This paper focuses on the development of a new computational model of the CNESTEN’s TRIGA Mark II researchreactor using the 3D continuous energy Monte-Carlo code TRIPOLI-4 (T4). This new model was ...developed toassess neutronic simulations and determine quantities of interest such as kinetic parameters of the reactor,control rods worth, power peaking factors and neutron flux distributions. This model is also a key tool used toaccurately design new experiments in the TRIGA reactor, to analyze these experiments and to carry out sensitivityand uncertainty studies. The geometry and materials data, as part of the MCNP reference model, were usedto build the T4 model. In this regard, the differences between the two models are mainly due to mathematicalapproaches of both codes. Indeed, the study presented in this article is divided into two parts: the first part dealswith the development and the validation of the T4 model. The results obtained with the T4 model were comparedto the existing MCNP reference model and to the experimental results from the Final Safety Analysis Report(FSAR). Different core configurations were investigated via simulations to test the computational model reliabilityin predicting the physical parameters of the reactor. As a fairly good agreement among the results wasdeduced, it seems reasonable to assume that the T4 model can accurately reproduce the MCNP calculated values.The second part of this study is devoted to the sensitivity and uncertainty (S/U) studies that were carried out toquantify the nuclear data uncertainty in the multiplication factor keff . For that purpose, the T4 model was used tocalculate the sensitivity profiles of the keff to the nuclear data. The integrated-sensitivities were compared to theresults obtained from the previous works that were carried out with MCNP and SCALE-6.2 simulation tools anddifferences of less than 5% were obtained for most of these quantities except for the C-graphite sensitivities.Moreover, the nuclear data uncertainties in the keff were derived using the COMAC-V2.1 covariance matriceslibrary and the calculated sensitivities. The results have shown that the total nuclear data uncertainty in the keff isaround 585 pcm using the COMAC-V2.1. This study also demonstrates that the contribution of zirconium isotopesto the nuclear data uncertainty in the keff is not negligible and should be taken into account when performingS/U analysis.
This article presents the preliminary characterization of a new reduced-height CALORRE differential calorimeter designed by Aix Marseille University and fabricated in order to be tested and qualified ...under irradiation in the Massachusetts Institute of Technology Research Reactor (MITR) experimental reactor within the framework of the CALOR-I program. This article begins by focusing on the preparation of the irradiation campaign, providing a concise description of the MITR core, the water loop facility, and the newly fabricated differential calorimeter. Then, this work summarizes neutronic calculations performed for the CALORRE differential calorimeter to provide data for the irradiation campaign. MCNP calculation code was used to predict the neutron and gamma flux spectra, and total nuclear heating rate to the components of the calorimeter in a variety of positions. The MCNP model parameters and methodology are detailed, and results are used to perform 3-D thermal modeling. Estimation of the response of the calorimeter calculated under real conditions considering local heat sources determined by the NRL of the Massachusetts Institute of Technology (MIT) using MCNP code is given. Next, this article presents the experimental characterization conducted under laboratory conditions. This section includes a detailed presentation of the updated experimental setup and the key metrological characteristics of the sensor response obtained from the experimental results. In conclusion, this article offers some final remarks and prospects to realize the irradiation campaign successfully.
The National Center for Energy, Sciences and Nuclear Techniques (CNESTEN)'s Training Research and Isotope Production General Atomics (TRIGA) Mark II is a pool-type light water moderated and cooled ...research reactor operating at a maximum steady state thermal power of 2 MW. The reactor was designed to be used as a training facility for reactor operators, neutron activation analysis, isotopes production, and for implementing different reactor physics experiments. This article deals with the numerical and experimental characterization of reaction rates (RRs) in different irradiation channels inside the CNESTEN's TRIGA Mark II research reactor, located in Rabat/Morocco. The main objective of this study is to validate the calculated neutron RRs against the measured ones and to prove that the new TRIPOLI-4 model of the reactor is capable to reproduce the measured quantities. Therefore, the measurements were carried out using the neutron activation technique and gamma spectrometry measurements. Preliminary simulations were performed with TRIPOLI-4 transport Monte Carlo code to establish the experimental design and set up for activation foils experiments. The selected set of foils with known characteristics were irradiated, at different power levels, inside the irradiation facilities of the TRIGA reactor. The resulting activities were evaluated via <inline-formula> <tex-math notation="LaTeX">\gamma </tex-math></inline-formula> spectrometry measurements. Normalized calculated and measured RRs were compared, and a good agreement was shown for most nuclides, which indicates that the new detailed TRIPOLI-4 model of the TRIGA reactor can accurately predict the relative experimental RRs values. Further work is ongoing to analyze absolute RR values, as well as to carry measurements in other irradiation channels.
Radiation detectors based on wide-bandgap semiconductors have received considerable attention in many applications such as the experiments in material testing reactors, high energy particle physics ...experiments, or fusion facilities for plasma diagnostics. In this paper, we compared a 4H-silicon-carbide (SiC)-based detector with a single crystal chemical vapor deposited (sCVD) diamond-based detector for 14-MeV neutron detection. For this purpose, the deuterium- tritium neutron generator of Technical University of Dresden with 14-MeV neutron output up to 10 11 n/sin 4π has been used. In this paper, we interpret the results of our first measurements with both 4H-SiC and sCVD diamond detectors at low neutron flux of 9.4 × 10 6 n/(cm 2 · s) and at room temperature.
This article reviews the work to date on the CALOrimeter with Radial thermal transfers for nuclear REactors (CALORRE) differential calorimeter patented by Aix-Marseille University (AMU) and the ...French Alternative Energies and Atomic Energy Commission (CEA) in 2015. The article presents the results obtained with the first prototype of the CALORRE calorimeter qualified under real conditions during an irradiation campaign in the MARIA reactor in 2015, including previously unpublished details. Then, studies of different CALORRE calorimetric cells characterized by experiments under laboratory conditions are described. Several configurations were studied to determine the influence of cell height, horizontal fin geometry, and structural material composition on calorimeter response. These calculations provide for a calibration protocol by generating a heat source inside each cell, with evaluation of linearity, sensitivity, range, reproducibility, response time, and absolute temperatures. Finally, within the framework of a new research program called Compact-CALORimeter Irradiations inside the MIT research reactor (CALOR-I) and financed by AMU Foundation (A*Midex), a design optimization of the calorimeter assembly was carried out in order to remove contact thermal resistances and provide a new very compact CALORRE calorimeter suited for the in-core water loop of the Massachusetts Institute of Technology (MIT) reactor (2 <inline-formula> <tex-math notation="LaTeX">\text{W}\cdot \text{g}^{-1} </tex-math></inline-formula> peak nuclear heating rate). The response of this new very compact calorimeter is estimated using 3-D numerical thermal simulations under real conditions.
The Jules Horowitz Reactor, a new material testing reactor, is currently under construction on the CEA Cadarache site (in the South of France). A nuclear heating rate unequaled in Europe will be ...provided: 20 W.g −1 for a nominal thermal power of 100 MW. There is no differential calorimeter in the state of the art that measures such a nuclear heating rate. This article presents a new differential calorimeter configuration dedicated to this very high nuclear heating rate. On the one hand, the chosen configuration is validated and calibrated experimentally under laboratory conditions by using a new heating system, allowing the application of a wide range of electrical power never tested in the literature and ten times higher compared to that commonly used. Then the calorimetric cell response is estimated under real conditions with an analytical model. Finally, 3-D thermal numerical simulations of the whole calorimeter are performed under real conditions. Some parameters, such as the size of the cell, the intercell space, and the nature of the sample, are tuned to propose a very compact differential calorimeter.
Neutron radiation detector for nuclear reactor applications plays an important role in getting information about the actual neutron flux. Such a detector must be able to operate at high neutron flux ...levels (>10 9 cm −2 s −1 ) and discriminate the neutron and gamma responses in the nuclear reactor's mixed neutron-gamma environment. Silicon carbide and diamond are the most attractive semiconductor materials for neutron detection, thanks to their outstanding properties, such as high displacement threshold energy and wide bandgap energy, which allow them to operate in high radiation levels and high temperature. The aim of this article is to compare the ability to detect thermal neutrons of these two semiconductors at the same irradiation conditions. For this purpose, the neutron irradiation tests of detectors were implemented at MINERVE research reactor at CEA Cadarache. The 4H-silicon carbide (SiC) p + n diode has demonstrated better neutron-gamma discrimination at 0-V bias voltage than at −200 V which is explained by its increased sensitivity to gamma photons at −200 V caused by a wider charge collection region than at 0 V. Therefore, it is preferable to use the 4H-SiC p + n diode without an external electric field for applications in the mixed neutron-gamma environment such as nuclear reactor environment. The results show that the single-crystal chemical vapor-deposited (sCVD) diamond-based detector has better neutron to gamma discrimination, thanks to the use of 6 Li as a neutron converter instead of 10 B. However, the study of the radiation stability of detectors showed that the sCVD diamond-based detector suffers from the "polarization effect" when it operates at a high neutron flux (~10 9 cm<inline-formula> <tex-math notation="LaTeX">^{-2}\,\,\cdot \,\,\text{s}^{-1} </tex-math></inline-formula>).
This paper presents experimental and theoretical studies of a new compact calorimetric cell under laboratory conditions. Producing a reduced-size calorimetric cell, intended to be used to quantify ...the nuclear heating rate inside material testing reactors by differential calorimetry, is a major challenge and offers new complementary measurement prospects. The new compact design, called CALOrimeter with radial thermal transfers for nuclear REactors, is obtained with a special geometry favoring heat transfers in the radial direction in order to decrease the height of the sensor. Results obtained during a crucial preliminary step corresponding to out-of-pile calibration without nuclear rays are presented and compared with those of three different configurations. The influence of different parameters, such as a specific area of the cell structure, fluid temperature and velocity, and the nature of the material of the cell structure, is shown and analyzed with a 1-D thermal model coupling conductive and radiative thermal exchanges. Comparisons of different configurations and conditions lead to a discussion of the advantages of this new compact design.
This work summarizes neutronic calculations performed for the CALORRE differential calorimeter specifically designed by Aix Marseille University to inform the irradiation campaign planning for ...testing in MITR within the framework of the CALOR-I research program. MCNP software was used to predict the neutron and gamma flux spectrum, and total nuclear heating rate to the components of the calorimeter in a variety of positions. Results were compared to evaluate spatial bias, core loading effects, optimization for axial position, and provide input data for thermal multi-physics modelling.
This paper presents the study of a new innovative heat flow single-cell calorimeter dedicated to the measurement of the nuclear heating rate in research reactors. Before irradiating this type of ...sensor, it is necessary to characterize it under laboratory conditions to determine its metrological properties.
A general description (design, geometry and materials nature) of this new calorimeter will be given, focusing on the motivations that led to its development. This part will be followed by a presentation of the experimental set-up and operating protocol used to characterize this sensor. The sensor sensitivity and response time will be quantified and discussed with a comparison of those obtained with previous calorimeters. In parallel with these experimental characterizations, parametric 3-D numerical simulations will be carried out using COMSOL Multiphysics software. These results, obtained both experimentally and numerically, will be compared to present a complete calorimeter study under laboratory conditions.
