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[en] The plate type IHX is the most challenging component for ANTARES due to the high temperature of helium at the core outlet (from 850 deg. C to 1000 deg. C). It is indeed a first of the kind as there is no past experience in nuclear or outside nuclear industries of such a component. It requires high performance materials and high technology manufacturing processes. It is also a key component regarding the efficiency and competitiveness of the plant. Then, an intensive work program was launched in AREVA NP in order to develop this component. Different units of AREVA NP and external organisations (R and D and industrials) are involved in this development. Collaboration agreements defining the framework and the rights of each partner were elaborated when necessary. Several potential technologies are investigated in parallel with the objective to select the best one before the end of 2008. This selection will be based on design studies, cost assessment, risk assessment and technological assessment including the realisation and tests of representative mock ups. These technologies are: - Plate Machined Heat Exchanger (PMHE) with CEA and EDF; - Plate Fin Heat Exchanger (PFHE) with industrials like Nordon, Brayton Energy; - Tubular concept. Plate type IHX, which is more compact but more challenging, is the reference concept for the conceptual design phase of ANTARES but tubular concept is also investigated as a fall back solution. It must be also noted that generic R and D on high temperature materials is in progress. It includes in particular creep, corrosion and nitriding tests on samples. Two alloys were selected (230 and 617) and the final selection of one alloy is planned for the end of 2006. PMHE is one of the most promising technologies. The plates are machined by high speed machining or electro chemical etching. First machining tests performed by the AREVA NP technical centre in Chalon are encouraging but the geometry of the drills still have to be optimised in order to increase the lifetime of the tools. The assembly process of the plates is based on HIP process or uni-axial diffusion bonding. CEA is in charge of the optimisation of the process parameters at the lab scale and AREVA NP is in charge of the industrialisation of the process. First tests showed the importance of the surfaces preparation prior to bonding. Most of the design studies (safety, thermo-mechanical, thermo-hydraulic analyses and integration of the IHX modules within the pressure vessel) are performed by AREVA NP with the support of CEA.. PFHE is a well known technology outside the nuclear field (cryogenic and automotive systems). It is developed for ANTARES in partnership with some industrials. The French company Nordon proposed a concept based on serrated offset strip fins which are assembled onto flat support plates by brazing. This concept is developed from existing Nordon know how and its experience of this technology but for lower temperature application (mainly aluminium materials). Another PFHE technology is also investigated with Brayton Energy (US company). It is based on wavy fins assembled on flat support plates by brazing. One feature of this concept is the modular assembly of independent cells which leads to a higher flexibility of the modules under thermal loads. Usual tubular concept (diameter around 20 mm) is investigated by AREVA NP. This concept is based on helical tubes bundles similar to the previous designs proposed in Germany for indirect cycle HTR MODULE or in Japan for HTTR. (authors) 188
[en] The presented study was carried out within the Work Package 2 'Recuperator' of the High Temperature Reactor-E European program. High Temperature gas cooled Reactor concepts with a direct cycle have become potentially interesting for the future. Theoretically, these concepts provide higher efficiency than a classical steam cycle. Within the Brayton cycle the helium/helium recuperator, required to achieve the high efficiency, has to work under very harsh conditions (temperature, pressure, and pressure difference between circuits). Within the project the most promising technologies for the compact recuperator were investigated. First, the requirements for the recuperator to operate under the direct Brayton cycle have been defined. Based on these requirements the various potential technologies available on the market have been investigated. Two particular technologies (HEATRIC Printed Circuit Heat Exchanger, NORDON plate fin concept) have been selected as most promising. For the former, a precise description has been given and a mock-up has been fabricated and tested in the Claire loop at CEA. In the Claire loop the Printed Circuit Heat Exchanger mock-up has been subjected to thermal shocks, which are considered to be representative for a recuperator. Prior to the experimental testing coupled Computational Fluid Dynamic (CFD) and Finite Element analyses have been performed to give insight into the thermal and mechanical behaviour of the mock-ups during the thermal shock. Based on these results the experimental measuring program has been optimized. Upon completion of the tests the experimental and numerical results have been compared. Based on the results from the investigation performed recommendations are given for the full-size recuperator using the selected technologies
[en] The diagnosis of heat exchangers on duty with respect to flow mal-distributions needs the development of non-intrusive inlet-outlet experimental techniques in order to perform an online fault diagnosis. Tracer experiments are an example of such techniques. They can be applied to mono-phase heat exchangers but also to multi-phase ones. In this case, the tracer experiments are more difficult to perform. In order to check for the capabilities of tracer experiments to be used for the flow mal-distribution diagnosis in the case of multi-phase heat exchangers, we present here a preliminary study on the simplest possible system: two-phase flows in a horizontal tube. 81mKr is used as gas tracer and properly collimated NaI (TI) crystal scintillators as detectors. The specific shape of the tracer response allows two-phase flow regimes to be characterized. Signal analysis allows the estimation of the gas phase real average velocity and consequently of the liquid phase real average velocity as well as of the volumetric void fraction. These results are compared successfully to those obtained with liquid phase tracer experiments previously presented by Oriol et al. 2007. Characterization of the two-phase flow regimes and liquid dispersion in horizontal and vertical tubes using coloured tracer and no intrusive optical detector. Chem. Eng. Sci. 63(1), 24-34, as well as to those given by correlations from literature
[en] The thermal solar energy production is a promising and strongly growing sector. However, these technologies must be integrated to electric power systems, i.e. coupled with fossil-fired or biomass-fired plants, and the energy must be stored. This production can be either centralised or decentralised: this corresponds to different situations, different markets, different technologies and equipment (rows of mirrors to concentrate solar heat on a tube, linear Fresnel reflectors to concentrate solar heat on a tube, heliostats or mirrors which concentrate heat at the top of a tower, and parabolic disks which produce electricity with a Stirling gas engine at their focal point). This road-map focuses on electric power generation, and discusses key variables of the present market, proposes a vision for 2050, identifies objectives to be reached by 2015, and barriers to be removed, outlines the needs of demonstrators and their administrative framework.
[en] This special issue of Clefs CEA journal examines CEA's involvement and achievements in the field of low-carbon energies. Content: 1 - Foreword; 2 - The power of the concept of energy; 3 - Searching for the ideal energy mix; 4 - Electrical energy and CO2 emissions; 5 - The nuclear sector post-Fukushima; 6 - The nuclear life cycle: the nuclear fuel cycle, Cleanup and dismantling of nuclear facilities; 7 - Astrid, Generation IV advanced sodium technological reactor for industrial demonstration; 8 - Fusion, an energy source for the future; 9 - Photovoltaic solar energy: Photovoltaic technologies and centralized electricity production, Decentralized electricity production - solar energy integrated into the building, Concentration photovoltaic; 10 - Concentrated solar power - the other alternative for electricity production: Concentrating the Sun's energy, The promise of thermal storage; 11 - 2. generation biofuels: the Syndiese project; 12 - Microalgae for the production of biofuels; 13 - Areas of R and D at CEA for developing economically and socially viable low-carbon energies; 14 - Energy in batteries: Batteries for electrical mobility, Batteries for stationary applications, Optimizing lithium battery safety; 15 - Hydrogen, an inexhaustible energy carrier: Storage of hydrogen, Hydrogen - a means of storing electricity; 16 - Smart grids - when electrical grids become intelligent; 17 - Solar mobility; 18 - Green chemistry, biocatalysis and biomimetics; 19 - Nanosciences and nanotechnologies working for energy; 20 - Electric transports, The competitiveness of electric travel; 21 - Improving energy performance in the home; 22 - Using nuclear heat for non-electric applications; 23 - Institutions and organizations: who does what? 24 - Glossary.