations, simulated by means of stochastic mean-field calculations, are successfully confronted with experimental data for single multifragmenting ...sources prepared at the same excitation energy per nucleon in 32
A MeV
129Xe
+
natSn and 36
A MeV
155Gd
+
natU central collisions. Relying thus on simulations, average freeze-out times of 200–240 fm/
c are estimated. The corresponding spatial distributions of fragments are more compact for the lighter system (
∼
3
–
4
V
0
vs.
∼
8
V
0
).
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