Results 1 - 10 of 19
Results 1 - 10 of 19. Search took: 0.02 seconds
|Sort by: date | relevance|
[en] Experiments were performed to assess the aging degradation and loss-of-coolant accident (LOCA) behavior of electrical cables subjected to long-term aging exposures. Four different cable types were tested in both the U.S. and France: (1) U.S. 2 conductor with ethylene propylene rubber (EPR) insulation and a Hypalon jacket. (2) U.S. 3 conductor with cross-linked polyethylene (XLPE) insulation and a Hypalon jacket. (3) French 3 conductor with EPR insulation and a Hypalon jacket. (4) French coaxial with polyethylene (PE) insulation and a PE jacket. The data represent up to 5 years of simultaneous aging where the cables were exposed to identical aging radiation doses at either 40 degrees C or 70 degrees C; however, the dose rate used for the aging irradiation was varied over a wide range (2-100 Gy/hr). Aging was followed by exposure to simulated French LOCA conditions. Several mechanical, electrical, and physical-chemical condition monitoring techniques were used to investigate the degradation behavior of the cables. All the cables, except for the French PE cable, performed acceptably during the aging and LOCA simulations. In general, cable degradation at a given dose was highest for the lowest dose rate, and the amount of degradation decreased as the dose rate was increased
[en] The VEILLE program (French acronym for study on long-term irradiation aging of electrical cables) was implemented in 1988 by the Institute of Protection and Nuclear Safety (IPSN) in collaboration with the U.S. Nuclear Regulatory Commission (NRC) for a period of six years. It is intended to validate the assumptions put forward as regards aging of electrical cables and to develop criteria for early detection of degradation likely to lead to functional failures. The tests were carried out partly at the Sandia National Laboratories in the United States, partly in France in the CIS Bio International Laboratories at the Saclay Nuclear Research Centre
[en] This study was conducted on electronic components and electrical cables taken from the Brennilis EL4 reactor, during dismantling, after 18 years of operation. Its aim was to examine the state of the equipment taken from the site and thus to check its characteristics and in particular for cables: to check, whenever possible, the suitability of the accelerated ageing methods by comparing the characteristics observed on the samples from EL4 with test samples held in storage and previously subjected to similar accelerated ageing: predicting medium and long-term ageing by extrapolation from the selected mathematical model. The result of this initial work confirmed the need for extreme caution regarding the accelerated ageing methods. Further work on cables and polymers is underway and will enable the laws currently used for qualification tests to be evaluated
[en] Samples of the stratigraphically placed (<400Ma) Pokiok batholith of New Brunswick give a Rb/Sr total-rock age of 431 +- 9 Ma. This age is some 40 Ma older than the estimated age of crystallization and is interpreted to result from the mixing of variable amounts of crustal strontium with mantle-like Sr at or about 390 Ma. The existence of inherited or crustal isochrons in the Pokiok batholith implies that all uncorroborated total-rock Rb/Sr ages for granite plutons in the Appalachians of eastern Canada should be carefully appraised in view of their importance in estimating the timing and duration of the Acadian Orogeny. (author)
[en] This study was conducted on electronic components and electrical cables taken from the Brennilis EL4 reactor, during dismantling, after 18 years of operation. Its aim was to examine the state of the equipment taken from the site and thus to check its characteristics and in particular for cables: to check, whenever possible, the suitability of the accelerated ageing methods by comparing the characteristics observed on the samples from EL4 with test samples held in storage and previously subjected to similar accelerated ageing: predicting medium and long-term ageing by extrapolation from the selected mathematical model. The result of this initial work confirmed the need for extreme caution regarding the accelerated ageing methods. Further work on cables and polymers is underway and will enable the laws currently used for qualification tests to be evaluated. (author)
[fr]Cette etude a ete menee sur des composants electroniques et des cables electriques preleves sur le reacteur EL4 de Brennilis, lors de son demantelement, au bout de 18 ans de fonctionnement. Le but poursuivi a ete, a partir du constat de l'etat des materiels preleves sur site, de controler leurs caracteristiques et, dans le cas particulier des cables: - de verifier, quand cela a ete possible, l'adequation des methodes de vieillissement accelere, en comparant les caracteristiques relevees sur les echantillons provenant d'EL4 a celles d'echantillons temoins, stockes en magasin, ayant subi un vieillissement accelere equivalent; - d'en deduire par extrapolation une prevision de vieillissement a moyen et a long terme a partir du modele mathematique retenu. Le resultat de ces premiers travaux a confirme la necessite d'observer la plus grande prudence vis-a-vis des methodes de vieillissement accelere. Des travaux complementaires en cours de realisation sur les cables et les polymeres permettront d'evaluer les lois actuellement utilisees pour les essais de qualification. (author)
[en] Hydro-Quebec has been using CFD to analyze the performance of its existing turbines for many years. Most of those analyses are based on the measurement of a single runner blade. However, due to manufacturing techniques, in-situ modifications or repairs, there are often small differences between individual blades of the same runner. The impact of this non uniformity was not known thus far and was often assumed to be negligible given the size of the runner. This paper highlights the impact of such differences by presenting the CFD analysis of various blades measured on the same runner. Two different geometries are used for demonstration: the AxialT model propeller and a 50-MW Francis turbine. In both cases, about 50% of the blades could not be considered as representative of the whole turbine and using them could lead to wrong conclusions regarding the turbine performance.
[en] The prototype of a high resolution PET camera consisting of two opposite arrays of detectors with independent solid state readout was built and tested. The basic detector unit is the RCA C30994 detector module consisting of two 3 x 5 x 20 mm BGO scintillators, each coupled to one silicon avalanche photodiode. The two-dimensional stacking capability of the module allows a high resolution multi-ring detection system to be assembled without crystal coding. This paper reports on the prototype used to simulate a 31 cm diameter dual ring tomograph suitable for animal studies. Coincident detector pair resolution was measured and the contributions to resolution loss estimated using a platinum sheathed .75 mm 68Ge line source
[en] As part of the safety studies of nuclear facilities, a series of experiments have been in progress over a number of years to determine the principal parameters for which allowance needs to be made in the testing of microprocessors in low dose rate nuclear irradiation environments. This paper contains a brief description of the results already published, followed by a review of the latest results obtained, specifically as concerns the effects of temperature, the origin of the batch, the angle of incidence of the radiation and the test routine used. (author)
[en] We address the issue of segregation in bidisperse suspensions of glass beads, by using a liquid fluidized bed in the inertialess regime and an acoustic technique for acquiring the axial composition along the column. Fluidization balances the buoyancy of the particles by a constant uniform upward flow, and therefore enables long-time experiments. From the analysis of the transient segregation fronts, we have collected precise measurements on the sedimentation velocities of small and large beads, Us and Ul, in homogeneous suspensions at the same volume fraction, Φ-bar/2, for both the bead species, and for different size ratios, 1.13≤λ≤1.64, and solid concentrations, 25%≤Φ-bar≤50%. Our measurements provide evidence for a difference in the sedimentation velocities, Us and Ul, over all the ranges of λ and Φ-bar covered. These results make one expect that a long-term fluidization should then result in a stationary segregated state, which was indeed always obtained for large enough particle size ratios, λ≥1.43. However, at high concentration and for particles of close sizes, λ≤1.41, we observed a surprising pseudo-periodic intermittency of slow segregation and quick mixing phases. The intermittency time is much longer than the batch sedimentation time and becomes noisy at very high concentration, for which metastable states have been observed. The origin of the mixing destabilization remains an open issue, but we note however that the domain of occurrence, λ≤1.41, also corresponds, in our experiments, to a continuous size distribution of the particles.