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[en] Exposure of V. subterranea seeds, a herbaceous plant from Madagascar belonging to the family of legumes, to gamma irradiation resulted in a polyunsaturated fatty acids decrease associated with the formation of UV-absorbing substances. The finding that products containing conjugated diene structure are formed during lipid extract irradiation indicates that hydroperoxy fatty acids may arise not only by enzymatic reactions but also by nonenzymatic oxygenation of polyunsaturated fatty acids promoted by ionizing radiation. Dehulled green seeds, flour made from dehulled green seeds, and lipid extract were studied for irradiation dose dependent changes in fatty acids compositions and hydroperoxydiene synthesis. The irradiation dose is more efficient in lipid extract than in dehulled green seeds or in flour made from these seeds, suggesting that the formation of UV-absorbing products is not a reliable clue for enzyme activity owing to the absence of protein in lipid extract. A homolytic pathway for the biogenesis of hydroperoxy fatty acids from polyunsaturated fatty acids is proposed. This involves an initiating radical which promotes a chain mechanism in which the O2 adsorbed is converted to hydroperoxide. Conclusively, preservation of fatty acid oxygenation should be a primary goal in the ionizing radiation processes of V. subterranea seeds and generally in the preservation of food of plant origin by ionizing radiation
Journal
Journal of agricultural and food chemistry; ISSN 0021-8561; 
; v. 40(9); p. 1663-1665
; v. 40(9); p. 1663-1665
[en] After a presentation of the experience gained in France, on fast neutron reactors PHENIX and SUPER-PHENIX, on high temperature fission chamber, we present the R and D programme engaged to develop and qualify for industrial applications, in the EFR fast reactor, for an integrated neutronic control
Source
Nuclear Energy Agency, 75 - Paris (France); 398 p; ISBN 92-64-03682-2; ; 1992; p. 25-32; Organisation for Economic Co-Operation and Development; Paris (France); Specialists' Meeting on in-core instrumentation and reactor core assessment; Pittsburgh, PA (United States); 1-4 Oct 1991
; 1992; p. 25-32; Organisation for Economic Co-Operation and Development; Paris (France); Specialists' Meeting on in-core instrumentation and reactor core assessment; Pittsburgh, PA (United States); 1-4 Oct 1991
[en] In nuclear power plants neutron detectors are subject to severe mechanical and thermal stresses. In addition they are expected to cover a measuring range of 1-1012, which makes it necessary to use various types of detector connected to cables through which the emitted signals can be transmitted satisfactorily in spite of the difficult environment. In many cases it has been found necessary to provide a close association of cable and detector in a unit that cannot be taken apart and in which the sealing of the connections is perfect. The different types of cable used and their electrical properties are reviewed, with particular reference to a cable which is largely unaffected by parasitic interference. The fission chambers for start-up and power generation of reactors and the collectrons are also discussed. (author)
Source
International Atomic Energy Agency, Vienna (Austria); Proceedings series; v. 2 p. 275-288; ISBN 92-0-050478-7; ; 1978; v. 2 p. 275-288; IAEA; Vienna; International symposium on nuclear power plant control and instrumentation; Cannes, France; 24 - 28 Apr 1978; IAEA-SM--226/43
; 1978; v. 2 p. 275-288; IAEA; Vienna; International symposium on nuclear power plant control and instrumentation; Cannes, France; 24 - 28 Apr 1978; IAEA-SM--226/43
[en] These ex-core measurements performed by means some neutron detectors located around the reactor vessel are used for reactor control and core protection. The conception takes into consideration safety requirements and stress of process. In particular, the safety requirements have led to a redundancy based on four channels for analogical processing and two channels for logical processing. The architecture includes: - Some neutron detectors: Boron lined proportional counters, Compensated boron ionization chambers, multisections boron ionization chambers. - The SIN (Nuclear Instrumentation System), which ensures the signals acquisition and processing and the control of the power distribution. - Numerous informations are provided by the SIN to the SPIN (Integrated Numerical Protection System) automatic control device using a numerical technology which generates automatic actions as emergency shutdowns in case of incidents
[fr]
Ces mesures effectuees a partir de detecteurs nucleaires places autour de la cuve du reacteur, sont utilisees d'une part pour le controle du processus nucleaire, pour le pilotage du reacteur et d'autre part pour initier des actions de protection du coeur en cas d'incidents. La conception de l'ensemble tient compte d'un certain nombre de contraintes liees au processus ou imposees par la surete. Les regles de surete, en particulier, ont conduit a concevoir une architecture de controle-commande avec une redondance basee sur quatre voies de traitement pour la partie analogique et deux voies pour la partie logique. L'architecture de l'ensemble comprend: - Des detecteurs neutroniques repartis autour de la cuve. Le controle du reacteur se fait en trois niveaux (source, intermediaire, puissance), chacun correspondant a un type particulier de detecteur: compteur proportionnel a depot de bore, chambre d'ionisation a bore compensee au rayonnement gamma, chambre a bore multietagee. - Le Systeme d'Instrumentation Nucleaire (SIN) de controle analogique qui effectue l'acquisition des signaux analogiques en provenance des detecteurs et assure leur conditionnement avant affichage ou utilisation par les autres systemes, et le SIN de controle numerique, systeme programme qui assure la fonction de controle de la distribution de puissance. - Enfin un grand nombre des informations elaborees par le SIN sont adressees au Systeme de Protection Integree Numerique (SPIN) automate de protection dont le role est de provoquer l'arret d'urgence du reacteur par coupure de l'alimentation des mecanismes de grappe et d'initier automatiquement des actions de sauvegarde, en particulier dans le cas de surpuissance nucleaire, surpuissance lineique et crise d'ebullitionJournal
[en] IPMCs consist of a Nafion ionic polymer film coated on both sides with a thin layer of metallic electrodes. The polymer completely dissociates when it is saturated with water, releasing small cations while anions remain bound to the polymer chains. When this strip is subject to an orthogonal electric field, the cations migrate towards the negative electrode, carrying water away by osmosis. This leads to the bending of the strip. We have previously published a modelling of this system based on the thermodynamics of irreversible processes. In this paper, we use this model to simulate numerically the bending of a strip. Since the amplitude of the deflection is large, we use a beam model in large displacements. In addition, the material permittivity may increase with ion concentration. We therefore test three permittivity models. We plot the profiles of the cations concentration, pressure, electric potential and induction, and we study the influence of the strip geometry on the tip displacement and on the blocking force. The results we obtain are in good agreement with the experimental data published in the literature. The variation of these quantities with the imposed electric potential allow us to discriminate between the three models. (paper)
Journal
Smart Materials and Structures (Print); ISSN 0964-1726; ; v. 29(8); [14 p.]
; v. 29(8); [14 p.]
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