Centrale nucléaire

Résumé

Une centrale nucléaire est un site industriel destiné à la production d'électricité, comprenant un ou plusieurs réacteurs nucléaires. La puissance électrique d'une centrale varie de quelques mégawatts à plusieurs milliers de mégawatts en fonction du nombre et du type de réacteur en service sur le site. L'énergie d'une centrale nucléaire provient de la fission de noyaux d'atomes lourds. Celle-ci dégage de la chaleur, qui sert dans un premier temps à vaporiser de l'eau, comme dans toute centrale électrique thermique conventionnelle, puis la vapeur d'eau produite entraîne en rotation une turbine accouplée à un alternateur qui produit à son tour de l'électricité. C'est la principale application de l'énergie nucléaire dans le domaine civil. On compte, dans le monde, environ nucléaires qui ont produit 10 % de l'électricité mondiale en 2020. Ces centrales comptent en un total de opérationnels, dont japonais en attente d'autorisation de redémarrage. Leur puissance atteint ( en moyenne p

Source officielle

https://fr.wikipedia.org/wiki/Centrale_nucl%C3%A9aire

À propos de ce résultat

Cette page est générée automatiquement et peut contenir des informations qui ne sont pas correctes, complètes, à jour ou pertinentes par rapport à votre recherche. Il en va de même pour toutes les autres pages de ce site. Veillez à vérifier les informations auprès des sources officielles de l'EPFL.

Publications associées (100)

Publications associées

Chargement

Personnes associées (33)

Personnes associées

Chargement

Unités associées (16)

Afficher plus

Unités associées

Chargement

Concepts associés (119)

Concepts associés

Chargement

Cours associés (49)

Cours associés

Chargement

Séances de cours associées (116)

Afficher plus

Séances de cours associées

Chargement

The calculations performed for the design and operation of a Nuclear Power Plant (NPP) are a key factor for their safety analyses. The standard for the computational analysis of NPPs is the so called conventional approach, which relies on coarse mesh diffusion for the neutronic solver and 1D channels for the T/H solver. The recent evolution of computing clusters allows the use of a novel approach, with codes performing first-principle based multi-physics simulations with high-resolution of the calculated parameters. Due to their computational cost, these methods can only be used as an audit tool of the conventional approach. In recent years, the nuclear industry has moved towards the establishment of Best Estimate Plus Uncertainty safety limits. The novel approach is a step forward to that direction. At the same time, VVER technology is expanding, with new reactors being built worldwide. However, there is currently no high-resolution tool available for VVER steady state and cycle analysis. There is a clear need for more refined simulation tools capable of handling hexagonal geometries.The goal of this PhD is the development of a novel computational scheme based on the 3D sub-pin neutron transport code nTRACER-FAST (nTF), coupled to the sub-channel code COBRA-TF (CTF) for VVER full core steady state and cycle analysis. The coupling of a neutronic code with sub-pin resolution to a sub-channel T/H solver, as well as the use of CTF for full core VVER sub-channel analysis are one of the main novelties of this work, to the extent of the writer's knowledge. In this thesis, nTF is verified & validated for VVER 3D core standalone neutronic calculations against data published in international benchmarks. The internal sub-pin coupling of nTF to CTF for hexagonal geometries is fully developed on the course of this study. A double domain decomposition scheme that allows both codes to be executed in parallel is designed. The multi-physics core solver is verified for steady state simulations. nTF/CTF is also compared with nTF using a simplified 1D T/H solver, proving that to achieve accurate predictions, computational tools of different fidelity should not be mixed. Finally, nTF/CTF is developed for 3D full core cycle analysis. The coupled code system is validated with experimental data, achieving the target accuracy set for industrial use. The capability of the solver for sub-pin predictions throughout the depletion cycle is demonstrated.A conventional computational route for VVER analysis, built with CASMO5-VVER as a lattice code for the nodal neutronic solver PARCS, is also established. The use of PARCS with CASMO5-VVER is another novelty of the present work. CASMO5-VVER/PARCS is verified and validated for VVER standalone neutronic and multi-physics steady state simulations and cycle analysis. The modeling options that optimize the use of the code system and the generation of CASMO5-VVER cross-sections for PARCS are described. The comparison of the novel and conventional computational routes demonstrates the accuracy enhancement enabled by the high-resolution core solver, during steady state and depletion calculations. The work performed during this thesis also showed that the nTF/CTF computational requirements are manageable for VVER cycle analysis, when a state-of-the-art computing cluster is used. This illustrates that such high fidelity, high-resolution computational scheme can be used as an audit tool for the conventional route.

EPFL2022

Chargement

The formation and growth of cracks by irradiation assisted stress corrosion cracking (IASCC) in light water reactor internals is a critical issue for a safe long-term operation of nuclear power plants. The IASCC susceptibility at relatively low dose is dominated by conventional mechanisms such as radiation-induced segregation and radiation hardening. However, the ageing of the nuclear fleet combined with the increase of their life-span reveals other mechanisms that could play an important role on IASCC susceptibility. Recent studies show that a huge amount of helium (He) can be accumulated in reactor internal components of pressurized water reactors (PWR) after long-term operation. This occurrence could significantly increase the IASCC susceptibility at high doses. The main objective was to investigate the He effects on IASCC susceptibility of the solution-annealed (SA) and 20% cold-worked (CW) austenitic steel 316L. SA and CW miniaturized tensile samples and a SA plate were homogeneously implanted up to 1000 appm He. He was implanted at ~45 MeV and 300°C at the cyclotron in CEMHTI/CNRS (France). Slow strain rate tests (SSRT) in air and in high-temperature water were then carried out on SA, CW, post-implantation annealed (PIA) and as-implanted samples; instrumented nanoindentation tests were performed at room temperature on non-implanted and implanted specimens; and scanning electron microscope and transmission electron microscope were employed for fractography and microstructural characterization. The results of SSRTs in high-temperature air and in hydrogenated high-temperature water showed that homogenized implanted He up to 1000 appm corresponding to a displacement damage of about 0.16 dpa (displacement per atom) does not produce intergranular cracking and IASCC. However, the deformation microstructure of non-implanted SA/CW is characterized by high dislocation density arranged in cell walls separated by relatively dislocation-free regions, while the as-implanted SA samples (> 0.05 dpa) exhibit a more planar deformation microstructure. Characterization of as-implanted CW and PIA samples did not show any significant implantation effect on the deformation microstructure. PIA of the He implanted plate was carried out from 650 to 1000°C for 1h to increase the helium grain boundary coverage, and to reproduce the observed microstructure of the replaced reactor internal components that showed IASCC and use the results for the PIA of tensile samples. The transmission electron microscope investigations showed that an increase of the annealing temperature causes an average bubble size increase and density decrease. The average He bubble size and distribution in the grain interior and on the grain boundary were similar in the range of temperatures studied. In both cases, bubbles grew by the Ostwald ripening mechanism. No preferential He build-up took place on the grain boundaries. The increase of yield stress produced by He bubbles was calculated with three distinct dislocation-localized obstacle and compared to the tensile test results. The bubble strength estimated for these models was used to assess their validity and to compare the results to published data. Finally, nano-indentation tests in SA, CW, as-implanted SA and PIA (650 to 850°C for 1h) samples did not show He effects on grain boundaries strength. However, the average hardness of the grain interior increased with the He implantation and decreased increasing the PIA temperature.

EPFL2018

Chargement

Thermo-economic optimisation of a tower/trough combination solar power plant

Jorge López Moreno

Today a crude oil barrel has five times the prize it had fifteen years ago, moreover, we have increased our global energy consumption by almost 40 percent since then and population growing rates are higher than ever before. In addition, recent tragic events in Fukushima nuclear power plant, Japan, earlier this year, have increased concerns even more about energetic schemes based on nuclear energy. This challenging energetic context requires rapid, economically feasible and reliable progress in the field of renewable energies. We have the great responsibility today of building the energetic scheme of tomorrow. Amongst renewable energies, thermal solar energy has already proven both reliable and competitive with adequate feed-in tariffs and offers some key advantages such as the possibility to store the energy as well as the good controllability of the transformed energy, which entails a great connectivity to the grid. The goal of this project is to perform a thermo-economic analysis and optimization of a solar thermal power plant combining both a tower and parabolic trough power plants and to find out whether or not the combination of these two (with different temperature levels) is advantageous from an energetic or an economic point of view. This idea is fairly innovative and no previous studies have been found on this particular research line. A new, detailed model has been developed for the trough power plant not only for the thermal side but also for the hydraulic and economical side. This model has been then combined with an existing model for the tower power plant. Afterwards, a performance analysis and a multi-objective optimization of the combination have been carried out. Energetic integration, modelling of the power cycles and multi objective optimization all have been performed using LENI tools to analyze and optimize energetic systems such as Energy Technologies and MOO. Trough – tower combination solar power plants present several advantages both from an energetic and economic perspective. Combination power plants feature important efficiency gains compared to either the tower or the trough power plant individually. This efficiency gain comes from the sake of combining both types of power plants, allowing better cycle efficiencies. Efficiency of these combined trough- tower power plants can reach 18.7% (solar to electricity) for certain combinations, with a levelised energy cost of 15 UScts/kWh. Other interesting combinations have been pointed out, for instance, an 80 MW combined power plant, with an efficiency of 16.9% and a levelised energy cost of 8.8 UScts/kWh which is fairly impressive compared to the current solar thermal power plants. Many different interesting combinations can be imagined, each one offering particular advantages. This project confirms that trough – tower combination, when properly integrated, result into more efficient, with a lower levelised energy cost with respect to tower schemes and larger power plants than either tower or trough schemes separately. This new possibility definitely contributes to make solar thermal power an even more promising and interesting technology.

2011

Chargement

Thermo-economic optimisation of a tower/trough combination solar power plant

Jorge López Moreno

2011

EPFL2018

EPFL2022