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1.
2.
All boiling water reactor (BWR) degraded core experiments performed prior to CORA-33 were conducted under ‘wet’ core degradation conditions, in which water remains within the core and continuous steaming feeds metal-steam oxidation reactions on the in-core metallic surfaces. However, one dominant set of accident scenarios would occur with reduced metal oxidation under ‘dry’ core degradation conditions and, prior to CORA-33, this set had been neglected experimentally. The CORA-33 experiment was designed specifically to address this dominant set of BWR ‘dry’ core severe accident scenarios and to resolve partially phenomenological uncertainties concerning the behavior of relocating metallic melts that drain into the lower regions of a ‘dry’ BWR core (the ex-reactor experiments at Sandia National Laboratories will further address these uncertainties). CORA-33 was conducted on 1 October 1992, in the CORA test facility at Karlsruhe. A review of the CORA-33 data indicates that the objectives were achieved; i.e. core degradation occurred at a core heat-up rate (characterized by the absence of any temperature escalation caused by oxidation) and a test section axial temperature profile (at incipient structural melting) that are prototypic of full-core nuclear power plant simulations under ‘dry’ core conditions. Simulations of the CORA-33 test at Oak Ridge National Laboratory (ORNL) have required the modification of existing control blade-canister materials interaction models to include the eutectic melting of the stainless steel-zircaloy interaction products and the heat of mixing of stainless steel and zircaloy. The timing and location of canister failure and melt intrusion into the fuel assembly appear to be adequately simulated by the ORNL models. This paper will present the results of the post-test analyses carried out at ORNL based on the experimental data and the post-test examination of the test bundle at Karlsruhe. The implications of these results with respect to degraded core modelling and the associated safety issues are also discussed. 相似文献
3.
The common way to construct Voronoi tessellations is to compare the distances between given reference points using a given
distance function. To generalize this distance-function concept we expand an existing approach which defines distance functions
by their ``unit circles'. Our new approach allows modeling the ``unit circles' by a closed Spline curve. Changing the control
polygon directly affects the tessellation's appearance. Typically generalized Voronoi diagrams are represented by Voronoi
vertices and curves separating the individual tiles. To obtain interactive modeling we extended an existing hardware accelerated
rendering approach computing a bitmap-representation using different colors for individual tiles. With our extension, we are
able to use our Spline distance representations as input for a growing process. This growing process easily takes into account
weighting approaches like multiplicative, additive, and even free functional weighting. 相似文献
4.
5.
M Fein JH Peters P Chandrasoma AP Ireland S Oberg MP Ritter CG Bremner JA Hagen TR DeMeester 《Canadian Metallurgical Quarterly》1998,2(3):260-268
Central nervous system (CNS) disease is a major feature of simian immunodeficiency virus (SIV) infection of macaques. To define the spectrum of CNS lesions in SIV-infected macaques and the potential associations with viral strain and disease course, we performed a retrospective analysis of necropsies on 124 macaques with SIV-induced AIDS. Histologic evidence of CNS disease was observed in 71 (57.3%) of the 124 animals. SIV encephalitis was the most common CNS lesion occurring in 43.7% (31/71) of the animals with CNS disease and 25% of all animals. The incidence of SIVE correlated significantly with shortened survival (P=0.0207). In addition, SIVE was seen in 42.9% (15/35) of rapid progressors (animals that died within 200 days) compared to only 18% (16/89) of normal progressors (animals that lived longer than 200 days) (P=0.011). Animals with SIVE had higher viral loads in peripheral blood than those that did not, but this difference did not reach statistical significance. Similarly, while animals infected with uncloned SIVmac251 had a higher incidence of SIVE (27.5%; 14/51) than animals infected with molecularly cloned SIVmac239 and its T-cell tropic derivatives (18.5%; 10/54) this difference was not statistically significant. In this study rapid disease progression and SIVE were highly correlated making separation of viral determinants of virulence from those of neurovirulence difficult. 相似文献
6.
Obermaier H Mohring J Deines E Hering-Bertram M Hagen H 《IEEE transactions on visualization and computer graphics》2012,18(2):270-282
Crease surfaces describe extremal structures of 3D scalar fields. We present a new region-growing-based approach to the meshless extraction of adaptive nonmanifold valley and ridge surfaces that overcomes limitations of previous approaches by decoupling point seeding and triangulation of the surface. Our method is capable of extracting valley surface skeletons as connected minimum structures. As our algorithm is inherently mesh-free and curvature adaptive, it is suitable for surface construction in fields with an arbitrary neighborhood structure. As an application for insightful visualization with valley surfaces, we choose a low frequency acoustics simulation. We use our valley surface construction approach to visualize the resulting complex-valued scalar pressure field for arbitrary frequencies to identify regions of sound cancellation. This provides an expressive visualization of the topology of wave node and antinode structures in simulated acoustics. 相似文献
7.
König Till Hagen S. P. Virtanen S. Galetz M. C. 《Metallurgical and Materials Transactions A》2022,53(11):4023-4033
Metallurgical and Materials Transactions A - Co-based superalloys have been developed as candidate materials to replace Ni-based superalloys in hot sections of turbine engines, however, their... 相似文献
8.
Influence of Molybdenum Silicide Additions on High-Temperature Oxidation Resistance of Silicon Nitride Materials 总被引:2,自引:0,他引:2
Hagen Klemm Katja Tangermann Christian Schubert Waldemar Hermel 《Journal of the American Ceramic Society》1996,79(9):2429-2435
The influence of additions of molybdenum disilicide (MoSi2 ) on the microstructure and the mechanical properties of a silicon nitride (Si3 N4 ) material, with neodymium oxide (Nd2 O3 ) and aluminum nitride (AIN) as sintering aids, was studied. The composites, containing 5, 10, and 17.6 wt% MoSi2 , were fabricated by hot pressing. All materials exhibited a similar phase composition, detected by X-ray diffractometry. Up to MoSi2 additions of 10 wt%, mechanical properties such as strength, fracture toughness, or creep at 1400°C were not affected significantly, in comparison to that of monolithic Si3 N4 . The oxidation resistance of the composites, in terms of weight gain, degraded. After 1000 h of oxidation at 1400° and 1450°C in air, a greater weight gain (by a factor of approximately three) was obtained, in comparison to that of the material without MoSi2 . Nevertheless, after 1000 h of oxidation, the degradation in strength of the composites was considerably less severe than that of the material without MoSi2 . An additional layer was formed, caused by processes at the surface of the Si3 N4 material, preventing the formation of pores, cracks, or glassy-phase-rich areas, which are common features of oxidation damage in Si3 N4 materials. This surface layer, containing Mo5 Si3 and silicon oxynitride (Si2 ON2 ), was the result of reactions between MoSi2 , Si3 N4 , and the oxygen penetrating by diffusion into the material during the hightemperature treatment. 相似文献
9.
In order to investigate the transmission properties in the whole solar spectrum for individual electrochromic layers in solid state devices incorporating polyaniline (PANI), Prussian Blue (PB) and tungsten oxide (WO3), the devices were fabricated with and without holes in the electrochromic coatings in several combinations. Both PANI and WO3 were deposited electrochemically on indium–tin oxide (ITO) glass substrates, while PB was deposited on top of the PANI coatings or directly on the ITO glass plates. Solid state devices were made by gluing the glass plates together with the solid polymer electrolyte poly(2-acrylamido-2-methyl-propane-sulphonic acid) (PAMPS), and thus, with and without holes in the three electrochromic coatings in different combinations, enabling us to study the optical properties of PANI, PB and WO3 separately, that is, the hole method. This method gives good qualitative, and to a certain degree quantitative, information, which may be of valuable help in designing electrochromic devices with specific tailor-made optical properties. 相似文献
10.
Dehydrogenation of Light Alkanes Over Rhenium Catalysts on Conventional and Mesoporous MFI Supports 总被引:1,自引:0,他引:1
Anne Krogh Rovik Anke Hagen Iver Schmidt Søren Dahl Ib Chorkendorff Claus Hviid Christensen 《Catalysis Letters》2006,109(3-4):153-156
Recently, Re/HZSM-5 (Si/Al = 15) was shown to be an efficient catalyst for ethane dehydrogenation and aromatization at 823 K
and atmospheric pressure. In this reaction, the major initial products were benzene, toluene and xylene (BTX), but increasing
amounts of ethene were produced with time on stream due to deactivation of the catalyst. We show that by use of rhenium impregnated
MFI supports with very few or no acidic sites (Si/Al > 500), highly selective ethane dehydrogenation catalysts are obtained
with ethene selectivities of 98%. By use of mesoporous MFI supports (Si/Al >500) the lifetime of the catalyst appears to be
slightly improved compared to conventional MFI crystals. The beneficial effect of a mesoporous MFI support is convincingly
demonstrated in propane dehydrogenation, where both conversion and selectivities on the mesoporous MFI (Si/Al > 500) impregnated
with Re are significantly higher than on Re supported on a comparable conventional MFI support. 相似文献