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Leibstadt, Switzerland

Papra M.,Paul Scherrer Institute | Papra M.,Leibstadt Nuclear Power Plant | Buchi F.N.,Paul Scherrer Institute | Kotz R.,Paul Scherrer Institute
Fuel Cells | Year: 2010

Hydrogen fuelled vehicles with a fuel cell based powertrain are considered to contribute to sustainable mobility by reducing CO2 emissions from road transport. In such vehicles the fuel cell system is typically hybridised with an energy storage device such as a battery or a supercapacitor (SC) to allow for recovering braking energy and assist the fuel cell system for peak power. The direct parallel combination of a polymer electrolyte fuel cell (PEFC) and a SC without any control electronics is investigated in the present study. It is demonstrated that the combination enhances the dynamics of the PEFC significantly during load changes. However, due to the lack of a power electronic interface the SC cannot be utilised to its optimum capacity. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Nusbaumer O.,Leibstadt Nuclear Power Plant | Rauzy A.,Ecole Polytechnique - Palaiseau
11th International Probabilistic Safety Assessment and Management Conference and the Annual European Safety and Reliability Conference 2012, PSAM11 ESREL 2012 | Year: 2012

Two well-known modeling approaches are in use in Probabilistic Risk Assessment (PSA/PRA): Fault Tree Linking (FTL) and Event Tree Linking (ETL). The question of which modeling approach is best appropriate for specific applications has been extensively, if not emotionally, debated among experts in the past two decades, addressing both modeling and quantification issues. In this article, we determine their degree of equivalence and build "methodological bridges" between the two approaches, from a mathematical and algorithmic perspective. We show that both modeling approaches are, despite appearances and under certain conditions, equivalent. Such a demonstration is made possible by recent algorithmic developments in the Binary Decision Diagram (BDD) framework. Since both Fault Tree Linking and Event Tree Linking approaches are subject to limitations and approximations, the established bridges make it possible to formulate important recommendations for PSA/PRA practitioners and quantification engine developers. In the sequel, we demonstrate a fundamental result that will allow to solve exactly any FTL models from its Minimal Cutsets, including the quantification of success paths in Event Trees, and show how this can be implemented in future quantification engines. Source


Nusbaumer O.,Leibstadt Nuclear Power Plant | Rauzy A.,Ecole Polytechnique - Palaiseau
Proceedings of the Institution of Mechanical Engineers, Part O: Journal of Risk and Reliability | Year: 2013

Two well-known modelling approaches are in use in probabilistic risk assessment: fault tree linking and event tree linking. The question of which modelling approach is m ost appropriate for specific applications has been extensively, if not emotionally, debated among experts in the past two decades, addressing both modelling and quantification issues. In this article, we determine their degree of equivalence and build 'methodological bridges' between the two approaches from a mathematical and algorithmic perspective. We show that, under certain conditions, both modelling approaches are equivalent. Since both fault tree linking and event tree linking approaches are subject to limitations and approximations, established bridges make it possible to formulate important recommendations for probabilistic risk assessment practitioners and quantification engine developers. © IMechE 2013. Source


Khvostov G.,Paul Scherrer Institute | Wiesenack W.,Institute for Energy Technology of Norway | Zimmermann M.A.,Paul Scherrer Institute | Ledergerber G.,Leibstadt Nuclear Power Plant
Nuclear Engineering and Design | Year: 2011

A model for axial gas flow in a fuel rod during the LOCA is integrated into the FRELAX model that deals with the thermal behaviour and fuel relocation in the fuel rods of the Halden LOCA test series. The first verification was carried out using the experimental data for the inner pressure during the gas outflow after cladding rupture in tests 3, 4 and 5. Furthermore, the modified FRELAX model is implicitly coupled to the FALCON fuel behaviour code. The analysis with the new methodology shows that the dynamics of axial gas-flow along the rod and through the cladding rupture can have a strong influence on the fuel rod behaviour. Specifically, a delayed axial gas redistribution during the heat-up phase of the LOCA can result in a drop of local pressure in the ballooned area, which is eventually able to affect the cladding burst. The results of the new model seem to be useful when analysing some of the Halden LOCA tests (showing considerable fuel relocation) and selected cases of LOCA in full-length fuel rods. While the short rods used in the Halden tests only show a very small effect of the delayed gas redistribution during the clad ballooning, such an effect is predicted to be significant in the full-scale rods - with a power peak located sufficiently away from the plenum - resulting in a considerable delay of the predicted moment of cladding rupture. © 2011 Elsevier B.V. All rights reserved. Source


Orlov A.,Paul Scherrer Institute | Degueldre C.,Paul Scherrer Institute | Wiese H.,Paul Scherrer Institute | Ledergerber G.,Leibstadt Nuclear Power Plant | Valizadeh S.,Westinghouse Electrical Sweden AB
Journal of Nuclear Materials | Year: 2011

Recent Eddy current investigations on the cladding of nuclear fuel pins have shown that the apparent oxide layers are falsified due to unexpected magnetic properties of corrosion product deposits. Analyses by Scanning Electron Microscopy (SEM) or Electron Probe Micro Analysis (EPMA) demonstrated that the deposit layer consists of complex 3-d element oxides (Ni, Mn, Fe) along with Zn, since the reactor operates with a Zn addition procedure to reduce buildup of radiation fields on the recirculation system surfaces. The oxides crystallise in ferritic spinel structures. These spinels are well-known for their magnetic behaviour. Since non-magnetic zinc ferrite (ZnFe2O4) may become magnetic when doped with even small amounts of Ni and/or Mn, their occurrence in the deposit layer has been analyzed. The magnetic permeability of zinc ferrite, trevorite and jacobsite and their solid solutions are estimated by magnetic moment additivity. From the void history examination, the low elevation sample (810 mm) did not face significant boiling during the irradiation cycles suggesting growth of (Mn0.092+Zn0.752+Fe0.293+)[(Fe1.713+Mn0. 032+Ni0.132+)O4] crystals with theoretical value of the magnetic permeability for the averaged heterogeneous CRUD layer of 9.5 ± 3. Meanwhile, (Mn0.162+Zn0.552+Fe0.293+)[(Fe1.713+Mn0.042+Ni0.252+)O4] crystallizes at the mid elevation (1810 mm) with theoretical magnetic permeability for the CRUD layer of 4.2 ± 1.5 at the investigated azimuthal location. These theoretical data are compared with the magnetic permeability of the corrosion product deposited layers gained from reactor pool side Eddy current (EC) analyses (9.0 ± 1.0 for low and 3.5 ± 1.0 for high elevation). The calculated thicknesses and magnetic permeability values of the deposition layers (estimated by MAGNACROX multifrequency EC method) match together with these estimated using an "ion magnetic moment additivity" model. Source

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