24 research outputs found
Nuclear power fleet replacement: an opportunity for the French energy mix?
International audienceâ In France, 27% of the electricity is to be produced by renewable resources by 2020. This share is intended to grow continuously up to 2050. The recent European agreement and the French " energy transition law " will promote such a development. The French power system is characterized by high nuclear penetration and nuclear power is meant to remain a significant contributor in the medium and long term, as a low-carbon power source. More than half the French nuclear power fleet was installed in the late seventies / early eighties. Thus, the issue of its replacement is at the core of the French power mix issue. The objective of this paper is to provide some insights about the opportunity it enables for the energy mix. Two plausible replacement scenarios are developed and analyzed as regards the energy cost provided by nuclear power. For a given target level of nuclear installed capacities, the penetration of non-dispatchable renewables with dispatch priority will increase the need for nuclear power modulation at reduced average load factor. The impact of modulation on the nuclear levelized cost of electricity is assessed, according to the considered replacement scenario and for different renewable and nuclear energy penetration scenarios. Results show that, according to the selected assumptions, implementing a progressive shutdown (based on an increased operation lifetime of Nuclear Power Plants) appears a relevant choice since it both provides a lowest power production cost even at reduced average load factor to participate to load following and allows the possibility of " waiting " for choosing most sustainable technologies
Nuclear and non-dispatchable renewables: two compatible supply options? The case of the French power mix
The complementary features of low-carbon power sources are a central issue in designing energy transition policies. The French current electricity mix is characterised by a high share of nuclear power which equalled 73% of the total electric production in 2013. With the increase of non-dispatchable renewable resources, nuclear flexibility is examined as part of the solution to balance electricity supply and demand. Our proposed methodology involves designing scenarios of nuclear and non-dispatchable renewable penetration levels, and developing residual load duration curves in each case. The load modulation impact on the nuclear production cost is estimated. This article shows to which extent the nuclear annual energy production will decrease with high shares of non-dispatchable renewables (down to load factors of 40% for proactive assumptions). However, the production cost increase could be compensated by implementing a progressive replacement of the plants. Besides, incentives proves required for nuclear to compete with combined cycle gas turbines as its alternative backup option. In order to make the social planner and plant operator goals coincide, the solution could be to find new outlets rather than reducing nuclear load factors. To conclude, nuclear flexibility could then be considered through the power use by producing heat or hydrogen
Activities of peroxidase (soluble and cell wall bound) and of other H2O2 scavenging enzymes are markers of the flower bud development stage in lemon
Specific activities of H2O2 scavenging enzymes, soluble peroxidase (G-POD), catalase (CAT) and ascorbate peroxidase (APX), and cell wall bound (CWB) G-POD, have been characterized in flower buds and leaves in potted lemon trees (Citrus limon L. Burm.) growing in a glasshouse in Tunisia. In leaves during the winter rest period (from September to December), enzyme activities did not change markedly. Then, leaf G-POD (soluble and CWB activity) increased 4-5 fold in January as the buds reached dormancy release. In growing buds, the activities of the three enzymes increased strongly (10-100-fold) between dormancy and full bloom and decreased slightly (3-fold) post-bloom (beginning of fruit-set). Along the shoots, the developmental stages of flower buds advanced from node 1 to node 5. G-POD activity increased from the shoot apex toward the base of the twig in both leaves and buds. A similar trend was observed for APX and CAT but their activities tended to decrease slightly far from the apex. Retardation of flowering by application of growth regulators strongly reduced leaf-specific activities of the H2O2 scavenging enzymes. Therefore, G-POD activity (APX and to a lesser extent CAT) appears to be a good marker of flower formation in lemon (from bud swelling to full bloom). The results also suggest a link between H2O2 production and flower bud development
Exploiter les centrales nucléaires dans la durée - les défis économiques
Lâaugmentation de la durĂ©e dâexploitation des rĂ©acteurs est un enjeu Ă©conomique important, tant pour lâexploitant (Ă©lectricien) que pour la collectivitĂ©. Les Ă©valuations Ă©conomiques menĂ©es Ă ce jour montrent quâau plan mondial ce choix est trĂšs gĂ©nĂ©ralement le meilleur. Pour la France, ces Ă©valuations ont Ă©tĂ© complĂ©tĂ©es par une analyse multicritĂšre. Il en ressort que ce choix est le meilleur du point de vue Ă©conomique (coĂ»t du kWh produit, et par suite PIB et emploi), mais aussi en termes de gestion de la dynamique du parc (possibilitĂ© de lissage de la charge industrielle induite par la construction des nouveaux rĂ©acteurs), ainsi que vis-Ă -vis des aspects environnementaux (absence de recours transitoire Ă des moyens de production Ă©metteurs de CO2 en cas de dĂ©crue ârapideâ de la puissance nuclĂ©aire, mĂȘme si remplacĂ©e par des EnR intermittentes : un back-up de lâintermittence par des centrales Ă©mettrices de CO2 serait nĂ©cessaire). Ces avantages de lâaccroissement de la durĂ©e dâexploitation ne sont Ă©videmment envisageables que si les impĂ©ratifs de sĂ»retĂ© sont atteints
Enjeux Ă©conomiques de lâĂ©nergie nuclĂ©aire
Le lecteur assidu des articles sur lâĂ©conomie du nuclĂ©aire constatera sans nul doute combien est diffĂ©rent aujourdâhui un article sur ce sujet de ce quâil aurait Ă©tĂ© il y a seulement 3 ou 4 ans. Plusieurs Ă©vĂ©nements dâampleur considĂ©rable sont en effet intervenus depuis : traduction effective dans le systĂšme français des directives sur la concurrence entre producteurs dâĂ©lectricitĂ© et en consĂ©quence rĂ©flexion en profondeur sur le calcul des prix Ă payer par les nouveaux entrants pour accĂ©der au nuclĂ©aire âhistoriqueâ, accident de Fukushima, campagne Ă©lectorale en cours avec une question jusquâici peu traitĂ©e relative au parc : que faut-il souhaiter en termes dâexploitation des rĂ©acteurs actuels ? Ainsi, la consĂ©quence majeure est que la rĂ©flexion Ă©conomique sâest intensifiĂ©e en regard des coĂ»ts du nuclĂ©aire existant, alors quâil y a peu, lâĂ©conomie du nuclĂ©aire Ă©tait surtout abordĂ©e en termes de compĂ©titivitĂ© vis-Ă -vis des autres moyens de production Ă©lectriques, dans une perspective donc de construction de nouvelles centrales (une logique dite âen dĂ©veloppementâ).
Cet article reflĂšte trĂšs nettement cette nouvelle tendance et une place importante est donnĂ©e Ă lâĂ©conomie du nuclĂ©aire existant. La question de son coĂ»t (ou de ses coĂ»ts) est prĂ©sentĂ©e en dĂ©tail. On constate une augmentation certaine des coĂ»ts, au regard des Ă©valuations encore rĂ©centes : elle est notamment la consĂ©quence de la meilleure prise en compte des coĂ»ts de maintien du parc, de dĂ©mantĂšlement et de stockage des dĂ©chets. Le nuclĂ©aire historique produit son Ă©nergie pour un coĂ»t courant Ă©conomique de lâordre de 50 euros/MWh, selon le rapport rĂ©cent de la Cour des Comptes sur lâĂ©conomie de la filiĂšre nuclĂ©aire, hors les options de rĂ©novation possibles. En comptant toutes les rĂ©novations envisageables, y compris induites par la prise en compte de lâaccident de Fukushima, ce coĂ»t courant Ă©conomique atteint 54 /MWh, sur la base de la mĂȘme mĂ©thode. Il existe Ă©galement dâautres mĂ©thodes de calcul dĂ©taillĂ©es dans cet article. un tel niveau est plus compĂ©titif que les autres moyens de production existants ou en dĂ©veloppement (hydraulique exceptĂ©). Câest ce qui explique lâintĂ©rĂȘt Ă©conomique de prolonger lâexploitation du parc actuel, tant que lâAutoritĂ© de sĂ»retĂ© le permet (compte tenu des travaux Ă rĂ©aliser et de leurs coĂ»ts).
Sous un autre angle, le rapport de la Commission âEnergies 2050â Ă©value le coĂ»t total actualisĂ© de lâarrĂȘt du parc actuel, selon lâhypothĂšse dâune durĂ©e dâexploitation limitĂ©e Ă 40 ans, Ă de lâordre de la centaine de milliards dâeuros.
Enfin, nous terminons cet article par un regard sur les coĂ»ts actuels des rĂ©acteurs en dĂ©veloppement, dont lâEPR. Nous concluons Ă une augmentation significative des coĂ»ts, laquelle doit cependant ĂȘtre relativisĂ©e.
Au total, le nuclĂ©aire ne fait pas exception dans lâĂ©volution des coĂ»ts de la production et de la distribution dâĂ©lectricitĂ© en France et dans le monde : les Ă©volutions rĂ©centes marquent une tendance significative Ă la hausse. MalgrĂ© cela, cette source dâĂ©lectricitĂ© est la plus compĂ©titive quand il sâagit du parc existant, et de loin, et reste lâune de plus compĂ©titives si lâon considĂšre des unitĂ©s en dĂ©veloppement
Economic appraisal of deployment schedules for high-level radioactive waste repositories
The deep geological repository (DGR) is considered as the definitive management solution for high-level waste (HLW). Countries defined different DGR implementation schedules, depending on their national context and political choices. We raise the question of the economic grounds of such political decisions by providing an economic analysis of different DGR schedules. We investigate the optimal timing for DGR commissioning based on available Nuclear Energy Agency (NEA) data (2013). Two scenarios are considered: (1) rescheduling the deployment of a DGR with the same initial operational period, and (2) rescheduling the deployment of a DGR with a shorter operational period, i.e. initial closure date. Given the long timescales of such projects, we also take into account the discounting effect. The first finding is that it appears more economically favorable to extend the interim storage than to dispose of the HLW immediately. Countries which chose âimmediateâ disposal are willing to accept higher costs to quickly solve the problem. Another interesting result is that there is an optimal solution with respect to the length of DGR operational period and the waste flow for disposal. Based on data provided by the Organisation for Economic Cooperation and Development (OECD)/Nuclear Energy Agency (NEA), we find an optimal operating period of about 15 years with a flow of 2000âtHM/year
COSI6: A Tool for Nuclear Transition Scenario Studies and Application to SFR Deployment Scenarios with Minor Actinide Transmutation
International audienc
Characterization of SLC26A9 in Patients with CF-Like Lung Disease
International audienceDiffuse bronchiectasis is a common problemin respiratory clinics. We hypothesized that mutations inthe solute carrier 26A9 (SLC26A9) gene, encoding for achloride (Clâ) transporter mainly expressed in lungs, maylead to defects in mucociliary clearance. We describe twomissense variants in theSLC26A9gene in heterozygotepatients presenting with diffuse idiopathic bronchiectasis: p.Arg575Trp, identified in a patient also heterozygotefor p.Phe508del in theCFTRgene; and p.Val486Ile.Expression of both mutants inXenopus laevisoocytesabolished SLC26A9-mediated Clâconductance withoutdecreasing protein membrane expression. Coexpressionof CFTR with SLC26A9âp.Val486Ile resulted in a sig-nificant increase in the Clâcurrent induced by PKAstimulation, similar to that obtained in oocytes express-ing CFTR and SLC26A9âWT. In contrast, coexpres-sion of CFTR with SLC26A9âp.Arg575Trp inhibitedSLC26A9-enhanced CFTR activation upon PKA. Fur-ther structureâfunction analyses led us to propose a siteencompassing Arg575 in the SLC26A9âSTAS domainfor CFTRâSLC26A9 interaction. We hypothesize thatSLC26A9âp.Arg575Trp prevented SLC26A9-mediatedfunctional activation of CFTR by altering SLC26A9âCFTR interaction. Although we cannot confirm that thesemutations by themselves are deleterious, we propose thatthey trigger the pathogenic role of a singleCFTRmuta-tion and provide insight into a novel mechanism of Clâtransport alteration across the respiratory mucosa, basedon functional inhibition of CFT